AP3591

Document number: DS36906 Rev. 1 - 2

12 of 18

www.diodes.com

March 2014

© Diodes Incorporated

AP3591

A Product Line of

Diodes Incorporated

Power On from EN (DEM Mode)

Figure 1. Start-up Behavior of AP3591

4. Power Good Output

The AP3591 features power good output to monitor the output voltage. It is an open-drain output and should be connected to a 5V power supply

node through a resistor. The power good function is active after the soft start is finished. PGOOD signal becomes high if output voltage reaches

±5% of the target value after 64µs delay building into the PGOOD circuitry. It will become low immediately if the output voltage goes beyond ±10%

of the target value.

5. Soft Stop

The AP3591 has a built in soft-stop circuitry. The output is discharged with an i

nternal 20Ω transistor when EN/DEM is low or the device is in a

fault condition including UVLO and OTP. The discharge time constant is determined by the output capacitance and resistance of the discharge

transistor.

6. Pre-biased Output

to a voltage less than the expected value, as shown by the magenta curve, the AP3591 will detect that condition. Neither MOSFET will turn on

expected value, as showed in the black curve, neither MOSFET will turn on until the output voltage is pulled down to the expected value through

external load. Any resistive load connected to the output will help pull down the voltage.

T0

T1

T2

GND

Figure 2. Start-up Behavior with Pre-biased Output Voltage

1V/div

20V/div

2V/div

5V/div

Time 400µs/div