LM2576, LM2576HV
SNVS107C –JUNE 1999–REVISED APRIL 2013
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Complete circuit not shown (see Figure 28).
Figure 31. Undervoltage Lockout
for Buck-Boost Circuit
DELAYED STARTUP
The ON /OFF pin can be used to provide a delayed startup feature as shown in Figure 32. With an input voltage
of 20V and for the part values shown, the circuit provides approximately 10 ms of delay time before the circuit
begins switching. Increasing the RC time constant can provide longer delay times. But excessively large RC time
constants can cause problems with input voltages that are high in 60 Hz or 120 Hz ripple, by coupling the ripple
into the ON /OFF pin.
ADJUSTABLE OUTPUT, LOW-RIPPLE POWER SUPPLY
A 3A power supply that features an adjustable output voltage is shown in Figure 33. An additional L-C filter that
reduces the output ripple by a factor of 10 or more is included in this circuit.
Complete circuit not shown.
Figure 32. Delayed Startup
Figure 33. 1.2V to 55V Adjustable 3A Power Supply with Low Output Ripple
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