ADPL12002/ADPL12003

20V, 2.5A/3.5A, Fully Integrated Synchronous

Buck Converter

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Applications Information

Setting the Output Voltage

The ADPL12002/ADPL12003 ICs are available with adjustable-output-voltage. The output voltage can be adjusted

between 0.8V and 12V using an external resistor-divider. Connect a resistor-divider from the buck output to FB to GND

and a feed-forward capacitor from the buck output to FB (see Typical Application Circuits section for more details). Select

RFB2 ≤ 50kΩ. Calculate RFB1 with the following equation:

Equation 1:

RFB1 = RFB2 [(

VOUT

VFB

) - 1] ; where VFB = 0.8V.

Table 1. Recommended Components for Adjustable Output

PART NUMBER

FREQUENCY

VOUT (V)

INDUCTOR (µH)

EFFECTIVE COUT (µF)

CFF (pF)

ADPL12002

400kHz

0.8V–1.5V

3.3μH

130µF

–

1.5V–3V

4.7μH

63µF

33pF

3V–6V

6.8μH

40µF

33pF

6V–12V

8.2μH

30µF

22pF

1.5MHz

0.8V–1.5V

0.68μH

120µF

–

1.5V–3V

1.5μH

55µF

47pF

3V–6V

2.2μH

42µF

47pF

6V–12V

4.7μH

25µF

82pF

ADPL12003

400kHz

0.8V–1.5V

3.3μH

130µF

–

1.5V–3V

3.3μH

70µF

33pF

3V–6V

6.8μH

50µF

33pF

6V–12V

8.2μH

40µF

22pF

1.5MHz

0.8V–1.5V

0.68μH

120µF

–

1.5V–3V

1.0μH

74µF

47pF

3V–6V

2.2μH

42µF

47pF

6V–12V

3.3μH

25µF

82pF

Table 1 provides component selection recommendations for each output voltage range. The feed-forward capacitor (CFF)

is recommended based on RFB1 = 50kΩ.

Input Capacitor

The input filter capacitor reduces peak currents drawn from the power source and reduces noise and voltage ripple on

the input caused by the circuit's switching. The ADPL12002/ADPL12003 ICs incorporate a symmetrical pinout to improve

EMI performance. It is recommended to split the input capacitors symmetrically between the two SUP pins. Connect a

2.2μF (min) ceramic capacitor on each SUP pin for low-input voltage ripple. For additional noise immunity, a high-

frequency 0603 or smaller capacitor with a recommended value of 0.1μF can be added on each SUP pin.

A bulk capacitor with higher equivalent series resistance (ESR), such as an electrolytic capacitor, is normally required as

well to lower the Q of the front-end circuit and provide the remaining capacitance needed to minimize input-voltage ripple.

The input capacitor RMS current requirement (IRMS) is defined by the following equation: