TDA4700 Datasheet, PDF (5/21 Pages) Siemens Semiconductor Group – Control IC for Single-Ended and Push-Pull Switched-Mode Power Supplies SMPS

TDA 4700
TDA 4718
Pin Definitions and Functions (TDA 4718)
Pin
Symbol
1
GND
2
R_R
3
C_R
4
I COMP
5
I SYNC
6
IUV
7
IOV
8
– I_DYN
9
+ I_DYN
10
+ V_REF
11
+ V_S
12
Q2
13
Q1
14
Q SYNC
15
C_{soft start}
16
R_T
17
C_filter
18
C_T
Function
Ground 0 V
Ramp generator R_R
Ramp generator C_R
+ Input comparator K2
Sync. input
Input undervoltage, ON/OFF
Input overvoltage
Input dynamic current limitation (–)
Input dynamic current limitation (+)
Reference voltage
Supply voltage
Output Q2
Output Q1
Sync. output
Soft start
VCO R_T
Capacitance
VCO C_T
Circuit Description
Voltage Controlled Oscillator (VCO)
The VCO generates a sawtooth voltage. The duration of the falling edge is determined
by the value of C_T. The duration of the rising edge of the waveform and, therefore,
approximately the frequency, is determined by the value of R_T. By varying the voltage at
C_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.
Semiconductor Group
5