Diodes ZXLD1352 - Manual (Page 2)

ZXLD1352
ZXLD1352
Document number: DS33469 Rev. 3 - 2
2 of 21
www.diodes.com
December 2010
© Diodes Incorporated
A Product Line of
Diodes Incorporated
Block Diagram
Figure 1. Block Diagram
Pin Description
Name Pin No. Description
LX 1 Drain of NDMOS switch
GND 2 Ground (0V)
ADJ 3
Multi-function On/Off and brightness control pin:
• Leave floating for normal operation. (V
ADJ
= V
REF
=1.25V giving nominal average output current
I
OUTnom
=0.1/R
S
)
• Drive to voltage below 0.2V to turn off output current
• Drive with DC voltage (0.3V
ADJ
<2.5V) to adjust output current from 25% to 200%
†
of I
OUTnom
• Drive with PWM signal from open-collector or open-drain transistor, to adjust output current.
o Adjustment range 0.1% to 100% of I
OUTnom
for 100Hz < f < 1kHz
• Connect a capacitor from this pin to ground to define soft-start time. Soft-start time is
approx.0.5ms/nF)
I
SENSE
4
Connect resistor R
S
from this to V
IN
to define nominal average output current I
OUTnom
=0.1/R
S
(Note: R
SMIN
=0.27V with ADJ pin open circuit)
V
IN
5
Input voltage (7V to 30V). Decouple to ground with 1µF of higher X7R ceramic capacitor close to
device
MN
-
+
V
IN
Comparator
R1
R2
R3
GND
-
+
LX V IN I SENSE
Current sense circuit
V
IN
ADJ
R
S
L1
D1
5V Voltage
regulator
Shutdown
circuit
Vref
50k
1.25V
600KHz
C1