SIP32434

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Vishay Siliconix

S22-0384-Rev. B, 02-May-2022

16

Document Number: 63147

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Fig. 38

CURRENT LIMIT SETTING

The SIP32434A and SIP32434B actively monitor the current flow through the switch and provide a quick response to

over-current conditions by actively regulating the current to a set limit. The current limit is set by connecting a resistor between

the ILIM pin and GND. RSET can be calculated by the following formula for a desired current limit:

When the load current exceeds the threshold (ILIM), the parts respond within 1 μs (typ.) to turn off the switch and then regulate

the switch gate voltage to limit the output current to the set ILIM level. During this brief period before the over-current protection

circuit is engaged, the parts will see a surge current, especially under a severe output short condition. The magnitude of the

surge current developed during the period when the over-current protection is not engaged is determined by impedance in the

loop from the input current source to ground and the response time. This impedance is the sum total of the current source

impedance, the path resistance and inductance, and the load impedance.

If the over-current condition persists for more than 6 ms / typ., the switch shuts off. When VOUT falls below 95 % of VIN, the PGD

is pulled low. The device will exit current limiting when the load current falls below ILIM before the end of the current limit period.

The control circuit will increase the gate drive in the same manner as the soft start when the switch exits from the current limit

mode.

IOUT

ILIM , OCP Threshold

50% EN to 10% VIN

VSS (VIN/9)

PGD

EN /UVLO

VIN

TON_DLY <550 μs

TOFF_DLY 1 μs

50% EN to 90% VIN

RLOA D =

5V

PGD is pulled thr ough a resistor to an external voltage source

VOUT

VIN

SR (V/ms) =

I

INRUSH (mA)

C

OUT (μF)

---------------------------------

R

SET =

0.6 V

I

LIM

------------- x 20 600