SP7611A, SP7612A, SP7614A
Solved by
TM
2-4 Channel Low Dropout Linear LED Driver
N/C
3
VLED1
CTRL
2
1
FEATURES
SP7614A
LED Drivers for parallel connected LEDs
No EMI, no switching noise
Integrated current matching
PWM and Analog brightness control
Enable/Shutdown control
Shutdown current < 0.01µA
Tiny, RoHS Compliant Lead-Free
Package: SC-70
Part #
Channels
Maximum Steady
State Current per LED
SP7611A
4
40mA
SP7612A
3
40mA
SP7614A
2
80mA
6 Pin SC70
4
5
6
GND
VLED2
ON/OFF
Pinouts for SP7611A and SP7612A on page 3
APPLICATIONS
Ultra low cost Handsets
PDA, DSC, MP3 players
Handheld Computers
LCD Display Modules
Keyboard Backlight
LCD Backlight
DESCRIPTION
The SP761X driver family provides a simple solution for a matched current source for any color LED. The
current in the LEDs can be programmed by an external resistor. The SP7611A is capable of driving four
LEDs, while the SP7612A can drive three LEDs. The SP7614A is designed to drive two high current LEDs.
LED1 should always be connected to an LED and never left open in order to have the other LEDs driven with
a matched current to LED1. The SP7612A and SP7614A feature Enable pins for flexible on/off
control and PWM dimming. SP7612A/4A has extremely low (0.01uA typical) shutdown current, prolonging
the battery life and giving the longest standby period possible in today's modern design. SP761X driver
family is available in a small footprint 6-pin SC-70 package.
TYPICAL APPLICATION SCHEMATIC
VIN
I SET
VCONTROL
RSET
LED1
CTRL
LED2
®
®
SP7614A
ENABLE
Feb 27-07 Rev O
GND
SP7611A/7612A/7614A Low Dropout Linear LED driver
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2007 Sipex Corporation
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.
VLED1, VLED2, VLED3, VLED4 and ENABLE Voltage to GND................................................................................-0.3V to 6V
CTRL Voltage to GND . .........................................................................................................................................0.5V
Output Current (IOUT)...............................................................(SP7611A and 7612A)..........................................40mA
Output Current (IOUT)..................................................................(SP7614A)..........................................................80mA
Power Dissipation per Package - 6-pin SC-70 at TA =85°C...............................................................................190mW
Junction Temperature .......................................................................................................................................+150°C
Storage Temperature.......................................................................................................................... -55°C to +150°C
ESD Level.........................................................................................................................................................................................................4kV HBM
ESD Level.........................................................................................................................................................................................................1kV CDM
ELECTRICAL SPECIFICATIONS
Specifications are at TA=25°C, VIN = 3.3 to 5.5, ENABLE =VIN, ♦ denotes the specifications which apply over the
full operating temperature range, unless otherwise specified.
PARAMETER
PART #
MIN
TYP
LED Cathode Voltage
(VLED)
Ambient Temperature
Output Current
Multiplication Ratio in
Saturation (Note1)
Output Current
Multiplication Ratio
(Gain) (Note1)
LED to LED Current
Matching
Current in OFF Mode
Min. ENABLE ""ON
Voltage" (Note 2)
Max. ENABLE ""OFF
Voltage" (Note 2)
-40
20
MAX
UNITS
5.5
V
85
ºC
♦
SP7611A
SP7612A
SP7614A
SP7611A
SP7612A
SP7614A
SP7612A
SP7614A
SP7612A
SP7614A
140
200
CONDITIONS
See graph for LED
Current vs. Cathode
Voltage
ISET = 100µA
VLED = 300mV
ISET = 100µA
VLED = 150mV
260
365
435
505
730
870
1010
-3
0.8
3
%
♦
0.01
1
µA
♦
ISET = 100µA
VLED = 300mV
VENABLE = 0.0V
V
♦
ISET = 150µA
V
♦
3
0.5
ISET = 25µA
VLED = 0.5V
Note 1: Output current Multiplication Ratio (ILED/ISET) is not linear. For actual ratio and ILED please refer to typical
performance characteristics on page 4 and page 5.
Note 2: ENABLE "ON" is VON/OFF where ILED1 > 20mA @ VLED1 = 0.3V.
ENABLE "OFF" is V where I < 1A @ V > 0.3V.
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PIN DESCRIPTION
Pin #
Pin Name
SP7611A
1
2
3
4
5
6
6
CTRL
LED2
LED1
GND
LED4
LED3
SP7612A
DESCRIPTION
SP7614A
CTRL
LED2
LED1
GND
LED3
CTRL
LED1
NC
GND
LED2
ENABLE
ENABLE
Sets L E D Current
Connect to Cathode of
Connect to Cathode of
Ground
Connect to Cathode of
Connect to Cathode of
C h i p ON/ OFF/ D i s a b l e
L E D
L E D
L E D
L E D
PINOUTS
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2007 Sipex Corporation
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APPLICATION INFORMATION
SETTING THE LED CURRENT
The LED current is controlled by ICONTROL and
RSET according to the following formula:
ILED = Gain X (VCONTROL - VCTRL) / RSET
Gain depends on mode of operation
VCONTROL is the voltage going into RSET
VCTRL is the voltage at the pin of the device
The voltage VCTRL can be determined using the
ISET vs Control voltage graph located in the typical
performance characteristics section. As an
example, to set the LED current for an SP761x the
procedure is:
Take the LED current and divide it by the Gain to
get ISET = ILED / Gain.
Look up the VCTRL pin voltage using ISET on the
graph “Ctrl Current vs. Control Voltage”.
Once VCTRL is known, use the following formula to
find RSET. The gain is not linear, the LED current
vs. Cathode voltage graph needs to be used to
determine gain. Typically, the gain is ~870 for
SP7614A and ~435 for SP7611A/12A when the
part is operating in the linear region.
RSET =(VCONTROL - VCTRL) / ISET
RSET Example
For an SP7614A with VCONTROL of 3V and LED
current of 20mA.
ISET = 20mA/870 (870 is the typical gain in linear
operation) = 22uA.
Using the graph on page 5 in the typical
performance section, the VCTRL voltage on the
control pin will be about 1.1V, then RSET will be
determined by:
RSET = (3V - 1.1V) / 22uA
RSET = 86KΩ
TEMPERATURE CONSIDERATIONS
LEDs are very sensitive to temperature. In most
cases the maximum allowed junction temperature
is 100ºC. The case of overtemperature due to
power dissipation is de-scribed by the following:
TJ = TA + ӨJA x I x VF
where TJ is the LED junction temperature,
TA is the ambient temperature,
ӨJA is the junction to ambient thermal resistance,
I is the LED current and
VF is the LED forward voltage.
When the temperature rises and the cathode
voltage increases, SP761X reduces the current
through LEDs. Refer to "LED Current vs. LED
Cathode Voltage" graph under the Typical
Performance Characteristics section.
EFFICIENCY
The system efficiency, defined as the ratio
between the LED's power and the input supplied
power can be calculated as follows:
Efficiency = (VIN - VCATHODE) / VIN
The lower the VCATHODE , the higher the system
efficiency. Efficiency can be further improved
using a higher VIN with more LEDs as shown in
example 3. The SP761X driver's low dropout
architecture can significantly improve the
efficiency compared to using simple ballast
resistors.
APPLICATION INFORMATION
The ultra-low voltage drop across the SP761X
series of LED drivers allows the devices to drive
white, blue, and other color LEDs in a wide range
of input voltages. The driver can be used in many
PWM FUNCTION
The LED's brightness can also be
adjusted by driving either the ENABLE or the
CTRL pin with a PWM signal. The driving signal
frequency should be greater than 100Hz to avoid
flickering, increasing to more than 1MHz, if
necessary.
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APPLICATION INFORMATION
applications. Any of the SP761X series of LED
drivers can be used in the applications presented
in this document, due to their similar operation.
Example 1:
Drive low VF white or blue LEDs directly from
single cell Li-Ion
When using white or blue low VF LEDs, and
utilizing the driver's low voltage drop, only 3.4V
VIN is needed for the full 20mA LED current. At
3.1V, there is still 5mA of typical current available
for the LEDs.
The single cell Li-Ion battery is utilized in many
applications like cell phones or digital still
cameras. In most cases, the Li-Ion battery voltage
level only goes down to 3.0V, and not down to the
full discharge level (2.7V) before requesting the
charger.
VDROP < 0.3V. This is the dropout voltage for the
SP7611A.
- VF = 3.1V. Low VF white LED forward voltage
drop
- VIN (at 20mA) needs to be greater than
(VDROP+VF)
3.1V+.3V= 3.4V
Key Advantages
Key Advantages
1) No boost circuit needed for the LCD or
keyboard backlight.
2) Drivers utilize existing bus.
3) Ultra-low voltage drop provides the full 20mA
LED current at the lowest possible voltage level.
Example 3: Drive white, blue, red, amber LED string
In a boost circuit, or existing voltage bus, the
SP761X series of LED drivers can be used to
drive a whole string of LEDs and achieve flexible
brightness control - whether using analog or PWM.
1) No boost circuit needed for the LCD or
keyboard backlight.
2) Drivers directly connected to a Li-Ion battery.
3) No EMI, no switching noise, no boost converter
efficiency loss, 1 capacitor, and no inductor.
Example 2: Drive high VF white or blue LEDs
from existing bus ~ 4.0V to 5.5V
High VF LEDs have a forward voltage drop in the
range of 3.2V to 4.0V. In order to drive these LEDs
with the maximum current of 20mA, enabling
maximum brightness usually requires a boost
circuit for a single cell Li-Ion power supply. The
SP761X series is capable of driving high VF white
or blue LEDs with its ultra-low dropout feature.
The VIN needs to be only 300mV higher than the
highest VF in the circuit.
- VDROP < 0.3V. Dropout voltage of the SP7611A
- VF (at 20mA) < 3.3V to 4.0V (High VF)
- VIN (at 20mA) = VDROP + VF = 3.6V to 4.3V
- VIN (at 5mA typical) ~ 3.3V
Where VIN = Existing bus = 3.3V to 4.3V
Feb 27-07 Rev O
VDROP = 0.3V. Dropout voltage of the SP7611A
- VIN_MIN = N x VF + VDROP
- VIN_MIN = N x VF + 0.3V
Where VIN_MIN = Existing bus, boost Voltage
‘N’ number of LEDs Per Branch
VF = Forward voltage of the LED
Key Advantages
1) No need for current matching resistors
and discrete transistors for brightness
control.
SP7611A/7612A/7614A Low Dropout Linear LED driver
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2007 Sipex Corporation
APPLICATION INFORMATION
LED Brightness Control
The SP761X LED Drivers feature analog and
PWM controls to give designers flexible
brightness control. To determine the value of
RSET , use the "ISET vs. VCRTL" graph under
the Typical Performance Characteristics.
1. SP761X/A
- Analog using VCONTROL
Set VCONTROL and RSET for LED current
SETTING THE LED CURRENT – page 6
-
PWM using Enable
- Set VCONTROL and RSET for LED current
SETTING THE LED CURRENT – page 6
ENABLE = PWM
-Amplitude has no effect on current
-Pulse width controls current between 0 and
maximum LED set current
- PWM - Vcontrol
-Amplitude of PWM signal sets maximum LED
current
-Pulse width controls current between 0 and
maximum LED Set current
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2007 Sipex Corporation
BLOCK DIAGRAM
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SP7611A/7612A/7614A Low Dropout Linear LED driver
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2007 Sipex Corporation
PACKAGE: 6 PIN SC-70
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2007 Sipex Corporation
ORDERING INFORMATION
Part Number
SP7611AEC6
SP7611AEC6/TR
SP7612EC6
SP7612EC6/TR
SP7612AEC6
SP7612AEC6/TR
SP7614EC6
SP7614EC6/TR
SP7614AEC6
SP7614AEC6/TR
Temperature
Range
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
Package
Type
6 Pin SC70
6 Pin SC70
6 Pin SC70
6 Pin SC70
6 Pin SC70
6 Pin SC70
6 Pin SC70
6 Pin SC70
6 Pin SC70
6 Pin SC70
Available in Lead Free packaging. To order add "-L" suffix to part number.
Example: SP7614AEC6/TR = standard; SP7614AEC6-L/TR = Lead Free.
/TR = Tape and Reel.
Pack quantity is 2500 for SC70.
Sipex Corporation
Solved by
TM
Headquarters and
Sales Office
233 South Hillview Drive
Milpitas, CA95035
tel: (408) 934-7500
FAX: (408) 935-7600
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.
Feb 27-07 Rev O
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2007 Sipex Corporation
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