AP2953AS8PR datasheet(7/9 Pages) CHIPOWN

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AP2953A

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2. Choose the compensation capacitor (C3) to achieve the

desired phase margin. For applications with typical inductor

values, setting the compensation zero, fZ1, below one-forth of

the crossover frequency provides sufficient phase margin.

Determine the C3 value by the following equation:

Where R3 is the compensation resistor.

3. Determine if the second compensation capacitor (C6) is

required. It is required if the ESR zero of the output capacitor

is located at less than half of the switching frequency, or the

following relationship is valid:

If this is the case, then add the second compensation

capacitor (C6) to set the pole fP3 at the location of the ESR

zero. Determine the C6 value by the equation:

External Bootstrap Diode

An external bootstrap diode may enhance the efficiency of the

regulator, the applicable conditions of external BS diode are:

●

VOUT is 5V or 3.3V; and

●

Duty cycle is high: D=VOUT/VIN >65%

In these cases, an external BS diode is recommended from the

output of the voltage regulator to BS pin, as shown in Figure4

Figure 4

Add Optional External Bootstrap Diode to

Enhance Efficiency

The recommended external BS diode is IN4148, and the BS

cap is 0.1~1µF.

Typical Performence Characteristics

Short circuit test (Channel3:ISW, Channel2:VO)

soft-start (Channel1:EN, Channel2:VO)

Transient response (Channel3:ISW, Channel2:VO)

Ripple

Typical Application Circuits

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