time without notice. ISSI assumes no liability arising out of the application or use of any information, products or services described herein. Customers are
advised to obtain the latest version of this device specification before relying on any published information and before placing orders for products.
Integrated Silicon Solution, Inc. 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 Integrated Silicon Solution, Inc. receives written assurance to its satisfaction, that:
a.) the risk of injury or damage has been minimized;
b.) the user assume all such risks; and
c.) potential liability of Integrated Silicon Solution, Inc is adequately protected under the circumstances
Integrated Silicon Solution, Inc. — www.issi.com
Rev.A, 11/08/2011
1
IS31LT3135
PIN CONFIGURATIONS
Package
Pin Configurations (Top View)
SOP-8
PIN DESCRIPTION
Name
V
CC
UV
I
SET
GND
MAIN
SUB
NC
No.
1
2
3
6
7
8
4 5
Description
Power supply input
The pin detects under-voltage. Decouple to ground with 0.1uF
capacitor close to device
The pin sets the main LED current with external resistor
The pin connects to ground.
Connect to the cathode of main LED
Connect to the cathode of sub LED
Not connected
ORDERING INFORMATION
Industrial Range: -40°C to +85°C
Order Part No.
IS31LT3135-V1GRLS2-TR
IS31LT3135-V1GRLS2-TR
Package
SOP-8, Lead-free
SOP-8, Lead-free
QTY/Reel
2500
2500
V
UV
1.13V~1.21V
1.19V~1.26V
Integrated Silicon Solution, Inc. — www.issi.com
Rev.A, 11/08/2011
2
IS31LT3135
ABSOLUTE MAXIMUM RATINGS
Supply voltage, V
CC
UV, Iset, Sub, Main
Junction temperature, T
JMAX
Storage temperature range, Tstg
ESD(human body mode)
I
MAIN
I
SUB
T
A
( Ambient temperature)
0.3V ~ +6.5V
-0.3V to 6.5V
+150°C
65°C ~ +150°C
4kV
500mA
300mA
40°C ~ +85°C
Note:
1. Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings
only and functional operation of the device at these or any other condition beyond those indicated in the operational sections of the
specifications is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability.
ELECTRICAL CHARACTERISTICS
(Test conditions: V
CC
=3.6V,Tamb=25
Symbol
V
CC
Icc
Iratio
V
ISET
Iaccuracy
Vdp
Rsub
Parameter
Input voltage
Quiescent current
Ratio of I
MAIN
to I
SET
Voltage of I
SET
pin
Current accuracy of main
LED
Main channel current
source dropout voltage
Sub-channel “ON”
resistance
unless otherwise stated)
Condition
Min
2.7
Vcc=2.7V~5.5V,no load
5.5V>Vuv>1.4V
V
CC
=4.2V
Rset=30K
250
8000
1.2
Vcc = 2.7V ~ 5.5V
Vmain=0.5V
±5
0.2
2.0
V
%
V
ohm
Typical
Max
5.5
320
Unit
V
A
Rset=47K,Iout=204mA
Vcc=2.7V~5.5V
Switch from
main-LED to
sub-LED when
VUV sweeps
from high
voltage to low
voltage
IS31LT3135-V1
1.13
1.17
121
V
V
UV
Undervoltage threshold of
UV pin
IS31LT3135-V2
1.19
1.23
1.26
V
UVHYS
Comparator hysteresis of
UV pin(Upper threshold -
Undervoltage threshold)
Switch from sub-LED to
main-LED when VUV
sweeps from low voltage to high
voltage(Upper threshold); Switch
from main-LED to sub-LED when
VUV sweeps from high voltage
to low voltage(Undervoltage
threshold)
80
mV
T
SD
R
JA
Thermal protection
Threshold
Junction to ambient
SOP-8
160
80
°C/W
Integrated Silicon Solution, Inc. — www.issi.com
Rev.A, 11/08/2011
3
IS31LT3135
TYPICAL OPERATING CONDITION
Figure 2
Iset pin voltage change with temperature
Figure 3
Main LED current change with power supply
Integrated Silicon Solution, Inc. — www.issi.com
Rev.A, 11/08/2011
4
IS31LT3135
APPLICATION NOTES
MAIN LED CURRENT SET
Current of the main LED is set by resistor connected to
Iset pin. Voltage of Iset pin is 1.2V. It is constant
even if the environment temperature and power supply
voltage changes.(Refer to figure2, figure3). The
current of main channel is 8000 times to the current of
Iset pin. It is obtained by:
Typically Li battery voltage maintains at 3.7V during
discharge. Therefore, it is recommended to set the
undervoltage threshold at 3.4V.
Typically, R1 and R2 are set to 10K Ohm magnitude
e.g. 51K Ohm , the current flows through R1 and R2
is large if the value of R1 and R2 are small, which will
reduce system efficiency. We can specify the value of
R2, and then calculate the value of R1 based on the
ratio.
MAIN LED SHORT PROTECTION
When the main LED is short circuit, chip will switch to
sub-channel automatically.
OVER-TEMPERATURE PROTECTION
When the chip temperature reaches 160 , the chip
turns off automatically. When temperature drops back
to 140 , the chip turns on again.
PCB LAYOUT REFERENCE
The switch should be placed at the low voltage point
(Refer to Figure 1) to avoid an instant spark while
switching. The traces between GND pin and Iset pin to
real ground should be as short as possible and as wide
as possible to improve the main LED current accuracy
and undervoltage threshold accuracy. Adding a 0.1uF
capacitor connected to UV pin can reduce the noise
pick-up at this pin.
I
main
8000 *
V
set
R
set
Main LED current flows through the MAIN pin to
ground. There is only 0.1V voltage dropout when the
main channel current is 200mA (Note 1).
SUB LED CURRENT SET
Sub-LED current flows through SUB to ground. This
current can be set by the resistor of SUB pin and is
given by:
I
sub
V
CC
V
F2
V
d2
R
SUB
V
CC
is power supply voltage, V
F2
is the sub-LED
voltage. V
d2
is the diode voltage Refer to Figure 1
its value should be as small as possible.
UNDERVOLTAGE THRESHOLD SET
UV pin has undervoltage detect function and the
undervoltage threshold gets a 0.8V hysteresis to avoid
error operation caused by power supply ripple.
Sweeping power supply from high voltage to low
voltage, the main channel switches to sub-channel
while UV pin is below undervoltage threshold, 1.17V
(IS31LT3135-V1 typical) or 1.23V (IS31LT3135-V2
typical). Sweeping power supply from low voltage to
high voltage, the sub-channel switches to the main
channel while UV pin is 80mV (typical) higher than the
undervoltage threshold. Uuv is set by the ratio of
resistor of R1 and R2 (Refer to Figure1).
When
R
2
V
CC
=1.17V or 1.23V, chip switches
R
1
R
2
Note 1:
When power supply voltage is larger than LED voltage, the
extra voltage would be added on the Main pin, which will reduce the
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