EXAR SP7682AEB

SP7682/SP7682A
Backlight and Flash Driver in QFN 3mm x 3mm
C2+
C2-
C1+
VOUT
SGND
LED 1
LED 2
LED 3
LED 4
FLASH
Output current up to 500mA for Flash LED
Up to 94% efficiency in 1x mode
Triple mode 1x, 1.5x and 2x charge pump
Built-in current setting DAC
SP7682 - I2C serial interface
VIN
SP7682A – Single Line Programmable Serial Interface
PGND
2.4MHz switching frequency
Flash LED output current adjustable in 10mA steps to 500mA
EN
Backlight LED output current adjustable in 0.5mA steps to 31.5mA
SCL (SETFL)
Power-saving shutdown mode of 1μA
Time Out function to protect the LED in Flash mode (2s)
Thermal shutdown protection
Built-in over-voltage and over-current protection
Automatic soft start limits in-rush current
Lead Free, RoHS Compliant Packaging:
Space saving 16-pin 3X3mm QFN package
SDA (SETBL)
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C1-
FEATURES
DESCRIPTION
The SP7682 or SP7682A provides a complete LED backlight and flash solution that is designed to drive 4 low
current LEDs for backlighting and a single channel high current output for a LED flash. The SP7682 and SP7682A
have serial interfaces that can program the backlight LED current in steps of 0.5mA up to 31.5mA and flash LED
current in steps of 10mA up to 500mA. The SP7682A uses two single line serial interfaces for programming the
backlight current and flash current. The SP7682 uses an I2C serial interface which also allows programming active,
standby and shutdown states, selecting flash timeout periods and switching individual LEDs for the backlight. The
data is loaded into internal registers upon power up and stored while in shutdown. When the chip is enabled, the
stored values set the LED currents. The SP7682/SP7682A automatically detects 1x, 1.5x or 2x operation for
optimal efficiency.
TYPICAL APPLICATION CIRCUIT
C1 1uF
C2 1uF
VIN = 2.7V to 5.5V
VIN C1+ C1- C2+
CIN
4.7uF
SDA (SETBL)
SDA (SETBL)
SCL (SETFL)
SCL (SETFL)
C2VOUT
FLASH
COUT
2.2uF
Flash
SP7682
(SP7682A)
EN
LED1
EN
LED2
LED3
LED4
PGND SGND
Sept 27-07 rev G
SP7682: Backlight and Flash Driver
Page 1
© 2007 Exar 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.
VCC, Enable, SCL, SDA, VFLASH, VLED..............-0.3V to 6.0V
1
Power Dissipation………………………….Internally limited
Storage Temperature..……..………………-65 °C to 150 °C
Junction Temperature................................-40°C to +125°C
ESD @ LED pins……………...…………………+/-4kV HBM
ESD all other pins………….…………………....+/-2kV HBM
ELECTRICAL SPECIFICATIONS
Unless otherwise specified: VIN =3.6V, CIN=4.7uF, COUT=2.2uF, CFLY=1uF, TA = -40°C to +85°C, Tj=-40°C to +125°C.
Bold values apply over the full operating temperature range (-40°C to 85°C).
PARAMETER
Operating VIN Range
MIN
2.7
Operating Input Current
Quiescent Current
Shutdown Supply Current
ILED Voltage for DAC=000000
ILED for DAC=000001
ILED for DAC=111111
30.2
IFLASH for DAC=000001
IFLASH for DAC=110010
TYP
MAX
UNITS
5.5
V
2
mA
25
0.01
μA
μA
mA
mA
mA
VEN = 0V (shutdown), Ta = 25°C
Measure LED1-LED4 and FLASH pins
Measure current into LED1-LED4
Measure current into LED1-LED4
mA
Measure current into FLASH
mA
Measure current into FLASH
0.5
31.5
1
0
34.8
10
465
Current DAC Resolution
500
535
6
Bit
Backlight Current DAC LSB
0.5
mA
Flash Current DAC LSB
10
mA
DAC Current Accuracy
-7
Switching Frequency
1.9
CONDITIONS
Standby Mode
7
%
5mA< ILED<30mA, 80mA< IFLASH<500mA
2.4
2.9
MHz
Equivalent Resistance, 1x mode
1.0
1.8
Ohm
Iout=200mA
Equivalent Resistance, 1.5x mode
10
Ohm
Iout=80mA
Equivalent Resistance, 2x mode
8
Ohm
Iout=500mA
LEDx Pin dropout voltage
0.25
V
ILED=20mA, measure mode switching
FLASH Pin dropout voltage
0.25
V
IFLASH=200mA, measure mode switching
Thermal Regulation
0.01
%/°C
170
°C
Driver turns off
1.2
6.0
100
°C
A
V
μs
Driver turns on again
Vout =0V
Vout open
To 1x mode from STANDBY mode
0.4
V
Thermal Shutdown Die Temperature
Thermal Shutdown Hysteresis
Over-current Protection
Over-voltage protection
Settle time (TS) after last count
SDA, SCL, SETB, SETFL input logic low
voltage
SDA, SCL, SETB, SETFL input logic
high voltage
Turn-off time (TOFF) into shutdown
150
160
20
0.7
5.4
V
1.6
50
μs
Time Duration before standby, SP7682
2
4
6
s
Time Duration before standby, SP7682A
Enable logic low voltage
Enable logic high voltage
1
2
3
0.4
s
V
V
Sept 27-07 rev G
1.6
SP7682: Backlight and Flash Driver
Page 2
EN pin high to low
TD0=TD1=0V, IFLASH>ITHRESHOLD (defined by
bits TOUT0, TOUT1)
IFLASH>ITHRESHOLD = 230mA
Driver shutdown
Driver enabled
© 2007 Exar Corporation
I2C SPECIFICATIONS
PARAMETER
SYMBOL
Serial Clock Frequency
Bus Free Time Between a STOP and a
START
Hold Time, Repeated START Condition
Repeated START Condition Setup Time
STOP Condition Setup Time
Data Hold Time
Input Data Hold Time
Data Setup Time
SCL Clock Low Period
SCL Clock High Period
Rise Time of Both SDA and SCL
Signals, receiving
Fall Time of Both SDA and SCL
Signals, Receiving
MIN
TYP
MAX
UNITS
400
kHz
fSCL
tBUF
1.3
µs
t HD_STA
t SU,STA
tSU,STO
0.6
0.6
0.6
225
0
100
1.3
0.6
20+
0.1Cb
20+
0.1Cb
20+
0.1Cb
0
400
1
µs
µs
µs
ns
ns
ns
µs
µs
tHD,DAT(OUT)
tHD,DAT(IN)
tSU,DAT
tLOW
tHIGH
tR
tF
Fall Time of SDA Transmitting
tF.TX
Pulse Width of Spike Suppressed
Capacitive Load for Each Bus Line
I²C startup time after UVLO clears
tSP
Cb
tSRT
900
900
300
ns
CONDITIONS
(Notes2, 3)
300
ns
(Note2, 3)
250
ns
(Note2, 3, 4)
50
400
1
ns
pF
µs
(Note5)
(Note 2)
(Note 2)
Note 1: All parameters tested at TA=25 °C. Specifications over temperature are guaranteed by design.
Note 2: Guaranteed by design.
Note 3: Cb = total capacitance of one bus line in pF. tR and tF measured between 0.3 x VDD and 0.7 x VDD.
Note 4: ISINK ≤6mA. Cb =total capacitance of one bus line in pF. tR and tF measured between 0.3 x VDD and 0.7 VDD.
Note5: Input filters on the SDA and SCL inputs suppress noise spikes less than 50ns.
SP7682A: SINGLE LINE PROGRAMMABLE SERIAL INTERFACE SPECIFICATIONS
PARAMETER
SET_BL, SET_FL logic low threshold
SET_BL, SET_FL logic high threshold
SET_BL, SET_FL logic low time
SET_BL, SET_FL logic high time
SET_BL shutdown delay
SET_FL shutdown delay
Sept 27-07 rev G
SYMBOL
VIL
VIH
tLO
tHI
tSHDN
tSHDN
MIN
1.6
0.5
225
325
SP7682: Backlight and Flash Driver
Page 3
TYP
0.4
MAX
250
0.5
500
500
800
700
UNITS
V
V
µs
µs
µs
µs
CONDITIONS
VSET_BL < 0.4V
VSET_BL > 1.6V
VSET_BL < 0.4V
VSET_FL < 0.4V
© 2007 Exar Corporation
PIN DESCRIPTION
PIN #
PIN
NAME
1
VIN
2
PGND
3
EN
4, 5
SCL,SDA
(SP7682)
4
5
SETFL
(SP7682A)
SETBL
(SP7682A)
6
FLASH
7,8,9,
10
LED1LED4
11
SGND
12
VOUT
13,14,
15,16
C2+, C2-,
C1+, C1Thermal
Pad
-
Sept 27-07 rev G
DESCRIPTION
Power supply input. Place a 4.7uF decoupling capacitor next to this pin.
Power ground pin.
Enable/Shutdown (Logic high = enable, logic low = shutdown). Used to immediately
disable the driver and reset the output current level.
These pins connect to the I2C bus. Multiple functions can be programmed through his
interface.
Used to serially program the Flash LED current
Used to serially program the Backlight LED’s output current
High current internal current source. Connect a high brightness LED between this pin and
VOUT. The value of the current can be programmed via the I2C interface between 0mA
and 500mA with 10mA increments. During operation this pin is monitored for dropout.
When dropout condition detected the charge pump increases operation mode from 1x to
1.5x to 2x. If the FLASH current is set to above the maximum threshold the time-out
protection circuit is activated. After the maximum time of constant operation, FLASH
current is reduced to zero.
Internal current source for LCD backlight. Connect an LED between each of these pins
and VOUT. The value of the current can be programmed via the I2C interface between
0mA and 32mA with 0.5mA increments. During operation this pin is monitored for dropout.
When dropout condition detected the charge pump increases operation mode from 1x to
1.5x to 2x. If any of the LEDs are not used connect the corresponding pin to Vout.
Signal ground pin.
Output voltage of the internal charge pump. Connect the LEDs between this pin and the
corresponding internal current source. Connect a 2.2uF capacitor between VOUT and
PGND.
Connect external flying capacitors between these pins.
Connect thermal pad to PGND pin.
SP7682: Backlight and Flash Driver
Page 4
© 2007 Exar Corporation
FUNCTIONAL DIAGRAM
Sept 27-07 rev G
SP7682: Backlight and Flash Driver
Page 5
© 2007 Exar Corporation
THEORY OF OPERATION
The SP7682 and SP7682A are charge pump based
backlight and flash LED drivers with I2C and serial single
wire interface (SWI) control respectively. The SP7682
family provides very accurate current drive capability for
up-to four backlight LED channels and a flash LED. The
backlight LED current can be set through a serial
interface controlled 6-bit current DAC with 0.5mA steps,
up to 31.5mA. Similarly, FLASH LED current is set thru a
serial interface controlled 6-bit current DAC with 10mA
steps, up to 500mA.
Backlight and Flash current loops make sure that the
corresponding output currents at each individual LED
output are regulated to their DAC set current values. The
inherent decision and control logic decides the operation
mode of the "gear-box" charge pump to maximize overall
efficiency. In order to decide on the most efficient
operation mode for the charge pump, the decision and
control logic observes the battery voltage, output
voltage, load current, dropout voltage, over-voltage,
over-current conditions and in-regulation feedback
signals and forces the charge pump to operate in one of
the 1x, 1.5x and 2x modes and dynamically switches
between modes to maximize overall efficiency.
The charge pump used in the heart of the design is a
regulated charge pump and regulates the minimum of
the LEDx outputs and FLASH output to be 350mV
typical. Regulated output voltage depends on the
forward voltage drop of the external LEDs used. The
Sept 27-07 rev G
SP7682: Backlight and Flash Driver
Page 6
charge pump switches at a high frequency of 2.4MHz
which allows tiny 1uF external capacitors to be used as
flying capacitors.
When any of the LED outputs or the FLASH output
voltage drops below the "dropout" voltage (200mV
typical), the charge pump decides to switch up to a less
efficient mode, i.e. in 1x mode it switches to 1.5x mode,
in 1.5x mode it switches to 2x mode. This switching to a
less efficient mode guarantees the part to sustain LED
currents in regulation. For the decision to switch back to
a more efficient mode, the mode decision logic uses
battery voltage, output voltage and load current
information and relies on preset margins on the mode
switching comparator thresholds.
The FLASH channel can be used in torch mode as well
as in Flash time-out mode. When used for a momentary
Flash output, it is recommended to activate the I2C
control for timeout. Once the I2C timeout is activated and
for as long as the Flash is active, the SP7682 charge
pump will operate in 2x mode in order to provide the
continuous voltage and high current needed for Flash.
For the SP7682A, which uses the single wire interface,
the Flash channel will be in 2x mode whenever the Flash
current is at least 230mA.
The SP7682 and SP7682A are furnished with undervoltage lockout, current limit, thermal shutdown and over
voltage protection features.
© 2007 Exar Corporation
TYPICAL PERFORMANCE CHARACTERISTICS
VIN = 3.6V, Typical Application Circuit, TA = 25°C unless otherwise noted.
Backlight VOUT Efficiency
100
95
95
90
90
85
85
Efficiency (%)
Efficiency (%)
100
80
75
70
65
60
50
3.0
3.3
3.6
3.9
4LEDs=20mA,Flash=0mA
4LEDs=20mA,Flash=100mA
4LEDs=20mA,Flash=200mA
80
75
70
65
60
4LEDs=15mA
4LEDs=20mA
4LEDs=25mA
55
Backlight & Flash VOUT Efficiency
55
50
3.0
4.2
3.3
110
Backlight Output Current Vs VIN
300
Output Current (mA)
Output Current (mA)
100
90
80
4LEDs=15mA
4LEDs=20mA
4LEDs=25mA
70
60
50
3.0
3.3
3.6
3.9
4LEDs=20mA,Flash=0mA
4LEDs=20mA,Flash=100mA
4LEDs=20mA,Flash=200mA
200
150
100
50
3.0
4.2
3.3
95
90
90
85
85
Efficiency (%)
Efficiency (%)
100
75
70
65
4.2
Vin (V)
Sept 27-07 rev G
4LEDs=20mA,Flash=0mA
4LEDs=20mA,Flash=100mA
4LEDs=20mA,Flash=200mA
65
55
3.9
Backlight & Flash LED Efficiency
70
60
3.6
50
3.0
3.3
3.6
Vin (V)
SP7682: Backlight and Flash Driver
Page 7
4.2
75
55
3.3
3.9
80
60
50
3.0
3.6
Vin (V)
4LEDs=15mA
4LEDs=20mA
4LEDs=25mA
80
4.2
250
Backlight LED Efficiency
95
3.9
Backlight & Flash Output Current Vs VIN
Vin (V)
100
3.6
Vin (V)
Vin (V)
© 2007 Exar Corporation
3.9
4.2
TYPICAL PERFORMANCE CHARACTERISTICS
VIN = 3.6V, Typical Application Circuit, TA = 25°C unless otherwise noted.
Flash PWF4 2x Timeout Mode, IOUT Vs VIN
500
Output Current (mA)
Vin(AC)
400
300
Vout(AC)
200
Flash=500mA 2x Timeout Mode
Flash=400mA 2x Timeout Mode
Flash=300mA 2x Timeout Mode
Flash=200mA Auto Mode
100
3.0
3.3
3.6
Vin (V)
3.9
4.2
400mA 2x Timeout Mode Ripple
Flash PWF4 1.5x Mode Forced, IOUT Vs VIN
Flash=500mA 1.5x Forced Mode
Flash=400mA 1.5x Forced Mode
Flash=300mA 1.5x Forced Mode
Flash=200mA 1.5x Forced Mode
500
Vin(AC)
Output Current (mA)
400
300
Vout(AC)
200
100
3.0
3.3
3.6
3.9
Vin (V)
4.2
400mA Forced 1.5x Mode Ripple
Flash PWF4 Auto Mode, IOUT Vs VIN
500
Vin(AC)
Output Current (mA)
400
300
Vout(AC)
200
100
3.0
Flash=500mA Auto Mode
Flash=400mA Auto Mode
Flash=300mA Auto Mode
Flash=200mA Auto Mode
3.3
3.6
Vin (V)
3.9
4.2
400mA Auto Mode 1.5x to 2x Mode Ripple
Sept 27-07 rev G
SP7682: Backlight and Flash Driver
Page 8
© 2007 Exar Corporation
TYPICAL PERFORMANCE CHARACTERISTICS
VIN = 3.6V, Typical Application Circuit, TA = 25°C unless otherwise noted.
Ch1=EN
Ch2=Vout
Ch2=Vout
Ch4=Iin
0.2A/div
Ch4=Iin
0.2A/div
LEDs = 20mA 1x Startup from Shutdown
LEDs = 20mA 1.5x Startup from Shutdown
Ch1=EN
Ch1=EN
Ch2=Vout
Ch2=Vout
Ch4=Iin
0.2A/div
Ch4=Iin
0.2A/div
Flash = 200mA 1x Startup from Shutdown
Flash = 200mA 1.5x Startup from Shutdown
Ch1=EN
Ch1=EN
Ch2=Vout
Ch2=Vout
Ch4=Iin
0.2A/div
Ch4=Iin
0.2A/div
Flash = 300mA 2x Timeout Startup from SHDN
Sept 27-07 rev G
Flash = 400mA 2x Timeout Startup from SHDN
SP7682: Backlight and Flash Driver
Page 9
© 2007 Exar Corporation
TYPICAL PERFORMANCE CHARACTERISTICS
VIN = 3.6V, Typical Application Circuit, TA = 25°C unless otherwise noted.
Ch1=SET_BL
Ch1=SET_BL
Ch2=Vout
Ch2=Vout
Ch4=Iin
0.2A/div
Ch4=Iin
0.2A/div
SP7682A SET_BL=41 Pulses LEDs=20mA 1x
SP7682A SET_BL=41 Pulses LEDs=20mA, 1.5x
Ch1=SET_FL
Ch1=SET_FL
Ch2=Vout
Ch2=Vout
Ch4=Iin
0.2A/div
Ch4=Iin
0.2A/div
SP7682A SET_FL=31 Pulses Flash=0.3A 1x
SP7682A SET_FL=31 Pulses Flash = 0.3A 2x
Ch1=SET_FL
Ch2=Vout
Ch2=Vout
Ch4=Iin
0.2A/div
Ch4=Iin
0.2A/div
SP7682A SET_FL=31 Pulses Flash=0.3A 2s
Sept 27-07 rev G
SP7682 TD0=TD1=0V Flash=0.3A 4s
SP7682: Backlight and Flash Driver
Page 10
© 2007 Exar Corporation
TYPICAL PERFORMANCE CHARACTERISTICS
VIN = 3.6V, Typical Application Circuit, TA = 25°C unless otherwise noted.
22
20mA Backlight Output Current Vs VIN
Ch1=Vin
LED1
LED2
Output Current (mA)
21
LED3
LED4
20
Ch2=Vout
19
18
3.0
3.3
3.6
3.9
4.2
Vin (V)
20mA Backlight: 1.5x Mode Ripple
Ch1=EN
Ch1=EN
Ch2=LEDx
Ch2=FLASH
Ch4=Iin
0.5A/div
Ch4=Iin
0.2A/div
Turn-off time into SHDN Flash=0.3A
Turn-off time into SHDN LEDs=20mA
Ch1=SCL
Ch1=SCL
Ch2=Vout
Ch2=Vout
Ch4=Iin
0.2A/div
Settle last count Standby LEDs=20mA 1x
Sept 27-07 rev G
Ch4=Iin
0.5A/div
Settle last count Standby LEDs=20mA 1.5x
SP7682: Backlight and Flash Driver
Page 11
© 2007 Exar Corporation
APPLICATIONS INFORMATION
I2C Specifications
The I2C protocol defines any device that sends data
to the bus as a transmitter and any device that reads
the data as a receiver. The device that controls the
data transfer is known as the master and the other
device as the slave. The master will always initiate a
data transfer and will provide the serial clock for
synchronization.
Data input format:
S SP7682 Address
7-bit
A
R/ W
1/0
Data for
Status1
8-bit
Acknowledge,
sent by slave
Start
Condition
A
Data for
Status2
8-bit
A
Data
For
LED
8-bit
A
A
Data
for
Flash
8-bit
SP
Stop
condition
Acknowledge, sent by slave when R/ W =0
Or, sent by master when R/ W =1
SP7682 I2C Slave Address Map: (7-bit Default Address: 0x28)
Fuses
Fuse1
0
0
1
1
Fuse0
0
1
0
1
A7
0
0
0
0
A6
1
1
1
1
A5
0
0
1
1
A4
1
0
1
0
A3
0
0
0
0
A2
0
0
0
0
The SP7682 has four data registers which can be
programmed serially via the I²C interface. The first
register is a status register which has two bits used
for shutdown/power up options, 4 bits used for
individual backlight LED ON/OFF control, and 2 bits
for charge pump mode.
The second STATUS
register contains settings of the FLASH time-out,
B7
A1
0
0
0
0
A0
0
0
0
0
0x28
0x20
0x38
0x30
Temperature OK, Voltage OK, and Flash time-out
expired conditions. After the Flash timeout has
expired the FTO bit will toggle on and then off for
intervals set by the TDO bits. The next two registers
are used to set the brightness levels of the backlight
LEDs and Flash LED.
Theory of Operation - I²C Serial Interface
REGISTER
7-bit
address
Hex
A7-A1
R/W
1/0
Device Address
The register bits are as follows:
B6
B5
B4
B3
B2
B1
B0
STATUS1
WZ
WP
PMP0
PMP1
LED0
LED1
LED2
LED3
STATUS2
TOUT0
TOUT1
TD0
TD1
TOK
VOK
FTO
dc
LEDS
D5
D4
D3
D2
D1
D0
dc
dc
FLASH
D5
D4
D3
D2
D1
D0
dc
dc
Sept 27-07 rev G
SP7682: Backlight and Flash Driver
Page 12
© 2007 Exar Corporation
APPLICATIONS INFORMATION
The following table defines the states for bits PMP0 and
PMP1. These bits can be used to set the operating
mode for the internal charge pump.
PMP0
PMP1
0
0
0
1
1
0
1
1
State
TOUT0
TOUT1
Automatic mode detection.
0
0
1x mode only. 1.5x and 2x
modes are prohibited
1.5x mode only. 1x and 2x
modes are prohibited.
1x or 1.5x mode auto detection.
2x mode is prohibited.
0
1
1
0
1
1
The following table defines the states for bits LED0 to
LED3. These bits can be used to turn LEDs On or OFF.
LED0
LED1
LED2
LED3
State
1
0
0
0
LED0 OFF, other
LEDs ON.
0
1
0
0
LED1 OFF, other
LEDs ON.
0
0
1
0
LED2 OFF, other
LEDs ON.
0
0
The following table defines the states for bits TOUT0 and
TOUT1. These bits can be used to adjust current
threshold for the time-out feature in Flash mode.
0
1
LED3 OFF, other
LEDs ON.
State
Time-out disabled
Timeout enabled for 110mA
and above
Timeout enabled for 160mA
and above
Timeout enabled for 230mA
and above
The following table defines the states for bits TD0 and TD1.
These bits can be used to adjust time-out delay for the
time-out feature in Flash mode.
TD0
TD1
State
0
0
4s
0
1
2s
1
0
1s
1
1
0.5s
Addressing and Writing Data to the SP7682
To write data to the SP7682 one of the following two
cycles must be obeyed:
Easy shutdown/startup sequence
The following table defines the states for bits WZ and
WP. These bits can be used to put the SP7682 into
shutdown, standby or active.
WZ
WP
0
0
0
1
1
0
1
1
Sept 27-07 rev G
State
Shutdown, data registers are reset
to 000000
Shutdown, data registers are
unchanged
Standby. Output current is zero, data
registers are unchanged.
Active. Output current corresponds
to the register contents
[Slave Address with write bit][Data for Status]
Full shutdown/startup sequence
[Slave Address with write bit][Data for Status1][Data for
Status2][Data for LEDs][Data for FLASH]
Addressing and Reading Data from the SP7682
To read data from the SP7682 the following data cycle
must be obeyed:
[Slave Address with read bit][Data for Status1][Data for
Status2][Data
for
LEDs][Data
for
FLASH]
SP7682: Backlight and Flash Driver
Page 13
© 2007 Exar Corporation
APPLICATIONS INFORMATION
DAC table for Backlight LED intensity
In the LED register bits B7, B6, B5, B4, B3 and B2
represent the DAC codes D5-D0 used to set the LED
current in the four LEDs. The following table lists the
DAC codes and the corresponding current for each
channel in mA:
B7-B2
000000
000001
000010
000011
000100
000101
000110
000111
001000
001001
001010
001011
001100
001101
001110
001111
010000
010001
010010
010011
010100
010101
010110
010111
011000
011001
011010
011011
011100
011101
011110
011111
Sept 27-07 rev G
BL
(mA)
0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
5.0
5.5
6.0
6.5
7.0
7.5
8.0
8.5
9.0
9.5
10.0
10.5
11.0
11.5
12.0
12.5
13.0
13.5
14.0
14.5
15.0
15.5
B7-B2
100000
100001
100010
100011
100100
100101
100110
100111
101000
101001
101010
101011
101100
101101
101110
101111
110000
110001
110010
110011
110100
110101
110110
110111
111000
111001
111010
111011
111100
111101
111110
111111
DAC table for FLASH LED intensity
In the FLASH register bits B7, B6, B5, B4, B3 and B2
represent the DAC codes D5-D0 used to set the LED
current in the four LEDs. The following table lists the
DAC codes and the corresponding current for each
channel in mA:
BL
(mA)
16.0
16.5
17.0
17.5
18.0
18.5
19.0
19.5
20.0
20.5
21.0
21.5
22.0
22.5
23.0
23.5
24.0
24.5
25.0
25.5
26.0
26.5
27.0
27.5
28.0
28.5
29.0
29.5
30.0
30.5
31.0
31.5
SP7682: Backlight and Flash Driver
Page 14
B7-B2
000000
000001
000010
000011
000100
000101
000110
000111
001000
001001
001010
001011
001100
001101
001110
001111
010000
010001
010010
010011
010100
010101
010110
010111
011000
011001
011010
011011
011100
011101
011110
011111
Flash
(mA)
0
10
20
30
40
50
60
70
80
90
100
110
120
130
140
150
160
170
180
190
200
210
220
230
240
250
260
270
280
290
300
310
B7-B2
100000
100001
100010
100011
100100
100101
100110
100111
101000
101001
101010
101011
101100
101101
101110
101111
110000
110001
110010
110011
110100
110101
110110
110111
111000
111001
111010
111011
111100
111101
111110
111111
Flash
(mA)
320
330
340
350
360
370
380
390
400
410
420
430
440
450
460
470
480
490
500
500
500
500
500
500
500
500
500
500
500
500
500
500
© 2007 Exar Corporation
SP7682A APPLICATIONS INFORMATION
SP7682A Single Line Programmable Serial
Interface
Backlight Code Table (programmed via SETBL)
SET_FL (or SET_BL) pin programming waveform
shown below:
EN
SET_FL
tHI=0.5us min
tLO=0.5us to 0.25ms
tSHDN=0.5ms
i
40mA
shutdown
10mA
IFLASH
0mA
In the above example code 5 is programmed as
there are five rising edges.
Serially Programmable Codes
Flash Code Table (programmed via SETFL)
code
Flash
(mA)
code
Flash
(mA)
code
Flash
(mA)
1
0
18
170
35
340
2
10
19
180
36
350
3
20
20
190
37
360
4
30
21
200
38
370
5
40
22
210
39
380
6
50
23
220
40
390
7
60
24
230
41
400
8
70
25
240
42
410
9
80
26
250
43
420
10
90
27
260
44
430
11
100
28
270
45
440
12
110
29
280
46
450
13
120
30
290
47
460
14
130
31
300
48
470
15
140
32
310
49
480
16
150
33
320
50
490
17
160
34
330
51
500
Sept 27-07 rev G
code
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
SP7682: Backlight and Flash Driver
Page 15
BL
(mA)
0
0.5
1
1.5
2
2.5
3
3.5
4
4.5
5
5.5
6
6.5
7
7.5
8
8.5
9
9.5
10
code
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
BL
(mA)
10.5
11
11.5
12
12.5
13
13.5
14
14.5
15
15.5
16
16.5
17
17.5
18
18.5
19
19.5
20
20.5
code
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
BL
(mA)
21
21.5
22
22.5
23
23.5
24
24.5
25
25.5
26
26.5
27
27.5
28
28.5
29
29.5
30
30.5
31
31.5
© 2007 Exar Corporation
APPLICATIONS INFORMATION
LED Selection
The SP7682 is designed as a driver for backlight
white LEDs and Flash white LEDs, but is
capable of driving other LED types with forward
voltage specifications ranging from 2.0V to 3.8V.
LED applications may include LCD display
backlighting, camera photo-flash applications,
infrared (IR) diodes for remotes, and other loads
benefiting from a controlled output current
generated from a varying input voltage. Since
the D1 to D4 output current-sinks are matched
with negligible voltage dependence, the LED
brightness will be matched regardless of the
specific LED forward voltage (VF) levels. In flash
applications, it may be necessary to drive highVF type LEDs. The typical characteristic curves
illustrate low VF Flash LEDs using the LumiLEDs PWF4 LED, but the low dropout currentsinks in the SP7682 make it capable of driving
LEDs with forward voltages as high as 4.0V from
an input supply as low as 3.2V but at a reduced
output current.
Device Switching Noise Performance
The SP7682 operates at a fixed frequency of
approximately 2.4MHz to control noise and
limit harmonics that can interfere with the RF
operation of cellular telephone handsets or other
communication devices. Back-injected noise
appearing on the input pin of the charge pump
can be much less than 100mV peak-to-peak,
typically less than inductor-based DC/DC boost
converter white LED backlight solutions. The
SP7682 soft-start feature helps prevent noise
transient effects associated with inrush currents
during startup of the charge pump circuit.
Power Efficiency
The charge pump efficiency shown in the typical
characteristic curves is shown for two cases.
The first case is called output efficiency which is
the power efficiency to the output as a ratio of
the output voltage power to the input voltage
power and expressed as a percentage. The
second case is called LED efficiency and is the
power efficiency to the LED outputs and is
expressed as a ratio of the power to the LEDs to
the input voltage power. These expressions are
shown at the end of this section in their
formulas. The first case is what is generally
shown in competitors’ datasheets and is shown
Sept 27-07 rev G
here for reference. The second case of LED
power efficiency is included to show the user the
true power delivered to the LEDs. As one can
see in the curves, the LED efficiency is greatest
when VIN is higher than the VF of the LEDs (and
higher than the voltage required on the constant
current-sink outputs of the LEDs) and that is
when the SP7682 is in the 1x mode. When VIN
is less than the VF (and less than the voltage
required on the constant current-sink outputs of
the LEDs) the SP7682 is in the 1.5x mode or 2x
mode and in these modes the input current is
1.5 times or 2 times the output current and
therefore the efficiency will be reduced.
VOUT efficiency = VOUT•IOUT/(VIN•IIN)•100%
LED efficiency =
(VOUT -VLED) •IOUt/(VIN•IIN)•100%
Refer to the Typical Characteristics section of
this document for measured plots of efficiency
versus input voltage and output load current
versus input voltage for given LED output
current options.
Capacitor Characteristics
Ceramic composition capacitors are highly
recommended over all other types of capacitors
for use with the SP7682. Ceramic capacitors
offer many advantages over their tantalum and
aluminum electrolytic counterparts. A ceramic
capacitor has very low ESR, is lower in cost, has
a smaller PCB footprint, and is non-polarized.
Low ESR ceramic capacitors help to maximize
charge pump transient response. Since ceramic
capacitors are non-polarized, they are not prone
to incorrect connection damage.
Equivalent Series Resistance (ESR)
ESR is an important characteristic to consider
when selecting a capacitor. ESR is a resistance
internal to a capacitor that is caused by the
leads, internal connections, size or area,
material composition, and ambient temperature.
Capacitor ESR is typically measured in
milliohms for ceramic capacitors and can range
to more than several Ohms for tantalum or
aluminum electrolytic capacitors.
SP7682: Backlight and Flash Driver
Page 16
© 2007 Exar Corporation
APPLICATIONS INFORMATION
can be 1μF for most applications for backlight
and Flash, and for light output currents flying
capacitors of 0.47uF can be used. For
applications when the 4 backlight LED drivers
are drive 20mA or more and the Flash driver is
driven to 100mA or more, it is advisable to use a
4.7μF input capacitor in order to reduce the input
ripple as seen by the battery. If the LED currentsinks are only programmed for low current
levels, or if the application is not very noise
sensitive, then a 2.2μF input capacitor may be
used. See table 1 for capacitor selection.
Ceramic Capacitor Materials
Capacitors with large output values are typically
composed of X7R, X5R, Z5U, or Y5V dielectric
materials, but Z5U and Y5V are not
recommended since they have a large change in
value with temperature. X5R and X7R
capacitors are recommended since they are
relatively low in cost and their output value
changes with temperature are relatively small.
Capacitor Selection
Careful selection of the four external capacitors
CIN, C1, C2, and COUT is important because
they will affect turn-on time, output ripple, and
transient performance. Optimum performance
will be obtained when low equivalent series
resistance (ESR) ceramic capacitors are used.
In general, low ESR may be defined as less than
100mΩ. A value of 4.7μF for the input and 2.2μF
for the output capacitor is sufficient for most
applications. The flying capacitors C1 and C2
Thermal Protection
The SP7682 has a thermal protection circuit that
will shut down the internal LDO and charge
pump if the die temperature rises above the
thermal limit, and will restart when the die
temperature drops about 20°C below the
thermal limit.
Table 1: SP7682/SP7682A Capacitor Selection
Manufacturers/ Website
Part Number
Capacitance/
Voltage
Capacitor
Size/Type/Thickness
ESR at
100kHz
TDK/www.tdk.com
TDK/www.tdk.com
TDK/www.tdk.com
TDK/www.tdk.com
Murata/www.murata.com
Murata/www.murata.com
Murata/www.murata.com
Murata/www.murata.com
C1005X5R0J474K
C1005X5R0J105K
C1608X5R0J225K
C1608X5R0J475K
GRM155R60J474KE19
GRM155R60J105KE19
GRM185R60J225KE26
GRM188R60J475KE19
0.47uF/6.3V
1uF/6.3V
2.2uF/6.3V
4.7uF/6.3V
0.47uF/6.3V
1uF/6.3V
2.2uF/6.3V
4.7uF/6.3V
0402/X5R/0.55mm
0402/X5R/0.55mm
0603/X5R/0.9mm
0603/X5R/0.9mm
0402/X5R/0.55mm
0402/X5R/0.55mm
0603/X5R/0.55mm
0603/X5R/0.8mm
0.05
0.03
0.03
0.02
0.05
0.03
0.03
0.02
FOOTPRINT: 3x3mm 16 pin QFN
Sept 27-07 rev G
SP7682: Backlight and Flash Driver
Page 17
© 2007 Exar Corporation
PACKAGE: 3x3mm 16 pin QFN
EXAR
Sept 27-07 rev G
SP7682: Backlight and Flash Driver
Page 18
© 2007 Exar Corporation
ORDERING INFORMATION
Part Number
Control
Min
Max
Theta JA
RoHS
Interface Temp ºC Temp ºC
ºC/W
85
Yes
33.3
L3 @ 260ºC
Canister
Any
2
-40
85
Yes
33.3
L3 @ 260ºC
Tape & Reel
3000
2
-40
85
-40
85
Yes
33.3
L3 @ 260ºC
Canister
Any
-40
85
Yes
33.3
L3 @ 260ºC
Tape & Reel
3000
-40
85
SP7682ER1-L/TR
IC
SP7682AER1L/TR
SP7682AEB
Quantity Package
-40
IC
SP7682AER1-L
Pack Type
2
SP7682ER1-L
SP7682EB
MSL Level
IC
Single
Wire
Single
Wire
Single
Wire
Not Applicable to Eval Board
Not Applicable to Eval Board
3x3 16 Pin
QFN
3x3 16 Pin
QFN
Board
3x3 16 Pin
QFN
3x3 16 Pin
QFN
Board
For further assistance:
Email:
WWW Support page:
Application Notes:
[email protected]
http://www.sipex.com/content.aspx?p=support
http://www.sipex.com/applicationNotes.aspx
EXAR Corporation reserves the right to make changes to the products contained in this publication in order to improve design, performance or
reliability. EXAR Corporation assumes no responsibility for the use of any circuits described herein, conveys no license under any patent or other right,
and makes no representation that the circuits are free of patent infringement. Charts and schedules contained here in are only for illustration purposes
and may vary depending upon a user’s specific application. While the information in this publication has been carefully checked; no responsibility,
however, is assumed for inaccuracies.
EXAR Corporation does not recommend the use of any of its products in life support applications where the failure or malfunction of the product can
reasonably be expected to cause failure of the life support system or to significantly affect its safety or effectiveness. Products are not authorized for
use in such applications unless EXAR Corporation receives, in writing, assurances to its satisfaction that: (a) the risk of injury or damage has been
minimized; (b) the user assumes all such risks; (c) potential liability of EXAR Corporation is adequately protected under the circumstances.
Sept 27-07 rev G
SP7682: Backlight and Flash Driver
Page 19
© 2007 Exar Corporation