IS31LT3135 [ISSI]
MAIN/SUB DUAL-CHANNEL LED DRIVER; MAIN / SUB双通道LED驱动器
| 型号： | IS31LT3135 |
| 厂家： | 
INTEGRATED SILICON SOLUTION, INC |
| 描述： | MAIN/SUB DUAL-CHANNEL LED DRIVER |
| 文件： | 总6页 (文件大小：216K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
IS31LT3135
MAIN/SUB DUAL-CHANNEL LED DRIVER
November 2011
Power supply undervoltage detect
Main channel short protection
Over-temperature protection
Input voltage range: 2.7V~5.5V
Main and sub-channel current set by external
resistor
Main channel Vdp=0.1V
GENERAL DESCRIPTION
FEATURES
IS31LT3135 is a main/sub dual-channel LED driver.
When the main channel works，it is a constant current
source driving the main LED and the current is set by
an external resistor connected to the ISET pin. It needs
only 0.1v dropout voltage for 200mA output current.
When the sub-channel works, the chip will pull down
the sub LED’s cathode to ground.
Low quiescent current
Assembled in SOP-8 package
Normally there is only one channel on, the main
channel and the sub channel can switch between each
other. Sweeping power supply from high voltage to low
voltage, main channel switches to sub-channel while
UV pin is below the 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. Additionally, the main channel
has short protection function, when the main LED is
shorted，the chip will switch to sub-channel
APPLICATIONS
Miner lamp
Other LED lighting
automatically.
TYPICAL APPLICATION CIRCUIT
IS31LT3135
Figure 1
.
Copyright © 2011 Integrated Silicon Solution, Inc. All rights reserved. ISSI reserves the right to make changes to this specification and its products at any
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
1
Integrated Silicon Solution, Inc. — www.issi.com
Rev.A, 11/08/2011
IS31LT3135
PIN CONFIGURATIONS
Package
Pin Configurations (Top View)
SOP-8
PIN DESCRIPTION
Name
No.
Description
VCC
1
Power supply input
The pin detects under-voltage. Decouple to ground with 0.1uF
capacitor close to device
UV
2
ISET
3
The pin sets the main LED current with external resistor
The pin connects to ground.
GND
MAIN
SUB
NC
6
7
Connect to the cathode of main LED
Connect to the cathode of sub LED
Not connected
8
4，5
ORDERING INFORMATION
Industrial Range: -40°C to +85°C
Order Part No.
Package
QTY/Reel
V UV
IS31LT3135-V1GRLS2-TR
IS31LT3135-V1GRLS2-TR
SOP-8, Lead-free
SOP-8, Lead-free
2500
2500
1.13V~1.21V
1.19V~1.26V
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Integrated Silicon Solution, Inc. — www.issi.com
Rev.A, 11/08/2011
IS31LT3135
ABSOLUTE MAXIMUM RATINGS
Supply voltage, VCC
UV, Iset, Sub, Main
Junction temperature, TJMAX
Storage temperature range, Tstg
-0.3V ~ +6.5V
-0.3V to 6.5V
+150°C
-65°C ~ +150°C
ESD(human body mode)
4kV
IMAIN
500mA
ISUB
300mA
TA( Ambient temperature)
-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: VCC=3.6V,Tamb=25℃ unless otherwise stated)
Symbol
Parameter
Input voltage
Condition
Min
Typical
Max
Unit
VCC
2.7
5.5
V
Vcc=2.7V~5.5V,no load，
5.5V>Vuv>1.4V
Icc
Quiescent current
250
320
μA
Iratio
VISET
Ratio of IMAIN to ISET
Voltage of ISET pin
V
CC=4.2V，Rset=30K
8000
1.2
V
Current accuracy of main
LED
Iaccuracy
Vdp
Vcc = 2.7V ~ 5.5V，Vmain=0.5V
±5
%
Main channel current
source dropout voltage
Rset=47K,Iout=204mA
0.2
2.0
V
Sub-channel “ON”
resistance
Rsub
Vcc=2.7V~5.5V
Switch from
ohm
main-LED to
sub-LED when
VUV sweeps
from high
voltage to low
voltage
IS31LT3135-V1 1.13
IS31LT3135-V2 1.19
1.17
1.23
121
Undervoltage threshold of
UV pin
VUV
V
1.26
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)
Comparator hysteresis of
UV pin(Upper threshold -
Undervoltage threshold)
VUVHYS
80
mV
Thermal protection
Threshold
TSD
160
80
℃
RθJA
Junction to ambient
SOP-8
°C/W
3
Integrated Silicon Solution, Inc. — www.issi.com
Rev.A, 11/08/2011
IS31LT3135
TYPICAL OPERATING CONDITION
1.2
1.19
1.18
1.17
1.16
1.15
10 20 30 40 50
60 70 80 90 100
temperature
Figure 2 Iset pin voltage change with temperature
350
348
346
344
342
340
338
336
334
332
330
4
4.2
4.4
4.6
4.8
(V)
Figure 3 Main LED current change with power supply
5
5.2
5.4
DC
V
4
Integrated Silicon Solution, Inc. — www.issi.com
Rev.A, 11/08/2011
IS31LT3135
APPLICATION NOTES
Typically，Li battery voltage maintains at 3.7V during
discharge. Therefore, it is recommended to set the
undervoltage threshold at 3.4V.
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, 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.
Vset
Imain 8000*
Rset
MAIN LED SHORT PROTECTION
When the main LED is short circuit, chip will switch to
sub-channel automatically.
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).
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.
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:
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.
VCC VF2 Vd2
Isub
RSUB
VCC is power supply voltage, VF2 is the sub-LED
voltage. Vd2 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).
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
efficiency of the whole system.
R2
V
When
CC =1.17V or 1.23V, chip switches
R1 R2
from the main channel to the sub-channel.
5
Integrated Silicon Solution, Inc. — www.issi.com
Rev.A, 11/08/2011
IS31LT3135
PACKAGE INFORMATION
SOP-8
6
Integrated Silicon Solution, Inc. — www.issi.com
Rev.A, 11/08/2011
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