SD42522 Silan, SD42522 Datasheet - Page 3

• Manufacturer Part Number: SD42522
• Description: 1A High Power LED Driver
• Manufacturer: Silan

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PIN CONFIGURATION
PIN DESCRIPTION
FUNCTION DESCRIPTION
The SD42522 is a current mode LED driver. The voltage on compensation pin COMP is proportional to the
current delivered to the load.
At the beginning of a cycle: the upper transistor M1 is off; the COMP pin voltage is higher than the current sense
amplifier output; and the current comparator’s output is low. The rising edge of the 280KHz CLK signal sets the
RS Flip-Flop whose output turns on M1 thus VIN, Rs, LED, inductor and M1 comprises a circuit loop and the
inductor current increases. The inductor current is sensed and amplified by the current sense amplifier. Ramp
compensation is summed to current sense amplifier output and compared to the Gm amplifier output by the
current comparator. When the current sense amplifier plus ramp compensation signal exceeds the comp pin
voltage, the RS Flip-Flop is reset and the chip reverts to its initial M1 off state. The inductor energy storage
released via the circuit loop composed by Rs, LED, inductor and M1 and the current decreases. When next clock
cycle arrives, the upper transistor M1 is on to enter next switch cycle. If the current sense amplifier plus slope
HANGZHOU SILAN MICROELECTRONICS CO.,LTD
Http://www.silan.com.cn
COMP Clamp Voltage
Switch Transistor on
Resistance
V
Sampling Voltage Threshold
Thermal Shutdown Threshold
Thermal Shutdown Hysteresis
Pin No.
DD
1
2
3
4
5
6
7
8
voltage
Characteristics
Pin Name
SENSE
COMP
GND
V
SW
V
NC
NC
DD
IN
I/O
I/O
O
O
-
-
I
I
I
TSD-hys
Power output.
Ground.
Current sense pin.
Input supply voltage.
Compensation pin, connects to external capacitor.
No Connected.
5V reference output.
No Connected.
Symbol
V
V
SENSE
TSD
R
COMP
V
V
ON
DD
IN
-
Open without load
1LED, I
No load
Drop voltage between
V
IN
Test Condition
and SENSE
OUT
=1A
Description
Min.
1.6
5.0
--
--
Typ.
0.40
160
1.9
5.2
88
30
REV:1.0
Max.
2.2
0.6
5.4
--
Page 3 of 8
2009.07.06
Unit
mV
°C
°C
Ω
V
V