LDS8680
800 mA White LED Driver for Photo Flash
FEATURES
o
o
1-x and 2-x Charge pump modes
Low dropout PowerLite™ Current Regulator*
o
Drives up to 2 LEDs at 400 mA
simultaneously or one LED at 800 mA
o
Smart OneWire™ LED current programming
and PWM mode LED current control
channel. Inclusion of a low dropout PowerLite™
Current Regulator (PCR) increases device’s
efficiency up to 90%.
o
o
Power efficiency up to 90%
Low current shutdown mode < 1 µA
o
o
Short circuit current limiting
Thermal shutdown protection
The EN/SET logic input functions as a chip enable
and a current setting interface.
o
Timeout to protect LED at high currents
o
8-pin 2 x 3 x 0.8 mm TDFN package
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
APPLICATION
o
Photo flash plus red eyes reduction
o
White LED photoflash for cell phones and
still cameras
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.
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
The device is available in 8-lead TDFN 2 mm x 3 mm
package with a max height of 0.8 mm.
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
Rating
2.7 to 5.5
-40 to +85
VIN
Ambient Temperature Range
Unit
V
°C
Typical application circuit with external components is shown on page 1.
ELECTRICAL OPERATING CHARACTERISTICS
(Over recommended operating conditions unless specified otherwise) VIN = 3.6V, C1 = 2.2 µF, Cin = Cout = 1 µF, EN = High, TAMB = 25°C
Name
Standby Current
Shutdown Current
LED Current Accuracy
LED Channel Matching
Output Resistance (open loop)
Conditions
1
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
Output Over Voltage protection
Flash LED Safety Timer
Note:
Min
V EN = 0V
1mA ≤ILED ≤400 mA
(ILED - ILEDAVG) / ILEDAVG
1-x mode
2-x mode
V OUT < 0.5V
At 200 mA
EN = VIN = 5.5 V
Typ
0.6
0.5
±8
±8
0.5
1.7
1
2
2
Max
Units
mA
µA
%
%
Ω
MHz
A
A
150
mV
800
1
µs
µA
1.4
0.4
160
25
2.3
5.6
°C
5.9
250
V
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 VIN 5.5V, over full ambient temperature range -40 to +85ºC.
Symbol
tSETUP- PWM
tSETUP-COM
tBO
tB1
tCLO1
tCLO2
tLO
tOFF
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
Typ
Max
Units
10
100
200
μs
300
400
2000
μs
1
8
2
16
4
200
μs
μs
2
25
50
μs
100
200
μs
0.3
30
ms
50
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
Hex
00 01
0000 0000 0000 0010
00 02
0000 0000 0000 0011
00 03
0000 0100 000Y YYYY
04 ZZ
0000 0110 000Y YYYY
0000 0010 0000 0001
0000 1000 0000 YYYY
0000 1010 0000 YYYY
0000 0010 0000 0010
Command Description
06 ZZ
02 01
08 0Z
0A 0Z
02 02
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”
© 2009 IXYS Corp.
Characteristics subject to change without notice
4
Doc. No. 8680_DS, Rev. N1.0
LDS8680
TYPICAL CHARACTERISTICS
V IN = 3.6V, IOUT = 800 mA (2 LEDs at 400mA), C IN = C1= 1μF, COUT = 2 μF, TAMB = 25°C unless otherwise specified
Power-Up in 1-x mode
Power-Up in 2-x Mode
VIN = 4.2 V, Ch1 – EN/SET, Ch2 – LED current (400 mA/div),
Ch3 – Output voltage
VIN = 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
VIN = 4.2 V, Ch1 – EN/SET, Ch2 – LED current (400 mA/div)
VIN = 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
LDS8680
PIN DESCRIPTION
Pin #
1
2
3
4
5
6
7
8
PAD
Name
V IN
C1+
C1EN/SET
LEDB
LEDA
GND
VOUT
PAD
Function
Charge pump input, connect to battery or supply
Flying capacitor 1 Positive terminal
Flying capacitor 1 Negative terminal
Device enable (active high) and Dimming Control
LEDB cathode terminal
LEDA cathode terminal
Ground Reference
Charge pump output connected to the LED anodes
Connect to GND on the PCB
Top view: TDFN 8-lead 2 X 3 mm
PIN FUNCTION
VIN is the supply pin for the charge pump. A small
1 μF ceramic bypass capacitor is required between
the V IN pin and ground near the device. The
operating input voltage range is from 2.7 V to 5.5 V. If
VIN falls below the under-voltage threshold, all LED
channels disable and the device enters shutdown
mode.
V OUT is the charge pump output that is connected to
the LED anodes. A small 2.2 μF ceramic bypass
capacitor is required between the VOUT pin and
ground near the device.
GND is the ground reference for the charge pump.
The pin must be connected to the ground plane on
the PCB.
EN/SET is the enable and one wire addressable
control logic input for all LED channels. Guaranteed
levels of logic high and logic low are set at 1.4 V and
0.4 V respectively. When EN/SET is initially taken
high, the device becomes enabled and all LED
currents remain at 0 mA. To start LED current, device
should be in PWM mode (See p. 5). To place the
device into zero current mode, the EN/SET pin must
be held low for more than 50 ms.
© 2009 IXYS Corp.
Characteristics subject to change without notice
C1+, C1- are connected to each side of the ceramic
flying capacitor C1
LEDA, LEDB provides the internal regulated current
source for each of the LED cathodes. These pins
enter high-impedance zero current state whenever
the device is in shutdown mode.
PAD is the exposed pad underneath the packag e.
For best thermal performance, the pad should be
soldered to the PCB and connected to the ground
plane
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Doc. No. 8680_DS, Rev. N1.0
LDS8680
BLOCK DIAGRAM
Figure 2. LDS8680 Functional Block Diagram
BASIC OPERATION
pin recognizes as command, both LEDA and LEDB
channels are off, and no current is flowing through
LEDs. Command mode is used to set other than
factory preset LED current value, turn on/off one of
the channels, or turn off timeout protection. After
command provided, device goes into PWM mode
with maximum current value and number of channels
in ON state in respect to command provided. EN pin
should be logic LOW for more than tLO to finalize
command mode
LDS8680 is a charge pump designed for converting
at Li-Ion battery voltage to drive a white LED used in
photo flash applications. The output current has a
maximum value of 800 mA/per channel if one LED
is used or 400 mA/per channel if both LEDs are
used simultaneously. The output current is
programmable via the Smart OneWire™ interface
signaled at the EN pin.
The LDS8680 is in standby mode after applying V IN
voltage until logic HIGH level is applied to EN pin.
The device requires approximately 50 µs to wake
up.
Device starts operating with soft-start at 1-x mode to
minimize inrush current
At 1-x mode, the V OUT is approximately equal to V IN
(less any internal voltage losses). If the output
voltage is sufficient to regulate all LED currents, the
device remains in 1-x operating mode.
The LDS8680 may operate in either PWM or
command mode.
PWM mode starts if first pulse applied to EN pin
after power-up is shorter than or equal tSETUP- PWM, At
this mode, second and every next pulse applied to
EN pin recognizes as PWM pulse, both LEDA and
LEDB channels are on, and maximum LED current is
equal factory preset value.
The charge pump has two modes of operation: 1-x ,
and 2-x. The device changes modes if the output
voltage drops below the minimum needed to support
the desired ILED current.
. The low dropout PowerLite™ Current regulator
(PCR) performs well at input voltages up to 150 mV
above LED forward voltage VF significantly increasing
driver’s efficiency. The LDS8680 monitors voltage
The command mode starts if first pulse applied to
EN pin after power-up is longer than or equal tSETUPCOM. At this mode, every next 16 pulses applied to EN
© 2009 IXYS Corp.
Characteristics subject to change without notice
7
Doc. No. 8680_DS, Rev. N1.0
LDS8680
drop Vd across PCR at every channel in ON state. If
this voltage falls below 150 mV (typical) at any one
channel, (channel with LED with highest forward
voltage), the Mode Control Block changes charge
pump mode to the next multiplication ratio.
20 µs after enable and is limited to ~ 90 mA after
that.
4. Over-Temperature Protection
If the die temperature exceeds +160°C, the driver will
enter shutdown mode. Device restores normal
operation after die temperature falls below 135°C.
Vd (LEDA/B) = VIN x M – VF – Rcp x IOUT , where Rcp
is a Charge Pump Output Resistance at given mode,
IOUT is sum of all LED currents, and M is a charge
pump’ multiplication ratio.
5. Input Voltage Under-Voltage Lockout
If VIN falls below 2.3 V but above 1.7 V (typical value),
LDS8680 will restart when input voltage rises above
2.3 V called lockout mode. If V IN continues fall below
1.7 V, LDS8680 device will enter shutdown mode and
reset all data register. To restart device, set EN/SET
pin logic low for more than 50 ms and program new
ILED current value using Smart OneWire™ interface.
If the input voltage is insufficient or falls to a level
where Vd ≤ 150 mV, and the regulated currents
cannot be maintained, the low dropout PowerLite™
Current Regulator switches the charge pump into 2-x
mode (after a fixed delay time of about 800μs). In 2-x
mode, the charge pump’ output voltage is
approximately equal to 2 times the input supply
voltage (less any internal voltage losses).
6. Open LED Definition
When LED becomes an open circuit, device will enter
into 2-x mode. Unless this unused LED channel was
disabled via Smart OneWire™ commands.
LED Current Setting
The current in each of the two LED channels is
programmable through the Smart OneWire™
EN/SET digital control input. By pulsing this signal
according to a shown above protocol, a set of internal
registers can be addressed and written into allowing
to configure each of LEDs with the desired current.
See recommended commands at the Table
“CURRENT SETTING COMMANDS”
7. LED protection
LDS8680 uses timeout ~250 ms to protect LEDs from
thermal damage at currents above 200 mA. This
function may be disabled in command mode.
LED Selection
If the power source is a Li-ion battery, LEDs with
lowest forward voltages are recommended to achieve
highest efficiency and extended operation on a single
battery charge.
Unused LED Channels
For applications with only one LED, unused LED can
be disabled via the register internally and connect to
VOUT .
The LDS8680 has follow protection modes:
LEDs with forward voltages (VF ) ranging from 1.6 V to
4 V may be used. Charge pump operates in highest
efficiency when V F voltage is close to V IN voltage
multiplied by switching mode, i.e. V IN x 1 or V IN x 2
1. LED short to VOUT protection
External Components
If LED pin is shorted to VOUT , LED burned out
becomes as short circuit, or LED pin voltage is within
from VOUT to (VOUT - 1.5V) range, LDS8680
recognizes this condition as “LED Short” and disables
this channel. If LED pin voltage is less than (Vout –
1.5V), LDS8680 restores LED current at this
particular channel to programmed value.
The driver requires three external ceramic capacitors
(C1, CIN , and COUT ) X5R or X7R type. In 2-x charge
pump mode, the input current ripple is very low, and
an input bypass capacitor of 1µF is sufficient.
2. VOUT Over-Voltage Protection
Recommended Layout
The charge pump’ output voltage VOUT automatically
limits at about 6.2 V maximum. This is to prevent the
output pin from exceeding its absolute maximum
rating.
In charge pump mode, the driver switches internally
at a high frequency. It is recommended to minimize
trace length to all capacitors. A ground plane should
cover the area under the driver IC as well as the
bypass capacitors. Short connection to ground on
capacitors CIN and COUT can be implemented with the
use of multiple via. A copper area matching the
TDFN exposed pad (PAD) must be connected to the
Protection Modes
In 1-x mode, the device operates in linear mode and
does not introduce switching noise back onto the
supply.
3. VOUT Short Circuit Protection
If VOUT is shorted to ground before LDS8680 is
enabled, input current may increase up to 1 A within
© 2009 IXYS Corp.
Characteristics subject to change without notice
8
Doc. No. 8680_DS, Rev. N1.0
LDS8680
ground plane underneath. The use of multiple via
improves the package heat dissipation.
© 2009 IXYS Corp.
Characteristics subject to change without notice
9
Doc. No. 8680_DS, Rev. N1.0
LDS8680
PACKAGE DRAWING AND DIMENSIONS
8-PIN TDFN (HV3), 2mm x 3mm, 0.5mm PITCH
SYMBOL
A
A1
A2
b
D
D1
E
E1
e
L
MIN
0.700
0.180
2.950
1.750
1.950
1.550
0.350
NOM
0.750
0.000
0.203 Ref.
0.230
3.000
1.800
2.000
1.600
0.500 Bsc
0.400
MAX
0.800
0.050
0.280
3.050
1.850
2.050
1.650
0.450
Note:
1. All dimensions are in millimeters
2. Complies with JEDEC Standard MO-220
© 2009 IXYS Corp.
Characteristics subject to change without notice
10
Doc. No. 8680_DS, Rev. N1.0
LDS8680
ORDERING INFORMATION
Part Number
LDS8680 008-T2
Notes:
1.
2.
Package
1)
TDFN-8 2 x 3mm
Package Marking
2)
680
Quantity per reel is 2000
Matte-Tin Plated Finish (RoHS-compliant)
EXAMPLE OF ORDERING INFORMATION
Prefix
LDS
Device #
Suffix
680
008
Product Number
Optional
Company ID
Package
T2
Tape & Reel
T: Tape & Reel
2: 2000/Reel
008: 2x3 TDFN
Notes:
1) All packages are RoHS-compliant (Lead-free, Halogen-free).
2) The standard lead finish is Matte-Tin.
3) The device used in the above example is a LDS8680 008–T2 ( 2x3 TDFN, Tape & Reel).
4) For additional package and temperature options, please contact your nearest IXYS Corp. Sales office.
© 2009 IXYS Corp.
Characteristics subject to change without notice
11
Doc. No. 8680_DS, Rev. N1.0
LDS8680
Warranty and Use
IXYS CORP. MAKES NO WARRANTY, REPRESENTATION OR GUARANTEE, EXPRESS OR IMPLIED, REGARDING THE SUITABILITY OF ITS PRODUCTS FOR ANY
PARTICULAR PURPOSE, NOR THAT THE USE OF ITS PRODUCTS WILL NOT INFRINGE ITS INTELLECTUAL PROPERTY RIGHTS OR THE RIGHTS OF THIRD
PARTIES WITH RESPECT TO ANY PARTICULAR USE OR APPLICATION AND SPECIFICALLY DISCLAIMS ANY AND ALL LIABILITY ARISING OUT OF ANY SUCH
USE OR APPLICATION, INCLUDING BUT NOT LIMITED TO, CONSEQUENTIAL OR INCIDENTAL DAMAGES.
IXYS Corp. products are not designed, intended, or authorized for use as components in systems intended for surgical implant into the body, or other applications intended
to support or sustain life, or for any other application in which the failure of the IXYS Corp. product could create a situation where personal injury or death may occur.
IXYS Corp. reserves the right to make changes to or discontinue any product or service described herein without notice. Products with data sheets labeled "Advance
Information" or "Preliminary" and other products described herein may not be in production or offered for sale.
IXYS Corp. advises customers to obtain the current version of the relevant product information before placing orders. Circuit diagrams illustrate typical semiconductor
applications and may not be complete.
IXYS Corp.
1590 Buckeye Dr.,
Milpitas, CA 95035-7418
Phone: 408. 457.9000
Fax:
408. 496.0222
http://www.ixys.com
© 2009 IXYS Corp.
Characteristics subject to change without notice
Document No:8680_DS
Revision:
N1.0
Issue date:
2/8/2011
12
Doc. No. 8680_DS, Rev. N1.0