T r i p a t h T e c h n o l o g y, I n c . - T e c h n i c a l I n f o r m a t i o n

TK2070 MC/2.1/10-03

TK2070

STEREO 70W (4

) CLASS-TTM DIGITAL AUDIO AMPLIFIER

DRIVER USING DIGITAL POWER PROCESSING (DPPTM)
TECHNOLOGY

P r e l i m i n a r y I n f o r m a t i o n R e v i s i o n 2 . 1 O c t o b e r 2 0 0 3

G E N E R A L D E S C R I P T I O N

The TK2070 (TC2001/TPS1035 chipset) is a bridged stereo 70W continuous average power per
channel, Class-T Digital Audio Power Amplifier using Tripath's proprietary Digital Power Processing

technology. The TK2070 chipset consists of 1 TC2001 and 4 TPS1035's to obtain a bridged stereo
configuration. Class-T amplifiers offer both the audio fidelity of Class-AB and the power efficiency of
Class-D amplifiers.

A P P L I C A T I O N S

5.1-Channel DVD

Mini/Micro Component Systems

Home Theater

Stereo applications (4 / 8)

Powered Subwoofer

B E N E F I T S

Single Supply Operation

Very High Efficiency

Wide Dynamic Range

Compact layout

F E A T U R E S

Class-T Architecture

High Output power

70W @ 4

, 10% THD+N Bridged

40W @ 8

, 10% THD+N Bridged

Audiophile Quality Sound

0.03% THD+N @ 35W 4

Bridged

0.03% THD+N @ 25W 8

Bridged

High Efficiency

86% @ 70W 4 Bridged

92% @ 40W 8 Bridged

Dynamic Range >100 dB

T r i p a t h T e c h n o l o g y, I n c . - T e c h n i c a l I n f o r m a t i o n

TK2070 MC/2.1/10-03

A B S O L U T E M A X I M U M R A T I N G S T C 2 0 0 1

(Note 1)

SYMBOL PARAMETER

Value

UNITS

5V Power Supply

Vlogic Input

Logic

Level

+0.3V V

Operating Free-air Temperature Range

-40 to 85

°C

STORE

Storage Temperature Range

-55 to 150

°C

JMAX

Maximum Junction Temperature

150

°C

ESD

ESD Susceptibility Human Body Model (Note 2), all pins

2000

Note 1: Absolute Maximum Ratings indicate limits beyond which damage to the device may occur.

See the table below for Operating Conditions.

Note 2: Human body model, 100pF discharged through a 1.5K

resistor.

A B S O L U T E M A X I M U M R A T I N G S T P S 1 0 3 5

(Note 1)

SYMBOL PARAMETER

Value

UNITS

Power Supply

Vlogic Input

Logic

Level

5.5

Operating Free-air Temperature Range

-40 to 85

°C

STORE

Storage Temperature Range

-40 to 150

°C

JMAX

Maximum Junction Temperature

150

°C

ESD

ESD Susceptibility Human Body Model (Note 2), all pins except 1, 8
Pins 1, 8

2000

400

ESD

ESD Susceptibility Machine Model (Note 3), all pins

200

Note 3: Machine model, 220pF 240pF discharged through all pins.

O P E R A T I N G C O N D I T I O N S T C 2 0 0 1

SYMBOL PARAMETER MIN.

TYP.

MAX.

UNITS

Supply Voltage

4.5

5.5

Logic Input High

V5-1.0

Logic Input Low

Operating Temperature Range

-40

°C

O P E R A T I N G C O N D I T I O N S T P S 1 0 3 5

SYMBOL PARAMETER

MIN.

TYP.

MAX.

UNITS

Power Supply

Logic Input High

TBD

Logic Input Low

TBD

Operating Temperature Range

-40

°C

T H E R M A L C H A R A C T E R I S T I C S

TC2001

SYMBOL PARAMETER

Value

UNITS

Junction-to-ambient Thermal Resistance (still air)

°C/W

T r i p a t h T e c h n o l o g y, I n c . - T e c h n i c a l I n f o r m a t i o n

TK2070 MC/2.1/10-03

TPS1035

SYMBOL PARAMETER

Value

UNITS

Junction-to-Ambient Thermal Resistance

°C/W

Junction-to-case Thermal Resistance

°C/W

E L E C T R I C A L C H A R A C T E R I S T I C S T C 2 0 0 1

SYMBOL PARAMETER MIN.

TYP.

MAX.

UNITS

Supply Current

fsw

Switching Frequency (adjustable via CFB)

600

650

kHz

Input

Sensitivity

1.5

OUTHI

High Output Voltage

V5-0.5

OUTLO

Low

Output

Voltage

100 mV

Input

Impedance

Input

Bias

2.5

E L E C T R I C A L C H A R A C T E R I S T I C S T K 2 0 7 0

= 25

°C. See Application/Test Circuit. Unless otherwise noted, the supply voltage is V

= 24V.

SYMBOL PARAMETER

CONDITIONS MIN.

TYP.

MAX.

UNITS

Quiescent Current
(No load, Mute = 0V)

= 24V

V5 = 5V

20
27

mA
mA

MUTE

Mute Supply Current
(No load, TC2001 Mute = 5V,
TPS1035 Sleep = 5V)

= 24V

V5 = 5V

4
7

µA

High-level input voltage (MUTE)

= See Mute Control Section

3.5

Low-level input voltage (MUTE)

= See Mute Control Section

1.0

Short circuit current limit

= 24V

7.5

VPPSENSE

VPPSENSE Threshold Currents

Over-voltage turn on (muted)
Over-voltage turn off (mute off)
Under-voltage turn off (mute off)
Under-voltage turn on (muted)

138

162
154

79
72

178

µA
µA
µA
µA

VPPSENSE

Threshold Voltages with

VPPSENSE

= 187K

(Note 4, Note 5)

Over-voltage turn on (muted)
Over-voltage turn off (mute off)
Under-voltage turn off (mute off)
Under-voltage turn on (muted)

25.8

11.6

30.3
28.8
14.8
13.5

33.3

16.3

V
V
V
V

Note 4: These supply voltages are calculated using the IVPPSENSE values shown in the Electrical Characteristics

table. The typical voltage values shown are calculated using a RVPPSENSE value of 187kohm without any
tolerance variation. The minimum and maximum voltage limits shown include either a +1% or 1% (+1% for
Over-voltage turn on and Under-voltage turn off, -1% for Over-voltage turn off and Under-voltage turn on)
variation of RVPPSENSE off the nominal value. These voltage specifications are examples to show both
typical and worst case voltage ranges for a given RVPPSENSE resistor values of 187kohm. Please refer to
the Application Information section for a more detailed description of how to calculate the over and under
voltage trip voltages for a given resistor value.

Note 5: The fact that the over-voltage turn on specifications exceed the absolute maximum of +26V for the TK2070

does not imply that the part will work at these elevated supply voltages. It also does not imply that the
TK2070 is tested or guaranteed at these supply voltages. The supply voltages are simply a calculation based
on the process spread of the IVPPSENSE currents (see note 7). The supply voltage must be maintained
below the absolute maximum of +26V or permanent damage to the TK2070 may occur.

T r i p a t h T e c h n o l o g y, I n c . - T e c h n i c a l I n f o r m a t i o n

TK2070 MC/2.1/10-03

P E R F O R M A N C E C H A R A C T E R I S T I C S T K 2 0 7 0

= 25

°C. Unless otherwise noted, V

= 24V, f=1kHz, and the measurement bandwidth is 20kHz.

SYMBOL PARAMETER

CONDITIONS MIN.

TYP.

MAX.

UNITS

OUT

Output Power
(Continuous Average/Channel)
(Note 13)

= 24V, R

= 8

THD+N = 0.02%

THD+N = 1.0%
THD+N = 10.0%

= 24V, R

= 4

THD+N = 0.05%
THD+N = 5.0%
THD+N = 10.0%

22
33
40

45
55
70

W
W
W

THD + N Total Harmonic Distortion Plus

Noise

OUT

= 24W/Channel, R

= 8

= 24V

OUT

= 40W/Channel, R

= 4

= 24V

0.03

0.04

IHF-IM IHF

Intermodulation

Distortion 19kHz, 20kHz, 1:1 (IHF), R

= 4

OUT

= 10W/Channel

95 dB

SNR Signal-to-Noise

Ratio

A-Weighted

0dB = 70W/Channel, R

= 4

105

CS Channel

Separation

0dB = 9W, R

= 4

, f=1kHz

100 dB

Amplifier

Gain

OUT

= 10W/Channel, R

= 8

See Application / Test Circuit

12 V/V

VERROR

Channel to Channel Gain Error

OUT

= 10W/Channel, R

= 8

See Application / Test Circuit

0.5

Power Efficiency

OUT

= 35W/Channel, R

= 8

OUT

= 70W/Channel, R

= 4

Output Noise Voltage

A-Weighted, input AC grounded,
R

FBC

= 11k

, R

FBB

= 1k

µV

T r i p a t h T e c h n o l o g y, I n c . - T e c h n i c a l I n f o r m a t i o n

TK2070 MC/2.1/10-03

T C 2 0 0 1 A U D I O S I G N A L P R O C E S S O R P I N D E S C R I P T I O N S

Pin

Function

Description

BIASCAP

Bandgap reference times two (typically 2.5VDC). Used to set the
common mode voltage for the input op amps. This pin is not capable of
driving external circuitry

2, 6

FBKGND2,

FBKGND1

Ground Kelvin feedback (Channels 1 & 2)

DCMP

Internal mode selection. This pin must be grounded for proper device
operation.

4, 7

FBKOUT2,

FBKOUT1

Switching feedback (Channels 1 & 2)

VPWR

Test pin. Must be left floating.

HMUTE

Logic output. A logic high indicates both amplifiers are muted, due to the
mute pin state, or a "fault".

9, 12

Y1, Y2

Non-inverted switching modulator outputs.

10, 11

Y1B, Y2B

Inverted switching modulator outputs.

13 NC

connect

14, 16

OCD2, OCD1

Over Current Detect pins. Not used on the TK2070, these pins should
be tied to ground.

REF

Internal bandgap reference voltage; approximately 1.2 VDC.

VNNSENSE

Negative supply voltage sense input. This pin is used for both over and
under voltage sensing for the VNN supply. Not used on the TK2070, this
pin should be tied to ground through a 10k

resistor.

OVRLDB

A logic low output indicates the input signal has overloaded the amplifier.

VPPSENSE

Positive supply voltage sense input. This pin is used for both over and
under voltage sensing for the VPP supply.

20 AGND

Analog

Ground.

5 Volt power supply input.

22, 27

OAOUT1, OAOUT2

Input stage output pins.

23, 28

INV1, INV2

Single-ended inputs. Inputs are a "virtual" ground of an inverting op-amp
with approximately 2.4VDC bias.

MUTE

When set to logic high, both amplifiers are muted and in idle mode.
When low (grounded), both amplifiers are fully operational. If left floating,
the device stays in the mute mode. Ground if not used.

25, 26

BBM1, BBM0

Break-before-make timing control to prevent shoot-through in the output
MOSFETs. When using with the TPS1035, these pins should both be
set to 5V.

T C 2 0 0 1 A U D I O S I G N A L P R O C E S S O R P I N O U T

REF

VNNSENSE

VPPSENSE

AGND

OAOUT1

MUTE

BBM1

BBM0

OAOUT2

INV2

FBKGND2

OCD2

Y2B

Y1B

HMUTE

FBKOUT1

FBKGND1

VPW R

FBKOUT2

DCMP

28-pin SOIC

(Top View)

BIASCAP

INV1

OVRLDB

OCD1

T r i p a t h T e c h n o l o g y, I n c . - T e c h n i c a l I n f o r m a t i o n

TK2070 MC/2.1/10-03

T P S 1 0 3 5 P O W E R S T A G E P I N D E S C R I P T I O N S

Pin Function

Description

INPUT

Input pin for power stage.

VDD

Positive supply pin.

3 OUTPUT

Output

pin.

PGND

Power Ground pin.

VBOOT

Bootstrapped voltage to supply drive to gate of high-side output MOSFET.

SLEEP

Sleep Input pin. When set to logic level high, sleep mode is enabled. When set
to logic level low (grounded), sleep mode is disabled.

BYPASS

Bypass pin for the gate drive power supply. The gate drive for the output mosfets
are internally generated from VDD. This pin should be connected to ground
through a 1.0uF or larger capacitor. This pin must be connected to the Fault pin
(pin 8) through a 27k

resistor.

FAULT

Fault Output pin. During normal operation this pin is high. If an overcurrent or
over temperature condition is detected the fault pin will become low. This pin
must be connected to the Bypass pin (pin 7) through a 27k

resistor.

T P S 1 0 3 5 P O W E R S T A G E P I N O U T

(Top view with heat slug down)

VBOOT

SLEEP

BYPASS

FAULT

VDD

PGND

OUTPUT

8-pin SOIC with Heatslug

(Top View)

INPUT

T r i p a t h T e c h n o l o g y, I n c . - T e c h n i c a l I n f o r m a t i o n

TK2070 MC/2.1/10-03

A P P L I C A T I O N / T E S T D I A G R A M

UTE

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T r i p a t h T e c h n o l o g y, I n c . - T e c h n i c a l I n f o r m a t i o n

TK2070 MC/2.1/10-03

E X T E R N A L C O M P O N E N T S D E S C R I P T I O N

(Refer to the Application/Test Circuit)

Components Description
R

Inverting input resistance to provide AC gain in conjunction with R

. This input is

biased at the BIASCAP voltage (approximately 2.5VDC).

Feedback resistor to set AC gain in conjunction with R

. Please refer to the Amplifier

Gain paragraph, in the Application Information section.

AC input coupling capacitor, which, in conjunction with R

, forms a high pass filter at

)

(

FBB

Feedback divider resistor connected to AGND. The value of this resistor depends
on the supply voltage setting and helps set the TK2070 gain in conjunction with R

FBA,

and R

FBC

. Please see the Modulator Feedback Design paragraphs in the

Application Information Section.

FBC

Feedback resistor connected from either the OUT1A/OUT2A to
FBKOUT1/FBKOUT2 or OUT1B/OUT2B to FBKGND1/FBKGND2. The value of this
resistor depends on the supply voltage setting and helps set the TK2070 gain in
conjunction with R

FBA,

and R

FBB

. It should be noted that the resistor from

OUT1/OUT2 to FBKOUT1/FBKOUT2 must have a power rating of greater than

)

(2R

VPP

FBC

DISS

. Please see the Modulator Feedback Design paragraphs in the

Application Information Section.

Feedback delay capacitor that both lowers the idle switching frequency and filters
high frequency noise from the feedback signal, which improves amplifier
performance. The value of C

should be offset between channel 1 and channel 2

so that the idle switching difference is greater than 40kHz. Please refer to the
Application / Test Circuit.

OFA

Potentiometer used to manually trim the DC offset on the output of the TK2070.

OFB

Resistor that limits the manual DC offset trim range and allows for more precise
adjustment.

REF

Bias resistor. Locate close to pin 15 and ground at pin 20.

Supply decoupling for the power supply pins. For optimum performance, these
components should be located close to the TC2001/TPS1035 and returned to their
respective ground as shown in the Application/Test Circuit.

Zobel capacitor, which in conjunction with R

, terminates the output filter at high

frequencies. Use a high quality film capacitor capable of sustaining the ripple current
caused by the switching outputs.

Zobel resistor, which in conjunction with C

, terminates the output filter at high

frequencies. The combination of R

and C

minimizes peaking of the output filter

under both no load conditions or with real world loads, including loudspeakers which
usually exhibit a rising impedance with increasing frequency. The recommended
power rating is 1 Watt.

Output inductor, which in conjunction with C

, demodulates (filters) the switching

waveform into an audio signal. Forms a second order filter with a cutoff frequency
of

)

(

and a quality factor of

Output capacitor, which, in conjunction with L

, demodulates (filters) the switching

waveform into an audio signal. Forms a second order low-pass filter with a cutoff
frequency of

)

(

and a quality factor of

Use

a high quality film capacitor capable of sustaining the ripple current caused by the
switching outputs. Electrolytic capacitors should not be used.

HBR

High-frequency bypass capacitor for V

GND on each supply pin. A 50V rating is

required for this component.

BOOT

Boot strap capacitor that enables the charge pump for the high side gate drive for
the internal H-bridge.

BOOT

Bootstrap diode. This diode charges up the bootstrap capacitor when the output is
at ground to drive the high side gate circuitry. A fast or ultra fast recovery diode is
recommended for the bootstrap circuitry. In addition, the bootstrap diode must be
able to sustain the entire VCC voltage. Thus a 50V (or greater) diode should be
used.

Differential mode capacitor that reduces residual switching noise.

T r i p a t h T e c h n o l o g y, I n c . - T e c h n i c a l I n f o r m a t i o n

TK2070 MC/2.1/10-03

Bypass capacitor for the internal regulator that powers the gate drive circuitry.

MOSFET protection diode. This diode absorbs any high frequency overshoots or
undershoots caused by the output inductor L

during high output current conditions.

In order for this diode to be effective it must be connected directly to the drain of the
topside MOSFET (pin 2) and the output (pin 3) and source of bottom side MOSFET
(pin 4) and the output (pin 3). An ultra fast recovery diode that can sustain the entire
VCC voltage should be used here. Thus, a 50V or greater diode must be used.

VPP1

Overvoltage and undervoltage sense resistor for the positive supply (VDD). Please
refer to the Electrical Characteristics Section for the trip points as well as the
hysteresis band. Also, please refer to the Over / Under-voltage Protection section in
the Application Information for a detailed discussion of the internal circuit operation
and external component selection.

VPP2

Secondary overvoltage and undervoltage sense resistor for the positive supply
(VDD). This resistor accounts for the internal V

PPSENSE

bias of 2.5V. Nominal

resistor value should be equal to that of R

VPP1

. Please refer to the Over / Under-

voltage Protection section in the Application Information for a detailed discussion of
the internal circuit operation and external component selection.

VNN

Not used on TK2070. Connect this pin to AGND through a 10k

resistor.

BIASCAP decoupling capacitor. Should be located close to pin 1 of the TC2001 and
grounded at pin 20 of the TC2001.

For proper operation for the TPS1035, the Fault pin (pin 8) must tied to the Bypass
pin (pin 7) through a 27kohm resistor.

T r i p a t h T e c h n o l o g y, I n c . - T e c h n i c a l I n f o r m a t i o n

TK2070 MC/2.1/10-03

T Y P I C A L P E R F O R M A N C E C H A R A C T E R I S T I C S

THD+N vs Output Power

0.01

0.02

0.05

0.1

0.2

0.5

THD

N (

)

100

Output Power (W)

f = 1kHz
R

= 4

VCC = 24V
BW = 22Hz-20kHz
AES 17 Filter

0.01

0.02

0.05

0.1

0.2

0.5

6 7 8 9 10

THD+N vs Output Power

THD +

N (%

)

Output Power (W)

f = 1kHz
R

= 8

VCC = 24V
BW = 22Hz-20kHz
AES 17 Filter

0.005

0.01

0.02

0.05

0.1

0.2

0.5

THD

(
%

)

20k

100

200

500

10k

Frequency (Hz)

THD+N vs Frequency

VCC = 24V
POUT = 10W/Channel
R

= 8

BW = 22Hz-20kHz
AES 17 Filter

0.005

0.01

0.02

0.05

0.1

0.2

0.5

20k

100

200

500

10k

THD+N vs Frequency

THD +

N (%)

Frequency (Hz)

VCC = 24V
POUT = 10W/Channel
R

= 4

BW = 22Hz-20kHz
AES 17 Filter

-120

-110

-100

-90

-80

-70

-60

-50

-40

-30

-20

-10

p
l
i
t
ud

e (

)

30k

100

200

500

10k

20k

Frequency (Hz)

Intermodulation Distortion

VCC = 24V
POUT = 10W/Channel
R

= 4

19kHz, 20kHz 1:1
0dB = 6.3Vrms
BW = 22Hz-20kHz

30k

100

200

500

10k

20k

Frequency (Hz)

-120

-110

-100

-90

-80

-70

-60

-50

-40

-30

-20

-10

i
t
ude

Br)

VCC = 24V
POUT = 10W/Channel
R

= 8

19kHz, 20kHz 1:1
0dB = 9Vrms
BW = 22Hz-20kHz

Intermodulation Distortion

T r i p a t h T e c h n o l o g y, I n c . - T e c h n i c a l I n f o r m a t i o n

TK2070 MC/2.1/10-03

T Y P I C A L P E R F O R M A N C E C H A R A C T E R I S T I C S

(cont'd)

-120

-110

-100

-90

-80

-70

-60

-50

-40

-30

-20

-10

i
t
ude

20k

100

200

500

10k

Frequency (Hz)

VCC = 24V
POUT = 9W/Channel
R

= 4

0dB = 8.8Vrms
BW = 22Hz-20kHz

Channel Seperation vs Frequency

-120

-110

-100

-90

-80

-70

-60

-50

-40

-30

-20

-10

i
t
ud

e (

d
B)

20k

100

200

500

10k

Frequency (Hz)

VCC = 24V
POUT = 4.5W/Channel
R

= 8

0dB = 6Vrms
BW = 22Hz-20kHz

Channel Seperation vs Frequency

-120

-108

-96

-84

-72

-60

-48

-36

-24

-12

pli

t
ud

)

20k

100

200

500

10k

Frequency (Hz)

Noise Floor

VCC = 24V
POUT = 0W/Channel
R

= 4

= 12V/V

BW = 22Hz-22kHz

Efficiency vs Output Power

100

Output Power (W)

f
f
i
c
i
enc

y
(

)

VCC = 24V
RL = 8

THD+N <10%

Efficiency vs Output Power

100

Output Power (W)

Effi

c
i
e
n
c
y
(

)

VCC = 24V
RL = 4

THD+N <10%

-100

-90

-80

-70

-60

-50

-40

-30

-20

-10

p
l
i
t
ud

e (

)

20k

100

200

500

10k

Frequency (Hz)

VCC = 24V
R

= 4

0dB = 200mVp-p
Vripple = 200mVp-p
BW = 22Hz-22kHz

Power Supply Rejection Ratio

T r i p a t h T e c h n o l o g y, I n c . - T e c h n i c a l I n f o r m a t i o n

TK2070 MC/2.1/10-03

A P P L I C A T I O N I N F O R M A T I O N
T K 2 0 7 0 B a s i c A m p l i f i e r O p e r a t i o n

The TC2001 is a 5V CMOS signal processor that amplifies the audio input signal and converts the
audio signal to a switching pattern. This switching pattern is spread spectrum with a typical idle
switching frequency of about 650kHz. The switching patterns for the two channels are not
synchronized and the idle switching frequencies should differ by at least 40kHz to avoid increasing
the audio band noise floor. The idle frequency difference can be accomplished by offsetting the value
of C

for each channel. Typical values of C

are 390pF for channel 1 and 560pF for channel 2.

The TPS1035 is a MOSFET output stage that level-shifts the signal processor's 5V switching patterns
to the power supply voltages and drives the power MOSFETs. The power MOSFETs are N-channel
devices configured in half-bridges and are used to supply power to the output load. The outputs of
the power MOSFETs must be low pass filtered to remove the high frequency switching pattern. A
residual voltage from the switching pattern will remain on the speaker outputs when the
recommended output LC filter is used, but this signal is outside of the audio band and will not affect
audio performance.

C i r c u i t B o a r d L a y o u t

The TK2070 is a power (high current) amplifier that operates at relatively high switching frequencies.
The output of the amplifier switches between VDD and GND at high speeds while driving large
currents. This high-frequency digital signal is passed through an LC low-pass filter to recover the
amplified audio signal. Since the amplifier must drive the inductive LC output filter and speaker loads,
the amplifier outputs can be pulled above the supply voltage and below ground by the energy in the
output inductanor. To avoid subjecting the TK2070 to potentially damaging voltage stress, it is critical
to have a good printed circuit board layout. It is recommended that Tripath's layout and application
circuit be used for all applications and only be deviated from after careful analysis of the effects of any
changes.

The following components are important to place near their associated TC2001/TPS1035 pins and
are ranked in order of layout importance, either for proper device operation or performance
considerations.

The capacitors C

HBR

provide high frequency bypassing of the amplifier power supplies and

will serve to reduce spikes across the supply rails. C

HBR

should be kept within 1/8" (3mm)

of the VDD pins. Please note that the four VDD pins must be decoupled separately. In
addition, the voltage rating for C

HBR

should be 50V as this capacitor is exposed to the full

supply range.

removes very high frequency components from the amplifier feedback signals and

lowers the output switching frequency by delaying the feedback signals. In addition, the
value of C

is different for channel 1 and channel 2 to keep the average switching

frequency difference greater than 40kHz. This minimizes in-band audio noise.

To minimize noise pickup and minimize THD+N, R

FBC

should be located as close to the

TC2001 as possible. Make sure that the routing of the high voltage feedback lines is kept
far away from the input op amps or significant noise coupling may occur. It is best to shield
the high voltage feedback lines by using a ground plane around these traces as well as the
input section.

In general, to enable placement as close to the TC2001/TPS1035, and minimize PCB parasitics, the
capacitors listed above (with the exception of the bulk capacitors) should be surface mount types.

T r i p a t h T e c h n o l o g y, I n c . - T e c h n i c a l I n f o r m a t i o n

TK2070 MC/2.1/10-03

Some components are not sensitive to location but are very sensitive to layout and trace routing.

To maximize the damping factor and reduce distortion and noise, the modulator feedback
connections should be routed directly to the pins of the output inductors, L

The modulator feedback resistors should all be grounded together. These connections will
serve to minimize common mode noise via the differential feedback.

T K 2 0 7 0 G r o u n d i n g

Proper grounding techniques are required to maximize TK2070 functionality and performance.
Parametric parameters such as THD+N, noise floor and cross talk can be adversely affected if proper
grounding techniques are not implemented on the PCB layout. The following discussion highlights
some recommendations about grounding both with respect to the TK2070 as well as general "audio
system" design rules.

The TK2070 is divided into two sections: the input section, and the output (high power) section. On
the TK2070 evaluation board, the ground is also divided into distinct sections, one for the input and
one for the output. To minimize ground loops and keep the audio noise floor as low as possible, the
input and output ground must be only connected at a single point. Depending on the system design,
the single point connection may be in the form of a ferrite bead or a PCB trace.

M o d u l a t o r F e e d b a c k D e s i g n

The modulator converts the signal from the input stage to the high-voltage output signal. The
optimum gain of the modulator is determined from the maximum allowable feedback level for the
modulator and maximum supply voltage for the power stage. Depending on the maximum supply
voltage, the feedback ratio will need to be adjusted to maximize performance. The values of RFBB
and RFBC (see explanation below) define the gain of the modulator. Once these values are chosen,
based on the maximum supply voltage, the gain of the modulator will be fixed even with as the supply
voltage fluctuates due to current draw.

For the best signal-to-noise ratio and lowest distortion, the maximum differential modulator feedback
voltage should be approximately 4Vpp. This will keep the gain of the modulator as low as possible
and still allow headroom so that the feedback signal does not clip the modulator feedback stage.

The modulator feedback resistors are:

FBB

= User specified; typically 1k

FBB

FBC

T K 2 0 7 0 A m p l i f i e r G a i n

The gain of the TK2070 is the product of the input stage gain and the modulator gain. Please refer to
the sections, Input Stage Design, and Modulator Feedback Design, for a complete explanation of how
to determine the external component values.

MODULATOR

STAGE

INPUT

TK2070

FBB

FBC

TK2070

T r i p a t h T e c h n o l o g y, I n c . - T e c h n i c a l I n f o r m a t i o n

TK2070 MC/2.1/10-03

For example, using a TK2070 with the following external components,

= 20k

FBB

= 1k

FBC

= 11k

)

11k

20k

TK2070

Please note that OUT1P (OUT2P), as shown in the Application/Test Diagram, is out of phase with
respect to the input signal. This phase reversal can be eliminated by connecting OUT1N and OUT2N
to the positive terminal at the speaker.

I n p u t S t a g e D e s i g n

The TC2001 input stage is configured as an inverting amplifier, allowing the system designer flexibility
in setting the input stage gain and frequency response. Figure 1 shows a typical application where
the input stage is a constant gain inverting amplifier. The input stage gain should be set so that the
maximum input signal level will drive the input stage output to 4Vpp.

TC2001

INPUT2

OAOUT2

OAOUT1

INV1

INPUT1

BIASCAP

AGND

INV2

Figure 1: Input Stage

The gain of the input stage, above the low frequency high pass filter point, is that of a simple inverting
amplifier: It should be noted that the input amplifiers are biased at approximately 2.5VDC. Thus, the
polarity of C

must be followed as shown in Figure 1 for a standard ground referenced input signal

STAGE

INPUT

I n p u t C a p a c i t o r S e l e c t i o n

can be calculated once a value for R

has been determined. C

and R

determine the input low

frequency pole. Typically this pole is set below 10Hz. C

is calculated according to:

where:

= Input resistor value in ohms.

= Input low frequency pole (typically 10Hz or below)

T r i p a t h T e c h n o l o g y, I n c . - T e c h n i c a l I n f o r m a t i o n

TK2070 MC/2.1/10-03

M u t e C o n t r o l

When a logic high signal is supplied to MUTE, both amplifier channels are muted (both high- and low-
side transistors are turned off). When a logic level low is supplied to MUTE, both amplifiers are fully
operational. There is a delay of approximately 200 milliseconds between the de-assertion of MUTE
and the un-muting of the TK2070.

To ensure proper device operation, including minimization of turn on/off transients that can result in
undesirable audio artifacts, Tripath recommends that the TK2070 device be muted prior to power up
or power down of the 5V supply. The "sensing" of the V5 supply can be easily accomplished by using
a "microcontroller supervisor" or equivalent to drive the TC2001 mute pin high when the V5 voltage is
below 4.5V. This will ensure proper operation of the TK2070 input circuitry. A micro-controller
supervisor such as the MCP101-450 from Microchip Corporation has been used by Tripath to
implement clean power up/down operation.

If turn-on and/or turn-off noise is still present with a TK2070 amplifier, the cause may be other
circuitry external to the TK2070. While the TK2070 has circuitry to suppress turn-on and turn-off
transients, the combination of power supply and other audio circuitry with the TK2070 in a particular
application may exhibit audible transients. One solution that will completely eliminate turn-on and
turn-off pops and clicks is to use a relay to connect/disconnect that amplifier from the speakers with
the appropriate timing during power on/off.

T K 2 0 7 0 O u t p u t C a p a b i l i t y

The TK2070 can drive two 4 Ohm loads with 70 Watts 10% THD+N. The maximum sustained
amplifier output power will be determined by a number of factors including the TC2001/TPS1035
junction temperatures, the load impedance and the power supply voltage.

Tripath does not recommend driving loads below 4 Ohms bridged as the amplifier efficiency will be
reduced and the amplifier will reach it's current limit at relatively low power output levels. With the
outputs connected in parallel, however, the TK2070 is capable of driving single channel loads down
to 2 Ohms with very high power capability. Please refer to the RB-TK2070 datasheet for parallel
mode operation of the TK2070.

O u t p u t V o l t a g e O f f s e t

The TK2070 does not have internal compensation for DC offset. The output offset voltage must be
trimmed with a potentiometer at the INV1/INV2 pins of the TC2001. If the output offset voltage is not
trimmed the efficiency of the TK2070 will be significantly reduced and the idle current will be
significantly increased.

O u t p u t F i l t e r D e s i g n

Tripath amplifiers generally have a higher switching frequency than PWM implementations, allowing
the use of higher cutoff frequency filters and reducing the load dependent peaking/drooping in the
20kHz audio band. This is especially important for applications where the end customer may attach
any speaker to the amplifier (as opposed to a system where speakers are shipped with the amplifier),
since speakers are not purely resistive loads and the impedance they present changes over
frequency and from speaker model to speaker model. An RC network, or "Zobel" (R

, C

) should be

placed at the filter output to control the impedance "seen" by the TP2051 when not attached to a
speaker load. The TK2070 works well with a 2

order, 80kHz LC filter with L

= 10uH and C

0.47uF and R

= 10 Ohm/1W and C

= 0.47uF.

Output inductor selection is a critical design step. The core material and geometry of the output filter
inductor affects the TK2070 distortion levels, efficiency, power dissipation and EMI output.

T r i p a t h T e c h n o l o g y, I n c . - T e c h n i c a l I n f o r m a t i o n

TK2070 MC/2.1/10-03

Wound iron powder toroidal cores are the recommended inductor choice for the TK2070. Toroidal
cores have less flux leakage compared to shielded bobbin or shielded SMD inductors, resulting in
reduced EMI and improved channel separation. For typical applications we recommend the
Micrometals Type-2 iron powder (Carbonyl-E) core. This core material has low permeability metal
powder and a distributed air gap for increased energy storage capability. This allows for a small
footprint with high peak current capability.

M i n i m u m a n d M a x i m u m S u p p l y V o l t a g e O p e r a t i n g R a n g e

The TK2070 can operate over a wide range of power supply voltages from +7.5V to +25V. In order to
optimize operation for either the low or high range, the user must select the proper values for R

FBB

and R

FBC

Over- and Under-Voltage Protection

The TC2001 senses the power rails through external resistor networks connected to VPPSENSE.
The over- and under-voltage limits are determined by the values of the resistors in the networks, as
described in the table "Test/Application Circuit Component Values". If the supply voltage falls outside
the upper and lower limits determined by the resistor networks, the TC2001 shuts off the TPS1035
output stage. The removal of the over-voltage or under-voltage condition returns the TK2070 to
normal operation. Please note that trip points specified in the Electrical Characteristics table are at
25

°C and may change over temperature.

The TC2001 has built-in over and under voltage protection the VDD supply rail. The nominal
operating voltage will typically be chosen as the supply "center point." This allows the supply voltage
to fluctuate, both above and below, the nominal supply voltage. For the TK2070 only the VDD supply
rail will be sensed and the VNN sensing will not be used so pin 17 of the TC2001 will be shorted to
ground.

VPPSENSE (pin 19) performs the over and undervoltage sensing for the positive supply, VDD. When
the current through R

VPPSENSE

goes below or above the values shown in the Electrical Characteristics

section (caused by changing the power supply voltage), the TK2070 will be muted. VPPSENSE (pin
19) is internally biased at 2.5V.

Once the supply comes back into the supply voltage operating range (as defined by the supply sense
resistors), the TK2070 will automatically be unmuted and will begin to amplify. There is a hysteresis
range on both the VPPSENSE and VNNSENSE pins. If the amplifier is powered up in the hysteresis
band the TK2070 will be muted. Thus, the usable supply range is the difference between the over-
voltage turn-off and under-voltage turn-off for the VDD supply. It should be noted that there is a timer
of approximately 200mS with respect to the over and under voltage sensing circuit. Thus, the supply
voltage must be outside of the user defined supply range for greater than 200mS for the TK2070 to
be muted.

The equation for calculating R

VPP1

is as follows:

VPPSENSE

VPP1

VPP

Set

VPP1

VPP2

VPPSENSE

can be any of the currents shown in the Electrical Characteristics table for

VPPSENSE.

VPP2

compensates for the internal bias point. Thus, R

VPP1

can be used for the direct calculation of

the actual VCC trip voltage without considering the effect of R

VPP2

T r i p a t h T e c h n o l o g y, I n c . - T e c h n i c a l I n f o r m a t i o n

TK2070 MC/2.1/10-03

Using the resistor values from above, the actual minimum over voltage turn off points will be:

RN_OFF)

(MIN_OV_TU

VPPSENSE

VPP1

N_OFF

MIN_OV_TUR

VPP

The other three trip points can be calculated using the same formula but inserting the appropriate
I

VPPSENSE

current value. As stated earlier, the usable supply range is the difference between the

minimum overvoltage turn off and maximum under voltage turn-off for the VPP supply.

N_OFF

MAX_UV_TUR

N_OFF

MIN_OV_TUR

RANGE

VPP

P r o t e c t i o n C i r c u i t s

The TK2070 is protected against over-current, over / under-voltage and over-temperature conditions.
Output overcurrent conditions are detected on the TPS1035.

TPS1035

FAULT

FDLL914

TPS1035

FAULT

FDLL914

10K

20K

510K

MUTE Pin

(Pin 24 of TC2001)

2N3906

Figure 2

Figure 2 shows an overcurrent detection circuit that will mute the amplifier whenever the TPS1035
detects an overcurrent condition. The fault pin (pin 8 of the TPS1035) is a overcurrent indicator that
is high (approximately 5.4V) during normal operation and low (0V) if an overcurrent condition is
detected. The fault pin will go low and turn on the PNP transistor and pull the Mute pin to 5V if the
switch is closed. In this circuit, whenever the switch is open the Mute pin will be at 5V and the
amplifier will be muted.

O v e r - t e m p e r a t u r e P r o t e c t i o n

An over-temperature fault occurs if the junction temperature of the part exceeds approximately
165

°C. The thermal hysteresis of the part is approximately 30°C, therefore the fault will automatically

clear when the junction temperature drops below 135

°C.

H M U T E

The HMUTE pin on the TC2001 is a 5V logic output that indicates various fault conditions within the
device. These conditions include: over-current, overvoltage and undervoltage. The HMUTE output is
high whenever a fault condition occurs and is capable of directly driving an LED through a series 2k

resistor.

T r i p a t h T e c h n o l o g y, I n c . - T e c h n i c a l I n f o r m a t i o n

TK2070 MC/2.1/10-03

O V R L D B

The OVRLDB pin is a 5V logic output that is asserted just at the onset of clipping. When low, it
indicates that the level of the input signal has overloaded the amplifier resulting in increased distortion
at the output. The OVRLDB signal can be used to control a distortion indicator light or LED through a
transistor, as the OVRLDB cannot drive an LED directly. There is a 20K resistor on chip in series with
the OVRLDB output.

P e r f o r m a n c e M e a s u r e m e n t s o f t h e T K 2 0 7 0

The TK2070 operates by generating a high frequency switching signal based on the audio input.

This

signal is sent through a low-pass filter (external to the Tripath amplifier) that recovers an amplified
version of the audio input

The frequency of the switching pattern is spread spectrum in nature and

typically varies between 100kHz and 1MHz, which is well above the 20Hz 20kHz audio band. The
pattern itself does not alter or distort the audio input signal, but it does introduce some inaudible
components.

The measurements of certain performance parameters, particularly noise related specifications such
as THD+N, are significantly affected by the design of the low-pass filter used on the output as well as
the bandwidth setting of the measurement instrument used. Unless the filter has a very sharp roll-off
just beyond the audio band or the bandwidth of the measurement instrument is limited, some of the
inaudible noise components introduced by the TK2070 amplifier switching pattern will degrade the
measurement.

One feature of the TK2070 is that it does not require large multi-pole filters to achieve excellent
performance in listening tests, usually a more critical factor than performance measurements.
Though using a multi-pole filter may remove high-frequency noise and improve THD+N type
measurements (when they are made with wide-bandwidth measuring equipment), these same filters
degrade frequency response. The TK2070 Reference Board uses the Application/Test Circuit of this
data sheet, which has a simple two-pole output filter and excellent performance in listening tests.
Measurements in this data sheet were taken using this same circuit with a limited bandwidth setting in
the measurement instrument.

T r i p a t h T e c h n o l o g y, I n c . - T e c h n i c a l I n f o r m a t i o n

TK2070 MC/2.1/10-03

Tripath and Digital Power Processing are trademarks of Tripath Technology Inc. Other trademarks
referenced in this document are owned by their respective companies

Tripath Technology Inc. reserves the right to make changes without further notice to any products
herein to improve reliability, function or design. Tripath does not assume any liability arising out of the
application or use of any product or circuit described herein; neither does it convey any license under
its patent rights, nor the rights of others.

TRIPATH'S PRODUCTS ARE NOT AUTHORIZED FOR USE AS CRITICAL COMPONENTS IN LIFE
SUPPORT DEVICES OR SYSTEMS WITHOUT THE EXPRESS WRITTEN CONSENT OF THE
PRESIDENT OF TRIPATH TECHNOLOGY INC. As used herein:
1. Life support devices or systems are devices or systems which, (a) are intended for surgical

implant into the body, or (b) support or sustain life, and whose failure to perform, when properly
used in accordance with instructions for use provided in this labeling, can be reasonably expected
to result in significant injury to the user.

2. A critical component is any component of a life support device or system whose failure to perform

can be reasonably expected to cause the failure of the life support device or system, or to affect
its safety or effectiveness.

For more information on Tripath products, visit our web site at:

http://www.tripath.com

C o n t a c t I n f o r m a t i o n

T R I P A T H T E C H N O L O G Y , I N C

2560 Orchard Parkway, San Jose, CA 95131
408.750.3000 - P
408.750.3001 - F

For more Sales Information, please visit us @

www.tripath.com/cont_s.htm

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