AP3441/L

Document number: DS39754 Rev. 3 - 2

9 of 13

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September 2019

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AP3441/L

Application Information

The AP3441/L is a 3A current mode control, synchronous buck regulator with integrated power MOSFETs. Current mode control assures excellent

line regulation, load regulation, and a wide loop bandwidth for fast response to load transients. See the Typical Applications Circuit and Functional

Block Diagram of AP3441/L for more details. The buck controller drives the internal high side P-FETs. The buck regulator can operate from an

unregulated DC source, such as a battery, with a voltage ranging from 2.7V to 5.5V. The converter output can be regulated as low as 0.6V to as

high as VIN. The feedback loop is compensated internally.

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 VIN is rising

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

Short Circuit Protection and Recovery

When the AP3441/L output node is shorted to GND that VFB drops under 0.42V, the AP3441 will enter hiccup mode to protect itself and the

AP3441L will enter latch-off mode. If short condition is removed, and VFB rises over 0.42V, the AP3441 will recover to normal operation again. The

AP3441L will remain in this state until VIN or EN pin voltage is recycled. If the AP3441/L reaches OCP threshold while short circuit, the AP3441

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

Over Voltage Protection (AP3441L Only)

The AP3441L has internal output OVP circuits. When VOUT is exceeds 120% of the regulation level for more than 40µs, the power switches will be

turned off. The AP3441L enters latch off mode and will restart until VIN or EN pin voltage is recycled.

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 +150°C, it shuts down the internal control circuit and switching power MOSFET.

The AP3441/L will restart automatically under the control of soft start circuit when the junction temperature decreases to +130°C.

Setting the Output Voltage

Choose R1 and R2 to program the proper output voltage. 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. Table 1 shows a list of resistors selection for common output voltages. An optional C1 of

10pF to 470pF used to boost the phase margin and improve stability. R2 in Figure 1 can be determined by the following equation:

6

.

0

V

6

.

0

R

R

OUT

1

2







Figure 1. Feedback Divider Network

Table 1. Recommended Component Selection

VOUT (V)

R1 (kΩ)

R2 (kΩ)

C1 (pF)

L1 (µH)

1.0V

68

kΩ

100

kΩ

22pF

1.0µH

1.2V

100

kΩ

100

kΩ

22pF

1.0µH

1.5V

150

kΩ

100

kΩ

22pF

1.5 to 2.2µH

1.8V

200

kΩ

100

kΩ

22pF

1.5 to 2.2µH

2.5V

317

kΩ

100

kΩ

22pF

2.2µH

2.8V

367

kΩ

100

kΩ

22pF

2.2µH

LX

FB

R1

R2

C1

L1