Diode selection

The rectifier diode (D1) should be a fast low

capacitance schottky diode with low reverse leakage

at the working voltage. It should also have a peak

current rating above the peak coil current and a

continuous current rating higher than the maximum

output load current.

The table below gives some typical characteristics for

diodes that can be used with the ZXLD1615:

Diode

Ic (mA)

Package

ZHCS400

300

1000

400

15

SOD323

ZHCS500

300

1000

500

15

SOT23

Layout considerations

PCB tracks should be kept as short as possible to

minimize ground bounce, and the ground pin of the

device should be soldered directly to the ground

plane. It is particularly important to mount the coil

and the input/output capacitors close to the device to

minimize parasitic resistance and inductance, which

will degrade efficiency. The FB pin is a high

impedance input, so PCB track lengths to this should

also be kept as short as possible to reduce noise

pickup. Excess capacitance from the FB pin to ground

should be avoided.

ZXLD1615

SEMICO NDUC TORS

ISSUE 3 - AUGUST 2004

9