2 Channel 5.5V 1.5A 1.5MHz DC-DC Step down PMU

where

���� =

where

•

: estimated output voltage ripple

•

: estimated current ripple

•

D

: Estimated duty factor

Output ripple can be estimated from the vector sum of the reactive (capacitance) voltage component and the real

(ESR) voltage component of the output capacitor:

2

2

where

where

•

estimated output ripple,

•

estimated real output ripple,

•

estimated reactive output ripple.

The device is designed to be used with ceramic capacitors on the outputs of the buck regulators. The recommended

dielectric type of these capacitors is X5R, X7R, or of comparable material to maintain proper tolerances over voltage

and temperature. The recommended value for the output capacitors is 10µF, 6.3V with an ESR of 2mΩ or less. The

output capacitors need to be mounted as close as possible to the output/ground terminals of the device.

BUCK Input Capacitor Selection

input capacitor should be located as close as possible to their corresponding VIN and GND terminals, tantalum

capacitor can also be located in the proximity of the device.

The input capacitor supplies the AC switching current drawn from the switching action of the internal power

MOSFETs. The input current of a buck converter is discontinuous, so the ripple current supplied by the input

capacitor is large. The input capacitor must be rated to handle both the RMS current and the dissipated power. The

input capacitor must be rated to handle this current:

The power dissipated in the input capacitor is given by:

2

The device is designed to be used with ceramic capacitors on the inputs of the buck regulators. The recommended

dielectric type of these capacitors is X5R, X7R, or of comparable material to maintain proper tolerances over voltage

HM5213