EVALUATION KIT AVAILABLE
MAX16822A/MAX16822B
2MHz, High-Brightness LED
Drivers with Integrated MOSFET
and High-Side Current Sense
General Description
Benefits and Features
The MAX16822A/MAX16822B step-down constant-current high-brightness LED (HB LED) drivers provide a
cost-effective design solution for automotive
interior/exterior lighting, architectural and ambient lighting, LED bulbs, and other LED illumination applications.
The MAX16822A/MAX16822B operate from a +6.5V to
+65V input-voltage range and can provide an output
current up to 350mA, if operated up to a temperature of
+125°C, or up to 500mA, if operated up to a temperature of +105°C. A high-side current-sense resistor
adjusts the output current and a dedicated pulse-width
modulation (PWM) input enables pulsed LED dimming
over a wide range of brightness levels.
• Cost-Effective Solution for Wide Range of LED
These devices are well suited for applications requiring
a wide input-voltage range. The high-side current sensing and an integrated current-setting circuitry minimize
the number of external components while delivering an
average output current with ±3% accuracy. A hysteretic
control method ensures excellent input supply rejection
and fast response during load transients and PWM dimming. The MAX16822A allows 10% current ripple and
the MAX16822B allows 30% current ripple. Both
devices operate up to a switching frequency of 2MHz,
thus allowing the use of small-sized components.
The MAX16822A/MAX16822B offer an analog dimming
feature that reduces the output current by applying an
external DC voltage below the internal 2V threshold voltage from TEMP_I to GND. TEMP_I also sources 25µA to
a negative temperature coefficient (NTC) thermistor connected between TEMP_I and GND, thus providing an
analog thermal-foldback feature that reduces the LED
current when the temperature of the LED string exceeds
a specified temperature point.
An additional feature includes thermal-shutdown protection that turns off the LX driver when the junction
temperature exceeds +165°C.
The MAX16822A/MAX16822B operate over the -40°C to
+125°C automotive temperature range and are available
in an 8-pin SO package.
Lighting Applications
• 6.5V to 65V Input Voltage Range
• Output Current Up to 500mA
• ±3% LED Current Accuracy
• Selectable Dimming Options: Linear or PWM
• Minimal Component Count Saves Cost and Space
• On-Board 65V, 0.85Ω Power MOSFET
• Resistor-Programmable Constant LED Current
• Integrated High-Side Current Sense with 200mV
Current-Sense Reference
• Hysteretic Control: Up to 2MHz Switching
Frequency
• Protection Features and Wide Operating
Temperature Range Improves Reliability
• Thermal-Foldback Protection Dims LEDs to
Minimize Overheating
• Thermal-Shutdown Protection
• Available in an 8-Pin SO Package
• Operation Over -40°C to +125°C Temperature
Range
Ordering Information
PART
TEMP RANGE
MAX16822AASA+
-40°C to +125°C
8 SO
MAX16822AASA/V+
-40°C to +125°C
8 SO
MAX16822BASA+
-40°C to +125°C
8 SO
+Denotes a lead(Pb)-free/RoHS-compliant package.
/V denotes an automotive qualified part.
Typical Application Circuit
D1
HB LEDs
VIN
RSENSE
L1
C2
Applications
Architectural, Industrial, and Ambient Lighting
1
Automotive RCL, DRL, and Fog Lights
2
Heads-Up Displays
Indicator and Emergency Lighting
PIN-PACKAGE
CS
TEMP_I
IN
DIM
C1
3
4
MAX16822A
MAX16822B
GND
LX
PGND
LX
8
7
NTC*
ON
OFF
6
5
Pin Configuration appears at end of data sheet.
*OPTIONAL
19-4141; Rev 4; 2/15
2MHz, High-Brightness LED
Drivers with Integrated MOSFET
and High-Side Current Sense
MAX16822A/MAX16822B
Absolute Maximum Ratings
IN, CS, LX, DIM to GND .........................................-0.3V to +70V
TEMP_I to GND .......................................................-0.3V to +6V
PGND to GND ......................................................-0.3V to +0.3V
CS to IN .................................................................-0.3V to +0.3V
Maximum Current into Any Pin
(except IN, LX, and PGND).............................................20mA
Continuous Power Dissipation (TA = +70°C)
8-Pin SO (derate 7.4mW/°C above +70°C)...............588.2mW
Junction-to-Ambient Thermal Resistance (θJA) (Note 1) ...136°C/W
Pin-to-Pin ESD Ratings......................................................±2.5kV
Operating Temperature Range
350mA (max) Output Current ........................-40°C to +125°C
500mA (max) Output Current ........................-40°C to +105°C
Junction Temperature ......................................................+150°C
Storage Temperature Range .............................-65°C to +150°C
Lead Temperature (soldering, 10s) .................................+300°C
Note 1: Package thermal resistances were obtained using the method described in JEDEC specification JESD51-7, using a fourlayer board. For detailed information on package thermal considerations, see www.maximintegrated.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 = +24V, VDIM = VIN, TA = TJ = -40°C to +125°C, unless otherwise noted. Typical values are at TA = +25°C.)
PARAMETER
SYMBOL
Input-Voltage Range
CONDITIONS
VIN
MIN
TYP
6.5
MAX
65
UNITS
V
Ground Current
No switching
1.5
mA
Supply Current
VDIM < 0.6V, VIN = 12V
350
μA
VCS = VIN - 100mV, VIN rising from 4V
until VLX < 0.5VIN
6.25
UNDERVOLTAGE LOCKOUT (UVLO)
Undervoltage Lockout
UVLO
6.5
V
VCS = VIN - 100mV, VIN falling from 6.5V
until VLX > 0.5VIN
6
Undervoltage-Lockout Hysteresis
0.5
V
SENSE COMPARATOR
Sense Voltage Threshold High
Sense Voltage Threshold Low
VSNSHI
VSNSLO
MAX16822A, VIN - VCS rising from 140mV
until VLX > 0.5VIN
201
210
216
MAX16822B, VIN - VCS rising from 140mV
until VLX > 0.5VIN
218
230
236
MAX16822A, VIN - VCS falling from
260mV until VLX < 0.5VIN
185
190
198
MAX16822B, VIN - VCS falling from
260mV until VLX < 0.5VIN
166
mV
mV
170
180
Propagation Delay to Output High
tDPDH
Falling edge of VIN - VCS from 140mV to
260mV to VLX > 0.5VIN
50
ns
Propagation Delay to Output Low
tDPDL
Rising edge of VCS - VIN from 260mV to
140mV to VLX < 0.5VIN
50
ns
CS Input Current
ICSIN
VIN - VCS = 200mV
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3.5
μA
Maxim Integrated | 2
2MHz, High-Brightness LED
Drivers with Integrated MOSFET
and High-Side Current Sense
MAX16822A/MAX16822B
Electrical Characteristics (continued)
(VIN = +24V, VDIM = VIN, TA = TJ = -40°C to +125°C, unless otherwise noted. Typical values are at TA = +25°C.)
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
VIN = VDIM = 24V, VCS = 23.9V,
ILX = 350mA
0.85
1.7
VIN = VDIM = 6.0V, VCS = 5.9V,
ILX = 350mA
1
UNITS
INTERNAL MOSFET
Drain-to-Source Resistance
RDSON
LX Leakage Current
ILX_LEAK
2
VDIM = 0V, VLX = 65V
10
μA
DIM INPUT
DIM Input-Voltage High
DIM Input-Voltage Low
DIM Turn-On Time
VIH
VIN - VCS = 100mV
VIL
VCS - VIN = 100mV
tDIM_ON
DIM Input Leakage High
2.8
0.6
VDIM rising edge to VLX < 0.5VIN
V
200
VDIM = VIN
VDIM = 0V
DIM Input Leakage Low
V
ns
-3
15
μA
0
μA
THERMAL SHUTDOWN
Thermal-Shutdown Threshold
Temperature rising
Thermal-Shutdown Threshold
Hsysteresis
165
°C
10
°C
THERMAL FOLDBACK
Thermal-Foldback Enable
Threshold Voltage
VTFB_ON
VDIM = 5V
Thermal-Foldback Slope
FBSLOPE
VDIM = 5V
TEMP_I Output Bias Current
1.9
2.0
2.12
V
0.75
ITEMP_I
25
1/V
26.5
28
μA
Typical Operating Characteristics
(VIN = VDIM = 48V, CVCC = 1µF, RSENSE = 0.62Ω, L = 220µH (connected between IN and CS). Typical values are at TA = +25°C,
unless otherwise noted.)
100
85
1 LED
80
75
70
15 LEDs
13 LEDs
80
70
7 LEDs 9 LEDs
5 LEDs
60
50
3 LEDs
1 LED
40
15
25
35
VIN (V)
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45
55
65
90
13 LEDs
80
9 LEDs
60
7 LEDs
5 LEDs
50
40
30
20
20
10
10
15 LEDs
11 LEDs
70
30
3 LEDs
1 LED
0
0
5
100
FREQUENCY (kHz)
90
11 LEDs
90
DUTY CYCLE (%)
EFFICIENCY (%)
95
11 LEDs13 LEDs 15 LEDs
MAX16822A toc02
7 LEDs 9 LEDs
5 LEDs
3 LEDs
MAX16822A toc01
100
FREQUENCY
vs. VIN
DUTY CYCLE
vs. VIN
MAX16822A toc03
EFFICIENCY
vs. VIN
5
15
25
35
VIN (V)
45
55
65
5
15
25
35
45
55
65
VIN (V)
Maxim Integrated | 3
2MHz, High-Brightness LED
Drivers with Integrated MOSFET
and High-Side Current Sense
MAX16822A/MAX16822B
Typical Operating Characteristics (continued)
(VIN = VDIM = 48V, CVCC = 1µF, RSENSE = 0.62Ω, L = 220µH (connected between IN and CS). Typical values are at TA = +25°C,
unless otherwise noted.)
QUIESCENT CURRENT
vs. VIN
NORMALIZED ILED
vs. VIN
NORMALIZED ILED
1.05
5 LEDs 7 LEDs
9 LEDs11 LEDs13 LEDs
15 LEDs
3 LEDs
1.00
1 LED
0.950
MAX16822A toc06
MAX16822A toc05
500
450
QUIESCENT CURRENT (μA)
MAX16822A toc04
1.10
PWM DIMMING
AT 200Hz DUTY CYCLE (10%)
400
350
ILED
200mA/div
300
250
0
200
VDIM
5V/div
0
150
100
50
0
0.90
VIN = 48V
8 LEDs
VDIM = 0V
0 5 10 15 20 25 30 35 40 45 50 55 60 65
0 5 10 15 20 25 30 35 40 45 50 55 60 65
VIN (V)
VIN (V)
1ms/div
PWM DIMMING
AT 20kHz DUTY CYCLE (90%)
PWM DIMMING
AT 200Hz DUTY CYCLE (90%)
MAX16822A toc08
MAX16822A toc07
ILED
200mA/div
ILED
200mA/div
0
0
VDIM
5V/div
0
VDIM
5V/div
0
VIN = 48V
8 LEDs
1ms/div
10μs/div
LED CURRENT
vs. VTEMP_I
ILED
vs. TEMPERATURE
400
MAX16822A toc10
450
0.4
350
300
ILED (A)
LED CURRENT (mA)
0.5
MAX16822A toc09
500
250
0.3
0.2
200
150
0.1
100
50
VIN = 48V
0
0
0
0.4
0.8
1.2
1.6
VTEMP_I (V)
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2.0
2.4
2.8
-40 -25 -10 5 20 35 50 65 80 95 110 125
TEMPERATURE (°C)
Maxim Integrated | 4
2MHz, High-Brightness LED
Drivers with Integrated MOSFET
and High-Side Current Sense
MAX16822A/MAX16822B
Typical Operating Characteristics (continued)
(VIN = VDIM = 48V, CVCC = 1µF, RSENSE = 0.62Ω, L = 220µH (connected between IN and CS). Typical values are at TA = +25°C,
unless otherwise noted.)
ITEMP_I
vs. TEMPERATURE
LXRDSON
vs. TEMPERATURE
29.5
29.0
28.5
0.8
VIN = 48V
VIN = 6.5V
0.7
0.6
ITEMP_I (μA)
LXRDSON (Ω)
0.9
30.0
MAX16822A toc12
VIN = 65V
MAX16822A toc11
1.0
28.0
27.5
27.0
26.5
26.0
0.5
25.5
25.0
0.4
VIN = 48V
-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)
Pin Description
PIN
NAME
1
CS
Current-Sense Input. Connect a resistor between IN and CS to program the LED current.
2
IN
Positive Supply Voltage Input. Bypass with a 1μF or higher value capacitor to GND.
3
GND
4
PGND
5, 6
LX
7
DIM
8
TEMP_I
FUNCTION
Ground
Power Ground
Switching Node
Logic-Level Dimming Input. Drive DIM low to turn off the current regulator. Drive DIM high to
enable the current regulator.
Thermal Foldback Control and Linear Input. Bypass with a 0.01μF capacitor to GND if thermal
foldback or analog dimming is used. See the Thermal Foldback section for more details.
Detailed Description
The MAX16822A/MAX16822B are step-down, constantcurrent, high-brightness LED (HB LED) drivers. These
devices operate from a +6.5V to +65V input-voltage
range. The maximum output current is 500mA, if the
part is used at temperatures up to +105°C, or 350mA, if
it is used up to +125°C. A high-side current-sense
resistor sets the output current and a dedicated PWM
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dimming input enables pulsed LED dimming over a
wide range of brightness levels.
A high-side current-sensing scheme and an on-board
current-setting circuitry minimize the number of external components while delivering LED current with ±3%
accuracy, using a 1% sense resistor. See Figure 1 for
an internal block diagram.
Maxim Integrated | 5
2MHz, High-Brightness LED
Drivers with Integrated MOSFET
and High-Side Current Sense
MAX16822A/MAX16822B
IN
VCC
REGULATOR
MAX16822A
MAX16822B
VCC _ANA
ISET
LX
VCC _ANA
CS
CURRENT-SENSE
COMPARATOR
0.85Ω, 65V
DMOS SWITCH
PWM
DIMMING
1.23V
BANDGAP
REFERENCE
GATE
DRIVER
UVLO
COMPARATOR
DIM
DIM
BUFFER
VCC _ANA
25μA
TEMP_I
PGND
VTFB_ON
2V
THERMAL
FOLDBACK
COMPARATOR
GND
Figure 1. Internal Block Diagram
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Maxim Integrated | 6
2MHz, High-Brightness LED
Drivers with Integrated MOSFET
and High-Side Current Sense
MAX16822A/MAX16822B
Undervoltage Lockout (UVLO)
The MAX16822A/MAX16822B include UVLO with
500mV hysteresis. The internal MOSFET turns off when
VIN falls below 5.5V to 6.0V.
DIM Input
LED dimming is achieved by applying a PWM signal at
DIM. A logic level below 0.6V at DIM forces the
MAX16822A/MAX16822B’s output low, thus turning off
the LED current. To turn the LED current on, the logic
level at DIM must be greater than 2.8V.
Thermal Shutdown
The MAX16822A/MAX16822B thermal-shutdown feature turns off the LX driver when the junction temperature exceeds +165°C. The LX driver turns back on
when the junction temperature drops 10°C below the
shutdown-temperature threshold.
Analog Dimming
The MAX16822A/MAX16822B offer an analog dimming
feature that reduces the output current when the voltage at TEMP_I is below the internal 2V threshold voltage. The MAX16822A/MAX16822B achieve analog
dimming by either an external DC voltage source connected between TEMP_I and ground or by a voltage on
a resistor connected across TEMP_I and ground
induced by an internal current source of 25µA. When
the voltage at TEMP_I is below the internal 2V threshold
limit, the MAX16822A/MAX16822B reduce the LED current. Use the following formula to set the analog dimming current.
⎤
⎡
⎛ 1⎞
I TF (A) = ILED (A) × ⎢1 − FB SLOPE ⎜ ⎟ × VTFB _ ON − V A D (V) ⎥
⎝
⎠
V
⎦
⎣
(
)
where VTFB_ON = 2V and FBSLOPE = 0.75 are obtained
from the Electrical Characteristics table and VAD is the
voltage at TEMP_I.
Applications Information
Selecting RSENSE to Set LED Current
The LED current is programmed with a current-sense
resistor connected between IN and CS. Use the equation below to calculate the value of this resistor:
R SENSE (Ω) =
where VSNSHI is the sense voltage threshold high and
V SNSLO is sense voltage threshold low (see the
Electrical Characteristics table for values).
Current-Regulator Operation
The MAX16822A/MAX16822B regulate the LED current
using a comparator with hysteresis (see Figure 2). As
the current through the inductor ramps up and the voltage across the sense resistor reaches the upper
threshold, the internal MOSFET turns off. The internal
MOSFET turns on again when the inductor current
ramps down through the freewheeling diode until the
voltage across the sense resistor equals the lower
threshold. Use the following equation to determine the
operating frequency:
fSW =
(VIN − nVLED ) × nVLED × R SENSE
VIN × Δ V × L
where n is the number of LEDs, VLED is the forward
voltage drop of 1 LED, and ΔV = (VSNSHI - VSNSLO).
Inductor Selection
The MAX16822A/MAX16822B operate up to a switching
frequency of 2MHz. For space-sensitive applications,
the high switching frequency allows the size of the
inductor to be reduced. Use the following formula to
calculate an approximate inductor value and use the
closest standard value:
Thermal Foldback
The MAX16822A/MAX16822B also include a thermalfoldback feature that reduces the output current when
the temperature of the LED string exceeds a specified
temperature point. These devices enter thermal-foldback mode when the voltage drop on the NTC thermistor, thermally attached to the LEDs and electrically
connected between TEMP_I and ground, drops below
the internal 2V threshold limit.
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1 (VSNSHI + VSNSLO )(V)
2
ILED (A)
L(approx.) =
(VIN − nVLED ) × nVLED × R SENSE
VIN × Δ V × fSW
For component selection, use the MAX16822A/B Design
Tool available at:www.maximintegrated.com/MAX16822software.
Maxim Integrated | 7
2MHz, High-Brightness LED
Drivers with Integrated MOSFET
and High-Side Current Sense
MAX16822A/MAX16822B
HYSTERETIC
MODE
fSW
ILED
ΔI
AVG. LED
CURRENT
t
VDIM
t1
t2
t
Figure 2. Current-Regulator Operation
Freewheeling-Diode Selection
For stability and best efficiency, a low forward-voltage
drop diode with fast reverse-recovery time and low
capacitance is recommended. A Schottky diode is a
good choice as long as its breakdown voltage is high
enough to withstand the maximum operating voltage.
PCB Layout Guidelines
Careful PCB layout is critical to achieve low switching
losses and stable operation. Use a multilayer board
whenever possible for better noise immunity. Minimize
ground noise by connecting high-current ground
returns, the input bypass-capacitor ground lead, and
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the output-filter ground lead to a single point (star
ground configuration). In normal operation, there are two
power loops. One is formed when the internal MOSFET
is on and the high current flows through IN, RSENSE,
LED load, the inductor, the internal MOSFET, and GND.
The other loop is formed when the internal MOSFET is
off and the high-current circulates through RSENSE, LED
load, the inductor, and the freewheeling diode. Minimize
each loop area to reduce noise interaction.
Place RSENSE as close as possible to CS and IN. For
better noise immunity, a Kelvin connection between CS
and RSENSE is strongly recommended.
Maxim Integrated | 8
MAX16822A/MAX16822B
Pin Configuration
2MHz, High-Brightness LED
Drivers with Integrated MOSFET
and High-Side Current Sense
Chip Information
PROCESS: BiCMOS
TOP VIEW
Package Information
+
CS
1
IN
2
GND
3
MAX16822A
MAX16822B
PGND 4
SO
www.maximintegrated.com
8
TEMP_I
7
DIM
6
LX
5
LX
For the latest package outline information and land patterns (footprints), go to www.maximintegrated.com/packages. Note that a
“+”, “#”, or “-” in the package code indicates RoHS status only.
Package drawings may show a different suffix character, but the
drawing pertains to the package regardless of RoHS status.
PACKAGE TYPE
PACKAGE CODE
DOCUMENT NO.
8 SO
S8-2
21-0041
Maxim Integrated | 9
2MHz, High-Brightness LED
Drivers with Integrated MOSFET
and High-Side Current Sense
MAX16822A/MAX16822B
Revision History
PAGES
CHANGED
REVISION
NUMBER
REVISION
DATE
0
5/08
Initial release
—
1
6/08
Updated Ordering Information table to release MAX16822B.
1
2
5/09
Revised General Description, Features, Absolute Maximum Ratings, and
Detailed Description.
DESCRIPTION
1, 2, 5
3
1/10
Added /V part number.
1
4
2/15
Updated Benefits and Features section
1
For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642, or visit Maxim Integrated’s website at www.maximintegrated.com.
Maxim Integrated cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim Integrated product. No circuit patent
licenses are implied. Maxim Integrated reserves the right to change the circuitry and specifications without notice at any time. The parametric values (min and
max limits) shown in the Electrical Characteristics table are guaranteed. Other parametric values quoted in this data sheet are provided for guidance.
Maxim Integrated and the Maxim Integrated logo are trademarks of Maxim Integrated Products, Inc.
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