LM4970
Audio Synchronized Color LED Driver
General Description
The LM4970 is a LED driver with an audio synchronization
mode that virtually eliminates the need for real time software
processing for LED lighting effects. The LM4970 includes
three individual PWM color LED drivers that provide up to
42mA of current drive for each PWM LED output.
The LM4970 features an audio synchronization mode where
the audio input signal that is mixed in from three audio inputs
is filtered into three frequency bands, with each frequency
band assigned to a specific PWM LED driver.
The PWM LED drivers can also be directly programmed
through an I
2
C compatible interface for applications where
user defined LED pattern, color, and intensity programmabil-
ity is a priority.
The LM4970 also features an audio input gain control which
allows the user to increase the gain if the audio input signal
does not create a bright enough effect on the LEDs. The
LM4970 is a feature rich LED driver that is available in a
space saving 14 pin non-pullback LLP package.
Key Specifications
j
LED Drive Current per channel
V
DD
= 5V
42mA (2X setting)
j
Shutdown Current, V
DD
= 5V
1.5A (typ)
Features
n
Audio synchronized color LED driver
n
User defined LED pattern, color, and intensity capability
n
Programmable:
LED Drive current
PWM frequency
High pass filter frequency select
Audio input signal gain
n
Eliminates external LED current limiting resistors
n
I
2
C compatible interface
n
Ultra low shutdown current
Applications
n
Cell Phones
n
Portable MP3, CD, DVD, AAC players
n
PDA's
Block Diagram
Boomer
is a registered trademark of National Semiconductor Corporation.
20121201
FIGURE 1. Block Diagram
February 2005
LM4970
Audio
Synchronized
Color
LED
Driver
2005 National Semiconductor Corporation
DS201212
www.national.com
Connection Diagram
14 pin SD Package
20121202
Top View
Order Number LM4970SD
See NS Package Number SDA14A
Pin Connection
Pin
Name
Pin Description
1
FILT
Low Pass Filter Input
2
V
DD
Power Supply Pin
3
M
IN
Mono Audio Input
4
GND
Ground
5
L
IN
Left Audio Input
6
R
IN
Right Audio Input
7
I
2
CV
DD
I
2
C Interface Power Supply
8
SDA
I
2
C Data
9
SCL
I
2
C Clock
10
ADR
I
2
C Address Select
11
LED3
LED output 3
12
LGND
LED ground
13
LED2
LED output 2
14
LED1
LED output 1
LM4970
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2
Absolute Maximum Ratings
(Notes 1, 2)
If Military/Aerospace specified devices are required,
please contact the National Semiconductor Sales Office/
Distributors for availability and specifications.
Supply Voltage
6.0V
Storage Temperature
-65C to +150C
Input Voltage
-0.3V to V
DD
+0.3V
Power Dissipation (Note 3)
Internally Limited
ESD Susceptibility (Note 4)
2000V
ESD Susceptibility (Note 5)
200V
ESD Susceptibility (Note 12)
100V
Junction Temperature
150C
Thermal Resistance
JA
(SDA14A)
57C/W
JC
(SDA14A)
12C/W
Operating Ratings
Temperature Range
T
MIN
T
A
T
MAX
-40C
T
A
+85C
Supply Voltage
2.7V
V
DD
5.5V (Note 13)
2.5V
I
2
CV
DD
5.5V
Control Interface Electrical Characteristics
(Notes 1, 2)
The following specifications apply for 3V
V
DD
5V unless otherwise specified. Limits apply for T
A
= 25C.
Symbol
Parameter
Conditions
LM4970
Units
(Limits)
Typical
(Note 6)
Limits
(Notes 7, 8)
t
1
SCL period
2.5
s (min)
t
2
SDA Setup Time
100
ns (min)
t
3
SDA Stable Time
0
ns (min)
t
4
Start Condition Time
100
ns (min)
t
5
Stop Condition Time
100
ns (min)
V
IH
Digital Input High Voltage
0.7 x I
2
CV
DD
V (min)
V
IL
Digital Input Low Voltage
0.3 x I
2
CV
DD
V (max)
Color LED Driver Electrical Characteristics V
DD
= 5.0V
(Notes 1, 2, 9)
The following specifications apply for V
DD
= 5.0V unless otherwise specified. Limits apply for T
A
= 25C.
Symbol
Parameter
Conditions
LM4970
Units
(Limits)
Typical
(Note 6)
Limits
(Notes 7, 8)
I
DDRGB
Supply Curent
2.5
4
mA (max)
I
SDRGB
Shutdown Current
Shutdown Mode
1.5
3.5
A (max)
I
LED
LED Drive Current
.66X current drive setting
14
mA
1X current drive setting
21
mA
1.33X current drive setting
30
mA
2X current drive setting
42
23
mA (min)
f
PWM
PWM Frequency
PWM_F
<
1:0
>
= '01'
60
Hz
Input Signal Level Gain Control
Maximum setting
12
dB
Minimum setting
11
dB
Color LED Driver Electrical Characteristics V
DD
= 3.0V
(Notes 1, 2, 9)
The following specifications apply for V
DD
= 3.0V unless otherwise specified. Limits apply for T
A
= 25C.
Symbol
Parameter
Conditions
LM4970
Units
(Limits)
Typical
(Note 6)
Limits
(Notes 7, 8)
I
DDRGB
Supply Curent
2.2
3
mA (max)
I
SDRGB
Shutdown Current
Shutdown Mode
0.5
2
A (max)
I
LED
LED Drive Current
.66X current drive setting
12
mA
1X current drive setting
18
mA
1.33X current drive setting
27
mA
2X current drive setting
35
21
mA (min)
LM4970
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Color LED Driver Electrical Characteristics V
DD
= 3.0V
(Notes 1, 2, 9) (Continued)
The following specifications apply for V
DD
= 3.0V unless otherwise specified. Limits apply for T
A
= 25C.
Symbol
Parameter
Conditions
LM4970
Units
(Limits)
Typical
(Note 6)
Limits
(Notes 7, 8)
f
PWM
PWM Frequency
PWM_F
<
1:0
>
= '01'
60
Hz
Input Signal Level Gain Control
Maximum setting
12
dB
Minimum setting
11
dB
Note 1: All voltages are measured with respect to the GND pin unless otherwise specified.
Note 2: Absolute Maximum Ratings indicate limits beyond which damage to the device may occur. Operating Ratings indicate conditions for which the device is
functional but do not guarantee specific performance limits. Electrical Characteristics state DC and AC electrical specifications under particular test conditions which
guarantee specific performance limits. This assumes that the device is within the Operating Ratings. Specifications are not guaranteed for parameters where no limit
is given, however, the typical value is a good indication of device performance.
Note 3: The maximum power dissipation must be derated at elevated temperatures and is dictated by T
JMAX
,
JA
, and the ambient temperature, T
A
. The maximum
allowable power dissipation is P
DMAX
= (T
JMAX
- T
A
) /
JA
or the number given in Absolute Maximum Ratings, whichever is lower.
Note 4: Human body model, 100pF discharged through a 1.5k
resistor.
Note 5: Machine Model, 200pF220pF discharged through all pins, except pins 13 and 14.
Note 6: Typicals are measured at +25C and represent the parametric norm.
Note 7: Limits are guaranteed to National's AOQL (Average Outgoing Quality Level).
Note 8: Datasheet min/max specification limits are guaranteed by design, test, or statistical analysis.
Note 9: Shutdown current and supply current are measured in a normal room environment. All digital input pins are connected to I
2
CV
DD
.
Note 10: The given
JA
is for an LM4970SD mounted on a PCB with a 2in
2
area of 1oz printed circuit board copper ground plane.
Note 11: Audio input level set at 1V
RMS
. The input summing amplifier gain is set to 12dB.
Note 12: Machine Model, 200pF220pF discharge through pins 13 and 14 (LED1 and LED2).
Note 13: V
DD
may be used to power the LEDs. It may be necessary to drive the LEDs from a boost (V
DDBOOST
) found within the system.
LM4970
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External Components Description
Components
Functional Description
1.
C
i
This is the input coupling capacitor. It blocks the DC voltage and couples the input signal to the
amplifier's input terminals. C
IN
also creates a highpass filter with an internal 20k
resistor at f
c
=
1/(2
.20000.C
i
).
2.
C
S
This is the supply bypass capacitor. It filters the supply voltage applied to the V
DD
pin and helps
reduce the noise at the V
DD
pin.
3.
C
filt
This capacitor creates a low pass filter with an internal 4k
resistor at f
c
= 1/(2
*4000*C
filt
). This pole
set at f
c
determines the high cutoff frequency for the low band PWM color LED driver output, LED1.
Typical Performance Characteristics
(Note 11)
Audio Sync LED Frequency Response
(Left - lowband, Mid - midband, Right - highband)
(Cfilt = 0.047F, HPF = 3.5kHz setting)
Audio Sync LED Frequency Response
(Left - lowband, Mid - midband, Right - highband)
(Cfilt = 0.068F, HPF = 3.5kHz setting)
20121265
20121266
Audio Sync LED Frequency Response
(Left - lowband, Mid - midband, Right - highband)
(Cfilt = 0.1F, HPF = 3.5kHz setting)
Audio Sync LED Frequency Response
(Left - lowband, Mid - midband, Right - highband)
(Cfilt = 0.22F, HPF = 3.5kHz setting)
20121267
20121268
LM4970
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