IS32LT3125/3125A
SINGLE CHANNEL 250mA LED DRIVER WITH FAULT DETECTION
June 2020
GENERAL DESCRIPTION
FEATURES
The IS32LT3125/3125A is a linear programmable
current regulator consisting of a single output channel
capable of 250mA. It features an EN pin to enable and
disable the output channel’s current source. It supports
PWM dimming via EN pin or power supply modulation
(PSM). The UV pin can be used to set external VCC
undervoltage lockout threshold via a resistor divider.
An external resistor programs the current level for the
channel
current
source.
In
addition,
IS32LT3125/3125A integrates fault protection for LED
open/short, ISET pin open/short and over temperature
condition for robust operation. Detection of these
failures is reported by the FAULTB pin. When a fault is
detected the device will disable itself and output an
open drain low signal. Multiple devices can have their
FAULTB pins connected to create a “one-fail-all-fail”
condition. Under a fault condition, the IS32LT3125 will
sink 30mA ICC current, while the IS32LT3125A will sink
a lower 2mA (Max.) ICC.
The IS32LT3125/3125A is targeted at the automotive
market with end applications to include interior and
exterior lighting. For 12V automotive applications the
low dropout driver can support one to several LEDs on
the output channel.
Both devices are offered in a small thermally enhanced
SOP-8-EP package.
Single channel, sources up to 250mA
5.0V to 28V input supply voltage range
- Withstand 42V load dump
External resister sets source current
Programmable VCC undervoltage lockout to
match the LED stack for High Side PWM operation
Shared fault flag for multiple devices operation
Fault protection with flag output:
- LED string open/short
- OUT pin short to VCC/GND
- ISET pin open/short
- Thermal shutdown
- ICC set to 30mA under fault condition
(IS32LT3125 only)
External CSTOR capacitor keeps fault status during
start/stop operation
SOP-8-EP package
AEC-Q100 Qualified
Operating temperature range from -40°C ~ +125°C
APPLICATIONS
Automotive interior/exterior lighting:
- Turn signal light
- Tail/stop light
- Position light
- Dome light
TYPICAL APPLICATION CIRCUIT
Figure 1
Lumissil Microsystems – www.lumissil.com
Rev.A, 06/08/2020
Typical Application Circuit
1
IS32LT3125/3125A
Figure 2
Typical Application Circuit (Several Devices in Parallel with FAULTB Interconnection)
Note 1: For PSM dimming application, high CVCC capacitor value will affect the dimming accuracy. To get better dimming performance,
recommend 0.1µF for it.
Lumissil Microsystems – www.lumissil.com
Rev.A, 06/08/2020
2
IS32LT3125/3125A
PIN CONFIGURATION
Package
Pin Configuration (Top view)
SOP-8-EP
PIN DESCRIPTION
No.
Pin
Description
1
CSTOR
2
ISET
3
FAULTB
4
OUT
Output current source channel.
5
VCC
Power supply input pin.
6
UV
External under voltage lockout threshold detection pin.
7
EN
Enable pin. It can be used for LED PWM dimming or device
ON/OFF.
8
GND
Ground.
Thermal Pad
Must be electrically connected to GND plane for better thermal
dissipation.
Keep-alive capacitor to maintain the deglitch timer and fault latch
status with collapsing VCC.
Output current setting for channel. Connect a resistor between this
pin and GND to set the maximum output current.
Open drain output with internal pull up to 4.5V. Active low to
indicate the fault conditions. This pin is also an input pin. Pulling
this pin low will shutdown the device.
Lumissil Microsystems – www.lumissil.com
Rev.A, 06/08/2020
3
IS32LT3125/3125A
ORDERING INFORMATION
Automotive Range: -40°C to +125°C
Order Part No.
Package
QTY/Reel
IS32LT3125-GRLA3-TR
IS32LT3125A-GRLA3-TR
SOP-8-EP, Lead-free
2500
Copyright © 2020 Lumissil Microsystems. All rights reserved. Lumissil Microsystems reserves the right to make changes to this specification and its
products at any time without notice. Lumissil Microsystems 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.
Lumissil Microsystems 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 Lumissil Microsystems 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 Lumissil Microsystems is adequately protected under the circumstances
Lumissil Microsystems – www.lumissil.com
Rev.A, 06/08/2020
4
IS32LT3125/3125A
ABSOLUTE MAXIMUM RATINGS
VCC, OUT, EN, UV
ISET, FAULTB, CSTOR
Operating temperature, TA=TJ
Storage temperature range, TSTG
Package thermal resistance, junction to ambient (4 layer standard
test PCB based on JESD 51-2A), θJA
Package thermal resistance, junction to thermal PAD (4 layer
standard test PCB based on JESD 51-8), θJP
Maximum power dissipation, PDMAX
ESD (HBM)
ESD (CDM)
-0.3V ~ +45V
-0.3V ~ +7.0V
-40°C ~ +150°C
-65°C ~ +150°C
43.3°C/W
1.39°C/W
2.31W
±2kV
±750V
Note 2: 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
TJ = -40°C ~ +125°C, VCC=12V, the detail refer to each condition description. Typical values are at TJ = 25°C.
Symbol
Parameter
Conditions
Min. Typ. Max.
Unit
Power Up Parameter
VCC
VUVLO
VUVLO_HY
Supply voltage range
VCC under voltage lockout
threshold voltage
VCC under voltage lockout
voltage hysteresis
5
VCC falling
4.2
4.5
VCC supply current
RISET=20kΩ, VEN =high, No Fault
condition.
2.5
ISD
Quiescent supply current
In shutdown mode (OUT turned off),
VEN = low
0.7
RISET=20kΩ, VEN=high. IS32LT3125
OUT connected to
Supply current during LED string GND (in fault master
IS32LT3125A
mode)
short or open
20
RISET=20kΩ, VEN= high, VFAULTB= low (in
fault slave mode).
tSD
EN low time for IC power
shutdown
tON
EN high time for IC power up
V
4.8
V
0.15
ICC
ISD_FLT
28
40
V
3.5
mA
mA
30
40
1
2
1
2
48
55
ms
40
μs
IOUT= -100mA, VCC= 12V, VEN= High
mA
Channel Parameter
VISET
ISET pin voltage
RISET= 20kΩ
IOUT
Output current (Note 3)
RISET= 20kΩ, VHR= 1V
Lumissil Microsystems – www.lumissil.com
Rev.A, 06/08/2020
1
-106 -100
V
-94
mA
5
IS32LT3125/3125A
ELECTRICAL CHARACTERISTICS (CONTINUE)
TJ = -40°C ~ +125°C, VCC=12V, the detail refer to each condition description. Typical values are at TJ = 25°C.
Symbol
VHR
Parameter
Minimum headroom voltage
Conditions
Min.
Typ.
Max.
VCC – VOUT, IOUT= -250mA
1500
VCC – VOUT, IOUT= -100mA
700
Unit
mV
IOUT_R
Channel output current range
RISET= 80kΩ, IOUT=-25mA
RISET= 8kΩ, IOUT=-250mA
-250
IOUT_L
Output limit current
RISET=5kΩ
-350
ILEAK
Channel leakage current
VEN=Low, VOUT=0V, VCC=28V
Current slew time
Enabled by EN pin, current
rise/fall between 0%~100%
4
μs
Fault deglitch time
Fault must be present at least this
long to trigger the fault detect
25
μs
VFAULTB
FAULTB pin voltage
Sink current = 20mA
0.2
0.4
V
RFAULTB
FAULTB pin pull up resistor
200
300
KΩ
2
V
tSL
-300
-25
mA
-260
mA
1
μA
Fault Protect Parameter
tFD
VFAULTB_IH
VFAULTB_IL
FAULTB pin input high enable
threshold
FAULTB pin input low disable
threshold
0.8
V
VSCD
OUT pin short to GND
threshold
Measured at OUT
VSCD_HY
OUT pin short to GND
hysteresis
Measured at OUT
VOCD
OUT pin open threshold
Measured at (VCC-VOUT)
VOC_HY
OUT pin open hysteresis
Measured at (VCC-VOUT)
100
ICST
CSTOR leakage current
VCSTOR = 5.5V
4.6
TSD
Thermal shutdown threshold
(Note 4)
165
°C
THY
Over-temperature hysteresis
(Note 4)
25
°C
EN input voltage threshold
Voltage rising
1.0
1.2
1.5
220
150
V
mV
300
mV
mV
10
μA
Logic Input
VEN
VENHY
EN input hysteresis
fPWM
PWM frequency to EN
(Note 4)
VUV
UV input voltage threshold
Voltage rising
VUVHY
1.18
1.23
1.28
40
UV input hysteresis
1.18
1.23
40
V
mV
1
kHz
1.28
V
mV
Note 3: Output current accuracy is not intended to be guaranteed at output voltages less than 1.8V.
Note 4: Guaranteed by design.
Lumissil Microsystems – www.lumissil.com
Rev.A, 06/08/2020
6
IS32LT3125/3125A
TYPICAL PERFORMANCE CHARACTERISTICS
300
110
105
TJ = -40°C
TJ = 25°C
100
TJ = 125°C
RISET = 8kΩ
VCC = 12V
TJ = -40°C
250
Output Current (mA)
Output Current (mA)
VHR = 2V
RISET = 20kΩ
200
150
RISET = 20kΩ
100
95
RISET = 80kΩ
50
90
5
15
25
35
0
45
0
1
2
3
7
8
9
10
9
10
110
125
300
300
RISET = 8kΩ
VCC = 12V
TJ = 25°C
200
150
RISET = 20kΩ
100
RISET = 80kΩ
50
0
1
2
3
4
5
RISET = 8kΩ
VCC = 12V
TJ = 125°C
250
Output Current (mA)
250
Output Current (mA)
6
Figure 4 IOUT vs. VHR
Figure 3 IOUT vs. VCC
200
150
RISET = 20kΩ
100
RISET = 80kΩ
50
6
7
8
9
0
10
0
1
2
3
6
7
8
330
300
RISET = 8kΩ
VCC = 12V
VHR = 2V
Output Current (mA)
325
200
150
RISET = 20kΩ
100
RISET = 80kΩ
50
0
-40
5
Figure 6 IOUT vs. VHR
Figure 5 IOUT vs. VHR
250
4
Headroom Voltage (V)
Headroom Voltage (V)
Output Current (mA)
5
Headroom Voltage (V)
Supply Voltage (V)
0
4
-25
-10
5
20
35
50
VCC = 12V
VHR = 2V
RISET = 5kΩ
320
315
310
305
65
80
Temperature (°C)
Figure 7 IOUT vs. TJ
Lumissil Microsystems – www.lumissil.com
Rev.A, 06/08/2020
95
110
125
300
-40
-25
-10
5
20
35
50
65
80
95
Temperature (°C)
Figure 8 IOUT_L vs. TJ
7
IS32LT3125/3125A
4
0.85
Supply Current (mA)
Supply Current (mA)
3.5
0.90
VCC = 12V
RISET = 20kΩ
EN = High
3
2.5
2
0.80
0.75
0.70
0.65
1.5
1
-40
VCC = 12V
EN = Low
-25
-10
5
20
35
50
65
80
95
110
0.60
-40
125
-25
-10
5
Temperature (°C)
Figure 9 ICC vs. TJ
65
80
95
110
125
80
95
110
125
80
95
110
125
Figure 10 ISD vs. TJ
VCC = 12V
Fault Slave Mode
29
Supply Current (mA)
Supply Current (mA)
50
1
VCC = 12V
Fault Master Mode
28
27
0.8
0.6
0.4
0.2
26
-25
-10
5
20
35
50
65
80
95
110
0
-40
125
-25
-10
5
Temperature (°C)
20
35
50
65
Temperature (°C)
Figure 11 ISD_FLT vs. TJ For IS32LT3125
Figure 12 ISD_FLT vs. TJ
1.5
1.1
VCC = 12V
Fault Master Mode
VCC = 12V
RISET = 12kΩ
1.2
1.05
VISET (V)
Supply Current (mA)
35
Temperature (°C)
30
25
-40
20
0.9
1
0.6
0.95
0.3
0
-40
-25
-10
5
20
35
50
65
80
Temperature (°C)
Figure 13 ISD_FLT vs. TJ for IS32LT3125A
Lumissil Microsystems – www.lumissil.com
Rev.A, 06/08/2020
95
110
125
0.9
-40
-25
-10
5
20
35
50
65
Temperature (°C)
Figure 14 VISET vs. TJ
8
IS32LT3125/3125A
4.8
1.25
VCC = 12V
1.24
VCC = 12V
VIH
4.75
1.23
4.7
VUVLO (V)
VUV (V)
1.22
1.21
1.2
VIL
1.19
VIH
4.65
4.6
4.55
VIL
1.18
4.5
1.17
4.45
1.16
1.15
-40
-25
-10
5
20
35
50
65
80
95
110
4.4
-40
125
-25
-10
Temperature (°C)
20
35
50
65
80
95
110
125
Temperature (°C)
Figure 15 VUV vs. TJ
Figure 16 VUVLO vs. TJ
1.25
100
VCC = 12V
VIH
Output Current (mA)
1.21
VIL
1.19
VCC = 12V
RISET = 20kΩ
PSM Dimming 1kHz
TJ = -40°C, 25°C, 125°C
90
1.23
VEN (V)
5
80
70
60
50
40
30
20
1.17
10
1.15
-40
-25
-10
5
20
35
50
65
80
95
110
0
125
0
20
Temperature (°C)
Figure 17 VEN vs. TJ
80
100
80
100
Figure 18 PSM Dimming at 1kHz
100
VCC = 12V
RISET = 20kΩ
PSM Dimming 500Hz
TJ = -40°C, 25°C, 125°C
80
70
60
50
40
80
70
60
50
40
30
30
20
20
10
10
0
20
VCC = 12V
RISET = 20kΩ
PSM Dimming 100Hz
TJ = -40°C, 25°C, 125°C
90
Output Current (mA)
90
Output Current (mA)
60
PSM Duty Cycle (%)
100
0
40
40
60
PSM Duty Cycle (%)
Figure 19 PSM Dimming at 500Hz
Lumissil Microsystems – www.lumissil.com
Rev.A, 06/08/2020
80
100
0
0
20
40
60
PSM Duty Cycle (%)
Figure 20 PSM Dimming at 100Hz
9
IS32LT3125/3125A
100
100
VCC = 12V
RISET = 20kΩ
PWM Dimming 1kHz
TJ = -40°C, 25°C, 125°C
80
70
60
50
40
80
70
60
50
40
30
30
20
20
10
10
0
0
20
VCC = 12V
RISET = 20kΩ
PWM Dimming 100Hz
TJ = -40°C, 25°C, 125°C
90
Output Current (mA)
Output Current (mA)
90
40
60
80
100
0
0
20
40
PWM Duty Cycle (%)
VCC = 12V
VHR = 2V
TA = -40°C
VCC = 12V
VHR = 2V
TA = -40°C
VISET
500mV/Div
VFAULT
2V/Div
VFAULT
2V/Div
IOUT
50mA/Div
IOUT
50mA/Div
Time (1µs/Div)
Time (4µs/Div)
Figure 23 EN Off
VEN
2V/Div
100
Figure 22 PWM Dimming at 100Hz
VEN
2V/Div
VISET
500mV/Div
80
PWM Duty Cycle (%)
Figure 21 PWM Dimming at 1kHz
VEN
2V/Div
60
VCC = 12V
VHR = 2V
TA = 25°C
Figure 24 EN On
VEN
2V/Div
VISET
500mV/Div
VISET
500mV/Div
VFAULT
2V/Div
VFAULT
2V/Div
IOUT
50mA/Div
IOUT
50mA/Div
Time (1µs/Div)
Figure 25 EN Off
Lumissil Microsystems – www.lumissil.com
Rev.A, 06/08/2020
VCC = 12V
VHR = 2V
TA = 25°C
Time (4µs/Div)
Figure 26 EN On
10
IS32LT3125/3125A
VEN
2V/Div
VCC = 12V
VHR = 2V
TA = 125°C
VEN
2V/Div
VISET
500mV/Div
VISET
500mV/Div
VFAULT
2V/Div
VFAULT
2V/Div
IOUT
50mA/Div
IOUT
50mA/Div
Time (2µs/Div)
Time (4µs/Div)
Figure 27 EN Off
VEN
2V/Div
VCC = 12V
VHR = 2V
TA = 125°C
Figure 28 EN On
VEN
2V/Div
VISET
500mV/Div
VISET
500mV/Div
VFAULT
2V/Div
VFAULT
2V/Div
IOUT
50mA/Div
IOUT
50mA/Div
Time (20ms/Div)
VCC = 12V
VHR = 2V
TA = 25°C
Time (20ms/Div)
Figure 29 tSD
VEN
2V/Div
VCC = 12V
VHR = 2V
TA = 125°C
Figure 30 tSD
VCC = 12V
VHR = 2V
TA = -40°C
VISET
500mV/Div
VFAULT
2V/Div
IOUT
50mA/Div
Time (20ms/Div)
Figure 31 tSD
Lumissil Microsystems – www.lumissil.com
Rev.A, 06/08/2020
11
IS32LT3125/3125A
FUNCTIONAL BLOCK DIAGRAM
Lumissil Microsystems – www.lumissil.com
Rev.A, 06/08/2020
12
IS32LT3125/3125A
APPLICATION INFORMATION
The IS32LT3125/3125A is a single channel linear
current driver optimized to drive automotive interior or
exterior LED light which can be dimmed via Power
Supply Modulation (PSM) or by digitally driving the EN
pin. The output current is set by a single reference
resistor (RISET) and capable of 250mA.
OUTPUT CURRENT SETTING
A single resistor (RISET) controls the maximum output
current for the channel. The resistor value for a specific
current level is calculated using the following Equation
(1):
RISET
2000
I SET
(1)
(8kΩ≤RISET≤80kΩ)
RISET need to be chosen 1% accuracy resistor with
good temperature characteristic to ensure stable
output current.
The device is protected from an output overcurrent
condition caused by a too low value RISET, by internally
limiting the maximum current to 300mA (Typ.). If ISET
pin is open, the output will be off and FAULTB will be
pulled low.
I LED I MAX DPWM
IMAX is computed using Equation (1) and DPWM is the
duty cycle. To guarantee a reasonably good dimming
effect, recommend PWM frequency in the range of
100Hz ~ 1kHz. Driving the EN pin with a PWM signal
can effectively adjust the LED intensity. The PWM
signal voltage levels must meet the EN pin input
voltage levels, VEN. Pull up to VCC via a 10KΩ resister
when EN pin is unused; do not leave it floating.
UNDER VOLTAGE PIN OPERATION
The IC has an internal VCC UVLO (Under Voltage
Lock Out) set at VUVLO. However, it may be desirable to
externally set an UVLO to track the number of LED’s
used in the string. For PSM dimming application, the
higher UVLO will track the PSM off time to a
pre-determined VCC level. In addition, it is necessary
to prevent false LED open detection due to the LED
string losing its headroom voltage, such as when VCC
rises up from zero during power up or PSM dimming.
The UV pin can be used to set a VCC under voltage
lockout threshold via a resistor divider.
VBattery
5
POWER SUPPLY MODULATION DIMMING
The IS32LT3125/3125A can operate with Power
Supply Modulation (PSM) where the device’s power
supply is pulse width modulated to achieve LED
dimming. The IS32LT3125/3125A stability is not
affected by operation with PSM. To get better dimming
linearity, the recommended PSM frequency can be in
the range of 100Hz to 300Hz, (200Hz Typ.) and input
capacitor, CVCC, should be low value (0.1uF typical) to
ensure rapid discharge during PSM low period.
CSTOR OPERATION
To keep the IC operating normally during condition of
PSM when VCC goes to zero, CSTOR capacitor provides
the keep-alive current needed to power the digital
counter and the fault flag circuits. A capacitor value of
2.2µF is recommended. The keep-alive time could be
roughly calculated by the following Equation (2):
t alive
2.5V C STOR
I CST
(2)
EN PIN OPERATION
The voltage at the EN pin must be higher than VEN to
enable the IC and below (VEN-VENHY) to disable the IC.
The EN pin of the IS32LT3125/3125A can accept a
PWM signal to implement LED dimming. LED average
current may be computed using the following Equation
(3).
Lumissil Microsystems – www.lumissil.com
Rev.A, 06/08/2020
(3)
VCC
PSM
R1
R2
Figure 32
6
UV
IS32LT3125
/IS32LT3125A
UV Pin Operation
This external UVLO threshold voltage can be
computed using the following Equation (4):
VCC _ UVLO VUV
R1 R2
R2
(4)
Pull up to VCC using a 10kΩ resister when UV pin is
unused; do not leave it floating.
To prevent false open detection, the external UVLO
threshold voltage should be set at Equation (5):
VCC _ UVLO VLED _ MAX VOCD
(5)
Where VLED_MAX is the maximum LED string forward
voltage on the output channel.
OUTPUT STATE
DIAGNOSTIC
DETECTION
AND
FAULT
IS32LT3125/3125A offers a fault diagnostic function.
LED string open/short, output shorted to GND/VCC,
13
IS32LT3125/3125A
ISET pin short/open or thermal shutdown will trigger
this function.
An output shorted to GND or VCC is detected as a
fault if the OUT pin voltage drops below the short
detect voltage threshold VSCD or VCC to OUT drop
voltage is lower than VOCD and remains below the
threshold for tFD. Then the channel will change to
source a 4mA current for recovery detection. The
FAULTB pin will be pulled low and the VCC standby
current will increase to ISD_FLT (typical, 30mA for
IS32LT3125, 1mA for IS32LT3125A) to indicate the
fault condition. This state will recover after the fault
condition is removed.
If the ISET pin is either shorted or open for tFD deglitch
time, the channel will turn off. The FAULTB pin will pull
low and the VCC standby current will increase to ISD_FLT
(typical, 30mA for IS32LT3125, 1mA for IS32LT3125A)
to indicate the fault condition. The state will recover
after the fault condition is removed.
FAULTB PARALLEL INTERCONNECTION
For LED lighting systems which require the complete
lighting system be shut down when a fault is detected,
the FAULTB pin can be used in a parallel connection
with multiple IS32LT3125/3125A devices as shown in
Figure 2. A detected fault output by one device (fault
master device) will pull low the FAULTB pins of the
other parallel connected devices (fault slave devices)
and simultaneously turn them off. This satisfies the
“One-Fail-All-Fail”
operating
requirement.
For
IS32LT3125, only the fault master device has 30mA
VCC standby current indication.
THERMAL SHUTDOWN
Figure 33
OUT Pin Shorted Operation
In the event the LED channel is open circuited, the
OUT pin voltage will go up close to VCC. If VCC to OUT
drop voltage remains below the threshold VOCD for tFD,
the channel will change to source a 4mA current for
recovery detection. The FAULTB pin will be pulled low
and the VCC standby current will increase to ISD_FLT
(typical, 30mA for IS32LT3125, 1mA for IS32LT3125A)
to indicate the fault condition. The state will recover
after the open condition is removed.
To protect the IC from damage due to high power
dissipation, the temperature of the die is monitored.
In the event that the die temperature exceeds 165°C,
the device will go into shutdown mode. The channel
(OUT) will turn off. The FAULTB pin will pull low and
the VCC standby current will increase to ISD_FLT (typical,
30mA for IS32LT3125, 1mA for IS32LT3125A) to
indicate the fault condition. At this point, the IC begins
to cool off. Any attempt to enable the channel back to
the source condition before the IC cooled to TJ
工商网监
湘ICP备2023018690号
