Solved by
SP7618
TM
Constant Current LED Driver
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FEATURES
Very low dropout voltage (00mV @ A)
Accurate current regulation down to dropout
voltage
No external components
Built-in current DAC
Output current adjustable with 33.3 mA/steps
Power-saving shutdown mode of µA
Fast turn-on (<50µs)
Timeout function to protect the LED
Thermal Shutdown protection
A current capability
RoHS compliant, Lead Free packaging:
Space saving 2mmx3mm 8pin DFN
LED
LED
VCC
EN
1
2
3
4
SP7618
8 Pin DFN
8
GNDP
7
GNDP
6
GND
5
CTRL
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APPLICATIONS
Next Generation Mobile Phones
PDA, DSC, MP3 Players
Handheld Computers
LCD Display Modules
Keyboard Backlight
GENERAL DESCRIPTION
The SP768 is a linear, low-side constant-current driver designed to drive high power LEDs
from an input voltage rail. The driver acts as a current source, ensuring constant LED current
for a range of input voltages. The SP768 allows implementing the lowest cost LED driver
for a variety of applications. Internal circuitry maintains the preset constant current output
for a wide voltage range at the LED input. The LED current can be adjusted up to 033mA
with an external clock applied to the CTRL pin. The built-in thermal protection automatically
stops LED current to prevent overheating. A timeout function serves as a failsafe, shutting
down the output for currents greater than 266mA after 4 seconds of continuous operation if
the enable input is not cycled. The part can be shut down by using the EN pin, or sent into
Sleep Mode holding the CTRL pin low for more than 00µS.
TYPICAL APPLICATION CIRCUIT
Date: Dec 5-06 Rev E
Constant Current LED Driver
© 2006 Sipex Corporation
Supply Voltage (Vcc) .………………………..6.0V
Input Voltage at any input .….-0.6V to Vcc +0.5V
8-pin DFN Package
Thermal Resistance................................ 59
0
C/W
Junction Temperature .......... -40
0
C to +70
0
C
*
Storage Temperature ..………...-65°C to +50°C
Soldering Temperature ...………………+240°C**
*) Internally limited
**) Duration 0s maximum
ABSOLUTE MAXIMUM RATINGS
These are stress ratings only and
functional operation of the device at
these ratings or any other above those
indicated in the operation sections of
the specifications below is not implied.
Exposure to absolute maximum rating
conditions for extended periods of time
may affect reliability.
ELECTRICAL CHARACTERISTICS
UNITS
V
µA
µA
nA
mA
8
0.5
6
00
85
20
%
%/V
%
%/°C
mV
°C
50
°C
µs
MHz
µs
µs
µs
s
V
ms
35mA <
I
led
< 033 mA
3.0 < Vcc < 5.5V,V
led
=V
< V
led
< 2.5V, Vcc =
5.5V
I
led
= 00 mA
I
led
= 00mA @ 25°C
I
led
= 700mA @ 25°C
I
led
= 033mA @ 25°C
I
led
= 35mA
CONDITIONS
I
led
= 35mA
EN = GND, CTRL = DC
EN = Vcc, CTRL = GND
EN = Vcc, CTRL = DC
V
led
= .0V, Vcc = 5.5V
Ambient temperature T
a
= 25°C, 3.0V < Vcc < 5.5V, .0V < VLED < 3.0V, 00mA < ILED <033A.
Bold
denotes
specifications which apply over the full operating temperature range, -40°C to +85°C.
PARAMETER
Vcc Voltage Operating Range
Quiescent Current
Shutdown Mode
Supply
Current
Sleep Mode
After Time Duration
2
LED
0 pulses on CTRL
3
Output
pulse on CTRL
4
Current
3 pulses on CTRL
4
after
3 pulses on CTRL
LED Current Accuracy
5
LED Current Line Regulation
6
LED Current Load Regulation
7
LED Current Thermal Regulation
V
LED
Dropout Voltage
8
Thermal Shutdown Die Tempera-
ture
Thermal Shutdown Hysteresis
Setup Time after last count
9
CTRL input Data Rate
Wake-up Time from Shutdown
Turn-off Time into Shutdown
Turn-off Time into Sleep Mode
Time Duration before Sleep Mode
EN and CTRL pin
Logic Voltage
Power-on-Reset
See notes on next page
Date: Dec 5-06 Rev E
MIN
2.5
TYP
350
MAX
5.5
420
350
350
25
35
02
033
-8
0.
.5
0.0
50
90
00
60
25
4
50
30
25
2
1.4
4
450
7
0.4
Vcc
10
20
LOW
HIGH
EN = LOW to HIGH,
CTRL = DC
EN = HIGH to LOW,
CTRL = DC
EN = HIGH, CTRL =
HIGH to LOW
I
led
> 266 mA, EN =
HIGH, CTRL = HIGH
Driver in Shutdown Mode
2.5V ≤ Vcc ≤ 5.5V
Constant Current LED Driver
© 2006 Sipex Corporation
2
Notes (Continued from previous page)
.
2.
3.
4.
5.
6.
7.
8.
9.
0.
.
Vcc must be always higher than LED pin voltage (V
led
)
After 4s at current higher than 266 mA
Power MOSFET leakage current
Three initial
I
led
current steps are higher than other 28
I
led
Variations from specified
I
led
value
I
led
Variations per volt Vcc change
I
led
Variations at V
led
change from to 2.5V
5% change of I
LED
compared with ILED value at V
led
= V
I
led
= 00 mA settles 50µs later after 3rd pulse
Logic HIGH level should never exceed Vcc voltage
Delay between applying Vcc voltage and operating condition
PIN ASSIGNMENTS
Pin Function
LED Current Sink. Connect LED cathode to this pin. Voltage at this pin
should be above 00 mV to maintain regulation.
Power Supply Input. Place µF decoupling capacitor next to this pin.
Enable/Shutdown pin used to enable/disable driver and reset DAC: Logic
High – enable, Logic Low – disable/reset.
DAC Serial Input pin is used to control LED current. Positive pulse edges
sequentially increase LED current with 33.33mA steps up to 033 mA (3
steps). When this pin is held LOW for longer than 00µs the part enters
Sleep Mode.
Ground pin for control and bias blocks.
Ground pin. LED current flows through this pin to ground.
Pin
#
-2
3
4
5
Pin
Name
LED
Vcc
EN
CTRL
6
7-8
GND
GNDP
BLOCK DIAGRAM
Date: Dec 5-06 Rev E
Constant Current LED Driver
© 2006 Sipex Corporation
3
APPLICATION INFORMATION
200
000
800
Iled, mA
600
400
200
0
0
0.5
.5
Vled, V
3 pulses
7 pulses
5 pulses
3 pulses
2
2.5
3
3.5
Load regulation at Vcc = 5.5V @ 25°C
200
000
800
Iled. mA
600
400
200
0
0
0.2
0.4
Vled, V
3 pulses
7 pulses
5 pulses
3 pulses
0.6
0.8
Load regulation at Vcc = 5.5V @ 25°C
00
050
000
950
900
850
800
750
700
0
00
200
300
25C
400
85C
500
600
700
Load regulation vs. temperature at
I
led
= A and Vcc = 5.5V
Date: Dec 5-06 Rev E
Constant Current LED Driver
© 2006 Sipex Corporation
4
APPLICATION INFORMATION
200
000
800
ILED, mA
600
400
200
0
0
5
0
5
20
25
30
35
Number of pulses
DAC linearity at V
led
= 500mV
0.3
0.2
0.
Line regulation, %
0
-0.
-0.2
-0.3
-0.4
-0.5
Vcc, V
2.5
3
3.5
4
4.5
5
5.5
6
Line regulation at V
led
= 00mA
Setup Time at
I
led
= 033A
Date: Dec 5-06 Rev E
Constant Current LED Driver
© 2006 Sipex Corporation
5
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