ZXLD1350EV4
ZXLD1350EV4 User Guide Iss. 1
5/8
10-04-07
ZXLD1350EV4 Connection Point Definition
Name
Description
+VIN
Positive supply voltage. Connect a +24V positive supply to this pin.
GND
Supply Ground (0V). Connect supply ground to this pin.
ADJ
Internal voltage ref. pin (1.25). This pin can be used to achieve dimming and soft-start,
and for switching the output current off.
•
Leave floating for normal operation.
•
See 'Other Features' section to achieve dimming, and soft-start and for switching
the output current off.
LED a
LED a connects to the ANODE of LED D3, and is the external LED anode connection
point. Disconnect the jumper JP2 when driving an external load.
LED k
LED k connects to the CATHODE of LED D1, and is the external LED cathode
connection point. Disconnect the jumper JP2 when driving external LEDs.
ZXDL1350EV2 OPERATION
ZXLD1350EV4 Power Up
1. Connect VIN to +24V of the power supply unit (PSU). Connect GND to the power supply ground (0V).
Warning: The board does not feature reverse battery/supply protection.
2. Set the PSU to +24V. (+24V at VIN pin with ref. to the GND pin.)
3. Turn on the PSU.
Warning: Do not stare at the LEDs directly.
4. Ensure jumper J2 is fitted. With JP1 and JP3 disconnected (jumper off), all three LEDs should illuminate and
will be regulated nominally at 300mA.
5. To change the number of LEDs connected in series, use jumper JP1 and JP3 to bypass LEDs D1 and D3
respectively.
Warning: The LEDs may be hot.
OTHER FEATURES
Dimming
The ZXLD1350 provides three dimming options: DC, high-frequency PWM, and low-frequency PWM dimming.
DC Voltage Dimming
1. Switch off the power supply.
2. Insert a 0R 0805 resistor across R1 pads.
3. Fit a 10nF capacitor at C3 to decouple the pin.
4. Drive the ADJ pin on the board with a DC voltage in the range 0.3V to 1.25V.
5. Do not exceed 1.25V, as this represents 100% of the LED current set by Rs. The current will increase in
proportion to this voltage. For example, if 2.5V is applied, the current will increase to 200%. That is, the
current will be twice the 1.25V rating. For such over-drive of the ADJ pin, the LED and ZXLD1350 are likely
to be damaged. The nominal LED current (output current), I
OUT
, is given by
I
OUT
= 0.08* V
ADJ
/Rs
where I
OUT
= the nominal LED current.
V
ADJ
= the DC dimming voltage at ADJ pin resistor.
0.08 is the multiplier for the reference voltage on ADJ pin.
Rs = the sense resistor value in ohms.
Do not use a resistor value lower than 0.27
Ω.
6. The dimming ratio is around 6:1. Note: as the voltage approaches 0.2V on the ADJ pin, the ZXLD1350 will
shut down.
7. Follow the ‘ZXLD1350EV4 Power Up’ sequence.
