TDA4700 Datasheet, PDF (17/21 Pages) Siemens Semiconductor Group – Control IC for Single-Ended and Push-Pull Switched-Mode Power Supplies SMPS

TDA 4700
TDA 4718
Dimensioning Notes for RC Network
1. Determination of the minimum time during which both outputs must be disabled
→ selection of C_T; selection of C_R ≤ C_T.
2. Determination of the VCO frequency = 2 x output frequency
→ selection of R_T.
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 R_R.
4. Duration of the soft start process
→ selection of C_{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 C_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:
C_filter favourable:
100 kHz
10 nF
50 Hz
1µF
Semiconductor Group
17