SD42522_Datasheet
1A High Power LED Driver with 6½36V Input
DESCRIPTION
The SD42522/22EH is a step-down PWM control LED driver with a
built-in power MOSFET. It achieves 1A continuous output current in
6~36V input voltage range. It provides thermal shutdown circuit,
current limit circuit.
The SD42522/22EH adopts current mode control which provides fast
transient response, excellent constant current characteristic and
simple loop stabilization design. It has high efficiency up to more than
96%, the excellent current accuracy is within ±1% when input/output
voltage change.
ESOP-8-225-1.27
(with heatsink at the bottom)
SOP-8-225-1.27
FEATURES
* 6-36V input voltage range
* Maximum 1A output current
* built-in power MOSFET: 0.40Ω(SD42522); 0.60Ω(SD42522EH)
* Integrate Jitter function
* 280kHz fixed frequency
* Excellent constant current accuracy ±1%
* High efficiency up to 96%
* Thermal shutdown
* Cycle-by-cycle over current protection
APPLICATIONS
* MR16 LED spotlight
* LED illuminance
* LED street lamp
ORDERING INFORMATION
Part No.
SD42522
SD42522TR
SD42522EH
SD42522EHTR
Package
SOP-8-225-1.27
SOP-8-225-1.27
ESOP-8-225-1.27
ESOP-8-225-1.27
Marking
SD42522
SD42522
SD42522EH
SD42522EH
Material
Pb free
Pb free
Pb free
Pb free
Package Type
Tube
Tape & Reel
Tube
Tape & Reel
HANGZHOU SILAN MICROELECTRONICS CO.,LTD
Http://www.silan.com.cn
REV:1.2
2010.11.03
Page 1 of 10
SD42522_Datasheet
BLOCK DIAGRAM
ABSOLUTE MAXIMUM RATING
Characteristics
Supply Voltage
Switch Voltage(SD42522)
Switch Voltage(SD42522EH)
Comp Voltage
SENSE voltage
Junction Temperature
Lead Temperature
Storage Temperature
Input Voltage
Operating Temperature
Symbol
V
IN
V
SW
V
SW
V
COMP
V
SENSE
T
j
T
L
T
STG
V
IN
T
OPR
Ratings
40
-1~V
IN
+1
60
-0.3~6
-0.3~VIN
150
260
-65~150
6~40
-40~125
Unit
V
V
V
V
V
°C
°C
°C
V
°C
ELECTRICAL CHARACTERISTICS
（Unless
otherwise specified, V
IN
=12V，I
OUT
=700mA,T
amb
=25°C）
Characteristics
Supply Voltage
Operating Current
Upper Switch Leakage
(SD42522)
Symbol
V
IN
I
IN
I
L
V
CC
=6/40V
V
SW
=36V
Test Condition
Min.
6
1.5
0
Typ.
Max.
36
2.0
10
Unit
V
mA
μA
HANGZHOU SILAN MICROELECTRONICS CO.,LTD
Http://www.silan.com.cn
REV:1.2
2010.11.03
Page 2 of 10
SD42522_Datasheet
Characteristics
Upper Switch Leakage
(SD42522EH)
Current Limit
Maximum Duty Cycle
(SD42522)
Maximum Duty Cycle
(SD42522EH)
Oscillator Frequency
COMP Clamp Voltage
Switch Transistor on
Resistance(SD42522)
Switch Transistor on
Resistance(SD42522EH)
V
DD
voltage
Sampling Voltage Threshold
Thermal Shutdown Threshold
Thermal Shutdown Hysteresis
Symbol
I
L
I
LIM
D
max
D
max
f
osc
V
COMP
R
ON
R
ON
V
DD
V
IN
-
V
SENSE
TSD
TSD-hys
Open without load
1LED, I
OUT
=0.7A
1LED, I
OUT
=0.7A
No load
Drop voltage between
V
IN
and SENSE
Test Condition
V
SW
=60V
V
IN
=SENSE=12V
3LED, V
IN
=9V
3LED, V
IN
=9V
1.6
--
--
250
1.6
--
--
5.0
--
Min.
Typ.
0
1.9
93
100
280
1.9
0.40
0.60
5.2
88
160
30
Max.
10
2.2
95
--
320
2.2
0.60
0.80
5.4
--
Unit
μA
A
%
%
kHz
V
Ω
Ω
V
mV
°C
°C
PIN CONFIGURATION
PIN DESCRIPTION
Pin No.
1
2
3
4
5
6
7
8
Pin Name
SW
GND
SENSE
V
IN
COMP
NC
V
DD
NC
I/O
I
O
I
O
I/O
-
I
-
Power output.
Ground.
Current sense pin.
Input supply voltage.
Compensation pin, connects to external capacitor.
No Connected.
5.2V reference output.
No Connected.
Description
FUNCTION DESCRIPTION
The SD42522/22EH is a current mode LED driver. The voltage on compensation pin COMP is proportional to the
HANGZHOU SILAN MICROELECTRONICS CO.,LTD
Http://www.silan.com.cn
REV:1.2
2010.11.03
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SD42522_Datasheet
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
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.
Output current setting
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).
I
OUT
=
V
IN
−
V
SENSE
R
S
2.
Current limiting
SD42522/22EH has internal current limiting function, and the voltage on COMP is clamped at about 1.6V, the
output current of the power MOSFET is limited at about 1.9A by current comparator.
3.
Frequency jitter
SD42522/22EH 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
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REV:1.2
2010.11.03
Page 4 of 10
SD42522_Datasheet
COMPONENTS SELECTION
1.
Input Capacitor Selection
The input capacitor provides the pulse current when the power MOSFET is on, and charge the capacitor when
the power MOSFET is off, thus to keep the stability of the input voltage. The input capacitor is recommended to
be more than 10μF, which can reduce the peak current drawn from input source and the switch noise. The input
capacitor should be near to the input pin in real routing.
2.
Output Capacitance Selection
Parallel connecting a capacitor between the two ends of LED can reduce the output voltage ripple accordingly
reduce the ripple current of LED, while this capacitor will not effect the operating frequency and efficiency, but the
start time will be longer by reducing the rising speed of the voltage on LED. The larger the output capacitor is, the
smaller the current ripple on LED is. It is recommend use the capacitor of 2.2μF or larger.
3.
Inductance Selection
The inductance is used to keep the output current constant, the bigger the inductance is, the smaller the output
current ripple is; while the bigger the physical size is, the bigger the series-wound resistor is. The selected
effective current (RMS current rating)of inductance current should be bigger than the maximum output current,
and the saturation current should be 30% bigger than maximum output current. In order to improve the efficiency,
the series-wound resistor (DCR) of inductance should be smaller than 0.2Ω.
The relation between inductance and ripple:
L
=
V
OUT
*
Where: L: Inductance value
F: Oscillator frequency
ΔI
is ripple current
V
IN
−
V
OUT
V
IN
* f *
ΔI
When select inductance, you should consider the combination of various factors to select suitable inductance.
4.
Diode Selection
SD42522/22EH is a non-synchronous step-down adjuster, so the diode should provide continuous current when
the power MOSFET is off. Because the forward voltage of Schottky diode is small, and the reverse continuous
current time is short, so it is usually used for continuous current. During the power MOSFET is conducting, the
diode will withstand high voltage, so the reverse voltage of selected diode should be bigger than the input voltage.
The average current through the diode is I
D:
ILED is the current of LED
When the input voltage is high with a small duty, ID increases, so the selected maximum continuous current
diode should be bigger than the output current.
I
D
=
(1
−
D) * I
LED
HANGZHOU SILAN MICROELECTRONICS CO.,LTD
Http://www.silan.com.cn
REV:1.2
2010.11.03
Page 5 of 10
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