AP3445/L

Document number: DS39755 Rev. 1 - 2

9 of 13

www.diodes.com

March 2018

© Diodes Incorporated

AP3445/L

Application Information

The AP3445/L is a 2A 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 application schematic

and functional block diagram of AP3445/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

Under Voltage Lockout (UVLO) Circuit

switch built-

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

Short Circuit Protection and Recovery

remain in this state until VIN or EN voltage is recycled.. If the AP3445/L reaches OCP threshold while short circuit, the AP3445 will enter cycle by

cycle current limit mode until the current under OCP threshold.

Over Voltage Protection (AP3445L only)

The AP3445L 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. AP3445L enters latch off mode and will restart until VIN or Enable voltage 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 AP3445/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 6 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

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

– 2.2µH

1.8V

200

kΩ

100

kΩ

22pF

1.5

– 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