Zxld1360, Application information – Diodes ZXLD1360 User Manual
Page 21
ZXLD1360
ZXLD1360
Document number: DS33471 Rev. 4 - 2
21 of 25
March 2011
© Diodes Incorporated
A Product Line of
Diodes Incorporated
Application Information
(cont.)
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 R
S
. Its best to connect VIN directly to one end of R
S
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 R
S
and V
IN
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
A number of ZXLD1360 evaluation boards are available on request for qualified opportunities.
For example:
ZXLD1360EV11 MR16 replacement interfaces to external LED.
The evaluation boards allow quick testing of the ZXLD1360 and provide a simple way of connecting external LEDs.
GND
ZXLD1360
ADJ
10k
100nF
GND