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1
Date: 08/31/05
SP7615 Four Channel Constant Current LED Driver Copyright 2005 Sipex Corporation
SP7615
The SP7615 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 SP7615 allows
implementing the lowest cost LED driver for a variety of applications. Internal circuitry
maintains the pre-set constant current output for a wide voltage range at the LED outputs
(LED1,2,3,4). LED current can be adjusted up to 125mA per string with an external resistor.
The dimming can be achieved by controlling the
I
SET
input or by feeding a PWM signal to
the EN pin. Fast EN turn-on and turn-off time allows for very fast PWM dimming frequencies,
completely eliminating flicker. The built-in thermal protection automatically adjusts LED
current to prevent overheating.
TYPICAL APPLICATION SCHEMATIC
FEATURES
Cost Effective LED driver
Constant current output ideal for Driving LED strings
Four Channel LED Driver provides matched LED
current
Current adjusted via an external resistor
PWM dimming possible
Small 2mm x 3mm DFN package
Outputs can be connected in parallel to
increase drive
Constant current for wide cathode voltage range
(1.0V to 16V)
Highly integrated design, minimal components
Thermal shutdown protects the driver
APPLICATIONS
Next Generation Mobile Phones
PDA, DSC, MP3 Players
Handheld Computers
LCD Display Modules
Keyboard Backlight
LED Displays
Four Channel Constant Current LED Driver
Preliminary
Now Available in Lead Free Packaging
DESCRIPTION
SP7615
8 Pin DFN
8
7
6
5
1
2
3
4
LED1
LED2
LED3
LED4
EN
GND
ISET
VCC
V
CC
EN
GND
C1
1n
R1
SP7615
EN
GND
LED1
V
CC
I
SET
LED2
LED3
LED4
2
Date: 08/31/05
SP7615 Four Channel Constant Current LED Driver Copyright 2005 Sipex Corporation
4.5V < V
CC
<16V , V
EN
= 5V, V
LED1
=V
LED2
=V
LED3
=V
LED4
=1.0V, R
SET
=10k or I
SET
=126A, -40 < T
A
< 85C,
Unless otherwise noted. Typical numbers are for T
A
= 25C.
ISET and EN Voltage to GND..................................... 6V
Output Current per LED (I
OUT
) ............................. 150mA
Power Dissipation per Package
8-pin DFN at TA = 85C ......................... 1.1W
Junction Temperature ..........................................+150C
Storage Temperature ........................... -55C to +150C
ESD Level. ....................................................... 2kV HBM
DFN Thermal Resistance......................................59C/W
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.
ABSOLUTE MAXIMUM RATINGS
Note 1. ENABLE "ON" is V
EN
for which I
LED
>
80mA
Note 2. ENABLE "OFF" is V
EN
for which I
LED
< 1uA@ V
LED1
> 1.0V
Vcc, V
LED1
, V
LED2
, V
LED3,
V
LED4
Voltage to GND 0.3V to 16V
ELECTRICAL CHARACTERISTICS
PARAMETER
MIN.
TYP.
MAX.
UNITS
CONDITIONS
Supply Voltage
4.5
5
16
V
Quiescent Supply Current
20
39
mA
I
LED1
= I
LED2
= I
LED3
= I
LED4
=126mA
Output/I
SET
Current Multiplication Ratio
700
1000
1200
LED Current (per diode)
126
mA
LED to LED Current Matching
-5
5
%
LED Current Line Voltage Regulation
0.15
0.6
%/V
I
OUT
change per volt V
CC
change
LED Current Load Voltage Regulation
2
4
%/V
0.4V < V
LED
< 5V, I
LED
= 25mA
9
%/V
1.0V < V
LED
< 5V, I
LED
= 126mA
LED Current Thermal Regulation
0.1
%/C
I
LED
= 126mA
I
SET
Pin Voltage
1.17
1.26
1.39
V
I
SET
= 1
A
Thermal Shutdown Threshold
150
C
Thermal Shutdown Hysteresis
20
C
Current in OFF Mode
1
A
V
EN
= ZeroV
Min. ENABLE "ON Voltage"
(Note1)
1.6
V
Max. ENABLE "OFF Voltage"
(Note 2)
0.4
V
3
Date: 08/31/05
SP7615 Four Channel Constant Current LED Driver Copyright 2005 Sipex Corporation
BLOCK DIAGRAM
Introduction
The SP7615 is a four channel constant current
source LED driver with programmable output
current level. The design consists of a regulator
bandgap, voltage to current converter, and
output mirror drivers. The bandgap ensures
good performance over voltage and
temperature. The four outputs are tightly
coupled allowing for excellent channel
matching.
Thermal Shutdown
The SP7615 uses a thermal comparator to
monitor the system temperature shutting the
device down if the internal temperature reaches
150
C. The device will remain off until the
internal temperature drops below 130
C.
Enable
The device has an enable function that is
designed for TTL level inputs. This input will
also track the V
CC
pin so levels up to V
CC
are
THEORY OF OPERATION
Figure 1. SP7615 Block Diagram
V
CC
GND
EN
I
SET
LED1
LED2
LED3
LED4
Bias
Driver
Thermal
Shutdown
V to I
Converter
acceptable. The enable pin can also be used to
control the LED brightness with a pulse width
modulated control signal. Duty Cycle or PWM
control of the LED current maintains constant
LED color while brightness is changing. The
SP7615 responds in less than 10s to PWM
signals applied to this pin.
I
SET
Pin
The I
SET
pin is the servo point of an amplifier
configured as a voltage to current converter.
The voltage at this pin trips servos to the
internal bandgap potential. A set resistor can
be connected from the I
SET
pin to ground to
generate a reference current for the following
current gain stages. A current could
alternately be applied to this pin in the form
of a current source or current output DAC.
This pin can also have a PWM signal applied
to control the LED brightness.
4
Date: 08/31/05
SP7615 Four Channel Constant Current LED Driver Copyright 2005 Sipex Corporation
THEORY OF OPERATION
V
CC
EN
GND
C1
1n
R1
D1
LED
SP7615
EN
GND
LED1
V
CC
I
SET
LED2
LED3
LED4
The R
SET
value may be determined as R
SET
=
1.26 * 1000/I
OUT,
k where 1.26 is a typical
I
SET
pin voltage, 1000 is a typical current
multiplication ratio, and I
OUT
is a required
LED current in mA.
The voltage applied to the cathode of each
LED determines the overall efficiency of the
SP7615 circuit. The SP7615 is designed to
be able to sink 125mA at each of its four
outputs; LED1 - 4. The SP7615 is also
designed to be able to handle up to 16V on
these pins. This voltage handling capability
assumes the total power can be dissipated
by the SP7615. The power dissipation inside
the SP7615 will de directly related to the
voltage and current applied to these pins.
For example, the typical operating cathode
voltage is 500mV. At maximum current the
V
CC
EN
GND
C1
1n
R1
R2
SP7615
EN
GND
LED1
V
CC
I
SET
LED2
LED3
LED4
SP7615
EN
GND
LED1
V
CC
I
SET
LED2
LED3
LED4
power dissipated by one LED driver output
is 125mA * 500mV = 62.5mW. The following
charts show the power dissipation of the
SP7615 under various conditions. The
power dissipation should be kept below
1.3W for safe operation and long term
reliability at room temperature and derates
to 530mW at 85
C. While the above
operating conditions are recommended, the
part cannot be damaged due to internal
temperature control as described above in
the thermal shutdown section.
CATHODE VOLTAGE, SUPPLY VOLTAGE
AND POWER DISSIPATION
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Date: 08/31/05
SP7615 Four Channel Constant Current LED Driver Copyright 2005 Sipex Corporation
PERFORMANCE GRAPHS
Figure 2 Four Channel Total Power Dissipation versus Cathode Voltage at V
CC
= 5V
Figure 3 Four Channel Total Power Dissipation versus Supply Voltage at Vcathode =
500mW
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Date: 08/31/05
SP7615 Four Channel Constant Current LED Driver Copyright 2005 Sipex Corporation
Figure 4 LED Current versus
I
SET
Current and Cathode Voltage, Vcc=5V, T= 27
C
TYPICAL PERFORMANCE CHARACTERISTICS
Figure 5 LED Current versus R
SET
Value
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Date: 08/31/05
SP7615 Four Channel Constant Current LED Driver Copyright 2005 Sipex Corporation
Figure 6 LED Current versus Temperature with Thermal Shutdown
Figure 7 I
SET
Voltage versus Temperature
TYPICAL PERFORMANCE CHARACTERISTICS
8
Date: 08/31/05
SP7615 Four Channel Constant Current LED Driver Copyright 2005 Sipex Corporation
Figure 8 PWM Signal Applied To The Enable Pin, Amplitude=5V, Duty Cycle=50%
TYPICAL PERFORMANCE CHARACTERISTICS
9
Date: 08/31/05
SP7615 Four Channel Constant Current LED Driver Copyright 2005 Sipex Corporation
PACKAGE: 8 PIN DFN
4
3
2
1
5
6
7
8
INDEX AREA
(D/2 x E/2)
BOTTOM VIEW
b
e
L
K
D2
E2
E2/2
D2/2
Pin1 Designator
to be within this
INDEX AREA
(D/2 x E/2)
TOP VIEW
D
E
E/2
D/2
(A3)
A1
A
SIDE VIEW
Seating Plane
MIN
NOM
MAX
MIN
NOM
MAX
A
0.80
0.90
1.00
0.032
0.036
0.039
A1
0.00
0.02
0.05
0.000
0.001
0.002
A3
K
0.20
-
-
0.008
-
-
0...
-
14...
0...
-
14...
b
0.18
0.25
0.30
0.008
0.010
0.012
D
D2
1.50
-
1.75
0.059
-
0.069
E
E2
1.60
-
1.90
0.063
-
0.075
e
L
0.30
0.40
0.50
0.012
0.016
0.020
2x3 8 Pin DFN JEDEC MO-229 VARIATION VCED-2
Dimensions in Millimeters:
Controlling Dimension
Dimensions in Inches
Conversion Factor:
1 Inch = 25.40 mm
3.00 BSC
0.118 BSC
SYMBOL
SIPEX Pkg Signoff Date/Rev: JL Aug18-05 / RevA
0.20 REF
0.008 REF
0.079 BSC
2.00 BSC
0.020 BSC
0.50 BSC
10
Date: 08/31/05
SP7615 Four Channel Constant Current LED Driver Copyright 2005 Sipex Corporation
Corporation
ANALOG EXCELLENCE
Sipex Corporation reserves the right to make changes to any products described herein. Sipex does not assume any liability arising out of the
application or use of any product or circuit described herein; neither does it convey any license under its patent rights nor the rights of others.
Sipex Corporation
Headquarters and
Sales Office
233 South Hillview Drive
Milpitas, CA 95035
TEL: (408) 934-7500
FAX: (408) 935-7600
Part Number
Operating Temperature Range
Package Type
SP7615ER .................................................. -40C to +85C ............................................ 8 Pin DFN (2 x 3mm)
SP7615ER/TR ............................................ -40C to +85C ............................................ 8 Pin DFN (2 x 3mm)
/TR = Tape and Reel
Pack quantity is 3000 for DFN.
Available in lead free packaging. To order add "-L" suffix to part number.
Example: SP7615ER/TR = standard; SP7615ER-L/TR = lead free
ORDERING INFORMATION
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