®
Advanced
SP7683
Four Channel Charge Pump Regulator LED Driver
FEATURES
■
2.7V to 5.5V Input Voltage Range
■
Up to 4 LEDS with matching currents
■
LEDs can be Driven from the Charge
Pump Output
■
1X and 1.5X Mode Charge Pump
■
High Efficiency Operation
■
1.2 MHz Switching Frequency
■
Programable LED Drive Capabliity
■
PWM Dimming Control
■
Low 0.5µA Shutdown Current
■
Soft-Start Limits Inrush Current
■
Output Overvoltage Protection
■
Thermal Shutdown Protection
■
QFN (4mm x 4mm) package
LED2
EN/ PWM
14
LED1
16
15
13
12 FB
I
SET
On/Off
LED3
LED4
1
2
3
4
SP7683
4x4 mm
16 Pin QFN
C2N
11
V
MODE
10
V
IN
9
C1P
8
5
6
7
C1N
Now Available in Lead Free Packaging
APPLICATIONS
■
Smart Phones
■
Cell Phones
■
PDA's
■
Digital Cameras
■
MP3 Players
■
Other Portables
DESCRIPTION
The SP7683 is high efficiency Charge Pump which regulates up to four white LEDs with matching
current. Based on the supply headroom available for the four precision current sinks, SP7683
automatically switches between 1X and 1.5X modes. The part powers up in 1X mode, with low
quiescent current of 70uA (typ) and remains in 1X mode as long as the LED current has not
decreased by more than 0.5%. If the current decreases, then it switches into 1.5X mode where
it regulates the lowest of the LED cathode voltages to 0.1V. Other features include soft-start, over
current protection, overvoltage protection and thermal shutdown at 140°C. Offered in 4X4 16 pin
QFN.
TYPICAL APPLICATION SCHEMATIC
D1
D2
D3
D4
R10
100k
U1
SP7683
EN
15 16 3 4
R1
50k - 200k
®
R
SET
Vin
C1
1uF
R4
270k
R2 1M
14
2
10
11
R3 100k
R9
100k
C3
0.1uF
SP7683
9 5 6 13
7
1
12
8
R5
10k
C2
1uF
GND
LED_EN
C4
1uF
C5
1uF
Date: 12/21/04
SP7683 Four Channel Charge Pump LED Driver
© Copyright 2004 Sipex Corporation
1
V
OUT
GND
C2P
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.
I
SET
Voltage to GND.....................................................0.5V
IN, OUT, EN1, EN2 to GND................................-0.3V to 6V
SET, LED1, LED2, LED3, LED4 to GND -0.3V to IN+0.3V
C1N, C2N to GND...........................................-0.3 to IN+1V
C1P, C2P to GND - 0.3V to greater than IN+1 or OUT+1V
OUT Short Circuit to GND.........................Continious
Storage Temperature ........................-65°C to 150°C
Operating Temperature......................-40°C to +85°C
Lead Temperature (Soldering, 10 sec)............300°C
ELECTRICAL CHARACTERISTICS
Unless otherwise specified: V
IN
= 3.6V, MODE = 0V, ILX = 0mA, T
A
= -40°C to +85°C, typical values at 27º unless
otherwise noted.
PARAMETER
Input Voltage
Quiescent Current
Shutdown Current
Maximum Load Current
V
OUT
Turn-on TIme
Output Current Multiplication
Ratio (Note 1)
LED Current Matching
LED Cathode Voltage
Current in OFF Mode
Oscillator Frequency
FB Reference Voltage
FB Pin Current
Output Resistance
MIN
2.7
TYP
MAX
5.5
UNITS
V
mA
µA
mA
CONDITIONS
.5
.5
200
250
140
-3
200
0.8
0.5
0.01
.7
.277
1.2
.310
0.01
8
3
3
1.5
V
IN
= 3V - 5.5V, V
OUT
= 3.6V,
I
OUT
= 100µA
V
EN
/PWM = 0V, V
IN
= 5.5V
V
IN
= 4.2V, V
OUT
= 3.6V
FB within 90% regulation
1.5X Mode, V
OUT
= 3.6, I
OUT
= 100µA
I
SET
= 100µA, V
LED
= .3V
500
260
3
µs
%
V
Any 2 LEDs
LEDs D1-D4
V
EN
= 0V
V
IN
= 2.7V - 5.5V
I
OUT
= 20mA, V
OUT
= 3.6V, 1.5X MODE
V
FB
= 1V
1.5X MODE, 100mA load
1
1.5
.342
0.5
15
µA
MHz
V
µA
Ohms
7
1.5
V
mV
0.5
µA
V
0.4
V
µA
1X MODE, 100mA load
V
IN
falling
V
MODE
Threshold Voltage
V
MODE
Hysteresis
V
MODE
Pin Current
ENABLE/PWM Logic High
ENABLE/PWM Logic Low
Enable/ PWM Pin Current
1
1.25
30
0.01
V
MODE
= 1.25V
1.6
0.01
0.5
V
EN
/ PWM = 4.2V
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 and page 5 of SP7614 datasheet.
Date: 12/21/04
SP7683 Four Channel Charge Pump LED Driver
© Copyright 2004 Sipex Corporation
2
ELECTRICAL CHARACTERISTICS
Unless otherwise specified: V
IN
=3.6V, MODE=0V, ILX=omA, T
A
=-40°C to +85°C, typical values at 27º unless otherwise
noted.
PARAMETER
Min ON/OFF "On Voltage"
Logic High (Note 2)
Max ON/OFF "Off Voltage"
Logic Low (Note 2)
MIN
3
TYP
MAX
UNITS
V
CONDITIONS
0.5
V
Note 2: "ON" is V
ON/OFF
where I
LED1
> 20mA @ V
LED1
= 0.3V.
"OFF" is V
ON/OFF
where I
LED1
< 1µA @ V
LED1
> 0.3V.
PIN DESCRIPTION
PIN #
1
2
3
PIN NAME
I
SET
ON/OFF
LED3
DESCRIPTION
A pull up resistor attached between V
OUT
and this pin sets the output current by
the relationship. I
LED
= 200(V
OUT
- V
ISET
) / R
SET
LED ON/OFF control (LED1 - LED4).
Cathode Connection for LED4. In 1.5X Mode the charge pump regulates V
OUT
so
that the lowest of LED1, LED2, LED3, and LED4 voltages is 150mV. Connect to
V
OUT
if not used.
Cathode Connection for LED3. In 1.5X Mode the charge pump regulates V
OUT
so
that the lowest of LED1, LED2, LED3, and LED4 voltages is 150mV. Connect to
V
OUT
if not used.
Flying Capacitor 1 Negative terminal.
Flying Capacitor 2 Positive Terminal
Output. Drives the anodes of all LEDs. Bypass to GND with a 1µF capacitor. High
Impedance Shutdown
Ground Connection
Flying Capacitor 1 Postive terminal.
Supply voltage input. Bypass with a 1µF ceramic capacitor to GND
Charge pump mode program pin. When Vmode is greater than 1.25V, a X1
charge pump is used. Otherwise, charge pump switches to X1.5 mode. A voltage
divider shown in typical application circuit programs the Vin threshold for charge
pump mode switching.
This is the feedback pin for output current or voltage regulation. The voltage of
this pin is compared with an internal 306mV reference.
Flying Capacitor 2 Negative terminal.
Enable/PWM dimming control input.
Cathode Connection for LED1. In 1.5X Mode the charge pump regulates V
OUT
so
that the lowest of LED1, LED2, LED3, and LED4 voltages is 150mV. Connect to
V
OUT
if not used.
Cathode Connection for LED2. In 1.5X Mode the charge pump regulates V
OUT
so
that the lowest of LED1, LED2, LED3, and LED4 voltages is 150mV. Connect to
V
OUT
if not used.
4
5
6
7
8
9
10
LED4
C1N
C2P
V
OUT
GND
C1P
V
IN
11
V
MODE
12
13
14
15
FB
C2N
EN/PWM
LED1
16
LED2
Date: 12/21/04
SP7683 Four Channel Charge Pump LED Driver
© Copyright 2004 Sipex Corporation
3
BLOCK DIAGRAM
V
IN
EN/PWM
Voltage
Reference
1.25V
600 kHz
Clock
Manager
C1P
Start-up
and
Charge
Pump
Switches
C1N
C2P
C2N
V
OUT
V
MODE
MODE
COMP
Mode Control
306mV
FB
Logic
Control
V
OUT
COMP
GND
ON/OFF
LDO Current
Regulator
LED1
LED2 LED3 LED4
Date: 12/21/04
SP7683 Four Channel Charge Pump LED Driver
© Copyright 2004 Sipex Corporation
4
CIRCUIT DESCRIPTION
The SP7683 is comprised of two stages. First is a regulated change pump to convert the input
voltage V
IN
into a stable output voltage or current depending on the mode used. The second stage
is a low dropout current matching regulator that provides stable identical currents in all four
channels to drive LED1 - LED4. The first stage can drive an additional four LEDs that are
connected in parallel to the V
OUT
pin. It is recommended to use resistors in series with these
additional diodes for current matching.
The SP7683 provides dimming control for the LEDs, with a constant ratio of brightness between
them. It can also be used to turn off the LEDs completely.
The Charge Pump
The regulated charge pump can operate in two modes 1X V
IN
and 1.5X V
IN
to optimize efficiency
over the entire battery voltage range. The input voltage trip point at which the charge pump will
automatically switch from a 1X mode to 1.5X mode is defined by an external voltage divider
connected to V
MODE
pin. Cycle-by-cycle regulation ensures that no mode change occurs during
a switching cycle. To achieve better efficiency it is recommended that the V
IN_TRIP
is set at
V
IN_TRIP
= V
F
+ 0.31 + MI
LED
*R
OUT
where V
F
is the LED forward voltage and (M) is the number of LEDs
connected to V
OUT
. R
OUT
is the output resistance. I
LED
is the current per LED.
The charge pump may be configured in voltage mode or as a current source. When used as a
voltage source the output voltage is determined by an external resistive divider connected to FB
pin as: V
OUT
= (1+R10/R5)*V
FB
(see Figure 2) where V
FB
= 0.31V.
When used as a current source the current in one single LED (D5 - D8) may be set by series
resistor R
S
as I
LED
= V
FB
/ R
S.
The current in the remaining LEDs will track based on the ballast
resistors. Three-wire LED modules with internal series resistors can also be driven in this way.
The flying capacitors C1 an C2 of the charge pump control the tade-off between the output voltage
ripple and the output current capability. Decreasing the flying capacitors will reduce the output
voltage ripple because less charge will be delivered to the output capacitor. However, smaller
flying capacitors lead to larger output resistance, thus decreasing the output current handling
capability and circuit efficiency. We recommend using ceramic capacitors in the range of 1µF -
4.7µF with low ESR, which helps reduce peak-to-peak output ripple and reduce high frequency
noise spikes.
Dimming control can be achieved by applying a PWM control signal to the EN/PWM pin. The
brightness of the LEDs is controlled by varying the duty cycle of the PWM signal. PWM repetition
rate from 60Hz - 700Hz. A repetition rate of at least 60Hz is required to prevent visible flickering.
Applying a logic low signal to EN/PWM control input turns of the device resulting in supply current
below 1µA and high impedance state of the V
OUT
pin.
Date: 12/21/04
SP7683 Four Channel Charge Pump LED Driver
© Copyright 2004 Sipex Corporation
5
