®
PRELIMINARY
SP7611A/7612/7614
Low Dropout LED Driver for any Color LED
FEATURES
■
LED Drivers for parallel connected LEDs
■
Ultra Low Dropout Voltage of 150mV
(SP7614)
■
No EMI, no switching noise
■
Integrated current matching
■
PWM and Analog brightness control
■
Enable/Shutdown control
■
Shutdown current < 1µA
■
Small footprint SC-70 Package
P/N
SP7611A
SP7612
SP7614
Channel
4
3
2
I
BIAS
160
120
160
I
BIAS
/LED
40
40
80
N/C
LED1
CTRL
3
2
1
SP7614
6 Pin SC70
4
GND
5
LED2
6
ON/OFF
Now Available in Lead Free Packaging
APPLICATIONS
■
Next Generation Mobile Phones
■
PDA, DSC, MP3 players
■
Handheld Computers
■
LCD Display Modules
■
Keyboard Backlight
■
LED Displays
DESCRIPTION
The SP761X driver family provides a simple solution for a matched current source any color LED.
The current in the LEDs can be programmed by an external resistor. The Individual LED currents
are 200 x ISET, where ISET is the current through the external resistor connected to the CTRL
pin. The SP7611A is capable of driving four LEDs, while the SP7612 can drive three LEDs. The
SP7614 is designated to drive two high current LEDs. LED1 should always be connected to an
LED in order to have the other LEDs driven with a matched current to LED1.
The SP7612 and SP7614 have Enable pins. When these devices are disabled, the supply current
drops to 0.01µA typical.
The SP7611A, SP7612 and SP7614 drivers are available in a small footprint 6-pin SC-70
package.
TYPICAL APPLICATION SCHEMATIC
VIN
I SET
V CONTROL
RSET
ENABLE
LED1
CTRL
®
LED2
SP7614
ON/OFF
GND
Date: 6/30/04
SP7611A/7612/7614 Low Dropout LED Driver for Any Color LED
© Copyright 2004 Sipex Corporation
1
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.
V
LED1
, V
LED2
, V
LED3,
V
LED4
and EN Voltage to GND......................................................................................-0.3V to 6V
CTRL Voltage to GND . .........................................................................................................................................0.5V
Output Current (I
OUT
).............................................................................................................................................80mA
Power Dissipation per Package - 6-pin SC-70 at T
A
=85°C...............................................................................190mW
Junction Temperature.........................................................................................................................................+150°C
Storage Temperature.......................................................................................................................... -55°C to +150°C
ESD Level.
......................................................................................................................................................................................................
4kV HBM
ESD Level.
......................................................................................................................................................................................................
1kV CDM
ELECTRICAL CHARACTERISTICS
Specifications are at T
A
=25°C, V
IN
=3.3to 5.5, ENABLE =V
IN
,
♦
denotes the specifications which apply over
the full operating temperature range, unless otherwise specified.
PARAMETER
LED Cathode Voltage
P/N
SP7611A
SP7612
SP7614
Ambient Temperature
SP7614
MIN.
0.3
0.5
0.15
-40
20
85
ºC
1
V
TYP.
MAX.
UNITS
PARAMETER
Output Current Multiplication
Ratio (Note 1)
P/N
SP7611A
SP7612
MIN.
TYP.
MAX.
UNITS
♦
CONDITIONS
I
SET
= 100µA
V
SAT
= 300mV
I
SET
= 100µA
V
SAT
= 150mV
I
SET
= 100µA
V
SAT
= 300mV
I
SET
= 100µA
V
SAT
= 150mV
No Load
V
IN
= 3V
V
EN
= 0V
I
SET
= 150µA
140
SP7614
LED Current I
LED
(Per Diode)
SP7611A
SP7612
200
260
♦
♦
20
mA
♦
-3
0.8
90
0.01
1
3
0.5
3
%
%
µA
V
V
♦
♦
♦
♦
♦
SP7614
LED to LED Current Matching
Peak Efficiency
Current in OFF Mode
Min. ENABLE "ON Voltage"
Max. ENABLE "OFF Voltage"
SP7612
SP7614
SP7612
SP7614
Note 1: Output current Multiplication Ratio (I
LED
/I
SET
) is not linear. For actual ratio and I
LED
please refer to typical
performance characteristics @ page 4.
Date: 6/30/04
SP7611A/7612/7614 Low Dropout LED Driver for Any Color LED
© Copyright 2004 Sipex Corporation
2
PIN DESCRIPTION
PIN NAME
Pin No.
SP7611A
1
2
3
4
5
6
ON/OFF
ON/OFF
Chip ON/OFF/Disable
CTRL
LED2
LED1
GND
LED4
LED3
SP7612
CTRL
LED2
LED1
GND
LED3
SP7614
CTRL
LED1
NC
GND
LED2
Sets LED Current
Connect to Cathode of LED
Connect to Cathode of LED
Ground
Connect to Cathode of LED
Connect to Cathode of LED
DESCRIPTION
PINOUT
LED1
LED2
CTRL
LED1
LED2
CTRL
3
2
1
3
2
1
SP7611A
6 Pin SC70
SP7612
6 Pin SC70
4
GND
5
LED4
6
LED3
4
GND
5
LED3
6
ON/OFF
N/C
LED1
CTRL
3
2
1
SP7614
6 Pin SC70
4
GND
5
LED2
6
ON/OFF
Date: 6/30/04
SP7611A/7612/7614 Low Dropout LED Driver for Any Color LED
© Copyright 2004 Sipex Corporation
3
TYPICAL PERFORMANCE CHARACTERISTICS
ISET versus CTRL Voltage
Vk=1V
200.0
180.0
140.0
120.0
100.0
80.0
60.0
40.0
20.0
0.0
0.00
0.20
0.40
0.60
0.80
1.00
1.20
1.40
1.60
1.80
Vk=150mV
LED Current versus Enable Voltage
18.000
LED Current (mA)
160.0
Set Current (µA)
16.000
14.000
12.000
10.000
8.000
6.000
4.000
2.000
0.000
CTRL Pin Voltage (V)
VEN Voltage (V)
ILED vs Set Resistor and Cathode Voltage
Vk=200mV
Vk=250mV
Vk=300mV
SP7614 LED Current vs. LED Cathode Voltage
35
20.0
18.0
16.0
LED Current (mA)
LED Current (mA)
14.0
12.0
Vk=100mV
Vk=150mV
30
25
20
15
10
5
0
0.2
0.4
0.6
0.8
1
LED Cathode Voltage (V)
For Iset = 25uA
For Iset = 50uA
10.0
8.0
Vk=50mV
6.0
4.0
2.0
10
20
30
40
50
60
70
80
90
100
Set Resistor (kOhms)
PWM LED Current vs. Temperature
Iset=100uA, Vcathode=150mV
25
24
ILED(mA)
23
22
21
-40 -30 -20 -10
0
10
20
30
40
50
60
70
80
Temperature (C)
Control Voltage Transient Response
[
T
Enable Voltage Transient Response
[
]
T
]
LED Current
(20mA/div)
LED Current
(20mA/div)
T
T
CTRL Voltage
(1V/div)
CTRL Voltage
(1V/div)
T
T
Time (1µs/div)
Time (1µs/div)
Date: 6/30/04
SP7611A/7612/7614 Low Dropout LED Driver for Any Color LED
© Copyright 2004 Sipex Corporation
4
APPLICATION INFORMATION
SETTING THE LED CURRENT
The current flowing into LEDs is approximately 200
times greater than the current I
SET
. The LED current is
controlled by I
CONTROL
and R
SET
according to the follow-
ing formula
:
I
LED
= 200 X (V
CONTROL
- V
CTRL
) / R
SET
For V
CONTROL
= 3V and a specified LED current, the R
SET
value can be evaluated using the diagram shown in the
Typical Performance Characteristics section. For any
other option, I
SET
vs. V
CTRL.
The LED's brightness can
also be adjusted by driving 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.
LEDs are very sensitive to temperature. In most cases
the maximum allowed junction temperature is 100ºC.
This temperature is the result of adding to the ambient
temperature the over temperature due to power dissipa-
tion, is described by the following:
T
j
= T
A
+ Ø
jA
x I xV
F
where T
j
is the LED junction temperature, T
A
is the
ambient temperature, Ø
jA
is the junction to ambient
thermal resistance, I is the LED current and V
F
is the LED
forward voltage
.
The SP7611AA to SP7614 are designed to reduce the
current through LEDs, when the temperature rises and
the cathode voltage increases, as can be seen from
typical the "LED Current vs. LED Cathode Voltage"
graph under the Typical Performance Characteristics
section.
APPLICATION NOTES
The ultra-low voltage drop across the SP761X series of
LED drivers, allow the devices to drive white, blue, and
other color LEDs in a wide range of input voltages. The
driver can be used in many applications. Although, only
the SP7611A is shown in all three examples, any of the
SP762X series of LED drivers can be used in the
applications presented in this document, due to their
similar operation.
Example 1: Drive low V
F
white or blue LEDs directly
from single cell Li-ion
When using white or blue low V
F
LEDs, and utilizing the
drivers low voltage drop, only 3.4V in V
IN
is needed for the
full 20mA LED current. At 3.1V, there is still 5mA typical
current available for the LEDs. The single cell Li-ion is
utilized in most applications like cell phones or digital still
cameras. In most cases, the Li-ion battery voltage level
only goes down to 3.0V voltage level, and not down to the
full discharge level (2.7V) before requesting the charger.
VIN
I SET
V CONTROL
RSET
ENABLE
LED4
CTRL
LED3
LED2
®
LED1
SP7611
ON/OFF
GND
- T
DROP
< 0.3V
- V
F
(at 20mA) < 3.1V (Low V
F
)
- V
IN
(at 20mA) < - V
DROP
+V
F
= 3.4V
- V
IN
(at 5mA typical) ~ 3.1V
Key Advantages
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 efficiency lost,
no capacitor, and no inductor
The SP761X driver's low dropout architecture can sig-
nificantly improve the efficiency compared to using simple
ballast resistors.
The system efficiency, defined as the ratio between the
LEDs power and the input supplied power can be
calculated as follows:
Efficiency = (V
IN
- V
CATHODE
) / V
IN
The lower the V
CATHODE
, the higher the system effi-
ciency. Efficiency can be further improved using a higher
V
IN
with more LEDs as shown in example 3.
Date: 6/30/04
SP7611A/7612/7614 Low Dropout LED Driver for Any Color LED
© Copyright 2004 Sipex Corporation
5
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