SP1821
Four Channels Constant Current LED Driver
DESCRIPTION
The SP1821 is a linear constant current driver designed
to drive multiple LEDs in series from a high input
voltage rail. The driver acts as a high current matched,
four-channel current source ensuring constant LED
current for a range of input voltages. The device can
drive up to 25mA load current per string with an
external resistor. The SP1821 can provide lowest cost
for various applications. Internal thermal protection
automatically turns off LED current to prevent
overheating. The dimming can be achieved by
controlling the I
SET
input or by feeding a PWM signal to
the EN pin. The device can be shut down by setting
Enable low.
APPLICATIONS
MR16 and other decoration light source
General reading lighting
Display Backlight
12V Battery powered devices
FEATURES
Low Cost LED Driver
Constant Current Output
Four Channels LED Driver Provides Matching
LED Current
Low Quiescent Current
Disconnects LEDs in Shutdown Mode
Thermal Shut Down Protection
Current Adjustable via external resistor
Dimming Control thru either Enable or Iset
PIN CONFIGURATION(SOP – 8P)
PART MARKING
2010/04/10
Ver.2
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SP1821
Four Channels Constant Current LED Driver
TYPICAL APPLCATION CIRCUIT
PIN DESCRIPTION
Pin
1
2
3
4
5
6
7
8
Symbol
VCC
GND
EN
I
SET
LED1
LED2
LED3
LED4
Description
Supply Voltage Input
Ground
High Enable Pin
Current Set Input
LED 1
LED 2
LED 3
LED 4
ORDERING INFORMATION
Part Number
SP1821S8RGB
Package
SOP- 8P
Part
Marking
SP1821
※
SP1821S8RGB : 13” Tape Reel ; Pb – Free ; Halogen – Free
2010/04/10
Ver.2
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SP1821
Four Channels Constant Current LED Driver
BLOCK DIAGRAM
ABSOULTE MAXIMUM RATINGS
(T
A
=25
℃
Unless otherwise specified)
Parameter
DC Supply Voltage
Output LED Current
Operating Temperature
Maximum Junction Temperature
Storage Temperature
Symbol
V
cc
I
LED
T
OPR
T
J(Max)
T
S
Value
12
25
-40½85
125
-65½150
Unit
V
mA
℃
℃
℃
The IC has a protection circuit against static electricity. Do not apply high static electricity or high voltage that
exceeds the performance of the protection circuit to the IC.
2010/04/10
Ver.2
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SP1821
Four Channels Constant Current LED Driver
ELECTRICAL CHARACTERISTICS
(T
A
=25
℃
, V
IN
=12V, R
SET
=31.6KOhm, V
LED
=12V, Unless otherwise specified)
Parameter
Operating Voltage
LED Current
Current Matching CH to CH
Quiescent Current
Line Regulation
I
SET
Voltage
Enable Voltage High
Enable Voltage Low
Thermal Shutdown Threshold
Thermal Shutdown Hysteresis
Current Off Mode
600
Conditions
Min.
10.5
22.5
700
4.5
Typ.
25
+/-1.5
800
5
1.5
5
130
20
700
800
Max.
12
27.5
+/-3.5
900
6
5.5
0.4
Unit
V
mA
%
μA
%/V
V
V
V
℃
℃
uA
ILED = 0A, Rset = Open
ILED change per volt Vcc change
10.5V≤Vin≤12V
10.5V≤Vin≤12V
2010/04/10
Ver.2
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SP1821
Four Channels Constant Current LED Driver
PERFORMANCE CHARACTERISTICS
(T
A
=25
℃
, unless otherwise specified.)
ILED vs. Vcc
27
Rset vs. ILED
24
22
20
24
21
18
16
IL E D (m A )
12
18
ILE D (m A )
15
14
12
10
8
6
4
2
0
20 30 40 50 60 70 80 90 100 110 120 130 140 150 160 170 180 190 200
Rset(KΩ)
12
ILED1(mA)
ILED2(mA)
9
ILED3(mA)
ILED4(mA)
6
3
0
10.5
11
11.5
Vcc(V)
APPLICATION INFORMATION
CIRCUIT DESCRIPTION
SP1821 is a four channels white-LED driver with matching current output. The matching current regulator has a
460:1 ratio between ILED and I
SET
. SP1821 is capable to supply 25mA for each channel with proper selection of
external resistor. The design has a band gap regulator, voltage to current converter and mirror drivers.
THERMAL PROTECTION
SP1821 has a thermal comparator to shut down the device when the internal temperature reaches 150℃. It will
remain shut down until the temperature drops to 130℃.
ENABLE
SP1821 has an enable pin that is designed for TTL input. The device will be active at voltage high. This pin can
also be used to control the brightness of LED with a PWM signal. The brightness is proportional to the duty cycle
of the PWM signal. When duty cycle is zero, LEDs are turned off. For 50% duty cycle, it will result an average
ILED to be half the programmed LED current which is set by R
SET.
ISET
The I
SET
Pin is a voltage input to set the current of LED. An external resistor is used to set the output current, as
approximated with the following equation:
R
SET
= 460 * (1.3V/ILED)
However, the R
SET
shall not be selected to exceed the maximum current delivery capability of the device, 25mA. A
PWM signal or analog signal can also be applied at I
SET
pin to control the LED brightness.
2010/04/10
Ver.2
Page 5
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