Rainbow Electronics MAX16822B User Manual
General Description
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. A high-side current-sense
resistor adjusts the output current up to 350mA and a
dedicated pulse-width modulation (PWM) input enables
pulsed LED dimming over a wide range of brightness
levels.
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.
Applications
Architectural, Industrial, and Ambient Lighting
Automotive RCL, DRL, and Fog Lights
Heads-Up Displays
Indicator and Emergency Lighting
Features
♦ High-Efficiency Solution
♦ 6.5V to 65V Input-Voltage Range
♦ On-Board 65V, 0.85Ω Power MOSFET
♦ Hysteretic Control: Up to 2MHz Switching
Frequency
♦ ±3% LED Current Accuracy
♦ 200mV Current-Sense Reference
♦ Resistor-Programmable Constant LED Current
♦ Integrated High-Side Current Sense
♦ Thermal-Foldback Protection/Linear Dimming
♦ Thermal-Shutdown Protection
♦ Available in an 8-Pin SO Package
♦ -40°C to +125°C Operating Temperature Range
MAX16822A/MAX16822B
2MHz, High-Brightness LED Drivers with
Integrated MOSFET and High-Side Current Sense
________________________________________________________________
Maxim Integrated Products
1
Ordering Information
LX
LXPGND
1
2
8
7
TEMP_I
DIMIN
GND
CS
3
4
6
5
MAX16822A
MAX16822B
L1
C2
ON
OFF
D1
HB LEDs
NTC
*
*
OPTIONAL
R
SENSE
V
IN
C1
Typical Application Circuit
19-4141; Rev 1; 6/08
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.
EVALUATION KIT
AVAILABLE
+
Denotes a lead-free/RoHS-compliant package.
PART TEMP RANGE
PIN-PACKAGE
-40°C to +125°C 8 SO
-40°C to +125°C 8 SO
Pin Configuration appears at end of data sheet.
MAX16822AASA+
MAX16822BASA+
MAX16822A/MAX16822B
2MHz, High-Brightness LED Drivers with
Integrated MOSFET and High-Side Current Sense
2 _______________________________________________________________________________________
ABSOLUTE MAXIMUM RATINGS
ELECTRICAL CHARACTERISTICS
(VIN= +24V, V
DIM
= VIN, TA= TJ= -40°C to +125°C, unless otherwise noted. Typical values are at TA = +25°C.)
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.
Note 1: Package thermal resistances were 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
.
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 (T
A
= +70°C)
8-Pin SO (derate 7.4mW/°C above +70°C)...............588.2mW
Junction-to-Ambient Thermal Resistance (θ
JA
) (Note 1) ...136°C/W
Pin-to-Pin ESD Ratings......................................................±2.5kV
Operating 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
Input-Voltage Range V
Ground Current No switching 1.5 mA
Supply Current V
UNDERVOLTAGE LOCKOUT (UVLO)
Undervoltage Lockout UVLO
Undervoltage-Lockout Hysteresis 0.5 V
SENSE COMPARATOR
Sense Voltage Threshold High V
Sense Voltage Threshold Low V
Propagation Delay to Output High t
Propagation Delay to Output Low t
CS Input Current I
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS
IN
SNSHI
SNSLO
DPDH
DPDL
CSIN
< 0.6V, VIN = 12V 350 µA
DIM
VCS = VIN - 100mV, VIN rising from 4V until
V
< 0.5V
LX
V
CS
until V
MAX16822A, (VIN - VCS) rising from
140mV until V
MAX16822B, VIN - VCS rising from 140mV
until V
MAX16822A, VIN - VCS falling from 260mV
until V
MAX16822B, VIN - VCS falling from 260mV
until V
Falling edge of VIN - VCS from 140mV to
260mV to V
Rising edge of VCS - VIN from 260mV to
140mV to V
VIN - VCS = 200mV 3.5 µA
IN
= VIN - 100mV, VIN falling from 6.5V
> 0.5V
LX
LX
LX
LX
> 0.5V
< 0.5V
< 0.5V
LX
LX
IN
> 0.5V
LX
IN
IN
IN
= 0.5V
< 0.5V
IN
IN
IN
6.5 65 V
201 210 216
218 230 236
185 190 198
166 170 180
6.25 6.5
6
50 ns
50 ns
V
mV
mV
MAX16822A/MAX16822B
2MHz, High-Brightness LED Drivers with
Integrated MOSFET and High-Side Current Sense
_______________________________________________________________________________________ 3
ELECTRICAL CHARACTERISTICS (continued)
(VIN= +24V, V
DIM
= VIN, TA= TJ= -40°C to +125°C, unless otherwise noted. Typical values are at TA = +25°C.)
EFFICIENCY
vs. V
IN
MAX16822A toc01
VIN (V)
EFFICIENCY (%)
5545352515
75
80
85
90
95
100
70
565
1 LED
3 LEDs
5 LEDs
7 LEDs
9 LEDs
11 LEDs
13 LEDs
15 LEDs
9 LEDs
DUTY CYCLE
vs. V
IN
MAX16822A toc02
VIN (V)
DUTY CYCLE (%)
5545352515
10
20
30
40
50
60
70
80
90
100
0
565
1 LED
3 LEDs
5 LEDs
7 LEDs
15 LEDs
11 LEDs
13 LEDs
FREQUENCY
vs. V
IN
MAX16822A toc03
VIN (V)
FREQUENCY (kHz)
5545352515
10
20
30
40
50
60
70
80
90
100
0
565
1 LED
3 LEDs
5 LEDs
7 LEDs
9 LEDs
11 LEDs
13 LEDs
15 LEDs
Typical Operating Characteristics
(VIN= V
DIM
= 48V, C
VCC
= 1µF, R
SENSE
= 0.62Ω, L = 220µH (connected between IN and CS). Typical values are at TA= +25°C,
unless otherwise noted.)
INTERNAL MOSFET
Drain-to-Source Resistance R
LX Leakage Current I
DIM INPUT
DIM Input-Voltage High V
DIM Input-Voltage Low V
DIM Turn-On Time t
DIM Input Leakage High V
DIM Input Leakage Low V
THERMAL SHUTDOWN
Thermal-Shutdown Threshold Temperature rising 165
Thermal-Shutdown Threshold
Hsysteresis
THERMAL FOLDBACK
Thermal-Foldback Enable
Threshold Voltage
Thermal-Foldback Slope FB
TEMP_I Output Bias Current I
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS
VIN = V
I
DSON
VIN = V
I
LX_LEAK
IH
IL
DIM_ON
V
TFBON_THRVDIM
SLOPEVDIM
TEMP_I
V
VIN - VCS = 100mV 2.8 V
VCS - VIN = 100mV 0.6 V
V
= 350mA
LX
= 350mA
LX
DIM
DIM
DIM
DIM
= 24V, VCS = 23.9V,
DIM
= 6.0V, VCS = 5.9V,
DIM
= 0V, VLX = 65V 10 µA
rising edge to VLX < 0.5V
= V
IN
IN
= 0V -3 0 µA
= 5V 1.9 2.0 2.12 V
= 5V 0.75 1/V
25 26.5 28 µA
0.85 1.7
12
200 ns
15 µA
10
Ω
o
C
o
C
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