MAX16822BASA+T [MAXIM]
LED Driver, BICMOS, PDSO8;
| 型号： | MAX16822BASA+T |
| 厂家： | 
MAXIM INTEGRATED PRODUCTS |
| 描述： | LED Driver, BICMOS, PDSO8 驱动器 |
| 文件： | 总10页 (文件大小：179K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
19-4141; Rev 3; 1/10
2MHz, High-Brightness LED Drivers with
Integrated MOSFET and High-Side Current Sense
/MAX1682B
General Description
Features
The MAX16822A/MAX16822B step-down constant-cur-
rent high-brightness LED (HB LED) drivers provide a
cost-effective design solution for automotive
interior/exterior lighting, architectural and ambient light-
ing, LED bulbs, and other LED illumination applications.
o High-Efficiency Solution
o 6.5V to 65V Input-Voltage Range
o Output Current Up to 500mA
o On-Board 65V, 0.85Ω Power MOSFET
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 tempera-
ture 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.
o Hysteretic Control: Up to 2MHz Switching
Frequency
o ±±3 ꢀEꢁ Current Accuracy
o 200mV Current-Sense Reference
o Resistor-Programmable Constant ꢀEꢁ Current
o Integrated High-Side Current Sense
o Thermal-Foldback Protection/ꢀinear ꢁimming
o Thermal-Shutdown Protection
These devices are well suited for applications requiring
a wide input-voltage range. The high-side current sens-
ing and an integrated current-setting circuitry minimize
the number of external components while delivering an
average output current with 3ꢀ accuracy. A hysteretic
control method ensures excellent input supply rejection
and fast response during load transients and PWM dim-
ming. The MAX16822A allows 10ꢀ current ripple and
the MAX16822B allows 30ꢀ current ripple. Both
devices operate up to a switching frequency of 2MHz,
thus allowing the use of small-sized components.
o Available in an 8-Pin SO Package
o -40°C to +125°C Operating Temperature Range
Ordering Information
PART
TEMP RANGE
-40°C to +125°C
-40°C to +125°C
-40°C to +125°C
PIN-PACKAGE
8 SO
MAX16822AASA+
MAX16822AASA/V+
MAX16822BASA+
The MAX16822A/MAX16822B offer an analog dimming
feature that reduces the output current by applying an
external DC voltage below the internal 2V threshold volt-
age from TEMP_I to GND. TEMP_I also sources 25µA to
a negative temperature coefficient (NTC) thermistor con-
nected 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.
8 SO
8 SO
+Denotes a lead(Pb)-free/RoHS-compliant package.
/V denotes an automotive qualified part.
Typical Application Circuit
D1
An additional feature includes thermal-shutdown pro-
tection that turns off the LX driver when the junction
temperature exceeds +165°C.
HB LEDs
V
IN
R
L1
SENSE
The MAX16822A/MAX16822B operate over the -40°C to
+125°C automotive temperature range and are available
in an 8-pin SO package.
C2
Applications
1
2
8
7
6
5
CS
TEMP_I
DIM
Architectural, Industrial, and Ambient Lighting
Automotive RCL, DRL, and Fog Lights
Heads-Up Displays
ON
*
NTC
OFF
IN
MAX16822A
MAX16822B
C1
3
4
GND
PGND
LX
LX
Indicator and Emergency Lighting
Pin Configuration appears at end of data sheet.
*
OPTIONAL
________________________________________________________________ Maxim Integrated Products
1
For pricing, delivery, and ordering information, please contact Maxim ꢁirect at 1-888-629-4642,
or visit Maxim’s website at www.maxim-ic.com.
2MHz, High-Brightness LED Drivers with
Integrated MOSFET and High-Side Current Sense
ABSOꢀUTE 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
Junction-to-Ambient Thermal Resistance (θ ) (Note 1)...136°C/W
JA
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
(except IN, LX, and PGND).............................................20mA
Continuous Power Dissipation (T = +70°C)
A
8-Pin SO (derate 7.4mW/°C above +70°C)...............588.2mW
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.
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.
EꢀECTRICAꢀ CHARACTERISTICS
(V = +24V, V
= V , T = T = -40°C to +125°C, unless otherwise noted. Typical values are at T = +25°C.)
IN
DIM
IN
A
J
A
PARAMETER
Input-Voltage Range
Ground Current
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
V
V
6.5
65
IN
No switching
1.5
mA
μA
Supply Current
V
DIM
< 0.6V, V = 12V
350
IN
/MAX1682B
UNDERVOLTAGE LOCKOUT (UVLO)
V
= V - 100mV, V rising from 4V
CS
IN
IN
6.25
0.5
6.5
6
until V < 0.5V
LX
IN
Undervoltage Lockout
UVLO
V
V
V
CS
= V - 100mV, V falling from 6.5V
IN IN
until V > 0.5V
LX
IN
Undervoltage-Lockout Hysteresis
SENSE COMPARATOR
MAX16822A, (V - V ) rising from
IN
CS
201
218
185
166
210
230
190
170
50
216
236
198
180
140mV until V > 0.5V
LX
IN
Sense Voltage Threshold High
V
mV
SNSHI
MAX16822B, V - V rising from 140mV
IN
CS
until V > 0.5V
LX
IN
MAX16822A, V - V falling from
IN
CS
260mV until V < 0.5V
LX
IN
Sense Voltage Threshold Low
Propagation Delay to Output High
V
mV
ns
SNSLO
MAX16822B, V - V falling from
IN
CS
260mV until V < 0.5V
LX
IN
Falling edge of V - V from 140mV to
IN
CS
t
DPDH
260mV to V = 0.5V
LX
IN
Rising edge of V - V from 260mV to
CS
IN
Propagation Delay to Output Low
CS Input Current
t
50
ns
DPDL
140mV to V < 0.5V
LX
IN
I
V
- V = 200mV
CS
3.5
μA
CSIN
IN
2
_______________________________________________________________________________________
2MHz, High-Brightness LED Drivers with
Integrated MOSFET and High-Side Current Sense
/MAX1682B
EꢀECTRICAꢀ CHARACTERISTICS (continued)
(V = +24V, V
= V , T = T = -40°C to +125°C, unless otherwise noted. Typical values are at T = +25°C.)
IN
DIM
IN
A
J
A
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
INTERNAL MOSFET
V
= V
= 350mA
= 24V, V = 23.9V,
IN
DIM CS
0.85
1
1.7
I
LX
Drain-to-Source Resistance
R
DSON
ꢀ
V
= V
= 6.0V, V = 5.9V,
IN
DIM CS
2
I
LX
= 350mA
LX Leakage Current
I
V
DIM
= 0V, V = 65V
10
μA
LX_LEAK
LX
DIM INPUT
DIM Input-Voltage High
DIM Input-Voltage Low
DIM Turn-On Time
V
V
V
V
V
V
- V = 100mV
2.8
-3
V
IH
IN
CS
V
- V = 100mV
0.6
V
IL
DIM_ON
CS
IN
t
rising edge to V < 0.5V
IN
200
ns
μA
μA
DIM
DIM
DIM
LX
DIM Input Leakage High
DIM Input Leakage Low
THERMAL SHUTDOWN
Thermal-Shutdown Threshold
= V
15
0
IN
= 0V
Temperature rising
165
10
°C
°C
Thermal-Shutdown Threshold
Hsysteresis
THERMAL FOLDBACK
Thermal-Foldback Enable
Threshold Voltage
V
V
V
= 5V
= 5V
1.9
25
2.0
2.12
28
V
TFBON_THR
DIM
Thermal-Foldback Slope
FB
SLOPE
I
TEMP_I
0.75
26.5
1/V
μA
DIM
TEMP_I Output Bias Current
Typical Operating Characteristics
(V = V
unless otherwise noted.)
= 48V, C
= 1µF, R
= 0.62Ω, L = 220µH (connected between IN and CS). Typical values are at T = +25°C,
SENSE A
IN
DIM
VCC
EFFICIENCY
vs. V
FREQUENCY
vs. V
DUTY CYCLE
vs. V
IN
13 LEDs 15 LEDs
IN
IN
11 LEDs
100
95
90
85
80
75
70
100
90
80
70
60
50
40
30
20
10
0
100
90
80
70
60
50
40
30
20
10
0
11 LEDs
9 LEDs
7 LEDs
5 LEDs
3 LEDs
15 LEDs
15 LEDs
13 LEDs
13 LEDs
11 LEDs
9 LEDs
7 LEDs
5 LEDs
7 LEDs 9 LEDs
5 LEDs
3 LEDs
1 LED
1 LED
3 LEDs
1 LED
5
15
25
35
(V)
45
55
65
5
15
25
35
(V)
45
55
65
5
15
25
35
(V)
45
55
65
V
V
IN
IN
V
IN
_______________________________________________________________________________________
±
2MHz, High-Brightness LED Drivers with
Integrated MOSFET and High-Side Current Sense
Typical Operating Characteristics (continued)
(V = V
unless otherwise noted.)
= 48V, C
= 1µF, R
= 0.62Ω, L = 220µH (connected between IN and CS). Typical values are at T = +25°C,
SENSE A
IN
DIM
VCC
QUIESCENT CURRENT
vs. V
PWM DIMMING
AT 200Hz DUTY CYCLE (10%)
NORMALIZED I
LED
IN
vs. V
IN
MAX16822A toc06
1.10
1.05
500
450
400
350
300
250
200
150
100
50
I
LED
5 LEDs 7 LEDs
3 LEDs
200mA/div
13 LEDs
9 LEDs
11 LEDs
15 LEDs
1.00
0
1 LED
V
DIM
5V/div
0
0.950
0.90
V
IN
= 48V
V
= 0V
DIM
8 LEDs
0
0
5
10 15 20 25 30 35 40 45 50 55 60 65
(V)
0
5
10 15 20 25 30 35 40 45 50 55 60 65
(V)
1ms/div
V
V
IN
IN
PWM DIMMING
AT 20kHz DUTY CYCLE (90%)
PWM DIMMING
AT 200Hz DUTY CYCLE (90%)
MAX16822A toc08
MAX16822A toc07
/MAX1682B
I
LED
I
LED
200mA/div
200mA/div
0
0
V
DIM
V
DIM
5V/div
0
5V/div
0
V
= 48V
IN
8 LEDs
10μs/div
1ms/div
I
LED CURRENT
LED
vs. TEMPERATURE
vs. V
TEMP_I
0.5
0.4
0.3
0.2
0.1
0
500
450
400
350
300
250
200
150
100
50
V
= 48V
IN
0
-40 -25 -10
5
20 35 50 65 80 95 110 125
TEMPERATURE (°C)
0
0.4 0.8 1.2 1.6 2.0 2.4 2.8
(V)
V
TEMP_I
4
_______________________________________________________________________________________
2MHz, High-Brightness LED Drivers with
Integrated MOSFET and High-Side Current Sense
/MAX1682B
Typical Operating Characteristics (continued)
(V = V
unless otherwise noted.)
= 48V, C
= 1µF, R
= 0.62Ω, L = 220µH (connected between IN and CS). Typical values are at T = +25°C,
SENSE A
IN
DIM
VCC
LX
I
TEMP_I
vs. TEMPERATURE
RDSON
vs. TEMPERATURE
30.0
29.5
29.0
28.5
28.0
27.5
27.0
26.5
26.0
25.5
25.0
1.0
0.9
0.8
0.7
0.6
0.5
V
= 65V
IN
V
= 48V
IN
V
IN
= 6.5V
V
= 48V
IN
0.4
-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
1
NAME
FUNCTION
CS
IN
Current-Sense Input. Connect a resistor between IN and CS to program the LED current.
2
Positive Supply Voltage Input. Bypass with a 1μF or higher value capacitor to GND.
3
GND
PGND
LX
Ground
4
Power Ground
Switching Node
5, 6
Logic-Level Dimming Input. Drive DIM low to turn off the current regulator. Drive DIM high to
enable the current regulator.
7
8
DIM
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.
TEMP_I
dimming input enables pulsed LED dimming over a
wide range of brightness levels.
Detailed Description
The MAX16822A/MAX16822B are step-down, constant-
current, 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
A high-side current-sensing scheme and an on-board
current-setting circuitry minimize the number of exter-
nal components while delivering LED current with 3ꢀ
accuracy, using a 1ꢀ sense resistor. See Figure 1 for
an internal block diagram.
_______________________________________________________________________________________
5
2MHz, High-Brightness LED Drivers with
Integrated MOSFET and High-Side Current Sense
IN
V
CC
MAX16822A
MAX16822B
REGULATOR
V
_ANA
CC
I
SET
LX
V
_ANA
CC
GATE
DRIVER
CS
0.85Ω, 65V
DMOS SWITCH
CURRENT-SENSE
COMPARATOR
PWM
DIMMING
1.23V
BANDGAP
REFERENCE
/MAX1682B
UVLO
COMPARATOR
DIM
DIM
BUFFER
V
_ANA
CC
25μA
TEMP_I
PGND
THERMAL
FOLDBACK
COMPARATOR
V
FTBON_THR
2V
GND
Figure 1. Internal Block Diagram
6
_______________________________________________________________________________________
2MHz, High-Brightness LED Drivers with
Integrated MOSFET and High-Side Current Sense
/MAX1682B
Undervoltage Lockout (UVLO)
Applications Information
The MAX16822A/MAX16822B include UVLO with
Selecting R
to Set LED Current
SENSE
500mV hysteresis. The internal MOSFET turns off when
The LED current is programmed with a current-sense
resistor connected between IN and CS. Use the equa-
tion below to calculate the value of this resistor:
V
IN
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.
(V
+ V
)(V)
1
2
SNSHI
I
SNSLO
(A)
R
(Ω) =
SENSE
LED
where V
SNSLO
is the sense voltage threshold high and
is sense voltage threshold low (see the
Electrical Characteristics table for values).
SNSHI
V
Thermal Shutdown
The MAX16822A/MAX16822B thermal-shutdown fea-
ture turns off the LX driver when the junction tempera-
ture exceeds +165°C. The LX driver turns back on
when the junction temperature drops 10°C below the
shutdown-temperature threshold.
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 volt-
age 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:
Analog Dimming
The MAX16822A/MAX16822B offer an analog dimming
feature that reduces the output current when the volt-
age at TEMP_I is below the internal 2V threshold volt-
age. The MAX16822A/MAX16822B achieve analog
dimming by either an external DC voltage source con-
nected 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 cur-
rent. Use the following formula to set the analog dim-
ming current.
(V − nV
IN LED
) × nV
× R
LED
× ΔV × L
SENSE
f
=
SW
V
IN
where n is the number of LEDs, V
voltage drop of 1 LED, and ΔV = (V
is the forward
LED
- V
).
SNSLO
SNSHI
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:
⎡
⎤
⎥
⎦
1
V
⎛
⎞
I
(A) = I
(A) × 1− FB
× V
− V
(V)
(
)
⎢
TF
LED
SLOPE
TFB_ON
AD
⎜
⎝
⎟
⎠
⎣
where V
= 2V and FB
from the Electrical Characteristics table and V
voltage at TEMP_I.
= 0.75 are obtained
TFB_ON
SLOPE
is the
AD
Thermal Foldback
The MAX16822A/MAX16822B also include a thermal-
foldback feature that reduces the output current when
the temperature of the LED string exceeds a specified
temperature point. These devices enter thermal-fold-
back mode when the voltage drop on the NTC thermis-
tor, thermally attached to the LEDs and electrically
connected between TEMP_I and ground, drops below
the internal 2V threshold limit.
(V − nV
IN LED
) × nV
× ΔV × f
× R
LED SENSE
L(approx.) =
V
IN
SW
For component selection, use the MAX16822A/B Design
Tool available at:www.maxim-ic.com/MAX16822-
software.
_______________________________________________________________________________________
7
2MHz, High-Brightness LED Drivers with
Integrated MOSFET and High-Side Current Sense
HYSTERETIC
MODE
f
SW
I
LED
ΔI
AVG. LED
CURRENT
t
V
DIM
/MAX1682B
t2
t
t1
Figure 2. Current-Regulator Operation
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
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.
is on and the high current flows through IN, R
,
SENSE
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 R , LED
SENSE
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
load, the inductor, and the freewheeling diode. Minimize
each loop area to reduce noise interaction.
Place R
as close as possible to CS and IN. For
SENSE
better noise immunity, a Kelvin connection between CS
and R is strongly recommended.
SENSE
8
_______________________________________________________________________________________
2MHz, High-Brightness LED Drivers with
Integrated MOSFET and High-Side Current Sense
/MAX1682B
Pin Configuration
Chip Information
PROCESS: BiCMOS
TOP VIEW
+
Package Information
CS
IN
1
2
3
4
8
7
6
5
TEMP_I
DIM
LX
For the latest package outline information and land patterns, go
to www.maxim-ic.com/packages. Note that a “+”, “#”, or “-” in
the package code indicates RoHS status only. Package draw-
ings may show a different suffix character, but the drawing per-
tains to the package regardless of RoHS status.
MAX16822A
MAX16822B
GND
PGND
LX
PACKAGE TYPE PACKAGE COꢁE ꢁOCUMENT NO.
8 SO
S8-2
21-0041
SO
_______________________________________________________________________________________
9
2MHz, High-Brightness LED Drivers with
Integrated MOSFET and High-Side Current Sense
Revision History
REVISION
NUMBER
REVISION
DATE
PAGES
CHANGED
DESCRIPTION
0
1
5/08
6/08
Initial release
—
1
Updated Ordering Information table to release MAX16822B.
Revised General Description, Features, Absolute Maximum Ratings, and
Detailed Description.
2
3
5/09
1/10
1, 2, 5
1
Added /V part number.
/MAX1682B
Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are
implied. Maxim reserves the right to change the circuitry and specifications without notice at any time.
10 ____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600
© 2010 Maxim Integrated Products
Maxim is a registered trademark of Maxim Integrated Products, Inc.
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