LDS8680
800 mA White LED Driver for Photo Flash
FEATURES
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1-x and 2-x Charge pump modes
Low dropout PowerLite™ Current Regulator*
Drives up to 2 LEDs at 400 mA
simultaneously or one LED at 800 mA
Smart OneWire™ LED current programming
and PWM mode LED current control
Power efficiency up to 90%
Low current shutdown mode < 1 µA
Short circuit current limiting
Thermal shutdown protection
Timeout to protect LED at high currents
8-pin 2 x 3 x 0.8 mm TDFN package
channel. Inclusion of a low dropout PowerLite™
Current Regulator (PCR) increases device’s
efficiency up to 90%.
The EN/SET logic input functions as a chip enable
and a current setting interface.
The LEDs current is programmable by Smart
OneWire™ digital interface in 32 steps from 52 to
800 mA for LEDA channel or in 16 steps from 52 to
400 mA for LEDB channel. Every LED may be turned
on/off or programmed separately
Low noise input ripple is achieved by operating at a
constant switching frequency, which allows the use of
small external ceramic capacitors. The charge pump
supports a range of input voltages from 2.7 V to
5.5 V.
The device is available in 8-lead TDFN 2 mm x 3 mm
package with a max height of 0.8 mm.
APPLICATION
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Photo flash plus red eyes reduction
White LED photoflash for cell phones and
still cameras
DESCRIPTION
The LDS8680 is a high efficiency charge pump with
low dropout voltage that can drive two LEDs at 400
mA each simultaneously or one LED at 800 mA per
TYPICAL APPLICATION CIRCUIT
© 2009 IXYS Corp.
Characteristics subject to change without notice
1
Doc. No. 8681_DS, Rev. N1.0
LDS8680
ABSOLUTE MAXIMUM RATINGS
Parameter
VIN, LEDx, C1± voltage
V
OUT
voltage
EN/SET voltage
Storage Temperature Range
Junction Temperature Range
Soldering Temperature
Rating
6
6
V
IN
+ 0.7V
-65 to +160
-40 to +125
300
Unit
V
V
V
°C
°C
°C
RECOMMENDED OPERATING CONDITIONS
Parameter
VIN
Ambient Temperature Range
Rating
2.7 to 5.5
-40 to +85
Unit
V
°C
Typical application circuit with external components is shown on page 1.
ELECTRICAL OPERATING CHARACTERISTICS
(Over recommended operating conditions unless specified otherwise) V
IN
= 3.6V, C1 = 2.2 µF, Cin = Cout = 1 µF, EN = High, T
AMB
= 25°C
Name
Standby Current
Shutdown Current
LED Current Accuracy
LED Channel Matching
Output Resistance (open loop)
1
Conditions
V
EN
= 0V
1mA
≤I
LED
≤400
mA
(I
LED
- I
LEDAVG
) / I
LEDAVG
1-x mode
2-x mode
V
OUT
< 0.5V
At 200 mA
EN = V
IN
= 5.5 V
Min
Charge Pump Frequency
Output short circuit Current Limit
Input Current Limit
1-x to 2-x
Transition Thresholds at any LED pin
Transition Filter Delay
Input current
EN/SET
Pin
High
Logic Level
Low
1
Thermal Shutdown
1
Thermal Hysteresis
Under Voltage Lockout (UVLO)
Threshold Voltage protection
Output Over
Flash LED Safety Timer
Note:
Typ
0.6
0.5
±8
±8
0.5
1.7
1
2
2
150
800
1
Max
Units
mA
µA
%
%
Ω
MHz
A
A
mV
µs
µA
1.4
0.4
160
25
2.3
5.6
250
5.9
V
°C
V
V
ms
1. Sample test only
2. Measusured from Flash LED ON command to ILED reaches 90% of regulated level
© 2009 IXYS Corp.
Characteristics subject to change without notice
2
Doc. No. 8680_DS, Rev. N1.0
LDS8680
RECOMMENDED EN/SET TIMING
For 2.7
V
IN
5.5V,
over full ambient temperature range -40 to +85ºC.
Symbol
t
SETUP- PWM
t
SETUP-COM
t
BO
t
B1
t
CLO1
t
CLO2
t
LO
t
OFF
Name
EN/SET setup from shutdown in
PWM mode
EN/SET setup from shutdown in
command mode
Bit “zero” positive pulse
Bit “one” positive pulse
Low time between 16 command
pulses
Low time between two 16-byte
command sets
EN LOW Time to finalize
command mode
EN/SET low time to shutdown
Conditions
Min
10
300
1
8
2
100
0.3
50
Typ
100
400
2
16
25
Max
200
2000
4
200
50
200
30
Units
μ
s
μ
s
μ
s
μ
s
μ
s
μ
s
ms
ms
Fig. 1 Command mode programming
Fig. 2 PWM mode with short pulse
Fig. 3 PWM mode with long pulse
© 2009 IXYS Corp.
Characteristics subject to change without notice
3
Doc. No. 8680_DS, Rev. N1.0
LDS8680
LED CURRENT SETTING COMMANDS
Command Value
Binary
0000 0000 0000 0001
0000 0000 0000 0010
0000 0000 0000 0011
0000 0100 000Y YYYY
Command Description
Hex
00 01
00 02
00 03
04 ZZ
Turn LEDA “ON” with LED current at factory preset maximum value, Safety
Timer is “ON”
Turn LEDB “ON” with LED current at factory preset maximum value, Safety
Timer is “ON”
Turn LEDA and LEDB “ON” with LED current at factory preset maximum
value, Safety Timer is “ON”
Turn LEDA “ON” with LED current other than factiry programmed value. Binary
code Y YYYY is determined as desired LED current value in mA divided by
25.6 mA minus 1. Safety Timer is “ON”
Example:
Binary Code to set 540 mA current is equal (540/25.6 – 1) = 20 (dec) = 1 0100
(bin) = 14 (hex)
Because LSB value is 25.6 mA, LED current can be set with this resolution
only.
Set of two commands to program LEDA current as above, but Safety Timer is
“OFF”
Turn LEDB “ON” with LED current other than factiry programmed value. Binary
code YYYY is determined as desired LED current value in mA divided by
25.6 mA minus 1. Safety Timer is “ON”
Example:
Binary Code to set 307 mA current is equal (307/25.6 – 1) = 11 (dec) = 1011
(bin) = B (hex)
Because LSB value is 25.6 mA, LED current can be set with this resolution
only.
Set of two commands to program LEDB current as above, but Safety Timer is
“OFF”
0000 0110 000Y YYYY
0000 0010 0000 0001
0000 1000 0000 YYYY
06 ZZ
02 01
08 0Z
0000 1010 0000 YYYY
0000 0010 0000 0010
0A 0Z
02 02
© 2009 IXYS Corp.
Characteristics subject to change without notice
4
Doc. No. 8680_DS, Rev. N1.0
LDS8680
TYPICAL CHARACTERISTICS
V
IN
= 3.6V, I
OUT
= 800 mA (2 LEDs at 400mA), C
IN
= C1= 1μ C
OUT
= 2
μ
T
AMB
= 25°C unless otherwise specified
F,
F,
Power-Up in 1-x mode
Power-Up in 2-x Mode
V
IN
= 4.2 V, Ch1 – EN/SET, Ch2 – LED current (400 mA/div),
Ch3 – Output voltage
V
IN
= 3.6 V, Ch1 –EN/SET, Ch2 – LED current (400 mA/div),
Ch3 – Output voltage
Operating Waveforms at 1kHz PWM mode
10% Duty Cycle
Operating Waveforms at 1kHz PWM mode
90% Duty Cycle
V
IN
= 4.2 V, Ch1 – EN/SET, Ch2 – LED current (400 mA/div)
V
IN
= 4.2 V, Ch1 –EN/SET, Ch2 – LED current (400 mA/div)
LED Current Setting Error vs. Duty Cycle
in PWM Mode
Power-Down Delay (1-x Mode)
V
IN
= 4.2 V, Ch1 – PWM, Ch2 – LED current (400 mA/div)
© 2009 IXYS Corp.
Characteristics subject to change without notice
5
Doc. No. 8680_DS, Rev. N1.0
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