Not for new design

These versatile SMPS control ICs comprise digital and
analog functions which are required to design high-
quality flyback, single-ended and push-pull converters
in normal, half-bridge and full-bridge configurations.
The component can also be used in single-ended
voltage multipliers and speed-controlled motors.
Malfunctions in electrical operation are recognized by
the integrated operational amplifiers, which activate
protective functions.

Type

Ordering Code

Package

Temp.-Range

TDA 4700 A

Q67000-Y594

P-DIP-24-1

0 to 70

TDA 4718 A

Q67000-Y639

P-DIP-18-1

0 to 70

Is now available for temperature range 25 to 85

Control IC for Single-Ended and Push-Pull
Switched-Mode Power Supplies (SMPS)

P-DIP-24-1

P-DIP-18-1

Features

Feed-forward control (line hum suppression)

Symmetry inputs for push-pull converter
(TDA 4700)

Push-pull outputs

Dynamic output current limitation

Overvoltage protection

Undervoltage protection

Soft start

Double pulse suppression

Semiconductor Group

05.95

TDA 4700
TDA 4718

TDA 4700
TDA 4718

Semiconductor Group

Pin Definitions and Functions (TDA 4700)

Pin

Symbol

Function

GND

Ground 0 V

2
3

REF

Reference voltage
Supply voltage

4
5

Q2
Q1

Output Q2
Output Q1

6
7
8

I SYM Q2
Q SYNC

soft start

Symmetry Q2
Sync. output
Soft start

9
10
11

filter

VCO

Capacitance
VCO

12
13

Ramp generator

14
15

I COMP
Q Op Amp

Comparator input
Operational amplifier output

I Op Amp

+ I Op Amp

I SYNC

Operational amplifier input ()

Operational amplifier input (+)

Sync. input

ON/OFF/IUV

ON/OFF, undervoltage

20
21

QOV
IOV

Overvoltage output
Overvoltage input

DYN

Dynamic current limitation ()

Dynamic current limitation (+)

I SYM Q1

Symmetry

TDA 4700
TDA 4718

Semiconductor Group

Pin Definitions and Functions (TDA 4718)

Circuit Description
Voltage Controlled Oscillator (VCO)

The VCO generates a sawtooth voltage. The duration of the falling edge is determined
by the value of

. The duration of the rising edge of the waveform and, therefore,

approximately the frequency, is determined by the value of

. By varying the voltage at

filter

, the oscillator frequency can be changed by its rated value. During the fall time, the

VCO provides a trigger signal for the ramp generator, as well as an L signal for a number
of IC parts to be controlled.

Pin

Symbol

Function

GND

Ground 0 V

2
3

Ramp generator

4
5

I COMP
I SYNC

+ Input comparator K2
Sync. input

6
7

IUV
IOV

Input undervoltage, ON/OFF
Input overvoltage

8
9

DYN

Input dynamic current limitation ()
Input dynamic current limitation (+)

10
11

REF

Reference voltage
Supply voltage

12
13

Q 2
Q 1

Output Q2
Output Q1

14
15

Q SYNC

soft start

Sync. output
Soft start

16
17
18

filter

VCO

Capacitance
VCO

TDA 4700
TDA 4718

Semiconductor Group

Ramp Generator

The ramp generator is triggered by the VCO and oscillates at the same frequency. The
duration of the falling edge of the ramp generator waveform is to be shorter than the fall
time of the VCO. To control the pulse width at the output, the voltage of the rising edge
of the ramp generator signal is compared with a DC voltage at comparator K2. The slope
of the rising edge of the ramp generator signal is controlled by the current through

This offers the possibility of an additional, superimposed control of the output duty cycle.
This additional control capability, called "feed-forward control", is utilized to compensate
for known interference such as ripple on the input voltage.

Phase Comparator

If the component is operated without external synchronization, the sync input must be
connected to the sync output for the phase comparator to set the rated voltage at

filter

The VCO then oscillates with rated frequency. In the case of external synchronization,
other components can be synchronized with the sync output. The component can be
frequency-synchronized, but not phase-synchronized, with the sync input. The duty
cycle of the squarewave voltage at the sync input is arbitrary. The best stability as to
small phase and frequency interference deviation is achieved with a duty cycle as
offered by the sync output.

Push-Pull Flipflop

The push-pull flipflop is switched by the falling edge of the VCO. This ensures that only
one output of the two push-pull outputs is enabled at a time.

Comparator K2

The two plus inputs of the comparator are switched such that the lower plus level is
always compared with the level of the minus input. As soon as the voltage of the rising
sawtooth edge exceeds the lower of the two plus levels, both outputs are disabled via
the pulse turn-off flipflop. The period during which the respective, active outputs is low
can be infinitely varied. As the frequency remains constant, this process corresponds to
a change in duty cycle.

Operational Amplifier K1 (TDA 4700; A)

The K1 op amp is a high-quality amplifier. Fluctuations in the output voltage of the power
supply are amplified by K1 and applied to the free + input of comparator K2. Variations
in output voltage are, in this way, converted to a corresponding change in output duty
cycle. K1 has a common-mode input voltage range between 0 V and + 5 V.

TDA 4700
TDA 4718

Semiconductor Group

Pulse-Turn-OFF Flipflop

The pulse turn-OFF flipflop enables the outputs at the start of each half cycle. If an error
signal from comparator K7 or a turn-off signal from K2 is present, the outputs will
immediately be switched off.

Comparator K3

Comparator K3 limits the voltage at capacitance

soft start

(and also at K2) to a maximum

of + 5 V. The voltage at the ramp generator output may, however rise to 5.5 V. With a
corresponding slope of the rising ramp generator edge, the duty cycle can be limited to
a desired maximum value.

Comparator K4

The comparator has its switching threshold at 1.5 V and sets the error flipflop with its
output if the voltage at capacitance

soft start

is below 1.5 V. However, the error flipflop

accepts the set signal only if no reset pulse (error) is applied. In this way the outputs
cannot be turned on again as long as an error signal is present.

Soft Start

The lower one of the two voltages at the plus inputs of K2 is a measure for the duty cycle
at the output. At the instant of turning on the component, the voltage at capacitor

soft start

equals 0 V. As long as no error is present, this capacitor is charged with a current of 6

to the maximum value of 5 V. In case of an error,

soft start

is discharged with a current of

A. A set signal is pending at the error flipflop below a charge of 1.5 V and the outputs

are enabled if no reset signal is pending simultaneously. As the minimum ramp
generator voltage, however, is 1.8 V, the duty cycle at the outputs is actually increased
slowly and continuously not before the voltage at

soft start

exceeds 1.8 V.

Error Flipflop

Error signals, which are led to input R of the error flipflop cause an immediate disabling
of the outputs, and after the error has been eliminated, cause the component to switch
on again by the soft start.

Comparator K5, K6, K8,

REF

Overcurrent Load

These are error detectors which cause immediate disabling of the outputs via the error
flipflop when an error occurs. After elimination of the error, the component switches on
again using the soft start. The output of K5 can be fed back to the input. This causes the
IC output stage to remain disabled even after elimination of the overvoltage. However, it
requires high-ohmic overvoltage coupling.

TDA 4700
TDA 4718

Semiconductor Group

Comparator K7

K7 serves to recognize overcurrents. This is the reason why both inputs of the op amp
have been brought out. Turning on is resumed after error recovery at the beginning of
the next half period but without using the soft start.

K7 has a common-mode range covers 0 V and + 4 V. The delay time between
occurrence of an error and disabling of the outputs is only 250 ns.

Symmetry (TDA 4700; A)

In push-pull converters, a saturation of the transformer core must be prevented. The
degree of saturation of the transformer can be determined with an external circuit, thus
the active periods of the outputs can be decreased unsymmetrically at the symmetry
inputs.

Outputs

Both outputs are transistors with open collectors and operate in a push-pull
arrangement. They are active low. The time in which only one of the two outputs is
conductive can be varied infinitely. The length of the falling edge at VCO is equal to the
minimum time during which both outputs are disabled simultaneously. The minimum
L voltage is 0.7 V.

Reference Voltage

The reference voltage source is a highly constant source with regard to its temperature
behavior. It can be utilized in the external wiring of the op amp, the error comparators,
the ramp generator, or other external components.

TDA 4700
TDA 4718

Semiconductor Group

Absolute Maximum Ratings

Parameter

Symbol

Limit Values

Unit

Test
Condition

min.

max.

Supply voltage
Voltage at Q1, Q2

0.3
0.3

33
33

V
V

Q1, Q2 high

Current at Q1, Q2

Q1, Q2 low

Symmetry 1, 2 TDA 4700; A

SYM

0.3

Sync output

SYNC Q

0.3
0

7
10

V
mA

SYNC Q high
SYNC Q low

Sync input
Input

filter

Input

Input comparator
K2, K5, K6, K7

SYNC I

I Cf

I RT

I CT

I RR

I CR

I K

0.3
0.3
0.3
0.3
0.3
10

0.3

33
7
7
7
7
10

V
V
V
V
V
mA

Output K5

Q K5

0.3

Input op amp

TDA 4700; A

I Op Amp

0.3

Output op amp TDA 4700; A

Q Op Amp

0.3

max. 7

V
V

Reference voltage

REF

0.3

REF

Input

soft start

I soft start

0.3

Junction temperature
Storage temperature

stg

150
125

Thermal resistance
system - air

TDA 4700; A
TDA 4718
TDA 4718 A

th SA

65
70
60

K/W
K/W
K/W

TDA 4700
TDA 4718

Semiconductor Group

Operating Range

Parameter

Symbol

Limit Values

Unit

Test
Condition

min.

max.

Supply voltage

10.5

Ambient temperature

TDA 4700
TDA 4718
TDA 4700 A
TDA 4718 A

VCO frequency
Ramp generator frequency

f
f

40
40

250 000
250 000

Hz
Hz

Characteristics

= 11 to 30 V;

= 25 to 85

Parameter

Symbol

Limit Values

Unit

Test
Condition

min.

typ.

max.

Supply current

= 1 nF

VCO

= 100 kHz

Reference

Reference voltage
Reference voltage
change
Reference voltage
change
Reference voltage
change
Temperature
coefficient
Response threshold
of

REF

overcurrent

REF

2.35

2.5

0.25

2.65

0.4

mV/K

0 mA <

REF

< 5 mA

14 V

20 %

25 V

20 %

0 mA <

REF

< 5 mA

= 0 to 70

C, this value falls to max. 5 mV

TDA 4700
TDA 4718

Semiconductor Group

Oscillator (VCO)

Frequency range
Frequency change
Frequency change
Tolerance
Fall time sawtooth

RC combination
VCO

VCO

t
t
C

1
7

0.82
5

0.5

1
10

100 000

1
7

47
700

Hz
%
%
%

nF
k

14 V

20 %

25 V

20 %

= 0;

= 0

= 1 nF

= 10 nF

Ramp Generator

Frequency range
Maximum voltage
at

Minimum voltage
at

Input current
through

Current
transformation ratio

5.5

1.8

1/4

100 000

400

Synchronization

Sync output

Sync input

Input current

Q H

Q L

I H

I L

0.4

0.8
5

V
V
V
V

Q H

= 200

Q L

= 1.6 mA

Characteristics (cont'd)

= 11 to 30 V;

= 25 to 85

Parameter

Symbol

Limit Values

Unit

Test
Condition

min.

typ.

max.

TDA 4700
TDA 4718

Semiconductor Group

Comparator K2

Input current
Turn-OFF delay

Input voltage

Common-mode input
voltage range

I K2

D OFF

I K2

I C

1.8
5

2
500

5.5

V
V

for duty cycle

= 0

= max.

Soft Start K3, K4

Charge current for

soft start

Discharge current for

soft start

Upper limiting voltage
Switching voltage K4

dch

lim

2
5
1.5

V
V

Operational Amplifier K1 (TDA 4700; TDA 4700 A)

Open-loop voltage
gain
Input offset voltage
Temperature
coefficient of

Input current
Common-mode input
voltage range
Output current
Rise time of output
voltage
Transition frequency
Phase at

Output voltage

Q H/L

60
10

0
3

1.5

1
3
120

30
2

5
1.5

5.5

dB
mV

V/K

V
mA

MHz
deg.
V

3 mA <

< 1.5 mA

At the input: step function

= 100 mV

= + 100 mV

Characteristics (cont'd)

= 11 to 30 V;

= 25 to 85

Parameter

Symbol

Limit Values

Unit

Test
Condition

min.

typ.

max.

TDA 4700
TDA 4718

Semiconductor Group

Symmetry (TDA 4700; TDA 4700 A)

Input voltage

Input current

I H

I L

2.0

0.8
2

V
V

Output Stages Q1, Q2

Output voltage

Output leakage
current

Q H

Q L

30
1.1

V
V

= 20 mA

Q H

= 30 V

ON, OFF, Undervoltage K6

Switching voltage
Input current
Turn-OFF delay time

Error detection time

D OFF

REF

0.03

250
50

REF

+ 0.03

ns
ns

Dynamic Current Limitation K7

Common-mode input
voltage range
Input offset voltage
Input current
Turn-OFF delay time

Error detection time

D OFF

0
10

250
50

4
10
2

V
mV

ns
ns

Overvoltage K5

Switching voltage
Input current
Output current
Turn-OFF delay time

Error detection time

D OFF

REF

0.03

250
50

REF

+ 0.03

2
200

ns
ns

QH min

= 5 V

At the input: step function

REF

100 mV

REF

+ 100 mV

At the input: step function

= 100 mV

= + 100 mV

Characteristics (cont'd)

= 11 to 30 V;

= 25 to 85

Parameter

Symbol

Limit Values

Unit

Test
Condition

min.

typ.

max.

TDA 4700
TDA 4718

Semiconductor Group

Supply Undervoltage

Turn-ON threshold for

rising

Turn-OFF threshold
for

falling

8.8

8.5

11
10.5
10.5
10

V
V
V
V

C <

< 70

C <

< 70

Input

filter

Rated voltage for
rated frequency
Frequency approx.
proportional to voltage
within the range
Voltage at open
sync input

C filter

1.6

Characteristics (cont'd)

= 11 to 30 V;

= 25 to 85

Parameter

Symbol

Limit Values

Unit

Test
Condition

min.

typ.

max.

TDA 4700
TDA 4718

Semiconductor Group

Dimensioning Notes for RC Network

1. Determination of the minimum time during which both outputs must be disabled

selection of

; selection of

2. Determination of the VCO frequency = 2 x output frequency

selection of

3. Determination of the rated slope of the rising ramp generator voltage, which the

maximum possible turn-on period per half wave depends on

selection of

4. Duration of the soft start process

selection of

soft start

5. In the case of a free-running VCO: connect sync output with sync input.

6. Wiring of the op amp according to the dynamic requirements and

connection of its output with the free input of K2. (TDA 4700; TDA 4700 A)

7. Capacitance

filter

is not required in the free-running operation (sync input connected

with sync output).

In the case of external synchronization, that value depends on the selected operating
frequency and the required maximum phase interference deviation.

Rated VCO frequency:

100 kHz

50 Hz

filter

favourable:

10 nF

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ÐÐ»ÐµÐºÑ‚Ñ€Ð¾Ð½Ð½Ñ‹Ð¹ ÐºÐ¾Ð¼Ð¿Ð¾Ð½ÐµÐ½Ñ‚: TDA4700A