WithBJT

IS31LT3117 53V, 350MA, 4-CHANNEL
CONSTANT CURRENT REGULATOR WITH OTP
DESCRIPTION
RECOMMENDED EQUIPMENT
The IS31LT3117 is a 4-channel, linear regulated,
constant current LED driver which can sink 4 equal
currents of up to 350mA per channel to drive high
brightness LEDs over an input voltage range of 6V to
53V, while maintaining an output leakage current of
less than 1uA. The sink current is easily programmed
using a single external resistor. The current sinks of
the IS31LT3117 may be connected in parallel to allow
greater than 350mA of LED current, i.e., all four VLEDx
pins tied together for a maximum 1.4A sink available
for one LED string. See limitations in the LED
CURRENT SETTING section



The IS31LT3117 also features a PWM input to enable
simple dimming control using a digital control signal
The IS31LT3117 features an optional 2.5V reference
voltage output capable of supplying up to 10mA (typ.).
This voltage may be used to drive the base of external
BJTs for high current applications which are driven by
a widely varying input voltage
FEATURES








6V to 53V input supply voltage range
Up to 1.4A total sink current
Over temperature protections
Thermal current regulation above 130°C
Sink current matching 3% between channels
PWM dimming and Shutdown control input
Optional 2.5V output to drive external standoff
BJTs
Very few external components
QUICK START

ABSOLUTE MAXIMUM RATINGS

≤ 53V power supply
Caution: Do not exceed the conditions listed above, otherwise
the board will be damaged.
EVALUATION BOARD OPERATION
The evaluation board can be configured to operate in
one of two current level modes. The device input
current is controlled by switch (S1), when S1 is pushed
UP, <With BJT> mode, the HBLED string current at
VLEDx pin is set to 350mA, when S1 is pushed DOWN,
<Without BJT> mode, the HBLED string current is set
to 100mA. The operating current (350mA or 100mA) is
set by S1 switch selection of a resistor value at
IS31LT3117 pin 8. See “LED CURRENT SETTING”
section of the datasheet for guidance in calculating
resistor values for specific currents.
PROCEDURE
The IS31LT3117 evaluation board is fully assembled
and tested. Follow the steps listed below to verify
board operation.
Caution: Do not turn on the power supply until all connections
are completed.
1)
2)
3)
Verify that the S1 is pushed UP to select <With
BJT> mode.
Connect each HBLED string as follows:
CHx: Connect the HBLED string cathode to the
CHx of CON3 and the anode to VCC on CON2
Where x is 1, 2, 3 and 4.
Unused CHx inputs should be connected to GND
Calculate the VCC, recommended value is 1V to
2V higher than the sum of the LED string’s total
forward voltage drop.
For example, if the LED string’s total forward
voltage is 10V@350mA (three LEDs with 3.33V
forward voltage drop each), the recommended
VCC is 11V to 12V.
Note: Selecting an input voltage much higher than the
LED string’s total forward voltage will cause power
dissipation on the on board BJTs (Q1 – Q4).
Figure 1: Photo of IS31LT3117-EBBJT Evaluation Board
4)
Integrated Silicon Solution, Inc. – www.issi.com
Rev. B, 7/16/2014
6.0V~53V, 2A DC power supply
One digital voltmeter
Four series-connected HB LED strings rated no
less than 350mA
A current probe to measure the HB LED current
Insert the current probe between the CHx terminal
(CON3) and the cathode of the CHx LED string to
measure the HBLED current.
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IS31LT3117 53V, 350MA, 4-CHANNEL
CONSTANT CURRENT REGULATOR WITH OTP
5)
JP1 is used to configure the PWM signal input
mode. When JP1 is “ON” the IS31LT3117 is
enabled and no external PWM signal should be
connected. When JP1 is “OFF” the IS31LT3117
must be driven by an external PWM signal source.
Caution: Always remove JP1 when driving the IS31LT3117
with an external PWM source. JP1 ON pulls up the TP1 pin
to a possibly high VCC voltage that may damage the PWM
signal source.
6)
7)
8)
Turn on the power supply (VCC) and measure the
HBLED current using the current probe and verify
all channels (CHx).
Slide S1 down to select <Without BJT> mode.
Measure the HBLED current using the current
probe and verify all channels (CHx).
POWER SUPPLY AND POWER DISSIPATION
The dissipation is proportional to the voltage across
the LED and the sink current that can be defined as:
PLEDx  VLEDS x  I OUTx
Where x is 1, 2, 3 or 4. VLEDSx is the total forward
voltage of LEDs in series, IOUTx is the current of the
LED series.
When working with BJT (S1 UP),
PBJTx  (VCC  VVLEDx  V LEDSx )  I OUTx
The voltage at VLEDx pin of the IS31LT3117 will be the
remaining value of VCC-VOUTx-VRx, and if it is larger than
1.8V@350mA，the IC dissipation will be high which
may trigger the IC over temperature protection (OTP).
Assume VCC=12V, IOUTx =100mA, VLEDSx=9.0V, Rx=24Ω,
IQ=5mA.
PLEDx=9.0V×0.1A=0.9W
PRx=0.1A×0.1A×24Ω=0.24W
P3117=(12V-(0.1A×24Ω) -9.0V)×0.1A×4+12V×0.005A
= 0.3W
LED CURRENT SETTING
The maximum sink current of all four channels
(VLEDx) is set by resistor (RISET) connected from the
IS31LT3117 ISET pin (8) to ground. The maximum
possible current is 350mA per VLEDx pin, however,
more than one VLEDx pin can be tied together to allow
for larger currents. Two combined VLEDx pins will
double the available sink current for the LED string,
while combining all four VLEDx pins will result in 4x the
sink current for one LED string. The VLEDx sink
current can be calculated by the following; VISET =
1.27V (typ):
I SINKx  1600 
4
P3117   (VVLEDx  I OUTx )  VCC  I Q
x 1
Where x is 1, 2, 3 or 4. VVLEDx is the voltage of the
IS31LT3117 VLEDx pin (Headroom voltage), see
Equation (3) of the datasheet for guidance in
calculating the VVLEDx. IOUTx is the current of the LED
series, IQ is the operation current of IS31LT3117 and
Q5. Assume IOUTx =350mA, VLEDSx=10V, VCC=12V,
IQ=18mA, VVLEDx=0.4V.
PLEDx=10V×0.35A=3.5W
PBJTx=(12V-10V-0.4V)×0.35A=0.56W
P3117=0.4V×0.35A×4+12V×0.018A= 0.582W
Caution: If VCC is much higher than VLEDSx, then verify that
PBJTx<1.5W for all conditions.
When working without BJT (S1 DOWN),
4
P3117   (VVLEDx  I OUTx )  VCC  I Q
x 1
4
  (VCC  V LEDSx  V Rx )  I OUTx )  VCC  I Q
x 1
Where x is 1, 2, 3 or 4. VRx is the voltage across
Rx(x=5 to 8), VLEDSx is the total forward voltage of
LEDs in series, see Figure 2 for details.
Integrated Silicon Solution, Inc. – www.issi.com
Rev. B, 7/16/2014
V ISET
R ISET
When S1 UP With BJT, RISET=R10//R12, and S1
DOWN Without BJT, RISET=R11 .For accurate LED
current, resistors should be 1% or better tolerance.
More information please refers to the IS31LT3117
datasheet.
HB LED DIGITAL-DIMMING CONTROL
The JP1 connector is used for configuring the dimming
function as in the table below:
JP1
Configuration Description
ON
No external PWM signal
OFF
Connect external PWM signal source
The evaluation board features a PWM input terminal
for connecting an external digital PWM signal. JP1
connector is used to connect or disconnect a 100k
ohm pull up resistor (R14) to the PWM input. Apply a
digital PWM signal with a 0.8V logic-low (or less) and a
2.1V logic high (or greater) level, and frequencies from
4kHz to 100kHz. To adjust the HB LED brightness,
vary the signal duty cycle from 0 to 100.
Caution: If JP1 is “ON” the PWM pin will be pulled up to the
input VCC which can be up to 53V.
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IS31LT3117 53V, 350MA, 4-CHANNEL
CONSTANT CURRENT REGULATOR WITH OTP
ORDERING INFORMATION
Part No.
Temperature Range
Package
IS31LT3117-ZLS4-EBBJT
-40°C ~ +125°C (Industrial Range)
eTSSOP-16, Lead-free
Table1: Ordering Information
For pricing, delivery, and ordering information, please contacts ISSI’s analog marketing team at
[email protected] or (408) 969-6600
VCC
C8
R9
VCC
33uF/100V
2.2K/0.5W
Q5
U1
VCC
GND
3
C7
VCC
S1
PBSS4160U
Vref
CON2
9
C6
R4 430
10uF/100V 0.1uF/100V
CON1
R8 24R/1W
R14
VLED1
100K
R3 430
JP1
PWM
1
16
VLED2
MJD31
Q4
MJD31
Q3
MJD31
Q2
CH1
R7 24R/1W
CH2
14
PWM
R2
430
R6
24R/1W
TP1
CH3
6
7
2
5
VLED3
12
AGND
AGND
R1
VLED4
PGND
PGND
Iset
430
R5
24R/1W
CH4
10
MJD31
8
IS31LT3117-EBBJT
C5
C4
C3
C2
1uF/10V
100nF/10V 100nF/10V 100nF/10V 100nF/10V
Q1
R11
20K
R13
NC
R10
6.2K
R12
91K
CON3
SS-62H01
C1
Figure 2: IS31LT3117 Application Schematic
Integrated Silicon Solution, Inc. – www.issi.com
Rev. B, 7/16/2014
3
IS31LT3117 53V, 350MA, 4-CHANNEL
CONSTANT CURRENT REGULATOR WITH OTP
BILL OF MATERIALS
Name
Symbol
LED Driver
U1
BJT
Q1~Q4
BJT
Description
Qty
Supplier
Part No.
Constant current LED driver
1
ISSI
IS31LT3117
NPN power Transistor
4
ONSEMI
MJD31
Q5
60V/1A NPN BISS Transistor
1
NXP
PBSS4160U
Resistors
R1~R4
RES, 430R,1/16W,±5%,SMD
4
YAGEO
RC0805JR-07430L
Resistors
R5~R8
RES, 24R,1W,±5%,DIP
4
Resistor
R9
RES, 2.2K,0.5W,±5%,DIP
1
Resistor
R10
RES, 6.2K,1/10W,±1%,SMD
1
YAGEO
RC0805FR-076.2KL
Resistor
R12
RES, 91K,1/10W,±1%,SMD
1
YAGEO
RC0805FR-0791KL
Resistor
R11
RES, 20K,1/10W,±1%,SMD
1
YAGEO
RC0805FR-0720KL
Resistor
R14
RES,100K,1/10W,±5%,SMD
1
YAGEO
RC0805JR-07100KL
Resistor
R13
NC
Capacitors
C1~C4
CAP, 0.1µF,10V,±10%,SMD
4
YAGEO
CC0805DKX7R6BB104
Capacitors
C5
CAP, 1µF,10V,±10%,SMD
1
YAGEO
CC0805DKX7R6BB105
Capacitor
C6
CAP, 0.1µF,100V,±10%,SMD
1
YAGEO
CC1206DKX7R0BB104
Capacitor
C7
CAP, 10µF,100V,±20%,SMD
1
Capacitor
C8
CAP, 33µF,100V,±20%,SMD
1
Switch
S1
6P2T DIP
1
Jumper
JP1
2.54mm Jumper
1
Connector
CON1,CON2
DC connector
2
Bill of materials, refer to Figure 2 above.
Integrated Silicon Solution, Inc. – www.issi.com
Rev. B, 7/16/2014
4
IS31LT3117 53V, 350MA, 4-CHANNEL
CONSTANT CURRENT REGULATOR WITH OTP
0
0
2
1
2
1
1
2
1
31
2
1
31
1
30
2
29
3
28
5
26
6
2
25
7
24
8
23
10
21
11
20
12
19
13
18
15
16
1
2
2
1
1
31
31
2
1
1
2
2
1
0
0
Figure 3: Board Component Placement Guide -Top Layer
Figure 4: Board PCB Layout- Top Layer
Integrated Silicon Solution, Inc. – www.issi.com
Rev. B, 7/16/2014
5
IS31LT3117 53V, 350MA, 4-CHANNEL
CONSTANT CURRENT REGULATOR WITH OTP
0
0
2
1
2
1
1
2
1
31
2
1
31
1
30
2
29
3
28
5
26
6
2
25
7
24
8
23
10
21
11
20
12
19
13
18
15
16
1
2
2
1
1
31
31
2
1
1
2
2
1
0
0
Figure 5: Board Component Placement Guide -Bottom Layer
Figure 6: Board PCB Layout-Bottom Layer
Copyright © 2014 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
Integrated Silicon Solution, Inc. – www.issi.com
Rev. B, 7/16/2014
6