Solved by
SP7619/19A
TM
Constant Current LED Driver
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FEATURES
Very low dropout voltage (60mV@200mA)
Accurate current regulation down to dropout
voltage
No external components
Selectable output current levels: 200mA &
500mA (700mA for SP769A)
Power-saving shutdown mode of µA
Fast turn-on (<50µs)
Timeout function to protect the LED
Thermal Shutdown protection
RoHS compliant, Lead Free packaging:
Space saving 2mmx3mm 8pin DFN
LED
LED
VCC
EN
1
2
3
4
SP7619
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
GENERAL DESCRIPTION
The SP769 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 cur-
rent across a range of input voltages. The SP769 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 set at 200mA
at torch mode or 500mA (700mA SP7619A) at flash mode by selecting CTRL pin low/high
respectively. Dimming or shutdown can be done by feeding a PWM signal to the EN pin.
Fast EN turn-on/off time allows for very fast dimming frequencies, completely eliminating
flicker. The built-in thermal protection automatically stops LED current to prevent overheat-
ing. A timeout function serves as a fail safe, shutting down the output at 500mA (700mA)
current after 4 seconds of continuous operation if the enable input is not cycled. The Enable
pin should be cycled HIGH/LOW/HIGH to restart the driver.
TYPICAL APPLICATION CIRCUIT
Feb 9-07 Rev E
Constant Current LED Driver
© 2007 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°C/W
Junction Temperature ............. -40°C to +70°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
CONDITIONS
EN = GND, CTRL = DC
EN = Vcc, CTRL = Vcc
CTRL pin LOW
SP769 CTRL pin HIGH
SP769A CTRL pin HIGH
3.0 < Vcc < 5.5V,V
led
=V
.0 < V
led
< 2.5V, Vcc = 5.5V
I
led
= 200 mA
I
led
= 500mA for
SP769@25°C
I
led
=700 mA for
SP769A@25°C
I
led
=200 mA for both SP769 &
SP769A @25°C
I
led
= 200mA
Ambient temperature T
a
= 25°C, 3.0V < Vcc < 5.5V, .0V <
V
led
< 3.0V.
Bold
denotes specifications which apply
over the full operating temperature range, -40°C to +85°C.
PARAMETER
Vcc Voltage Operating Range
Shutdown
Mode
Supply Current
After Time
Duration
2
LED Output Current
LED Current Line Regulation
3
LED Current Load
Regulation
4
LED Current Thermal
Regulation
MIN
2.5
TYP
MAX
5.5
UNITS
V
µA
350
80
450
630
200
500
700
0.
.5
0.0
75
420
220
550
770
0.5
6
mA
%/V
%
%/°C
60
85
40
°C
50
50
30
°C
µs
µs
µs
s
V
mV
V
LED
Dropout Voltage
5
90
60
Thermal Shutdown Die
Temperature
Thermal Shutdown Hysteresis
Setup Time
6
Wake-up Time from Shutdown
Turn-off Time into Shutdown
Time Duration before Sleep
Mode
LOW
EN and CTRL pin
Logic Voltage
HIGH
Notes:
.
2.
3.
4.
5.
6.
7.
60
25
2
1.4
4
7
0.4
Vcc
7
EN = LOW to HIGH, CTRL =
DC
EN = HIGH to LOW, CTRL = DC
I
led
= 500/700 mA, EN = HIGH,
CTRL = HIGH
Driver in Shutdown Mode
2.5V ≤ Vcc ≤ 5.5V
Vcc must be always higher than LED pin voltage (V
led
)
After 4s at 500 (700) mA current
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
I
led
value at V
led
= V
I
led
settles 50µs
later after CTRL from LOW to HIGH or from HIGH to LOW
Logic HIGH level should never exceed Vcc voltage
Constant Current LED Driver
© 2007 Sipex Corporation
Feb 9-07 Rev E
2
PIN ASSIGNMENTS
Pin #
-2
3
4
5
6
7-8
Pin
Name
LED
Vcc
EN
CTRL
GND
GNDP
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 time count
Logic High – enable, Logic Low – disable/reset.
This pin is used to switch
I
led
current between two internally preset levels for
Flash or Torch mode. CTRL = LOW selects Torch mode (200mA), CTRL =
HIGH selects Flash mode 500 (700)mA.
Ground pin for control and bias blocks.
Ground pin. LED current flows through this pin to ground.
BLOCK DIAGRAM
Feb 9-07 Rev E
Constant Current LED Driver
© 2007 Sipex Corporation
3
APPLICATION INFORMATION
24
22
20
3
2
Error, %
Iled, mA
208
206
204
202
200
98
0
00
200
300
Vled, mV
25C
85C
400
500
600
0
-
-2
-3
-4
-5
Vled, V
200mA
700mA
0
0.5
.5
2
2.5
3
3.5
SP769 Load regulation at 200mA
I
led
current
SP769A Load Regulation at 25
°
C
550
500
450
Iled, mA
400
350
300
250
200
0
00
200
Vled, mV
25C
85C
300
400
500
SP769 Load regulation at 500mA
I
led
current
SP769 PWM modulation (Channel – PWM
signal 1kHz, 20% Duty cycle, 2V/div, Channel 3
-I
led
current - 1mV is equal 10mA current)
0.3
0.2
0.
Error, %
0
-0.
-0.2
-0.3
-0.4
Vcc, V
200mA
700mA
2.5
3
3.5
4
4.5
5
5.5
6
SP769A Line Regulation at 25
°
C
Feb 9-07 Rev E
Constant Current LED Driver
© 2007 Sipex Corporation
4
THEORY OF OPERATION
Introduction
The SP769 is a linear low-side constant
-current driver designed to drive high power
LEDs from an input voltage rail. The design
consists of a regulator reference voltage
source, voltage-to-current converter, thermal
shutdown, timeout shutdown, and output
driver. The precision reference voltage en-
sures good performance over voltage and
temperature. The built-in thermal protection
automatically stops LED current to prevent
overheating. A timeout function serves as a
failsafe, shutting down the output at Flash
Mode after 4 seconds of continuous opera-
tion if the enable input is not cycled.
Current Setting
The LED output current is defined by internal
circuitry. The input to this circuitry is the CTRL
pin. LOW logic level determines Torch Mode
while HIGH logic level determines Flash
Mode with appropriate output currents. The
ENABLE pin and CTRL pin logic HIGH level
may be applied with Vcc voltage. At Flash
Mode the maximum Time Duration is 4s.
After that, the device is automatically sent
into Sleep Mode. This function is intended
to protect the LED if, for example, the device
was left on in a high current condition for a
long period of time.
To return the device to the Flash Mode use
Shutdown (EN = HIGH to LOW/LOW to
HIGH). Switching the CTRL pin LOW during
Sleep Mode sets the device into Torch Mode.
The LED output current will reach its final
value 50µs after the CTRL pin transition from
LOW to HIGH or from HIGH to LOW.
Output Driver
The SP769 features a low-side regulated
output current driver. A large MOSFET device
is connected between the LED and GNDP
Feb 9-07 Rev E
pins. The MOSFET drain is connected to
the LED pins and the MOSFET source is
connected to the GNDP pins. There are
two pins on each terminal of the MOSFET
in order to minimize power dissipation inside
the package. Even though there are two LED
and GNDP pins, there is actually only one
output intended to drive one LED.
The light emitting diode connects from VCC
to LED pins. The
I
led
current regulation is
guaranteed at dropout at the LED pins to be
less than 00mV. The regulation attempts to
maintain the output current to within five per-
cent of nominal even if the voltage between
the LED and GNDP pins varies over a wide
range. The nominal output is guaranteed
within ±10% of the defined current.
Thermal Protection
The SP769 has built-in thermal protec-
tion. An internal
p
-
n
junction is compared
to the internal temperature-compensated
reference. When the
p
-
n
junction reaches a
temperature specific voltage it trips a com-
parator which shuts down the driver stage of
the part, placing the device into sleep mode
while current setting circuitry remains active.
The shutdown temperature is defined to be
60°C typical.
The comparator circuit has built-in hysteresis
corresponding to 25
°
C. The output stage will
resume operation and start sinking the cur-
rent that was defined prior to shutdown when
the internal temperature drops by 25
°
C. If the
part remains in a high ambient temperature
environment or if a high power dissipation
condition exists, the output stage will cycle on
and off to maintain a preset internal junction
temperature to avoid catastrophic damage.
In that case, the LED will appear to be blink-
ing. Lower the LED voltage to avoid excess
power dissipation in the IC.
© 2007 Sipex Corporation
Constant Current LED Driver
5
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