is32lt3180 75ma, 8-channel constant current regulator with otp

IS32LT3180 75MA, 8-CHANNEL CONSTANT CURRENT
REGULATOR WITH OTP FOR AUTOMOTIVE REAR TAIL LIGHT
DESCRIPTION
QUICK START
The IS32LT3180 is an eight channel linear current
regulator for automotive rear tail light applications such
as RCL (Rear Combination Lamps) and CHMSL
(Center High Mounted Stop Lamps). It is fully
programmable with two LED brightness levels for the
different intensity requirements of “stop” bright (DC
mode) and “tail” dim (PWM mode).
A logic level at the PWM pin is used to select between
the tail and stop output conditions. The stop condition
provides the highest intensity output, while the tail
condition utilizes an internally generated PWM signal
to reduce the intensity of the LEDs’ light output.
The sink current at the OUTx pins is easily set with a
single resistor at the STOP pin. A second resistor at
the TAIL pin sets the duty cycle of the internal PWM
oscillator for dimming (less bright) the LED output
when operating in the tail condition.
An external FET (optional) can be implemented for
operation with wide varying supply voltages.
The IS32LT3180 is offered in an eTSSOP-16 package.
Figure 1: Photo of IS32LT3180 Evaluation Board
RECOMMENDED EQUIPMENT



6V~50V, 1A DC power supply
Multimeter
8 strings LEDs (3 LEDs in series of each string, the
rated current is not less than 100mA)
FEATURES

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Output current programmable from 10mA to
75mA
Tail duty cycle programmable from 1% to 95%
Linear voltage regulator to optimize consumption
on device
Low dropout voltage of 0.8V@35mA
Slew rate control on each output for better EMI
performance
PWM logic level input selects between full
brightness and PWM dimming levels
FAULT reporting
LED open/short circuit detection
Input overvoltage protection
STOP pin overcurrent protection
Thermal rollback of output current
Withstand 50V load dump
AEC-Q100 qualification (pending)
ABSOLUTE MAXIMUM RATINGS

≤ 50V power supply
Caution: Do not exceed the conditions listed above; otherw
ise the board will be damaged.
PROCEDURE
The IS32LT3180 demo 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) Connect the negative terminal of power supply to
GND header (TP6).
2) Connect the positive terminal of power supply to
connector VCC header (TP1).
3) Select JP2~JP9 to configure output LED strings
(refer to JUMPER/SWITCH SETTING TABLE)
4) Close JP10 to use the onboard LEDs
Note: Open JP10 only if external LEDs are to be used
Connect Pin1 of TP7 to each anode of the external LED
strings. Connect Pin2~Pin9 to the corresponding cathode
of the external LED string.
Integrated Silicon Solution, Inc. – www.issi.com
Rev. B, 12/18/2014
1
IS32LT3180 75MA, 8-CHANNEL CONSTANT CURRENT
REGULATOR WITH OTP FOR AUTOMOTIVE REAR TAIL LIGHT
5) Close JP1.
The device FAULT flag can be monitored by an
external circuit on TP5.
Note: The voltage level of this fault signal is pulled up to
the supply voltage, disconnect JP1 if this voltage level
exceeds the monitoring circuit’s logic high parameter
rating. Since the Fault flag output of the IS32LT3180 is open
drain, it is possible to supply a lower voltage at R12’s JP1
pin which will not damage the monitoring circuit.
6) The output current of all channels in “STOP” mode
can be adjusted by the potentiometer resistor RW1.
Turn RW1 counter clockwise to increase and
clockwise to decrease the output current of all
channels. The final resistance can be measured
with an ohm meter across test point “Rstop” and
GND point.
7) The PWM duty cycle of “TAIL” mode can be
adjusted by the potentiometer resistor RW2. Turn
RW2 counter clockwise to decrease and clockwise
to increase the duty cycle. The final resistance can
be measured with an ohm meter across test point
“Rtail” and GND point.
8) If the total forward voltage drop between VCC to
LED string (VCC - VSTRING) is high the IS32LT3180
may begin to overheat. It is recommended to use
the onboard linear regulator to minimize the voltage
across the OUT1~8 pins. Toggle SW2 up to “With
LDO” to enable the onboard PMOS FET and
transfer some power consumption from the
IS32LT3180 to the external PMOS FET.
Toggle SW2 down to “without LDO” to disable the
onboard PMOS FET if the (VCC – VSTRING) can be
kept low so the IS32LT3180 does not over heat.
Note: The (VCC - VSTRING) can be minimized by either
increasing the total LED string forward voltage drop, ie
adding more LEDs in the string or by lowering the VCC
supply voltage.
9) Toggle SW1 up and down to choose between
“STOP” and “TAIL” modes.
10) Turn on the power supply.
ORDERING INFORMATION
Part No.
Temperature Range
Package
IS32LT3180-ZLA3-EB
-40°C to +125°C (Automotive)
eTSSOP-16, Lead-free
Table 1: Ordering Information
For pricing, delivery, and ordering information, please contacts ISSI’s analog marketing team at
[email protected] or (408) 969-6600.
JUMPER/SWITCH SETTING TABLE
Jumper/Switch
Options
Setting
JP1
Pulls the FAULT flag pin up to onboard VCC.
Close: pull up
Open: floating
JP10
Enable/disable the onboard LED strings (D3 ~ D26)
Close: enable
Open: disable
JP2-JP9
Correspond to OUT1-OUT8. Enable/disable the
corresponding LED strings.
Unused channel(s) must connect their corresponding
jumper to ‘L’ (GND), otherwise it will mistakenly trigger the
fault flag.
H: enable
L: disable
TP7
External LED string connector, Pin1 connects to the
common anode of the external LED strings, Pin2-Pin9
correspond to OUT1-OUT8, connect to the 1~8 cathode of
the external LED strings.
JP10 must be Open
SW1
Choose operation mode: ‘STOP’ or ‘TAIL’
Up: TAIL
Down: STOP
SW2
Enable/disable onboard linear regulator
Up: enable
Down: disable
Integrated Silicon Solution, Inc. – www.issi.com
Rev. B, 12/18/2014
2
IS32LT3180 75MA, 8-CHANNEL CONSTANT CURRENT
REGULATOR WITH OTP FOR AUTOMOTIVE REAR TAIL LIGHT
PROGRAMMING THE OUTPUT CURRENT
A single programming resistor (RSTOP) controls the
maximum sink current for each LED channel. The
STOP pin provides a reference voltage of 1.08V (Typ.).
The programming resistor may be computed using the
following Equation (1):
I OUT  100 
1.08
RSTOP
Where x is a number of 1~8. VOUTx is the OUTx pin
voltage of IS32LT3180. VSTRING is the LDO output
voltage. IQ is the operation current of IS32LT3180.
8
PFET   (VCC  VSTRING )  I OUTx
x 1

R
VSTRING  VFB   11  1

 R10
(1)
The current which is drawn from the STOP pin is
internally mirrored to each of the 8 outputs with a
multiplication factor of 100A/A. Thus, an output current
of 50mA would require a current to be drawn from
STOP of 500µA, corresponding to an external
programming resistance of 2.16kΩ.
PROGRAMMING THE PWM DUTY CYCLE
The PWM duty cycle which determines the lower
intensity TAIL condition, is also set using a single
external resistor. The PWM duty cycle (DC) is set by
the following Equation (2):
 100A  RTAIL

 0.1  100%
DC  
4


(2)
Where the TAIL pin supplies a constant current of
100µA. Internally, a 1kHz sawtooth waveform is
compared to the voltage of the TAIL pin resulting in a
1kHz PWM signal at the programmed duty cycle. For
example, a 50% duty cycle would require the reference
voltage at TAIL pin to be 2.4V, corresponding to an
external resistor (RTAIL) value of 24kΩ.
POWER DISSIPATION
The LED power is proportional to the voltage across
the LED and the sink current that can be defined as:
Note: The recommended R10 is 1kΩ. Setting VSTRING should
remain sufficient VOUTx to insure the current sink operation.
Please refer to datasheet to set a proper VOUTx.
The power dissipation on IS32LT3180:
8
P3180   (VOUTx  I OUTx )  VCC  I Q
x 1
VOUTx  VSTRING  VLEDSx
Assume all channels are on, IOUTx=35mA, VLEDSx=9.6V,
VCC=14V, IQ=6mA, R11=9.1kΩ, R10=1kΩ.
PLED=9.6V×0.035A×8=2.688W
VSTRING=1.05V×(9.1kΩ/1kΩ+1)=10.605V
PFET=(14V-10.605V)×0.035A×8=0.9506W
P3180=(10.605V-9.6V)×0.035A×8+14V×0.006A
=0.3654W
When input voltage VCC varies, the LDO will keep
VSTRING constant and the power dissipation on
IS32LT3180 also will be constant.
Caution: VCC must be higher than VSTRING to insure stable system
operation. The PMOS FET and IS32LT3180 must be mounted
over a large area copper plate on the PCB to enhance heat-sink
performance.
8
PLED   V LEDSx  I OUTx
x 1
Where x is a number of 1~8. PLED is the power all LED
strings. VLEDSx is the total forward voltage of each
LEDs string. IOUTx is the current of each LED string.
When working with the LDO in the ‘STOP’ condition,
the power dissipation on the PMOS FET:
Integrated Silicon Solution, Inc. – www.issi.com
Rev. B, 12/18/2014
3
IS32LT3180 75MA, 8-CHANNEL CONSTANT CURRENT
REGULATOR WITH OTP FOR AUTOMOTIVE REAR TAIL LIGHT
R1
JP10
TP6
VTAIL
D1
SW1
TP1
Q1
C3
C4
R2
VCC
D2
C2
R3
TP8
VSTOP
With LDO
SW2
L
H
JP2
D3
D4
D5
JP3
D6
D7
D8
D9
D10
D11
D12
D13
D14
D15
D16
D17
D18
D19
D20
JP8
D21
D22
D23
H
JP9
D24
D25
D26
Without LDO
L
H
L
H
L
H
TP4
FB
R11
R10
U1
IS32LT3180_TSSOP16
JP1
4
3
R12
R5
C1
2
TP3 FAULT
6
TP2 PWM R4
5
Rstop
7
Rtail
8
13
C5
R6
RW1
RW2
FB
OUT1
ERC
OUT2
VIN
OUT3
FAULT
OUT4
PWM
OUT5
RSTOP
OUT6
RTAIL
OUT7
GND
OUT8
JP4
1
JP5
16
15
L
H
L
H
L
H
JP6
14
12
JP7
11
10
9
R7
L
TP7
1
2
3
4
5
6
7
8
9
10
R9
R8
TP5 GND
Figure 2: IS32LT3180 Application Schematic
BILL OF MATERIALS
Name
Symbol
Description
Qty
Supplier
Part No.
LED Driver
U1
Constant current LED driver
1
ISSI
IS32LT3180
E-Cap
C1
CAP,10µF,50V,±10%
1
Capacitor
C2
CAP,0.22µF,50V,±10%,SMD
1
Yageo
CC0603KKX7R9BB224
Capacitor
C3,C4
CAP,1µF,50V,±10%,SMD
2
Yageo
CC0805KKX7R9BB105
Capacitor
C5
CAP,10nF,50V,±10%,SMD
1
Yageo
CC0805KKX7R9BB103
5
Yageo
RC0805FR-0701KL
Resistor
R1,R3,R8,R9,R10 RES,1k,1/4W,±1%,SMD
Resistor
R6,R7
Not connect
2
Resistor
R2
RES, 50R,1/4W,±5%,SMD
1
Yageo
RC0805JR-0750R0L
Resistor
R4,R5
RES,10K,1/4W,±5%,SMD
5
Yageo
RC0805JR-0710KL
Resistor
R11
RES,6.8K,1/4W,±1%,SMD
1
Yageo
RC0805FR-076K8L
PFET
Q1
60V/12A, P−Channel MOS
1
ONsemi
NT2955G
Potentiometer
RW1
0-20k,19mm×19mm
1
Potentiometer
RW2
0-50k,19mm×19mm
1
Diode
D1,D2
1N4007,1A,1000V,SMA
1
LED
D3~D26
F8mm,0.5W
24
Switch
SW1
SPDT, 13mm*6.5mm, 1A
1
Switch
SW2
3PDT, 16.5mm*12.7mm, 1A
1
Header
JP1~JP20
2 pin headers
20
Header
TP1~TP6
2 pin headers
6
Bill of Materials refers to Figure 2 above.
Integrated Silicon Solution, Inc. – www.issi.com
Rev. B, 12/18/2014
4
IS32LT3180 75MA, 8-CHANNEL CONSTANT CURRENT
REGULATOR WITH OTP FOR AUTOMOTIVE REAR TAIL LIGHT
Figure 3: Board PCB Layout - Top Layer
Figure 4: Board Component Placement Guide - Top Layer
Integrated Silicon Solution, Inc. – www.issi.com
Rev. B, 12/18/2014
5
IS32LT3180 75MA, 8-CHANNEL CONSTANT CURRENT
REGULATOR WITH OTP FOR AUTOMOTIVE REAR TAIL LIGHT
Figure 5: Board PCB Layout - Bottom Layer
Figure 6: Board Component Placement Guide - 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, 12/18/2014
6