Diodes ZXLD1374 - Manual (Page 2)

ZXLD1374
Document number: DS35032 Rev. 3 - 2
2 of 39
www.diodes.com
September 2012
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ZXLD1374
A Product Line of
Diodes Incorporated
Pin Descriptions
Pin
Name
Pin
Type
(Note 4)
Function
ADJ 1 I
Adjust Input (for DC Output Current Control).
Connect to REF to set 100% output current.
Drive with dc voltage (125mV
ADJ
< 2.5V) to adjust output current from 10% to 200% of set value. The
ADJ pin has an internal clamp that limits the internal node to less than 3V. This prevents the LED and power
switch from delivering too much current should ADJ get overdriven.
REF 2 O Internal 1.25V reference voltage output
T
ADJ
3 I
Temperature Adjust (Input for LED Thermal Current Control).
Connect thermistor/resistor network to this pin to reduce output current above a preset temperature threshold.
Connect to REF to disable thermal compensation function (See section on thermal control).
SHP 4 I/O
Shaping capacitor for feedback control loop.
Connect 100pF ±20% capacitor from this pin to ground to provide loop compensation
STATUS 5 O
Operation Status Output (analog output).
Pin is at 4.5V (nominal) during normal operation.
Pin switches to a lower voltage to indicate specific operation warnings or fault conditions (See section on
STATUS output).
Status pin voltage is low during shutdown mode.
SGND 6 P
Signal Ground.
Connect to 0V and pins 7 and 8.
PGND 7, 8 P
Power Ground.
Connect to 0V and pin 6 to maximize copper area.
N/C 9, 10, 11, 12 —
Not Connected Internally.
To maximize PCB copper for thermal dissipation connect to pins 7 and 8.
LX 13, 14 O Low-Side Power-Switch Output
V
AUX
15 P
Auxiliary Positive Supply to Internal Switch Gate Driver.
Connect to V
IN
, or auxiliary supply from 6V to 15V supply to reduce internal power dissipation (Refer to
application section for more details).
At V
IN
>24V; to reduce power dissipation, V
AUX
can be connected to a 12V to 15V auxiliary power supply
(see Applications section).
Decouple to ground with capacitor close to device (refer to Applications section).
V
IN
16 P
Input Supply to Device (6.3V to 60V).
Decouple to ground with capacitor close to device (refer to Applications section).
ISM 17 I
Current Monitor Input.
Connect current sense resistor between this pin and V
IN
.
The nominal voltage, V
SENSE
, across the resistor is 218mV fixed in Buck mode and initially 225mV in Boost
and Buck-Boost modes, varying with duty cycle.
FLAG 18 O
Flag Open Drain Output.
Pin is high impedance during normal operation.
Pin switches low to indicate a fault, or warning condition.
PWM 19 I
Digital PWM Output Current Control.
Pin driven either by open Drain or push-pull 3.3V or 5V logic levels.
Drive with frequency higher than 100Hz to gate output ‘on’ and ‘off’ during dimming control.
The device enters standby mode when PWM pin is driven with logic low level for more than 15ms nominal
(Refer to application section for more details).
GI 20 I
Gain Setting Input.
Used to set the LED current in Boost and Buck-Boost modes.
In Buck mode operation the GI pin must be connected to ADJ.
For Boost and Buck-boost modes, connect to resistive divider from ADJ to SGND. This defines the ratio of
switch current to LED current (see application section). The GI pin has an internal clamp that limits the
internal
node to less than 3V. This provides some failsafe should the GI pin get overdriven.
EP PAD P
Exposed Pad.
Connect to 0V plane for electrical and thermal management.
Note: 4. Type refers to whether or not pin is an Input, Output, Input/Output or Power supply pin.