SP7120/22
2 or 3 Channel Low Dropout
High Side Linear LED Driver
FEATURES
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LED Driver for common cathode parallel
connected LEDs
Ultra Low Dropout Voltage of 150mV
No EMI, no switching noise
Integrated current matching
PWM and Analog brightness control
Enable/Shutdown control
Shutdown current < 1μA
Lead Free, RoHS Compliant Package:
Small footprint SOT23-6
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APPLICATIONS
Mobile Phones
PDA, DSC, MP3 players
Handheld Computers
Keypads and display backlight
GENERAL DESCRIPTION
The SP712X driver’s family provides a simple solution for a matched current source for any
color common cathode LED configuration. The common cathode connection allows the user to
increase the LED power dissipation by having the cathodes heat-sinked to the ground plane of
the circuit board. The SP7120 may drive two LEDs or one LED at twice the current with two
channels connected in parallel. The SP7122 can drive three LEDs or one LED at three times
the current. The factory preset current values are 15mA (version A), 20mA (version B), or 25mA
(version C) per channel. In shutdown mode (EN pin is LOW), the supply current drops to 40nA
typical.
The SP712x drivers are available in a small footprint 6-pin SOT23-6 package.
APPLICATION SCHEMATIC
C1 1nF
SP7120 Powering 2 LEDs
Jan 7 ‘08 RevE
SP7120/22 Low Dropout LED Driver
© 2007 Sipex Corporation
page
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
period may affect reliability.
RECOMMENDED OPERATING CONDITIONS
Ambient operating temperature ..…. -40 to+85°C
Vcc, V
LED1
, V
LED2
, and EN to GND -0.3V to 6V
Junction Temperature............................+150°C
Operating Temperature…..........….-40 to +85
o
C
Storage Temperature...............-65°C to +150°C
Package Thermal resistance
θ
JA
….…190°C/W
ESD Level...........................................2kV HBM
ESD Level...........................................200V MM
ESD Level EN……………….……….1.5kV HBM
Lead Temperature (Soldering, 10 sec) …300°C
ELECTRICAL CHARACTERISTICS
Specifications are at T
A
=25˚C, Vcc = 2.7 to 5.5, ENABLE =Vcc
Parameter
Vcc
Shutdown Current
VLED Dropout Voltage, Vd
1
VLED Dropout voltage, Vd
1
Version A
LED Current
Version B
Accuracy
2
Version C
Version A
Version B
Quiescent
Version C
Current
Version A
Version B
Version C
LED to LED Current Matching
6
LED Current Line Regulation
3
LED Current Load Regulation
4
LED Current Thermal Regulation
EN ON Voltage (HIGH)
5
EN OFF Voltage (LOW)
EN Input Bias Current
EN Switching Frequency
EN ON Minimum Pulse Width
Min
2.7
Typ
0.04
160
140
15
20
25
0.5
0.7
0.86
0.6
0.9
0.99
0.8
0.01
14
19
24
Max
5.5
1
200
180
16
21
26
0.7
1.1
1.7
0.8
1.2
1.9
.25
1.0
Units
V
μA
mV
mV
mA
Conditions
EN = LOW
Vcc = 5.5V,
I
LED
= 20mA
Vcc = 5.5V,
I
LED
= 15mA
300mV<V
D
<1.0V
300mV<V
D
<1.0V
300mV<V
D
<1.0V
SP7120 at V
D
= 300mV
mA
SP7122 at V
D
= 300mV
%
%/V
%/mA
%/
0
C
V
V
μA
kHz
μs
Vcc = 5.5V, V
D
> 300mV
2.7V < Vcc < 5.5V
300mV < V
D
< 1.0V
V
D
= 300mV
2
0
2
3
Vcc
0.8
5
20
15
V
EN
= Vcc = 5.5V
1) Difference between Vcc voltage and LED anode voltage at which
I
LED current drops 10% from nominal value
2)
I
LED Current Variations from specified value
3)
I
LED Current Variations per volt Vcc change for any given temperature
4)
I
LED Current Variations at V
D
change from 0.3V to 1.0V
5) EN input voltage should not exceed Vcc voltage at any condition
6) This condition is part of the LED current accuracy and it shall not exceed that specification
Jan 7 ‘08 RevE
SP7120/22 Low Dropout LED Driver
© 2007 Sipex Corporation
page
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PIN ASSIGNMENTS
LED1
LED2
5
SP7120
SOT23-6
6
1
Vcc
2
GND
Pin Name
Vcc
GND
EN
NC
LED3
LED2
LED1
SP7120
1
2
3
4
5
6
EN
SP7122
1
2
3
4
5
6
NC
4
3
Pin Description
Power input pin. Bypass Vcc to GND with 1nF
capacitor as close to V
IN
as possible
Ground pin
Enable pin. Device is active if EN is logic HIGH
No Connect should be left floating
Connect anode of LED3
Connect anode of LED2
Connect anode of LED1
BLOCK DIAGRAM
VLED3
VLED2
VLED1
VCC
Rset
Jan 7 ‘08 RevE
SP7120/22 Low Dropout LED Driver
© 2007 Sipex Corporation
page
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OUTPUT CURRENT SELECTION TABLE
Part Number
SP7120A
SP7120B
SP7120C
SP7122A
SP7122B
SP7122C
Output
Current per
channel
Number
of
Channels
2
2
2
3
3
3
Comments
Channels can be combined for higher output current
Channels can be combined for higher output current
Channels can be combined for higher output current
Channels can be combined for higher output current
Channels can be combined for higher output current
Channels can be combined for higher output current
15mA
20mA
25mA
15mA
20mA
25mA
CIRCUIT DESCRIPTION
The SP712X drivers are regulated current
sources with an enable input. The SP7120
and SP7122 have factory preset LED
current at three programmed levels: 15mA,
20mA or 25mA (versions A, B, and C
respectively). The SP712X circuit consists
of enable, bandgap reference, and current
amplifier circuit blocks. Enable circuit block
provides the enable and PWM function for
the SP712x. The bandgap reference
provides a stable voltage source from which
the output current is derived.
ENABLE
The SP712X drivers have a low current
shutdown function. In shutdown mode, the
part draws less than 1μA current maximum.
The part can be set into shutdown mode
using the EN pin (EN = LOW). The enable
pin cannot be left floating. There are no
predefined internal states, so leaving this
pin open will cause the part to operate
incorrectly.
PWM Dimming
The SP712X drivers allow LED-dimming
control by applying PWM signaling to EN
pin. The acceptable frequency range of this
signal is 100Hz to 20 kHz. The minimum
ON time that is required for the Enable pin
is 15μs. Thus for a 2kHz PWM signal, the
acceptable duty cycle range is 3% to 100%.
To find the minimum PWM duty cycle the
following steps are needed:
%Minimum Duty cycle = 3%
Fault Operation
If one of LEDs is shorted, the voltage across
The Sp712X for that LED pin will be Vcc,
but that channel will still provide the nominal
current value thus increasing power
dissipation. If all channels are shorted,
excessive power dissipation may damage
the device. If an LED is open, the LED pin
voltage will be pulled up to Vcc, and LED
© 2007 Sipex Corporation
Step 1: Determine the time period of the
PWM frequency
Where PWM
f
is the PWM frequency
Step 2: take the minimum enable ON time;
this is 15μS for the SP712x parts
Example
For a 2kHz signal the minimum duty
cycle for the PWM signal is
Jan 7 ‘08 RevE
SP7120/22 Low Dropout LED Driver
page
4
current will be reduced to 3mA for the other
channels.
APPLICATION CIRCUITS
Powering 1 high power LED
I
OUT
up to 75mA with C version
Powering 1 high power LED
I
OUT
up to 50mA with C version
C1 1nF
SP7122 Powering 3 LED’s
Jan 7 ‘08 RevE
SP7120/22 Low Dropout LED Driver
© 2007 Sipex Corporation
page
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PCB Design
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