MAXIM MAX16835

19-4028; Rev 1; 5/08
High-Voltage, 350mA, Adjustable Linear
High-Brightness LED Driver
The MAX16835 current regulator operates from a 6.5V
to 40V input voltage range and delivers up to a total of
350mA to one or more strings of high-brightness LEDs
(HB LEDs). The output current of the MAX16835 is
adjusted by using an external current-sense resistor in
series with the LEDs. An enable input allows widerange “pulsed” dimming. Wave-shaping circuitry
reduces EMI. The differential current-sense input
increases noise immunity. The MAX16835 is well suited
for applications requiring high-voltage input and is able
to withstand automotive load-dump events up to 40V.
An on-board pass element minimizes external components while providing ±3.5% output current accuracy.
Additional features include a 5V regulated output and
short-circuit and thermal protection.
The MAX16835 is available in a thermally enhanced,
5mm x 5mm, 16-pin TQFN package and is specified
over the automotive -40°C to +125°C temperature range.
Applications
Automotive Interior: Map, Courtesy, and Cluster
Lighting
Features
o
o
o
o
o
o
o
o
o
o
o
o
o
o
+6.5V to +40V Operating Range
Adjustable LED Current (35mA to 350mA)
±3.5% Output Current Accuracy
Integrated Pass Element with Low-Dropout
Voltage (0.55V typ)
Output Short-Circuit Protection
+5V Regulated Output with 4mA Source
Capability
Thermal Shutdown
Differential LED Current Sense
High-Voltage Enable Pin for Dimming Interface
Low Shutdown Supply Current (35µA typ)
Low 200mV Current-Sense Reference Reduces
Power Losses
Wave-Shaped Edges Reduce Radiated EMI During
PWM Dimming
Available in Small, Thermally Enhanced,
5mm x 5mm, 16-Pin TQFN Package
-40°C to +125°C Operating Temperature Range
Automotive Exterior: Tail Lights and CHMSL
Ordering Information
Warning Lights for Emergency Vehicles
PART
Navigation and Marine Indicators
TEMP RANGE
MAX16835ATE+
General Illumination
-40°C to +125°C
+Denotes a lead-free package.
*EP = Exposed pad.
Signage, Gasoline Canopies, Beacons
GND
V5
CS-
CS+
Pin Configuration
TOP VIEW
12
11
10
9
PIN-PACKAGE
16 TQFN-EP*
Simplified Diagram
+6.5V TO +40V
IN
OUT
0.1μF
8
N.C. 13
+5V REG
N.C.
V5
LEDs
0.1μF
N.C. 14
MAX16835
EN 15
OUT 16
+
7
N.C.
6
N.C.
5
N.C.
MAX16835
CS+
RSENSE
PWM DIMMING
2
3
4
OUT
IN
IN
N.C.
EN
1
CSGND
TQFN
________________________________________________________________ Maxim Integrated Products
For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642,
or visit Maxim’s website at www.maxim-ic.com.
1
MAX16835
General Description
MAX16835
High-Voltage, 350mA, Adjustable Linear
High-Brightness LED Driver
ABSOLUTE MAXIMUM RATINGS
IN to GND ...............................................................-0.3V to +45V
OUT, EN to GND..........................................-0.3V to (VIN + 0.3V)
CS+, CS-, and V5 to GND ........................................-0.3V to +6V
OUT Short Circuited to GND Duration
(at VIN = +16V) ........................................................60 minutes
Maximum Current into Any Pin (except IN and OUT) .........±20mA
Continuous Power Dissipation (TA = +70°C)
16-Pin TQFN 5mm x 5mm
(derate 33.3mW/°C above +70°C) ...........................2666.7mW
Junction to Case Thermal Resistance (θJC) (Note 1) ........2°C/W
Junction to Ambient Thermal Resistance (θJA) (Note 1) ....30°C/W
Operating Junction Temperature Range ...........-40°C to +125°C
Junction Temperature ......................................................+150°C
Storage Temperature Range .............................-65°C to +150°C
Lead Temperature (soldering, 10s) .................................+300°C
Note 1: Package thermal resistances obtained using the method described in JEDEC specification JESD51-7, using a four-layer
board. For detailed information on package thermal considerations, see www.maxim-ic.com/thermal-tutorial.
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 conditions 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
(VIN = VEN = +12V, CV5 = 0.1µF to GND, IV5 = 0, CS- = GND, connect RSENSE = 0.58Ω between CS+ and CS-. TA = -40°C to
+125°C, unless otherwise noted. Typical values are at TA = +25°C.) (Notes 2 and 3)
PARAMETER
Supply Voltage Range
Ground Current
Shutdown Supply Current
Guaranteed Output Current
SYMBOL
(Note 2)
IG
ILOAD = 350mA
ISHDN
IOUT
Output Current Accuracy
Dropout Voltage (Note 4)
CONDITIONS
VIN
ΔVDO
Output Current Slew Rate
Short-Circuit Current
MIN
VEN ≤ 0.6V
RSENSE = 0.55Ω
TYP
MAX
UNITS
40.0
V
1.28
3
mA
35
70
6.5
350
µA
mA
35mA < IOUT < 350mA
±3.5
IOUT = 350mA (current pulsed),
12V < VIN < 40V
0.55
1.2
V
IOUT = 350mA (current pulsed),
6.5V < VIN < 40V
0.55
1.5
V
Current rising
7.8
Current falling
7.8
VIN = 12V, VCS+ = 0V
%
mA/µs
400
500
650
mA
-1.0
-0.2
µA
LOGIC INPUT
EN Input Current
IEN
-2.5
EN Input Voltage High
VIH
2.8
EN Input Voltage Low
VIL
Turn-On Time
tON
V
0.6
V
110
350
µs
193
200
207
mV
2.7
7.0
µA
-50
-17.2
VEN rising edge to 90% of OUT
CURRENT SENSE
Regulated RSENSE Voltage
VSENSE
VSENSE = VCS+ - VCS-
Input Current (CS+)
VCS+ = 220mV
Input Current (CS-)
VCS+ = 220mV
2
_______________________________________________________________________________________
µA
High-Voltage, 350mA, Adjustable Linear
High-Brightness LED Driver
(VIN = VEN = +12V, CV5 = 0.1µF to GND, IV5 = 0, CS- = GND, connect RSENSE = 0.58Ω between CS+ and CS-. TA = -40°C to
+125°C, unless otherwise noted. Typical values are at TA = +25°C.) (Notes 2 and 3)
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
THERMAL OVERLOAD
Thermal-Shutdown Temperature
+159
°C
24
°C
Thermal-Shutdown Hysteresis
+5V REGULATOR
Output Voltage
VV5
Output Voltage Load Regulation
ΔV5
4.85
V5 Short-Circuit Current
5.00
5.20
V
0 < ILOAD < 4mA (Note 5)
12
20
mV/mA
V5 = 0V (Note 6)
15
mA
Note 2: Resistors were added from OUT to CS+ to aid with the power dissipation during testing.
Note 3: All devices 100% production tested at TA = +25°C. Limits over the operating temperature range are guaranteed by design.
Note 4: Dropout is measured as follows:
Connect RO = 27Ω from OUT to CS+. Connect RSENSE = 0.58Ω from CS+ to CS-. Set VIN = +12V (record VOUT as VOUT1).
Reduce VIN until VOUT = 0.97 x VOUT1 (record as VIN2 and VOUT2). ΔVDO = VIN2 - VOUT2.
Note 5: Current regulation varies with V5 load (see the Typical Operating Characteristics).
Note 6: Thermal shutdown does not function if the output of the 5V reference is shorted to ground.
Typical Operating Characteristics
(VIN = VEN = +12V, TA = +25°C, unless otherwise noted.)
OUTPUT CURRENT
vs. TEMPERATURE
300
250
ILOAD = 200mA
200
150
ILOAD = 100mA
100
50
ILOAD = 35mA
0
0.206
0.204
0.202
0.200
MAX16835 toc03
400
350
OUTPUT CURRENT (mA)
350
0.208
OUTPUT CURRENT
vs. INPUT VOLTAGE
MAX16835 toc02
ILOAD = 350mA
(VCS+ - VCS-) (V)
OUTPUT CURRENT (mA)
400
MAX16835 toc01
450
(VCS+ - VCS-)
vs. OUTPUT CURRENT
300
250
200
150
100
50
0.198
0
-40 -25 -10 5 20 35 50 65 80 95 110 125
20 50 80 110 140 170 200 230 260 290 320 350
TEMPERATURE (°C)
OUTPUT CURRENT (mA)
0
5
10
15
20
25
30
35
40
INPUT VOLTAGE (V)
_______________________________________________________________________________________
3
MAX16835
ELECTRICAL CHARACTERISTICS (continued)
Typical Operating Characteristics (continued)
(VIN = VEN = +12V, TA = +25°C, unless otherwise noted.)
ILOAD = 350mA
0.6
0.5
0.4
0.3
90
VIN = 40V
80
70
VIN = 20V
60
50
40
30
20
0.2
VIN = 12V
5.1
IV5 = 1mA
NO LOAD
5.0
4.9
VIN = 6.5V
10
0.1
5.2
+5V REGULATOR OUTPUT (V)
DROPOUT VOLTAGE (V)
0.8
100
MAX16835 toc05
0.9
SHUTDOWN CURRENT (μA)
MAX16835 toc04
1.0
0.7
+5V REGULATOR OUTPUT
vs. TEMPERATURE
SHUTDOWN CURRENT
vs. TEMPERATURE
MAX16835 toc06
DROPOUT VOLTAGE
vs. TEMPERATURE
IV5 = 5mA
0
0
4.8
-40 -25 -10 5 20 35 50 65 80 95 110 125
-40 -25 -10 5 20 35 50 65 80 95 110 125
-40 -25 -10 5 20 35 50 65 80 95 110 125
TEMPERATURE (°C)
TEMPERATURE (°C)
TEMPERATURE (°C)
(VCS+ - VCS-) vs. IV5
+5V REGULATOR OUTPUT vs. VIN
0.202
0.200
ILOAD = 350mA
0.198
MAX16835 toc09
MAX16835 toc08
0.204
200Hz DIMMED OPERATION
5.2
+5V REGULATOR OUTPUT (V)
MAX16835 toc07
0.206
(VCS+ - VCS-) (V)
MAX16835
High-Voltage, 350mA, Adjustable Linear
High-Brightness LED Driver
IV5 = 5mA
NO LOAD
0V
5.0
ILOAD
200mA/div
4.9
0
IV5 = 5mA
0.196
ILOAD = 350mA, VIN = VEN,
VIN PULSED AT 200Hz (50% DUTY CYCLE)
4.8
0
1
2
3
4
5
5
IV5 (mA)
10
15
20
25
30
35
40
1ms/div
VIN (V)
200Hz DIMMED OPERATION EXPANDED
200Hz DIMMED OPERATION EXPANDED
MAX16835 toc10
MAX16835 toc11
0V
ILOAD
200mA/div
200Hz DIMMED OPERATION
MAX16835 toc12
VIN
5V/div
VIN
5V/div
ILOAD = 350mA
VIN = VEN
VIN PULSED AT 200Hz
(50% DUTY CYCLE)
VIN
5V/div
5.1
ILOAD = 350mA
VIN = VEN
VIN PULSED AT 200Hz
(50% DUTY CYCLE)
0
EN
10V/div
0V
0V
ILED
200mA/div
ILED
200mA/div
0
0
ILOAD = 350mA, VIN = 12V,
EN PULSED AT 200Hz (50% DUTY CYCLE)
20μs/div
4
4μs/div
1ms/div
_______________________________________________________________________________________
High-Voltage, 350mA, Adjustable Linear
High-Brightness LED Driver
PIN
NAME
1, 16
OUT
FUNCTION
2, 3
IN
4–8, 13, 14
N.C.
No Connection. Not internally connected.
9
CS+
Positive Input of the Internal Differential Amplifier. Connect the current-sense resistor between CS+
and CS- to program the output current level.
10
CS-
Negative Input of the Internal Differential Amplifier. Connect the current-sense resistor between
CS- and CS+ to program the output current level.
11
V5
+5V Regulated Output. Connect a 0.1µF capacitor from V5 to GND.
12
GND
15
EN
Enable Input. Drive EN high to enable the output.
—
EP
Exposed Pad. Connect to the ground plane for effective power dissipation. Do not use as the only
ground connection.
Current-Regulated Output. Connect pin 1 to pin 16.
Positive Input Supply. Bypass IN with a 0.1µF (min) capacitor to GND. Connect pin 2 to pin 3.
Ground
Functional Diagram
V5
IN
REGULATOR
IN
EN
ENABLE
REFERENCE
GENERATOR
I-REG
OUT
DIFFERENTIAL
SENSE
AMPLIFIER
MAX16835
CS+
CS-
THERMAL
SHUTDOWN
Detailed Description
The MAX16835 is a high-current regulator capable of
providing up to a total of 350mA of current to one or
more strings of high-brightness LEDs. A wide operating
input voltage range of +6.5V to +40V makes the
MAX16835 ideal for automotive applications. A +5V
regulated output provides up to 4mA of current to
power external circuitry. In addition, the MAX16835
features thermal and output short-circuit protection.
The wide operating voltage range helps protect the
MAX16835 against large transients such as those
found in load-dump situations up to 40V.
The MAX16835 uses a feedback loop to control the output current. The differential voltage across the sense
resistor is compared to a fixed reference voltage, and
the error is amplified to serve as the drive to the internal
_______________________________________________________________________________________
5
MAX16835
Pin Description
MAX16835
High-Voltage, 350mA, Adjustable Linear
High-Brightness LED Driver
power series pass device (see the Functional Diagram).
The regulation point is factory set at (VCS+ - VCS-) =
200mV ±3.5%. The regulated current is user defined by
the value of RSENSE.
The MAX16835 is a current controller internally optimized for driving the impedance range expected from
one or more HB LEDs.
connected across RSENSE provides ground-loop immunity and low-frequency noise rejection. The LED current
is given by the equation below:
ILED = VSENSE/RSENSE
+5V Regulator
VIN(MIN) ≥ VSENSE(MAX) + VFT(MAX + ΔVDO(MAX)
where VFT(MAX) is the total forward voltage of all seriesconnected LEDs. The minimum operating voltage of the
device is +6.5V. The device operates below +6.5V;
However, the output current may not meet the full regulation specification.
The MAX16835 includes a fixed +5V output regulator
that delivers up to 4mA of load current for low-power
applications throughout the +6.5V to +40V input voltage range. Connect a 0.1µF compensation capacitor
from V5 to ground. Shorting V5 to ground disables the
thermal shutdown. When EN is low, V5 is off.
Input Voltage Considerations
For proper operation, the minimum input voltage must
always be:
Low-Frequency PWM
at the Output
Thermal Protection
The MAX16835 enters a thermal-shutdown mode in the
event of overheating. This typically occurs in overload or
output short-circuit conditions. When the junction temperature exceeds TJ = +159°C (typ), the internal thermal-protection circuitry turns off the series pass device.
The MAX16835 recovers from thermal-shutdown mode
once the junction temperature drops by 24°C (typ). The
part therefore protects itself by thermally cycling in the
event of a short-circuit or overload condition. Shorting V5
to ground disables the thermal shutdown.
Applications Information
Programming the LED Current
The MAX16835 uses a sense resistor across CS+ and
CS- to set the LED current. The differential sense amplifier
The MAX16835 provides pulsed or chopped current
dimming. Generally, HB LEDs are binned to match at
their full-rated current; however, LEDs from the same
bin exhibit poor matching at currents other than fullrated current. To achieve uniformity, HB LED manufacturers recommend PWM pulsing of the LED current at
their full-rated value. There are two methods for producing a PWM output. One method is by pulsing the
enable input (EN) while having a constant voltage at IN.
The other method is to connect EN to IN and pulse both
EN and IN. Both methods generate a regulated-amplitude PWM current (variable duty cycle) that can provide control over the LED brightness (see Figures 1
and 2).
VEN
1
OUT
2
IN
3
IN
4
N.C.
16
15
14
13
16
15
14
13
OUT
EN
N.C.
N.C.
OUT
EN
N.C.
N.C.
ILED
GND 12
D1
VIN
VIN
V5 11
C1
C2
MAX16835
CS- 10
RSENSE
CS+ 9
OUT
2
IN
3
IN
4
N.C.
ILED
GND 12
D1
V5 11
C1
C2
MAX16835
CS- 10
CS+ 9
N.C.
N.C.
N.C.
N.C.
N.C.
N.C.
N.C.
N.C.
5
6
7
8
5
6
7
8
Figure 1. Pulse Application with VIN at a Constant Voltage
6
1
Figure 2. Pulse Application with EN Connected to VIN
_______________________________________________________________________________________
RSENSE
High-Voltage, 350mA, Adjustable Linear
High-Brightness LED Driver
Chip Information
PROCESS: BiCMOS
1
OUT
2
IN
3
IN
4
N.C.
16
15
14
13
OUT
EN
N.C.
N.C.
Package Information
For the latest package outline information and land patterns, go
to www.maxim-ic.com/packages.
GND 12
D1
VIN
V5 11
C1
C2
MAX16835
CS- 10
RSENSE
PACKAGE TYPE
PACKAGE CODE
DOCUMENT NO.
16 TQFN
T1655-3
21-0140
CS+ 9
N.C.
N.C.
N.C.
N.C.
5
6
7
8
_______________________________________________________________________________________
7
MAX16835
Typical Operating Circuit
MAX16835
High-Voltage, 350mA, Adjustable Linear
High-Brightness LED Driver
Revision History
REVISION
NUMBER
REVISION
DATE
0
2/08
Initial release
5/08
Updated Ordering Information, Electrical Characteristics, and Package
Information.
1
DESCRIPTION
PAGES
CHANGED
—
1, 2, 8, 9
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implied. Maxim reserves the right to change the circuitry and specifications without notice at any time.
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