SD42522 Silan, SD42522 Datasheet - Page 4

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

www.DataSheet4U.com
compensation signal does not exceed the comp voltage in one cycle, then the falling edge of the CLK resets the
Flip-Flop.
The Gm amplifier compares the output current with the threshold current (threshold current is set by internal).
When the output current is higher than threshold current, the COMP pin’s voltage is lower down. Since the
COMP pin’s voltage is proportional to the peak inductor current a decrease in its voltage decreases current
delivered to the output. When the output current is lower than threshold current, the COMP pin’s voltage is up
while the output current increases. The output current is stable at the set value by adjusting the circuit loop.
1.
The output current is determined by the sampling resistor and setting voltage. The sampling voltage of VIN-
VSENSE(Drop voltage on Rs) is 88mV, and adjust the output current by adjusting the sampling resistor Rs (refer
to Typical Application Circuit).
2.
SD42522 has internal current limiting function, and the voltage on COMP is clamped at about 1.9V, the output
current of the power MOSFET is limited at about 1.9A by current comparator.
3.
SD42522 has internal frequency jitter function to improve the EMI performance of the system. The internal
frequency is hopping in a very small range to reduce the single frequency radiation which simplifies the EMI
design.
HANGZHOU SILAN MICROELECTRONICS CO.,LTD
Http://www.silan.com.cn
Output current setting
Current limiting
Frequency jitter
I
OUT
=
V
IN
−
R
V
S
SENSE
REV:1.0
Page 4 of 8
2009.07.06