STV8172A Datasheet, PDF (9/14 Pages) STMicroelectronics – Vertical Deflection Booster for 3-APPTV/Monitor Applications with 70-V Flyback Generator

STV8172A
Application Hints
4.3.1
Centring
When idle, both driver outputs provide i_cm and the yoke current should be null (R₁ is negligible),
hence:
icm ⋅ R7 = icm ⋅ R2 therefore R7 = R2
4.3.2
Peak Current
Scanning current should be I_P when positive and negative driver outputs provide respectively
i_cm - i_p and i_cm + i_p, therefore
(icm – i) ⋅ R7 = Ip ⋅ R1 + (icm + i) ⋅ R2 ^{and since R}7 ^{= R}2^:
I---pi- _{= –-2--R-R---1--7--}
Choose R₁ in the 1Ω range, the value of R₂ = R₇ follows. Remember that i is one-quarter of driver
peak-peak differential signal! Also check that the voltages on the driver outputs remain inside
allowed range.
● Example: for i_cm = 0.4mA, i = 0.2mA (corresponding to 0.8mA of peak-peak differential
current), I_p = 1A
Choose R₁ = 0.75Ω, it follows R₂ = R₇ = 1.875kΩ.
4.3.3 Ripple Rejection
Make sure to connect R₇ directly to the ground side of R₁.
4.3.4 Secondary Breakdown Diagrams
Figure 8: Output Transistor Safe Operating Area (SOA) for Secondary Breakdown
The diagram has been arbitrarily limited to max I0 (2 A).
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