SP7680 [SIPEX]
Complete Backlight Solution; 完整的背光解决方案
| 型号： | SP7680 |
| 厂家： | 
SIPEX CORPORATION |
| 描述： | Complete Backlight Solution |
| 文件： | 总16页 (文件大小：445K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
Solved by
SP7680
TM
Complete Backlight Solution
FEATURES
ꢀ Complete Backlight Solution
ꢀ Separate control for 4 main, 2 sub, and keypad LEDs
ꢀ Built-in 6-bit DAC for precise current setting
ꢀ I2C serial interface
ꢀ Data is stored in shutdown
ꢀ 1x and 1.5x mode operation with automatic switchover
ꢀ Very low dropout: 200mV typ
16 15 14 13
1
2
3
4
12
11
10
9
LED 1
GND
C2+
LED 6
LED 7
SDA
ꢀ Very low 31µA current (LSB)
C2-
SCL
ꢀ 2MHz switching frequency reduces external components
ꢀ Power-saving shutdown mode of 1µA
ꢀ Built-in over-temperature protection
ꢀ Available in Lead Free, RoHS compliant package:
Small 16-pin 3x3 QFN
5
6
7
8
DESCRIPTION
The SP7680 is a complete backlight display solution that is designed to independently control LEDs for
main and auxiliary displays as well as the keypad. A two line I2C serial interface allows a simple way to
adjust each current individually in order to provide ultimate flexibility in driving LEDs. 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. Extra low 33µA LSB allows trickle current through the LEDs for non-
reflecting LCD displays. The SP7680 automatically detects 1x or 1.5x operation for optimal efficiency.
TYPICAL APPLICATION CIRCUIT
MAIN
SUB
AUX
VIN
VIN
2.2µF
VOUT
SP7680
1µF
SDA
C1
C2
SCL
0.47µF
0.47µF
June 21-07 revH
SP7680: Complete Backlight Solution
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
periods of time may affect reliability.
VIN, SDA, SCL, LEDx, VOUT.....................................-0.3V to 6.0V
Power Dissipation ……………………...………… Internally limited
Junction Temperature
(T = T + P •33.3°C/W)……………………….. 40°C to +125°C
J
A
D
Storage Temperature..………..…………………….-65°C to 150°C
ꢀJA (1 square 1oz Cu)……………...…….………….33.3°C/W
ELECTRICAL SPECIFICATIONS
Unless otherwise specified: VIN= 2.7V-5.5V, CIN = 2.2µF, COUT = 1µF, CFL2 =0.47µF, CFL2 = 0.47µF, TA =
-40°C to +85°C, Tj=-40°C to +125°C. Bold values apply over the full operating temperature range.
PARAMETER
MIN
2.7
TYP
MAX
5.5
UNITS
CONDITIONS
Operating Input Voltage Range
V
V
IN=4.0V, VLED = 3.3V
Status = 11000000
Operating Input Current
(4 MAIN LEDs operating at 33uA
each, all other LEDs off, in 1X
mode)
400
300
5
CNTRL = 00011110
Main=Sub=Aux=00000000
µA
V
IN = 3.0V, VLED = 3.3V
Status = 11000000
Operating Input Current
(Charge pump in 1.5X mode with
all LEDs at 33uA each)
8
mA
CNTRL = 11111110
Main=Sub=Aux=00000001
VIn=4.0V
Status = 10000000
CNTRL = 00000000
Main=Sub=Aux=00000000
300
Standby mode Quiescent Current
200
200
µA
Maximum Output Current (Note 1)
LED Current accuracy
mA
%
VIN = 3.4V, VLED = 3.3V
-10
10
+3
I
LED = 20mA
LED = 20mA
-3
I
LED Current matching
%
Current DAC Resolution
Current for DAC=000000
Current for DAC=000001
Current DAC LSB DAC=00010
Current DAC LSB DAC=00010
6
0
bits
mA
µA
5
50
31
1
1x mode only
mA
mA
MAIN and SUB LEDs
AUX LED
2
I
LED =20mA for MAIN and SUB;
0.2
LED Dropout Voltage (Note 2)
Maximum LED Current
V
ILED =40mA for AUX
After 63 counts MAIN and SUB
LEDs
31.5
mA
Maximum LED Current
Switching Frequency
63
2
mA
After 63 counts AUX LED
1.6
2.4
5
MHz
Equivalent Resistance, 1x mode
Equivalent Resistance, 1.5x mode
Control Clock Frequency
3
6
ꢁ
ꢁ
V
V
IN=3.4V
IN=3.4V
10
0.4
MHz
June 21-07 revH
SP7680: Complete Backlight Solution
2007 Sipex Corporation
Page 2
ELECTRICAL SPECIFICATIONS continued
PARAMETER
MIN
TYP
MAX
UNITS
CONDITIONS
V
IN = 4.2V, VLED=3.3V
Initial State: Status = 00000000
Final State: Status = 11000000
CNTRL = 11111110
Power-up time from Shutdown
(Note 3)
1.5
2
ms
Main=Sub=Aux=00000000
Time measured from stop bit of
final state I2C command to point
where VOUT = 4.1V
V
IN = 4.0V, VLED=3.3V
Initial State: Status = 11000000
CNTRL = 11111110
Main=Sub=Aux=00000000
Final State: Status = 11000000
CNTRL = 11111110
Soft Start Interval
(within 1X mode)
(Note 4)
5
µs
Main=Sub=Aux=11111100
Time measured from the raising
edge of STATUS acknowledge bit
of final state command to the point
where all current is within 5% of its
final value.
V
IN = 3.4V, VLED = 3.3V
Initial State: Status = 11000000
CNTRL = 11111110
Main=Sub=Aux=00000000
Final State: Status = 11000000
CNTRL = 11111110
Soft Start Interval
(transition 1X to 1.5X)
(Note 5)
140
µs
Main=Sub=Aux=11111100
Time measured from the raising
edge of CNTRL acknowledge bit of
final state command to the point
where output voltage is within 5%
of its final value.
If both SDA and SCL are low for
50ms, the part goes into shutdown
Shutdown Supply Current @ 25 °C
0.01
2
µA
µA
mode, set
VSUPPLY = 4.2V
STATUS=00000000,
If both SDA and SCL are low for
50ms, part goes into shutdown
Shutdown Supply Current @ 85 °C
5
mode set
VSUPPLY = 4.2V
STATUS=00000000,
VOUT
– 0.5V
V
OUT –
1V
Short LED threshold
Thermal Shutdown Die Temperature
Thermal Shutdown Hysteresis
170
25
Regulator turns off
°C
°C
Regulator turns on again @ 150°C
If both SDA and SCL are low for
50ms, part goes into shutdown
mode set STATUS=00000000
SDA, SCL low timeout
50
65
ms
0.4
SDA, SCL input logic low voltage
SDL, SCA input logic high voltage
V
V
Regulator shutdown
Regulator enabled
1.6
Note 1: The maximum output current is a derived spec IOUTMAX
=
(VIN*1.5 – VLED - VDROPOUT)/(max Req 1.5X mode).
Note 2: Dropout is defined when LED current goes 10% below nominal value as VIN is lowered.
June 21-07 revH
SP7680: Complete Backlight Solution
2007 Sipex Corporation
Page 3
TIMING CHARACTERISTICS
Note 3: Power-up time from Shutdown
I2C data input
START ADDRESS A STATUS
A
CNTRL
A
MAIN
A
SUB
A
AUX
A
STOP
Power-up time (Softstart time)
1.5x mode
1x mode
V
OUT
1x mode
5%
IOUT
Drivers ON
Note 4: Soft Start Interval (within 1x Mode)
Soft Start Interval within 1X mode
I2C data input (Final state)
START ADDRESS A STATUS
A
CNTRL
A
MAIN
A
SUB
A
AUX
A
STOP
Output Current within
5% of final value
5%
ILED
The softstart interval within 1x mode: After mode changes from Standby to Active, the time from the rising edge of
“STATUS” acknowledge bit to the point where the ILED is within 5% of its final value at full load. This softstart is
tested with VIN = 4.0V to ensure 1x mode.
Note 5: Soft Start Interval (Transition 1x to 1.5x Mode)
Soft Start Interval within 1.5X mode
I2C data input (Final state)
START ADDRESS A STATUS
A
CNTRL
A
MAIN
A
SUB
A
AUX
A
STOP
Mode of charge pump changes from
1x mode to 1.5x mode at the full load.
5%
V
OUT
1x mode
1.5x mode
The softstart interval from 1x to 1.5x mode: After mode changing from 1x mode to 1.5x mode, the time from the
rising edge of “CNTRL” acknowledge bit to the point where VOUT is within 5% of its final value at full load. This is
the measurement to know the boosting time of the charge pump at full load current. In this case, it is easier to
measure VOUT than IOUT. Softstart is tested with VIN = 3.4V to force a mode transition.
June 21-07 revH
SP7680: Complete Backlight Solution
2007 Sipex Corporation
Page 4
TIMING CHARACTERISTICS
(Typical Operating Circuit, VIN =2.7V to 5.5 V, Tj =-40°C to 125°C, unless otherwise noted. Typical
Values are at VIN=3.3V, TA=+25 °C)
PARAMETER
SYMBOL
fSCL
CONDITIONS
MIN
TYP MAX
UNITS
kHz
Serial Clock Frequency
400
Bus Free Time Between a
STOP and a START
tBUF
1.3
µs
Hold Time, Repeated
START Condition
t HD_STA
TSU,STA
0.6
0.6
µs
µs
Repeated START Condition
Setup Time
STOP Condition Setup Time
Data Hold Time
tSU,STO
tHD,DAT(OUT)
tHD,DAT(IN)
tSU,DAT
tLOW
0.6
225
0
µs
ns
ns
ns
µs
µs
900
Input Data Hold Time
Data Setup Time
900
100
1.3
0.6
SCL Clock Low Period
SCL Clock High Period
tHIGH
Rise Time of Both SDA and
SCL Signals, receiving
tR
(Notes2, 3)
(Note2, 3)
(Note2, 3, 4)
(Note5)
20+
0.1Cb
300
300
ns
ns
Fall Time of Both SDA and
SCL Signals, Receiving
tF
20+
0.1Cb
Fall Time of SDA
Transmitting
tF.TX
tSP
20+
0.1Cb
ns
ns
pF
µs
250
50
Pulse Width of Spike
Suppressed
0
Capacitive Load for Each
Bus Line
Cb
(Note 2)
400
1
I²C startup time after UVLO
clears
Tsrt
(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.
Note 5: Input filters on the SDA and SCL inputs suppress noise spikes less than 50ns.
June 21-07 revH
SP7680: Complete Backlight Solution
2007 Sipex Corporation
Page 5
PIN DESCRIPTION
PIN #
PIN NAME
DESCRIPTION
Input voltage for the regulator. Connect a 2.2µF decoupling capacitor
between this pin and ground.
6
VIN
Connect an LED between each pin and VOUT. Current value is
controlled by the serial interface. The current level through each pin is
internally matched within 3%. This current value can be programmed
to any level for MAIN or SUB LEDs with 0.5mA step (64 steps total).
Voltage at these pins is internally monitored to control the switching
between 1x and 1.5x mode in order to ensure the best possible
efficiency.
12-16
1,2
LED1-LED 5
LED6,LED7
Output of the charge pump. Place a 1µF decoupling capacitor from
this pin to ground. This voltage is regulated by the 1x or 1.5x charge
pump to create voltage sufficient to operate the current sources.
5
VOUT
11
3,4
GND
Ground pin.
Clock and data inputs for I2C interface. Connect a 100Kꢁ pull-up to
SDA,SCL
C1-, C1+
C21, C2+
VIN or Vcc.
7,8
Connect 0.47µF ceramic capacitor between these pins.
Connect 0.47µF ceramic capacitor between these pins.
9,10
-
Thermal Pad Connect to GND.
SP7680 FUNCTIONAL DIAGRAM
2.2uF
June 21-07 revH
SP7680: Complete Backlight Solution
2007 Sipex Corporation
Page 6
THEORY OF OPERATION
Overtemperature Protection
The SP7680 is a charge pump regulator
designed for converting an input voltage of 2.7V
to 5.5V to drive backlight white LEDs used in
portable applications. It has a total of 7 LED
driver outputs consisting of 4 Main, 2 Sub and
one Auxiliary keypad output. The Main and Sub
outputs can drive up to 31.5mA for each LED
while the Aux output can drive up to 63mA. With
the I2C serial interface, each LED can be turned
on/off independently so any combination of 7
outputs is available. Three 6-bit DACs are
included to provide precise current level setting.
The drive current is set simultaneously for one
group. The brightness integrity and good current
matching among channels are assured by this
control method.
When the temperature of the SP7680 Rises
above 170°C, the overtemperature protection
circuitry turns off the output switches to prevent
damage to the device. If the temperature drops
back down below 145°C, the SP7680
automatically recovers and executes a soft start
cycle.
Overvoltage Protection
The SP7680 has overvoltage protection. In
normal operation if the current-sinks are all
open-circuited, the output voltage will rise only to
the regulation voltage of 4.2V. When the current-
sinks are no longer open-circuited, the device
resumes normal operation.
The SP7680 is a fractional charge pump and
can multiply the input voltage by 1 or 1.5 times.
The charge pump switches at a high fixed
frequency of 2MHz which allows for reduced
external component sizes. The internal mode
selection circuit automatically switches the mode
between 1x and 1.5x mode based on the input
voltage, output voltage and load current. This
mode switching maximizes the efficiency
throughout the entire load range. When the
battery voltage is high enough, the SP7680
operates in 1x mode to provide maximum
efficiency. Dropout detection is provided on all
four MAIN LED outputs and the two SUB LED
outputs, to determine when the SP7680 needs
to transition to 1.5X mode. If the battery voltage
is too low to sustain the LED current, the 1.5x
mode is automatically enabled. As the battery
discharges and the voltage decays, the SP7680
automatically switches between modes to
maintain a constant current to drive LEDs
throughout the battery life.
Shorted LED Protection
Shorted LED protection is provided. If the
shorted
SP7680
detects
a
LED
the
corresponding LED output will turn off (no
current).
I²C interface
The I²C interface allows a simple way to adjust
each bank of channel currents in order to
provide ultimate flexibility in driving LEDs. The
SP7680 has five data registers which can be
programmed serially via the I²C interface.
The STATUS register is used to enable/disable
the part as well as for fault mode readback. The
CNTRL register contains information regarding
the state of each of the 7 individual LEDs. The
final three registers contain information
regarding the current level for the MAIN, SUB
and AUX channels.
June 21-07 revH
SP7680: Complete Backlight Solution
2007 Sipex Corporation
Page 7
TYPICAL PERFORMANCE CHARACTERISTICS
= 25°C unless otherwise noted. For 7 LED curves, LED7 anode
VIN = 3.6V, Typical Application Circuit, T
A
is connected to VOUT, not VIN
.
Output Efficiency Vs VIN, 6 WLEDs
Output Efficiency Vs VIN, 7 WLEDs
100
100
95
90
85
80
75
70
65
60
95
90
85
80
75
ILED=15mA,Vf=3.4V
ILED=20mA,Vf=3.6V
ILED=25mA,Vf=3.8V
70
65
60
ILED=15mA,Vf=3.4V
ILED=20mA,Vf=3.6V
ILED=25mA,Vf=3.8V
3.0
3.3
3.6
IN (V)
3.9
4.2
3.0
3.3
3.6
IN (V)
3.9
4.2
V
V
Output Current Vs VIN, 6 WLEDs
Output Current Vs VIN, 7 WLEDs
200
150
100
50
200
150
100
50
ILED=25mA,Vf=3.4V
ILED=20mA,Vf=3.6V
ILED=15mA,Vf=3.8V
ILED=15mA,Vf=3.4V
ILED=20mA,Vf=3.6V
ILED=25mA,Vf=3.8V
3.0
3.3
3.6
IN(V)
3.9
4.2
3.0
3.3
3.6
VIN (V)
3.9
4.2
V
LED Efficiency Vs VIN, 6 WLEDs
LED Efficiency Vs VIN, 7 WLEDs
100
95
90
85
80
75
70
65
60
100
95
90
85
80
75
70
65
60
ILED=15mA,Vf=3.4V
ILED=20mA,Vf=3.6V
ILED=25mA,Vf=3.8V
ILED=15mA,Vf=3.4V
ILED=20mA,Vf=3.6V
ILED=25mA,Vf=3.8V
3.0
3.3
3.6
IN (V)
3.9
4.2
3.0
3.3
3.6
VIN (V)
3.9
4.2
V
June 21-07 revH
SP7680: Complete Backlight Solution
2007 Sipex Corporation
Page 8
TYPICAL PERFORMANCE CHARACTERISTICS
IN = 3.6V, Typical Application Circuit, TA = 25°C unless otherwise noted.
V
Scope Photo #1 Startup from Shutdown
Scope Photo #2 Soft start Interval (within 1X)
ch1=VOUT
ch1=VOUT
ch2=SCL
ch4=IOUT 10mA/div
ch4= IOUT 100mA/div
Scope Photo #3 Soft start Interval (1X to 1.5X) Scope Photo #4 Voltage Ripple (1.5X Mode)
ch1=VOUT
V
IN(AC)
ch2=SCL
V
OUT(AC)
ch4=
I
OUT 100mA/div
Scope Photo #5 Startup in 1.5X Mode
6 LEDs at 20mA
Scope Photo #6 Startup in 1X Mode
6 LEDs at 20mA
V
OUT
V
OUT
I
IN 0.2A/div
I
IN 0.2A/div
June 21-07 revH
SP7680: Complete Backlight Solution
2007 Sipex Corporation
Page 9
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
SP7680
Address
7-bit
A
Data
for
Status
8-bit
A
Data
for
CNTRL
8-bit
A
Data
for
Main
8-bit
A
Data
for
Sub
8-bit
A
Data
for
Aux
8-bit
A
SP
R/
W
1/0
Acknowledge,
sent by slave
Stop
condition
Start
Condition
Acknowledge, sent by slave when R/
Or, sent by master when R/ =1
W
=0
W
SP7680 I2C Slave Address Map: (Default Address: 28H)
Fuses
Device Address
Fuse1
Fuse0
A7
A6
A5
A4
A3
A2
A1
A0
0
0
0
1
0
0
0
0
1
1
0
0
1
0
0
0
0
0
0
0
1
1
0
1
0
0
0
0
1
1
1
1
1
0
0
0
0
0
0
0
I²C Serial Interface
Registers
STATUS Register
The SP7680 has five data registers which can be
programmed serially via the I²C interface. The
STATUS register is used to enable/disable the part
as well as for fault mode readback. The CNTRL
register contains information regarding the state of
each of the 7 individual LEDs. The final three
registers contain information regarding the current
level for the MAIN, SUB and AUX channels.
In the STATUS register, b7 and b6 are used to
enable/disable the SP7680. The following table
defines the states for bits WZ and WP. These bits
are used to put the SP7680 into shutdown, standby
or active mode.
The register bits are as follows:
June 21-07 revH
SP7680: Complete Backlight Solution
2007 Sipex Corporation
Page 10
APPLICATIONS INFORMATION
LED
drivers
Fault Conditions
WZ WP
State
Shutdown
Iq
and
0
0
0
1
reset registers to
00000000
0uA
Off
Off
For all three fault conditions:
Shutdown - keep
register contents
Under Voltage Lockout
Over Temperature Detection
Over Voltage Protection
0uA
Standby
-
keep
Upon entering any of these fault modes, the LED
drivers should turn off but the register contents
should remain unchanged with the exception of the
fault mode readback bits of the status register. The
WZ and WP bits of the status register should also
remain unchanged. The microprocessor should not
have to reset the SP7680 if it goes into fault mode.
The chip should continuously monitor its fault
indicators and when the fault condition is no longer
present, normal operation can resume.
register contents –
bandgap and other
1
1
0
1
analog
circuits 200uA
Off
On
active, Vin shorted
to Vout through
internal switch
Active
Iq
Active
*When WZ=0 and WP=0 all registers are set to zero.
Bits B5, B4, B3, B2 and B1 are for read back only.
Bit B5 is held high whenever any kind of fault
condition exists on the SP7680. Bits B4, B3 and B2
indicate the specific fault condition, over-voltage
(B4=1), over-temp (B3=1) or undervoltage lockout
(B2=1). B1 communicates the state of the charge
pump, (B1=1 for 1.5x mode or B1=0 for 1x mode).
CNTRL Register
In the CNTRL register B1, B2, B3 and B4 are used
to control the four MAIN LEDs, bits B5 and B6 are
used for the two SUB LEDs, and B7 is used for the
AUX LED. To enable an individual LED the
corresponding bit is active high.
B0 of the STATUS register is used to select between
automatic charge pump mode selection and forced
charge pump mode selection. If B0 is low then the
charge pump mode (1X or 1.5X) is automatically
selected. If B0 is high then the charge pump is
forced into either 1X mode or 1.5X mode depending
upon B0 of the CNTRL register.
When B0 of the STATUS register is high, B0 of the
CNTRL register is used to force the charge pump
into 1X mode (CNTRL B0=low) or 1.5X mode
(CNTRL B0=high). When B0 of the STATUS
register is low then CNTRL B0 is ignored.
June 21-07 revH
SP7680: Complete Backlight Solution
2007 Sipex Corporation
Page 11
APPLICATIONS INFORMATION
B7…B2 Main Sub
Aux
17.0
MAIN, SUB and AUX registers
010001
010010
010011
010100
010101
010110
010111
011000
011001
011010
011011
011100
011101
011110
011111
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
8.5
9.0
8.5
9.0
18.0
19.0
20.0
21.0
22.0
23.0
24.0
25.0
26.0
27.0
28.0
29.0
30.0
31.0
32.0
33.0
34.0
35.0
36.0
37.0
38.0
39.0
40.0
41.0
42.0
43.0
44.0
45.0
46.0
47.0
48.0
49.0
50.0
51.0
52.0
53.0
54.0
55.0
56.0
57.0
58.0
59.0
60.0
61.0
62.0
63.0
9.5
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
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
10.0
10.5
11.0
11.5
12.0
12.5
13.0
13.5
14.0
14.5
15.0
15.5
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
In the MAIN, SUB and AUX registers bits B7, B6,
B5, B4, B3 and B2 represent the DAC codes D5-D0
used to set the LED current in the MAIN, SUB and
AUX channels. Bits B1 and B0 are don’t care. The
following table lists the DAC codes and the
corresponding current for each channel in mA; the
table appears below and continues on the right
column.
Addressing and Writing Data to the SP7680
To write data to the SP7680 the following data
cycle must be obeyed:
[Slave
Address
with
write
bit][Data
for
STATUS][Data for CNTRL][Data for MAIN][Data
for SUB][Data for AUX]
Six bytes are communicated each data cycle. All
the settings will take effect right after the
acknowledgement bit of the current data byte.
B7…B2 Main Sub
Aux
000000
000001
000010
000011
000100
000101
000110
000111
001000
001001
001010
001011
001100
001101
001110
001111
010000
0
0
0
0.031 0.031 0.031
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
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
2.0
3.0
4.0
5.0
6.0
7.0
8.0
9.0
10.0
11.0
12.0
13.0
14.0
15.0
16.0
June 21-07 revH
SP7680: Complete Backlight Solution
2007 Sipex Corporation
Page 12
APPLICATIONS INFORMATION
LED Selection
here for reference. The second case of LED
power efficiency is included to show the user the
true power delivered to the LEDs. As you can
see in the curves, the LED efficiency is greatest
The SP7680 is designed as a driver for backlight
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
main and sub LCD display backlighting, camera
photo-flash applications, color (RGB) LEDs,
infrared (IR) diodes for remotes, and other loads
benefiting from a controlled output current
generated from a varying input voltage. Since
the D1 to D6 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 high-
VF type LEDs. The low dropout current-sinks in
the SP7680 make it capable of driving main
LEDs with forward voltages as high as 4.0V at
full current from an input supply as low as 3.2V.
LED current-sink inputs can be paralleled to
drive high-current LEDs without complication.
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 SP7680 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 SP7680 is in the 1.5x mode and
in this mode the input current is 1.5 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.
Device Switching Noise Performance
The SP7680 operates at a fixed frequency of
approximately 2MHz 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 is
20mV peak-to-peak, typically ten times less than
inductor-based DC/DC boost converter white
LED backlight solutions. The SP7680 soft-start
feature prevents noise transient effects
associated with inrush currents during startup of
the charge pump circuit.
Capacitor Characteristics
Ceramic composition capacitors are highly
recommended over all other types of capacitors
for use with the SP7680. 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.
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. The 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
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.
June 21-07 revH
SP7680: Complete Backlight Solution
2007 Sipex Corporation
Page 13
APPLICATIONS INFORMATION
Ceramic Capacitor Materials
applications. The fly capacitors C1 and C2 can
be 0.47ꢂF for most applications. For applications
with all 7 LED drivers used and driven to 20mA
or more, it is advisable to use a 2.2ꢂF input
capacitor in order to reduce the input ripple as
seen by the battery. In very noise sensitive
applications, the input capacitor can even be
increased to 4.7ꢂF. If the LED current-sinks are
only programmed for low current levels, or if the
application is not very noise sensitive, then a
1ꢂF input capacitor may be used. See table 1 for
capacitor selection.
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
C
IN, C1, C2, and COUT is important because
Thermal Protection
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
100mꢁ. A value of 2.2ꢂF for the input and 1ꢂF
for the output capacitor is sufficient for most
The SP7680 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 25°C below the
thermal limit.
Manufacturers/ Website
Part Number
Capacitance/
Voltage
Capacitor
ESR at
100kHz
Size/Type/Thickness
TDK/www.tdk.com
TDK/www.tdk.com
TDK/www.tdk.com
C1005X5R0J474K
C1005X5R0J105K
C1608X5R0J225K
0.47uF/6.3V
1uF/6.3V
2.2uF/6.3V
4.7uF/6.3V
0.47uF/6.3V
1uF/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
TDK/www.tdk.com
C1608X5R0J475K
Murata/www.murata.com
Murata/www.murata.com
Murata/www.murata.com
Murata/www.murata.com
GRM155R60J474KE19
GRM155R60J105KE19
GRM185R60J225KE26
GRM188R60J475KE19
2.2uF/6.3V
4.7uF/6.3V
Table 1: SP7680 Capacitor Selection
June 21-07 revH
SP7680: Complete Backlight Solution
2007 Sipex Corporation
Page 14
PACKAGE: 3x3mm 16 pin QFN
June 21-07 revH
SP7680: Complete Backlight Solution
2007 Sipex Corporation
Page 15
ORDERING INFORMATION
Min
Max
Theta JA
ºC/W
Part Number
Status
RoHS
MSL Level
L3 @ 260ºC
L3 @ 260ºC Tape & Reel
Pack Type Quantity Package
Temp ºC Temp ºC
3x3 16 Pin
SP7680ER1-L
Active
-40
85
Yes
Yes
33.3
33.3
Canister
Any
QFN
3x3 16 Pin
QFN
SP7680ER1-L/TR
SP7680EB
Active
Active
-40
-40
85
85
3000
Not Applicable to Eval Board
Board
For further assistance:
Email:
WWW Support page:
Sipex Application Notes:
Sipexsupport@sipex.com
http://www.sipex.com/content.aspx?p=support
http://www.sipex.com/applicationNotes.aspx
Sipex Corporation
Solved by
Headquarters and
Sales Office
233 South Hillview Drive
Milpitas, CA95035
tel: (408) 934-7500
FAX: (408) 935-7600
TM
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.
June 21-07 revH
SP7680: Complete Backlight Solution
2007 Sipex Corporation
Page 16
相关型号：
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