ZXLD1360

ZXLD1360

Document number: DS33471 Rev. 3 - 2

21 of 25

www.diodes.com

December 2010

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Layout Considerations

LX pin

The LX pin of the device is a fast switching node, so PCB tracks should be kept as short as possible. To minimize ground

'bounce', the ground pin of the device should be soldered directly to the ground plane.

Coil and decoupling capacitors and current sense resistor

It is particularly important to mount the coil and the input decoupling capacitor as close to the device pins as possible to

minimize parasitic resistance and inductance, which will degrade efficiency. It is also important to minimize any track

resistance in series with current sense resistor RS. Its best to connect VIN directly to one end of RS and Isense directly to the

opposite end of RS with no other currents flowing in these tracks. It is important that the cathode current of the Schottky

diode does not flow in a track between RS and VIN as this may give an apparent higher measure of current than is actual

because of track resistance.

ADJ pin

The ADJ pin is a high impedance input for voltages up to 1.35V so, when left floating, PCB tracks to this pin should be as

short as possible to reduce noise pickup. A 100nF capacitor from the ADJ pin to ground will reduce frequency modulation of

the output under these conditions. An additional series 10k

Ω resistor can also be used when driving the ADJ pin from an

external circuit (see below). This resistor will provide filtering for low frequency noise and provide protection against high

voltage transients.

High voltage tracks

Avoid running any high voltage tracks close to the ADJ pin, to reduce the risk of leakage currents due to board contamination.

The ADJ pin is soft-clamped for voltages above 1.35V to desensitize it to leakage that might raise the ADJ pin voltage and

cause excessive output current. However, a ground ring placed around the ADJ pin is recommended to minimize changes in

output current under these conditions.

Evaluation PCB

The ZXLD1360EV1, 2 or 3 evaluation boards are available on request. These boards contain a Lumileds K2 or multiple Ostar

LEW type LEDs to allow quick testing of the 1360 device. Additional terminals allow for interfacing to customers own LED

products.

GND

ZXLD1360

ADJ

10k

100nF

GND