PFS7623L datasheet(17/38 Pages) POWERINT

17 / 38 page

Rev. F 08/20

PFS7x23-7x29/7633-7636

www.power.com

Resistors, R1 to R4 comprise of the main output voltage divider

network. The sum of resistors R1, R2 and R3 is the upper divider

resistor and the lower feedback resistor is R4. Capacitor C1 is to filter

any switching noise from coupling into the FEEDBACK pin. Resistor R5,

capacitor C2 and C3 is the loop compensation network required to

tailor the loop response to ensure low cross-over frequency and

sufficient phase margin. The recommended values for the compo-

nents used are as follows:

R1 = 3.74 MW

R2 = 6.2 MW

R3 = 6.2 MW

R5 = 30.1 kW

C1 = 470 pF

C2 = 1 mF

C3 = 100 nF

When the above component values are used, the value of resistor R4

can be calculated using the equation below:

^ h

Output voltage.

FB(REF) FEEDBACK pin voltage, 3.85 V.

The value of resistor R5 will have to be adjusted in some designs and

as a guideline the value from the following calculation can be used:

Maximum continuous output power in watts.

Nominal PFC output voltage in volts.

PFC output capacitance in farads.

Heat Sinking and Thermal Design

Figures 15, 16, 17 show an example of the recommended assembly

for the HiperPFS-4. In this assembly, no insulation pad is required

and HiperPFS-4 can be directly connected to the heat sink by mechan-

ical clip or adhesive thermal compound.

It is required, on the PCB, that the heat sink is connected to the

HiperPFS-4 source terminal in order to reduce EMI and optimize

operation.

Figure 15. Heat Sink Assembly – using Thermally Conductive Adhesive.

(2X)

2. Screw

1. Heat Sink

4. HiperPFS-4

3. Thermally Conductive Adhesive

5. Eyelet Terminal − Electrical Connection to Heat Sink

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