VIPER319XDTR datasheet(24/39 Pages) STMICROELECTRONICS

Part #	VIPER319XDTR

Description	Energy saving offline high voltage converter

PDF	39 Pages

Scroll/Zoom	100%

Manufacturer	STMICROELECTRONICS [STMicroelectronics]

Direct Link	http://www.st.com

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24 / 39 page

Figure 37. Connection for input and output overvoltage protections (iso/non-iso topologies)

GND

DRAIN

GND

VCC

UVP

COMP

CONTROL

VIPER31

CIN

DIN

~ AC

OVP

from VAUX or VOUT

The voltage divider equations are:

Equation 7

(7)

Vin_UVP= VUVPtℎRL−IUVP_pull−up · RH+RM+RL +RL·IUVP_pull−up

Equation 8

(8)

Vin_OVP= VOVPtℎ− RH

RH+RM+RL· RL·IUVP_pull−up ·RH+RM+RL

RM+RL

Considering that the value of RH is much higher than the values of RM and RL (Mohms vs. kohms), equations 7

and 8 can be approximated into Eq. 7.a) and Eq. 8.a) respectively:

Equation 7.a

(7.a)

Vin_UVP VUVPtℎRL−IUVP_pull−up ·RH+RL·IUVP_pull−up

Equation 8.a

(8.a)

Vin_OVP VOVPtℎ−RL·IUVP_pull−up · RHRM+RL

Selecting arbitrarily the RH value, Equation 7.a) can be solved for RL:

Equation 9

(9)

VIPER31

General description

DS13285 - Rev 6

page 24/39

VIPER319XDTR Datasheet(PDF) 24 Page - STMicroelectronics