LM2578A, LM3578A

SNVS767E – AUGUST 2000 – REVISED APRIL 2013

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Figure 16. Current Limit, Vin Referred

CURRENT LIMIT TRANSIENT SUPPRESSION

When noise spikes and switching transients interfere with proper current limit operation, R1 and C1 act together

as a low pass filter to control the current limit circuitry's response time.

Because the sense current of the current limit terminal varies according to where it is referenced, R1 should be

less than 2 k

Ω when referenced to ground, and less than 100Ω when referenced to Vin.

Figure 17. Current Limit Transient Suppressor, Ground Referred

Figure 18. Current Limit Transient Suppressor, Vin Referred

C.L. SENSE VOLTAGE MULTIPLICATION

When a larger sense resistor value is desired, the voltage divider network, consisting of R1 and R2, may be

used. This effectively multiplies the sense voltage by (1 + R1/R2). Also, R1 can be replaced by a diode to

increase current limit sense voltage to about 800 mV (diode Vf + 110 mV).

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