VPC BLK

t

100 ns

R22

18 pF

-

-

=

VSC(max)

OUT(max)

VSC(max)

R23

V

(

)

V

R11 R23

V

1.74 V

ª

º

u

«

»

¬

¼

VSC(min)

OUT(min)

VSC(min)

R23

V

(

)

V

R11 R23

V

0.52 V

ª

º

u

«

»

¬

¼

VPC _ VSC

R9 R21

R9

R11

1

R23

Ratio

1.1

R23

47 k

R11 115 k

é

ù

+

æ

ö

ê

ú

ç

÷

=

-

´

ê

ú

ç

÷

´

ê

ú

ç

÷

ç

÷

ê

ú

è

=

ø

ë

û

=

W

W

25

UCC24636

www.ti.com

SLUSCG2A – MARCH 2016 – REVISED MARCH 2016

Product Folder Links: UCC24636

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Copyright © 2016, Texas Instruments Incorporated

9.2.3.2 VSC Input

The value of R23 is recommended to be with the range of 25 k

Ω to 50 kΩ.

There is a 10% margin included for the initial value calculation of R11 to provide timing margin during initial

operation verification.

(11)

With R11 = 115 k

Ω, the operating range of the VSC pin is:

(12)

(13)

The UCC24636 SR timing can be optimized (SR on time increased) by increasing the R115 value after initial

for VPC and VSC should allow reducing the 10% initial SR timing margin.

9.2.3.3 TBLK Input

The blanking time is set with resistor R22.

Select the blanking time to meet the following criteria based on 660-ns minimum primary on-time at high line.

spacer

(14)

A value of R22 = 20 k

Ω results in a blanking time of approximately 460 ns.