IS32LT3172/73

IS32LT3172/73
10-TO-200MA CONSTANT-CURRENT LED DRIVER FOR AUTOMOTIVE
Preliminary Information
September 2015
GENERAL DESCRIPTION
FEATURES
The IS32LT3172 and IS32LT3173 are adjustable
linear current devices with excellent temperature
stability. A single resistor is all that is required to set
the operating current from 10mA to 200mA. The
devices can operate from an input voltage from 2.5V
to 42V with a minimal voltage headroom of 0.6V.
Designed with a low dropout voltage; the device can
drive LED strings close to the supply voltage without
switch capacitors or inductors.

The IS32LT3172/73 simplifies designs by
providing a stable current without the additional
requirement of input or output capacitors,
inductors, FETs or diodes. The complete constant
current driver requires only a current set resistor
and a small PCB area making designs both
efficient and cost effective.


The EN pin of the IS32LT3173 can function as the
PWM signal input used for LED dimming
purposes.


As a current sink it is ideal for LED lighting
applications or current limiter for power supplies.
APPLICATIONS
The device is provided in a lead (Pb) free, SOP-8-EP
package.







Low-side current sink
- Current preset to 10mA
- Adjustable from 10mA to 200mA with external
resistor selection
Wide input voltage range from
- 2.5V to 42V (IS32LT3173)
- 5V to 42V (IS32LT3172)
with a low dropout of 0.6V
Up to 10kHz PWM input (IS32LT3173 only)
Protection features:
- 0.26%/K negative temperature coefficient at
high temp for thermal protection
Up to 1.8W power dissipation in a small SOP-8EP package
RoHS compliant (Pb-free) package
Automotive AEC-Q100 qualified (pending)
Automotive and avionic lighting
Architectural LED lighting
Channel letters for advertising, LED strips for
decorative lighting
Retail lighting in fridge, freezer case and
vending machines
Emergency lighting (e.g. steps lighting, exit way
sign etc.)
TYPICAL APPLICATION CIRCUIT
Figure 1 Typical Application Circuit
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PIN CONFIGURATION
Package
Pin Configuration (Top View)
SOP-8-EP
PIN DESCRIPTION
No.
Pin
Description
1, 2
OUT
Current sink.
3
EN
Enable pin (PWM input IS32LT3173 only).
4
REXT
Optional current adjust.
5
GND
Ground.
6~8
NC
Floating or connect to GND.
Thermal Pad
Connect to GND.
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ORDERING INFORMATION
Automotive Range: -40°C to +125°C
Order Part No.
Package
QTY/Reel
IS32LT3172-GRLA3-TR
IS32LT3173-GRLA3-TR
SOP-8-EP, Lead-free
2500
Copyright © 2015 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. 0A, 09/09/2015 3 IS32LT3172/73
ABSOLUTE MAXIMUM RATINGS (Note 1)
Maximum enable voltage, VEN(MAX) only for IS32LT3172-GRLA3-TR
VEN(MAX) only for IS32LT3173-GRLA3-TR
Maximum output current, IOUT(MAX)
Maximum output voltage, VOUT(MAX)
Reverse voltage between all terminals, VR
Junction to ambient, θJA
Power dissipation, PD(MAX) (Note 2)
Maximum junction temperature, TJMAX
Storage temperature range, TSTG
Operating temperature range, TA
ESD (HBM)
ESD (CDM)
45V
6V
200mA
45V
0.5V
55.4°C/W
1.8W
150°C
-65°C ~ +150°C
−40°C ~ +125°C
Class H1C
Class C3A
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.
Note 2:
Detail information please refer to package thermal de-rating curve on Page 13.
ELECTRICAL CHARACTERISTICS
“●” This symbol in the table means these parameters are for IS32LT3172-GRLA3-TR.
“○” This symbol in the table means these parameters are for IS32LT3173-GRLA3-TR.
“♦” This symbol in the table means these limits are guaranteed at room temp TA = TJ = 25°C.
“◊” This symbol in the table means these limits are guaranteed at full temp range TA = TJ = -40°C~125°C.
Test condition is TA = TJ = -40°C~125°C, unless otherwise specified.
Symbol
Parameter
VBD_OUT
OUT pin breakdown voltage
IEN
Enable current
RINT
Internal resistor
Condition
VEN= 0V
Typ.
0.35
VEN= 3.3V
○
0.35
IRINT = 10mA
●
VOUT = 1.4V, VEN = 3.3V,
REXT OPEN
○
VOUT > 2.0V, VEN = 24V,
REXT = 10Ω
●
Output current
VOUT > 2.0V, VEN = 3.3V,
REXT = 10Ω
○
VOUT > 2.0V, VEN = 24V,
REXT = 5.6Ω
●
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Unit
V
●
VOUT > 2.0V, VEN = 3.3V,
REXT = 5.6Ω
Max.
42
VEN= 24V
VOUT = 1.4V, VEN = 24V,
REXT OPEN
IOUT
Min.
mA
100
106
112
♦
9
10
11
◊
8
10
11
♦
9
10
11
◊
8
10
11
♦
110
116
122
◊
100
116
123
♦
110
116
122
◊
100
116
123
♦
200
◊
200
♦
200
◊
200
Ω
mA
mA
mA
4 IS32LT3172/73
DC CHARACTERISTICS WITH STABILIZED LED LOAD
“●” This symbol in the table means these parameters are for IS32LT3172-GRLA3-TR.
“○” This symbol in the table means these parameters are for IS32LT3173-GRLA3-TR.
Test condition is TA = TJ = -40°C~125°C, unless otherwise specified.
Symbol
Parameter
VS
Sufficient supply voltage on EN
pin
VHR
Lowest sufficient headroom
voltage on OUT pin
Output current change versus
ambient temp change
∆IOUT/IOUT
(Note 3)
Output current change versus
Vout
Condition
Min.
Typ.
Max.
●
5
42
○
2.5
5.5
IOUT = 100mA
0.6
1
VOUT > 2.0V, VEN = 24V,
REXT = 10Ω
●
-0.26
VOUT > 2.0V, VEN = 3.3V,
REXT = 10Ω
○
-0.26
VOUT > 2.0V, VEN = 24V,
REXT = 10Ω
●
1.9
VOUT > 2.0V, VEN = 3.3V,
REXT = 10Ω
○
Unit
V
V
%/K
%/V
1.9
Note 3: Guaranteed by design.
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FUNCTIONAL BLOCK DIAGRAM
IS32LT3172
IS32LT3173
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TYPICAL PERFORMANCE CHARACTERISTICS
IS32LT3172
80
12.5
VEN = 42V
REXT = 20Ω
VEN = 42V
REXT Open
TA = 25°C
TA = 85°C
Output Current (mA)
Output Current (mA)
15
10
TA = 125°C
7.5 TA = -40°C
5
TA = 125°C
TA = 25°C
60
TA = 85°C
TA = -40°C
40
20
2.5
0
0.5
2
3.5
5
6.5
8
9.5
11
12.5
0
0.5
14
2
3.5
5
8
9.5
11
12.5
14
Output Voltage (V)
Output Voltage (V)
Figure 3 IOUT vs. VOUT
Figure 2 IOUT vs. VOUT
200
200
VEN = 42V
REXT = 10Ω
VEN = 42V
REXT = 7.5Ω
180
150
TA = 25°C
TA = 85°C
100
Output Current (mA)
Output Current (mA)
6.5
TA = 125°C
TA = -40°C
50
TA = 85°C
TA = 25°C
160
140
TA = 125°C
120
TA = -40°C
100
80
60
40
20
0
0.5
2
3.5
5
6.5
8
9.5
11
12.5
0
0.5
14
2
3.5
5
TA = 85°C
250
TA = 25°C
Output Current (mA)
Output Current (mA)
11
12.5
14
300
VEN = 3.3V
REXT = 5.6Ω
200
TA = -40°C
TA = 125°C
150
100
VEN = 42V
TA = 25°C
250
3.5
5
6.5
8
9.5
11
12.5
Output Voltage (V)
Figure 6 IOUT vs. VOUT
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REXT = 5.6Ω
200
REXT = 7.5Ω
150
REXT = 10Ω
100
REXT = 20Ω
50
50
2
9.5
Figure 5 IOUT vs. VOUT
Figure 4 IOUT vs. VOUT
0
0.5
8
Output Voltage (V)
Output Voltage (V)
300
6.5
0
REXT Open
0
2
4
6
8
10
12
14
Output Voltage (V)
Figure 7 IOUT vs. VOUT
7 IS32LT3172/73
250
Output Current (mA)
20
VEN = 5V
fPWM = 100Hz@1% Duty Cycle
TA = 25°C
VOUT = 2V
REXT Open
REXT = 5.6Ω
200
REXT = 7.5Ω
150
REXT = 10Ω
100
REXT= 20Ω
16
12
8
TA = 125°C
TA = -40°C
REXT Open
0
2
4
6
8
10
12
0
14
5
15
25
Output Voltage (V)
42
35
VEN (V)
Figure 8 IOUT vs. VOUT
Figure 9 IOUT vs. VEN
80
150
VOUT = 2V
REXT = 20Ω
TA = 85°C
VOUT = 2V
REXT = 10Ω
TA = 25°C
Output Current (mA)
Output Current (mA)
TA = 85°C
TA = 25°C
4
50
0
Output Current (mA)
300
60
TA = 125°C
TA = -40°C
40
TA = 85°C
TA = 125°C
120
TA = 25°C
TA = -40°C
90
60
20
30
0
5
15
25
35
0
42
5
15
25
VEN (V)
42
VEN (V)
Figure 10 IOUT vs. VEN
Figure 11 IOUT vs. VEN
200
300
VOUT = 2V
REXT = 7.5Ω
TA = 85°C
150
TA = 25°C
125
VOUT = 2V
REXT = 5.6Ω
TA = 125°C
Output Current (mA)
175
Output Current (mA)
35
TA = -40°C
100
75
250
200
TA = 85°C
TA = 125°C
TA = 25°C
150 TA = -40°C
100
50
50
25
0
5
15
25
35
VEN (V)
Figure 12 IOUT vs. VEN
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0
2.5
3
3.5
4
4.5
5
VEN (V)
Figure 13 IOUT vs. VEN
8 IS32LT3172/73
250
VOUT = 2V
TA = 25°C
VEN = 42V
VOUT = 2V
250
REXT = 5.6Ω
200
REXT = 7.5Ω
150
REXT = 10Ω
100
REXT = 20Ω
200
150
100
50
50
0
Output Current (mA)
Output Current (mA)
300
REXT Open
5
10
15
20
25
30
35
40 42
0
1
10
100
1000
REXT (Ω)
VEN (V)
Figure 15 IOUT vs. REXT
Figure 14 IOUT vs. VEN
500
IOUT = 0A
REXT Open
Supply Current (µA)
400
TA = -40°C
TA = 25°C
300
TA = 85°C
200
TA = 125°C
100
0
0
5
10
15
20
25
30
35
40 42
VEN (V)
Figure 16 IEN vs. VEN
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IS32LT3173
80
VEN = 3.3V
REXT = 20Ω
VEN = 3.3V
REXT Open
25
Output Current (mA)
Output Current (mA)
30
20
15
TA = 25°C
TA = 85°C
10
0
0.5
2
3.5
5
60
TA = 125°C
TA = -40°C
40
20
TA = 125°C
5 TA = -40°C
6.5
8
9.5
11
12.5
0
0.5
14
2
3.5
5
8
9.5
11
12.5
14
Figure 18 IOUT vs. VOUT
Figure 17 IOUT vs. VOUT
180
150
TA = 25°C
TA = 85°C
100
TA = 125°C
TA = -40°C
VEN = 3.3V
REXT = 7.5Ω
160
Output Current (mA)
VEN = 3.3V
REXT = 10Ω
6.5
Output Voltage (V)
Output Voltage (V)
Output Current (mA)
TA = 25°C
TA = 85°C
50
TA = 25°C
TA = 85°C
140
120
TA = 125°C
TA = -40°C
100
80
60
40
20
0
0.5
2
3.5
5
6.5
8
9.5
11
12.5
0
0.5
14
2
3.5
5
Output Voltage (V)
TA = 25°C
200
TA = 125°C
TA = -40°C
100
2
12.5
14
3.5
5
6.5
8
9.5
11
12.5
Output Voltage (V)
Figure 21 IOUT vs. VOUT
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REXT = 5.6Ω
REXT = 7.5Ω
200
REXT = 10Ω
150
100
REXT = 20Ω
50
50
0.5
VEN = 3.3V
TA = 25°C
250
250
0
11
300
VEN = 3.3V
REXT = 5.6Ω
TA = 85°C
150
9.5
Figure 20 IOUT vs. VOUT
Output Current (mA)
Output Current (mA)
300
8
Output Voltage (V)
Figure 19 IOUT vs. VOUT
350
6.5
0
REXT Open
0
2
4
6
8
10
12
14
Output Voltage (V)
Figure 22 IOUT vs. VOUT
10 IS32LT3172/73
20
VEN = 5V
fPWM = 100Hz@1% Duty Cycle
TA = 25°C
250
VOUT = 2V
REXT Open
REXT = 5.6Ω
200
REXT = 7.5Ω
150
REXT = 10Ω
100
REXT= 20Ω
16
12
8
TA = -40°C
TA = 125°C
REXT Open
0
2
4
6
8
10
12
0
14
2.5
3
3.5
4
4.5
5
VEN (V)
Output Voltage (V)
Figure 24 IOUT vs. VEN
Figure 23 IOUT vs. VOUT
150
80
VOUT = 2V
REXT = 20Ω
TA = 85°C
VOUT = 2V
REXT = 10Ω
TA = 25°C
Output Current (mA)
Output Current (mA)
TA = 85°C
TA = 25°C
4
50
0
Output Current (mA)
Output Current (mA)
300
60
TA = 125°C
TA = -40°C
40
TA = 85°C
TA = 125°C
120
TA = 25°C
TA = -40°C
90
60
20
30
0
2.5
3
3.5
4
4.5
0
5
2.5
3
3.5
300
200
VOUT = 2V
REXT = 5.6Ω
TA = 85°C
Output Current (mA)
Output Current (mA)
TA = 125°C
150
TA = 25°C
125
5
Figure 26 IOUT vs. VEN
Figure 25 IOUT vs. VEN
VOUT = 2V
REXT = 7.5Ω
4.5
VEN (V)
VEN (V)
175
4
TA = -40°C
100
75
TA = 85°C
250
TA = 125°C
TA = 25°C
200
TA = -40°C
150
100
50
50
25
0
2.5
3
3.5
4
4.5
VEN (V)
Figure 27 IOUT vs. VEN
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0
2.5
3
3.5
4
4.5
5
VEN (V)
Figure 28 IOUT vs. VEN
11 IS32LT3172/73
250
VOUT = 2V
TA = 25°C
250
VEN = 3.3V
VOUT = 2V
REXT = 5.6Ω
Output Current (mA)
Output Current (mA)
300
200
REXT = 7.5Ω
150
REXT = 10Ω
100
REXT = 20Ω
150
100
50
50
0
200
REXT Open
2.5
3
3.5
4
4.5
5
0
1
10
100
REXT (Ω)
VEN (V)
Figure 30 IOUT vs. REXT
Figure 29 IOUT vs. VEN
500
IOUT = 0A
REXT Open
Supply Current (µA)
400
TA = -40°C
TA = 25°C
300
200
TA = 85°C
TA = 125°C
100
0
0.5
1
1.5
2
2.5
3
3.5
4
4.5
5
VEN (V)
Figure 31 IEN vs. VEN
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APPLICATIONS INFORMATION
IS32LT3172/73 provides an easy constant current
source solution for LED lighting applications. It uses
an external resistor to adjust the LED current from
10mA to 200mA. The LED current can be
determined by the external resistor REXT as Equation
(1):
REXT 
10mA  106
I SET  10mA
(1)
When operating the chip at high ambient
temperatures, or when driving maximum load
current, care must be taken to avoid exceeding the
package power dissipation limits. Exceeding the
package dissipation will cause the device to enter
thermal protection mode. The maximum package
power dissipation can be calculated using the
following Equation (2):
PD ( MAX ) 
Where ISET is in mA.
Paralleling a low tolerance resistor REXT with the
internal resistor RINT will improve the overall
accuracy of the current sense resistance. The
resulting output current will vary slightly lower due to
the negative temperature coefficient (NTC) resulting
from the self heating of the IS32LT3172/73.
HIGH INPUT VOLTAGE APPLICATION
When driving a long string of LEDs whose total
forward voltage drop exceeds the IS32LT3172
VBD_OUT limit of 42V, it is possible to stack several
LEDs (such as 2 LEDs) between the EN pin and the
OUT pins, and so the voltage on the EN pin is higher
than 5V. The remaining string of LEDs can then be
placed between power supply +VS and EN pin,
(Figure 3). The number of LEDs required to stack at
EN pin will depend on the LED’s forward voltage
drop (VF) and the +VS value.
TJ ( MAX )  TA
(2)
 JA
Where TJ(MAX) is the maximum junction temperature,
TA is the ambient temperature, and θJA is the junction
to ambient thermal resistance; a metric for the
relative thermal performance of a package.
The recommended maximum operating junction
temperature, TJ(MAX), is 125°C and so the maximum
ambient temperature is determined by the package
parameter; θJA. The θJA for the IS32LT3172/73 SOP8-EP package is 55.4°C/W.
Therefore the maximum power dissipation at TA =
25°C is:
PD ( MAX ) 
125C  25C
 1.8W
55.4C / W
The actual power dissipation PD is:
PD  VOUT  I OUT  VEN  I EN
(3)
To ensure the performance, the die temperature (TJ)
of the IS32LT3172/73 should not exceed 125°C. The
graph below gives details for the package power
derating.
2.5
Figure 32 High Input Voltage Application Circuit
Note: when operating the IS32LT3172 at voltages
exceeding the device operating limits, care needs to
be taken to keep the EN pin and OUT pin voltage
below 42V.
THERMAL PROTECTION AND DISSIPATION
The IS32LT3172/73 implements thermal foldback
protection to reduce the LED current when the
package’s thermal dissipation is exceeded and
prevent “thermal runaway”. The thermal foldback
implements a negative temperature coefficient
(NTC) of -0.26%/K.
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SOP-8-EP
2
1.5
1
0.5
0
-40
-25
-10
5
20
35
50
65
80
95
110
125
Temperature (°C)
Figure 33 PD vs. TA (SOP-8-EP)
The thermal resistance is achieved by mounting the
IS32LT3172/73 on a standard FR4 double-sided
printed circuit board (PCB) with a copper area of a
few square inches on each side of the board under
13 IS32LT3172/73
the IS32LT3172/73. Multiple thermal vias, as shown
in Figure 34, help to conduct the heat from the
exposed pad of the IS32LT3172/73 to the copper on
each side of the board. The thermal resistance can
be reduced by using a metal substrate or by adding
a heatsink.
Figure 34 Board Via Layout For Thermal Dissipation
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CLASSIFICATION REFLOW PROFILES
Profile Feature
Preheat & Soak
Temperature min (Tsmin)
Temperature max (Tsmax)
Time (Tsmin to Tsmax) (ts)
Pb-Free Assembly
150°C
200°C
60-120 seconds
Average ramp-up rate (Tsmax to Tp)
3°C/second max.
Liquidous temperature (TL)
217°C
Time at liquidous (tL)
60-150 seconds
Peak package body temperature (Tp)*
Max 260°C
Time (tp)** within 5°C of the specified
classification temperature (Tc)
Max 30 seconds
Average ramp-down rate (Tp to Tsmax)
6°C/second max.
Time 25°C to peak temperature
8 minutes max.
Figure 35 Classification Profile
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PACKAGE INFORMATION
SOP-8-EP
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RECOMMENDED LAND PATTERN
Note:
1. Land pattern complies to IPC-7351.
2. All dimensions in MM.
3. This document (including dimensions, notes & specs) is a recommendation based on typical circuit board manufacturing parameters. Since
land pattern design depends on many factors unknown (eg. user’s board manufacturing specs), user must determine suitability for use.
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