AP3428/A

Document number: DS37417 Rev. 5 - 2

8 of 14

www.diodes.com

May 2021

© Diodes Incorporated

AP3428/A

Application Information

Typical application circuit is shown in the Typical Applications Circuit and for the circuit parameters setting please refers to the following

descriptions.

Under Voltage Lockout (UVLO) Circuit

When the VIN drops lower than the UVLO detector threshold, the UVLO circuit starts to operate, VREF stops, and high-side switch and low-side

switch built-

in switch transistors turn “OFF”. As a result, VOUT drops according to the COUT capacitance value and the load. When the V

IN is rising

higher than UVLO released voltage, the IC will restart the operation.

Short Circuit Protection and Recovery

When the AP3428/A output node is shorted to GND that VFB drops under 0.42V, AP3428/A will enter hiccup mode to protect itself. If short circuit is

removed, and VFB rises over 0.42V, the AP3428/A recovers to normal operation again. If the AP3428/A reaches OCP threshold while short circuit,

the AP3428/A will enter cycle by cycle current limit mode until the current under OCP threshold.

Over Temperature Protection

The internal thermal temperature protection circuitry is provided to protect the integrated circuit in the event that the maximum junction

temperature is exceeded. When the junction temperature exceeds +160°C, it shuts down the internal control circuit and switching power MOSFET.

The AP3428/A will restart automatically under the control of soft start circuit when the junction temperature decreases to +145°C.

Setting the Output Voltage

The output voltage can be adjusted from 1 to 5V using an external resistor divider. Table 1 shows a list of resistor selections for common output

voltages. Resistor R1 is selected based on a design tradeoff between efficiency and output voltage accuracy. For high values of R1 there is less

current consumption in the feedback network. However the tradeoff is output voltage accuracy due to the bias current in the error amplifier. R1 can

be determined by the following equation. Meanwhile, the input capacitor should close to IC for preventing unexpected influences.

Figure 1. Feedback Divider Network

Table 1. Resistor Selection for Common Output

Out Voltage

R1

R2

C1

1.0V

91k

Ω

120k

Ω

22pF

1.2V

100k

Ω

100k

Ω

22pF

1.5V

150k

Ω

100k

Ω

22pF

1.8V

300k

Ω

150k

Ω

22pF

2.5V

380k

Ω

120k

Ω

22pF

2.8V

440k

Ω

120k

Ω

22pF

3.3V

430k

Ω

100k

Ω

22pF

LX

FB

R1

R2

C1