WT7527V データシートの表示（PDF） - Weltrend Semiconductor

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WT7527V

PC POWER SUPPLY SUPERVISOR

Weltrend Semiconductor 

WT7527V

Rev. 1.01

APPLICATION NOTE

IL

+ VL -

RL

R

VS

IS

+ VR -

IR

V12A

-

+

OCP

IR=8*IREF=8* ( VREF/RI )

VREF = 1.2V

V12A

V12A

+

-

IREF

RI

IREF=VREF / RI

RI

When the load current increased, the voltage (VL) cross the inductor is increased.

And when inductor voltage exceeds the resistor voltage (VR), the OCP is active.

Sometimes power-on or load dynamics will cause false output of over-current detection. It can be

solved by connecting a capacitor between VS pin and IS pin. In typical case, C ≥ 1uF is suggested.

OCP point can be calculated by the following equation:

Let VR = VL

R × IR = RL × IL

Q IR = 8 × IREF = 8 × VREF

RI

∴ R = RL × IL

8 × VREF

RI

For example：

Assume RI=30KΩ, RL=5mΩ, OCP IL=20A.

Sol：R = ( IL * RL ) / ( 8 * IREF )

= ( 20A * 5mΩ) / { 8 * ( 1.2V / 30KΩ)}

= 312.5Ω

Weltrend Semiconductor, Inc.

Page 8

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