Diodes ZXLD1321 - Manual (Page 4)

ZXLD1321
Issue 1 - January 2008 4 www.zetex.com
© Zetex Semiconductors plc 2008
Pin description
Name Pin # Description
ADJ 1 Adjust input
• Leave floating, or connect to VREF to set 100% output current.
• Drive with dc voltage. (50mV
current from 10% to 100% of set value. (DC brightness control
mode)
• Drive with low frequency (200Hz) PWM control signal to gate
output ‘on’ and ‘off’ at the PWM frequency. (PWM brightness
control mode)
• Drive with low level dc voltage (VADJ<28mV) to turn off device
(Standby mode)
BIAS 2 Bias pin for setting base current of internal switch transistor
• Short pin to ground to define maximum base drive current for
output switch (Maximum output current condition)
• Connect resistor (R
BIAS
) from this pin to ground to reduce base
drive current (Reduced output current condition)
CFB 3 Compensation point
• Connect 10nF capacitor from this pin to ground to provide loop
compensation
N/C 4 No connection to this pin (open circuit)
ISENSE 5 Switch peak current sense pin
• Connect resistor (R
SENSE
) from this pin to ground to define peak
switch current (ISW
PEAK
)=V
SENSE
/R
SENSE
EMITTER 6, 7 Switch emitters (connect both pins to top of R
SENSE
to sense emitter current)
COLLECTOR 8, 9 Switch collectors (connect both pins to lower side of coil)
M_LOAD 10 Load side input of high side current monitor
M_VIN 11 Input supply to high side current monitor
• Connect to output voltage (cathode of Schottky)
• Connect resistor (R
M
) between M_LOAD and M_VIN to define
nominal average output (LED) current of 0.1/R
M
VIN 12 Positive supply to device (1.2-12V)
• Decouple to ground with capacitor close to device
TADJ 13 Temperature adjust input for LED thermal compensation
• Connect thermistor/resistor network to this pin to reduce output
current above a preset temperature threshold.
• Connect to VREF to disable thermal compensation function
(see section on temperature control for details)
VREF 14 Internal 0.5V reference voltage output
Exposed pad 15 Connect to ground (0V)