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19-0706; Rev 0; 12/06
2MHz High-Brightness LED Drivers with High-Side Current Sense and 5000:1 Dimming
General Description
The MAX16819/MAX16820, step-down constant-current high-brightness LED (HB LED) drivers provide a costeffective solution for automotive interior/exterior lighting, architectural and ambient lighting, LED bulbs such as MR16 and other LED illumination applications. The MAX16819/MAX16820 operate from a 4.5V to 28V input voltage range and feature a 5V/10mA on-board regulator. A high-side current-sense resistor adjusts the output current and a dedicated PWM input (DIM) enables a wide range of pulsed dimming. The MAX16819/MAX16820 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 LED current with 5% accuracy. A hysteretic control algorithm ensures excellent input-supply rejection and fast response during load transients and PWM dimming. The MAX16819 features a 30% inductor current ripple and the MAX16820 features a 10% current ripple. These devices operate up to 2MHz switching frequency, thus allowing for small component size. The MAX16819/MAX16820 operate over the -40C to +125C automotive temperature range and are available in 3mm x 3mm x 0.8mm, 6-pin TDFN packages.
Features
High-Side Current Sense Dedicated Dimming Control Input 20kHz Maximum Dimming Efficiency Hysteretic Control: No Compensation Up to 2MHz Switching Frequency 5% LED Current Accuracy Adjustable Constant LED Current 4.5V to 28V Input Voltage Range Over 25W Output Power 5V, 10mA On-Board Regulator -40C to +125C Operating Temperature Range
MAX16819/MAX16820
Ordering Information
PART MAX16819ATT+T MAX16820ATT+T PIN-PACKAGE 6 TDFN-EP* 6 TDFN-EP* PKG CODE T633-2 T633-2 TOP MARK +ATB +ATC
Note: All devices are specified over the -40C to +125C operating temperature range.
+Denotes lead-free package. *EP = Exposed paddle.
Applications
Architectural, Industrial, and Ambient Lighting Automotive RCL, DRL, and Fog Lights MR16 and Other LED Bulbs Indicators and Emergency Lighting
Typical Operating Circuit
VIN RSENSE CIN L
Pin Configuration
GND 4 DRV 5
TOP VIEW
VCC 6
CVCC
MAX16819 MAX16820 +
1 IN 2 CSN 3 DIM
IN
VCC
CSN
MAX16819 MAX16820
DRV
DIM
GND
TDFN ________________________________________________________________ Maxim Integrated Products 1
For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at 1-888-629-4642, or visit Maxim's website at www.maxim-ic.com.
2MHz High-Brightness LED Drivers with High-Side Current Sense and 5000:1 Dimming MAX16819/MAX16820
ABSOLUTE MAXIMUM RATINGS
IN, CSN, DIM to GND .............................................-0.3V to +30V VCC, DRV to GND ....................................................-0.3V to +6V CSN to IN...............................................................-0.3V to +0.3V Maximum Current into Any Pin (except IN, VCC, and DRV)............................................20mA Continuous Power Dissipation (TA = +70C) 6-Pin TDFN (derate 18.17mW/oC* above +70C).......1454mW Operating Temperature Range .........................-40C to +125C Junction Temperature ......................................................+150C Storage Temperature Range .............................-65C to +150C Lead Temperature (soldering, 10s) .................................+300C Pin-to-Pin ESD Ratings (HB Model).....................................2.5kV *As per JEDEC51 Standard (Single-Layer Board).
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 = 12V, VDIM = VIN, CVCC = 1F, RSENSE = 0.5, TA = TJ = -40C to +125C, unless otherwise noted. Typical values are at TA = +25C.) (Note 1)
PARAMETER Input Voltage Range Maximum Current Regulator Switching Frequency Ground Current Supply Current SYMBOL VIN fSW IGND IIN DRV open VDIM < 0.6V VIN = VCSN = VDIM, VIN rising from 4V until VDRV > VCC - 0.5V VIN = VCSN = VDIM, VIN falling from 6V, VDRV < 0.5V Undervoltage Lockout Hysteresis SENSE COMPARATOR (VIN - VCSN) rising from 0V until VDRV < 0.5V (MAX16820) Sense Voltage Threshold High VSNSHI (VIN - VCSN) rising from 0V until VDRV < 0.5V (MAX16819) (VIN - VCSN) falling from 0.26V until VDRV > (VCC - 0.5V) (MAX16820) (VIN - VCSN) falling from 0.26V until VDRV > (VCC - 0.5V) (MAX16819) Falling edge of (VIN - VCSN) from 0.26V to 0V to DRV high, CDRV = 1nF Rising edge of (VIN - VCSN) from 0V to 0.26V to DRV low, CDRV = 1nF (VIN - VCSN) = 200mV MAX16819 MAX16820 56 17 195 213 176 158 210 230 190 170 82 82 1 70 35 225 mV 246 204 mV 182 ns ns A mV mV 0.5 4.7 CONDITIONS MIN 4.5 TYP MAX 28.0 2 1.5 425 5.0 V 4.5 V UNITS V MHz mA A
Undervoltage Lockout
UVLO
Sense Voltage Threshold Low
VSNSLO
Propagation Delay to Output High Propagation Delay to Output Low Current-Sense Input Current Current-Sense Threshold Hysteresis
tDPDH tDPDL ICSN CSHYS
2
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2MHz High-Brightness LED Drivers with High-Side Current Sense and 5000:1 Dimming
ELECTRICAL CHARACTERISTICS (continued)
(VIN = 12V, VDIM = VIN, CVCC = 1F, RSENSE = 0.5, TA = TJ = -40C to +125C, unless otherwise noted. Typical values are at TA = +25C.) (Note 1)
PARAMETER GATE DRIVER Gate Driver Source Current Gate Driver Sink Current Gate Driver Output-Voltage High Gate Driver Output-Voltage Low DIM INPUT Maximum DIM Frequency DIM Input-Voltage High DIM Input-Voltage Low DIM Hysteresis DIM Turn-On Time DIM Turn-Off Time DIM Input Leakage High DIM Input Leakage Low VCC REGULATOR Regulator Output Voltage Load Regulation Line Regulation Power-Supply Rejection Ratio Current Limit Regulator Startup Time PSRR ILIM tSTRAT VCC IVCC = 0.1mA to 10mA, VIN = 5.5V to 28V IVCC = 0.1mA to 10mA, VIN = 4.5V to 28V IVCC = 0.1mA to 10mA, VIN = 12V VIN = 6V to 28V, IVCC = 10mA VIN = 12V, IVCC = 5mA, fIN = 10kHz VIN = 4.5V, VCC = 0V VIN = 4.5V, VCC = 4V VCC = 0 to 4.5V 4.5 4.0 4 11 -35 45 18 350 5.5 5.5 V V mV dB mA mA s fDIM VIH VIL DIMHYS tDIMON tDIMOFF DIM rising edge to VDRV = 0.5 x VCC, CDRV = 1nF DIM falling edge to VDRV = 0.5 x VCC, CDRV = 1nF VDIM = VIN VDIM = 0V -1 VCSN = VIN, increase DIM until VDRV > (VCC - 0.5V) VCSN = VIN, decrease DIM until VDRV < 0.5V 200 100 100 10 +1 2.8 0.6 20 kHz V V mV ns ns A A VOH VOL VCSN = VIN, VDRV = 0.5 x VCC VCSN = VIN - 250mV, VDRV = 0.5 x VCC IDRV = 10mA IDRV = -10mA VCC - 0.5 0.5 0.5 1 A A V V SYMBOL CONDITIONS MIN TYP MAX UNITS
MAX16819/MAX16820
Note 1: All devices are 100% production tested at TJ = +25C and +125C. Limits to -40C are guaranteed by design.
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3
2MHz High-Brightness LED Drivers with High-Side Current Sense and 5000:1 Dimming MAX16819/MAX16820
Typical Operating Characteristics
(VIN = VDIM = 12V, CVCC = 1F, RSENSE = 0.5 connected between IN and CSN. Typical values at TA = +25C, unless otherwise noted.)
EFFICIENCY vs. VIN
MAX16819 toc01
DRV SWITCHING FREQUENCY vs. VIN
L = 47H 1500 1400 1300 1200 1100 1000 900 800 700 600 500 400 300 200 100 0 4 LED CURRENT VARIATION FROM SET CURRENT (%)
MAX16819 toc02
LED CURRENT VARIATION vs. VIN
1.5 1.0 0.5 0 -0.5 -1.0 -1.5 -2.0 5 10 15 VIN (V) 20 25 30 LED 3 LED 4 LED 5 LED 1 ILED(NOMINAL) = 400mA L = 47H LED 2
MAX16819 toc03 MAX16819 toc06
100
2.0
LED 5
95 90 EFFICIENCY (%) 85 80 75 70 65 60 5 10 15 VIN (V) 20 LED 1 LED 2 LED 3 LED 4
LED 5 LED 4 LED 3 LED 2 LED 1
DRV SWITCHING FREQUENCY (kHz)
L = 47H 8 12 16 VIN (V) 20 24 28
25
30
VCC vs. VIN
MAX16819 toc04
VCC vs. TEMPERATURE
5.39 5.38 5.37 VCC (V) 5.36 5.35 5.34 5.33 5.32 ILED = 0 5.31 5.30 VDIM = 0V -40 -25 -10 5 20 35 50 65 80 95 110 125 TEMPERATURE (C) VIN = 12V VIN = 24V
MAX16819 toc05
SUPPLY CURRENT vs. VIN
300 250 SUPPLY CURRENT (A) 200 150 100 50 VDIM = 0V 0 4.5 8.5 12.5 16.5 VIN (V) 20.5 24.5 28.5
5.5 5.4 5.3 5.2 VCC (V) 5.1 5.0 4.9 4.8 4.7 4.6 4.5
5.40
5.0 7.5 10.0 12.5 15.0 17.5 20.0 22.5 25.0 27.5 VIN (V)
PWM DIMMING AT 200Hz (10% DUTY CYCLE)
MAX16819 toc07
PWM DIMMING AT 200Hz (90% DUTY CYCLE)
MAX16819 toc08
VIN = 12V, L = 47H, 1 LED MAX16819 VDIM 2V/div
VIN = 12V, L = 47H, 1 LED MAX16819 VDIM 2V/div 0V ILED 200mA/div 0A
0V ILED 200mA/div 0A
1ms/div
1ms/div
4
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2MHz High-Brightness LED Drivers with High-Side Current Sense and 5000:1 Dimming
Typical Operating Characteristics (continued)
(VIN = VDIM = 12V, CVCC = 1F, RSENSE = 0.5 connected between IN and CSN. Typical values at TA = +25C, unless otherwise noted.)
MAX16819/MAX16820
PWM DIMMING AT 200Hz (1% DUTY CYCLE)
MAX16819 toc09
PWM DIMMING EXPANDED (50% DUTY CYCLE)
MAX16819 toc10
PWM DIMMING EXPANDED (50% DUTY CYCLE)
MAX16819 toc11
VIN = 12V, L = 47H, 1 LED MAX16819 VDIM 2V/div
VIN = 24V, L = 33H, 4 LEDS MAX16820 VDIM 2V/div
VIN = 12V, L = 47H, 1 LED MAX16819 VDIM 2V/div
0V ILED 200mA/div 0A
0V ILED 200mA/div 0A
0V ILED 200mA/div 0A
10s/div
1s/div
4s/div
PWM DIMMING AT 20kHz (10% DUTY CYCLE)
MAX16819 toc12
PWM DIMMING AT 20kHz (90% DUTY CYCLE)
MAX16819 toc13
ILED VARIATION vs. TEMPERATURE
LED CURRENT VARIATION FROM SET CURRENT (%) 1.5 1.0 0.5 0 -0.5 -1.0 -1.5 ILED(NOMINAL) = 400mA L = 47H
MAX16819 toc14
VIN = 24V, L = 47H, 4 LEDS MAX16820 VDIM 2V/div 0V ILED 200mA/div 0A
VIN = 24V, L = 33H, 4 LEDS MAX16820 VDIM 2V/div 0V ILED 200mA/div
2.0
VIN = 24V
VIN = 12V
0A
VDIM = 0V
-2.0 -40 -25 -10 5 20 35 50 65 80 95 110 125 TEMPERATURE (C)
10s/div
10s/div
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5
2MHz High-Brightness LED Drivers with High-Side Current Sense and 5000:1 Dimming MAX16819/MAX16820
Pin Description
PIN 1 2 3 4 5 6 EP NAME IN CSN DIM GND DRV VCC -- Current-Sense Input Logic-Level Dimming Input. Drive DIM low to turn off the current regulator. Drive DIM high to enable the current regulator. Ground Gate Drive Output. Connect to the gate of an external n-channel MOSFET. Voltage Regulator Output. Connect a 1F capacitor from VCC to GND. Exposed Paddle. Connect to a large-area ground plane for improved power dissipation. Do not use as the only ground connection for the device. FUNCTION Positive Supply Voltage Input. Bypass with a 1F or higher value capacitor to GND.
Functional Diagram
IN
REGULATOR
VCC
+ CSN CS COMPARATOR GATE DRIVER 1.23V BANDGAP REF + UVLO COMPARATOR GND DIM BUFFER DRV
DIM
MAX16819 MAX16820
Detailed Description
The MAX16819/MAX16820 are step-down, constantcurrent, high-brightness LED (HB LED) drivers. These devices operate from a 4.5V to 28V input voltage range and provide up to 0.5A of source and 1A of sink drive capability to the gate of an external MOSFET. A highside current-sense resistor sets the output current and
6
a dedicated PWM dimming input (DIM) allows for a wide range of independent pulsed dimming. The high-side current-sensing scheme and on-board current-setting circuitry minimize the number of external components while delivering LED current with a 5% accuracy, using a 1% sense resistor. See the Functional Diagram.
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2MHz High-Brightness LED Drivers with High-Side Current Sense and 5000:1 Dimming
Undervoltage Lockout (UVLO)
The MAX16819/MAX16820 include a 4.5V undervoltage lockout (UVLO) with 500mV hysteresis. When VIN falls below 4.5V, DRV goes low, turning off the external n-channel MOSFET. DRV goes high once VIN is 5V or higher. For the values of VSNSHI and VSNSLO, see the Electrical Characteristics.
MAX16819/MAX16820
Current Regulator Operation
The MAX16819/MAX16820 regulate the LED output current using an input comparator with hysteresis (Figure 1). As the current through the inductor ramps up and the voltage across the sense resistor reaches the upper threshold, the voltage at DRV goes low, turning off the external MOSFET. The 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 =
5V Regulator
VCC is the output of a 5V regulator capable of sourcing 10mA. Bypass VCC to GND with a 1F capacitor.
DIM Input
The MAX16819/MAX16820 allow dimming with a PWM signal at the DIM input. A logic level below 0.6V at DIM forces the MAX16819/MAX16820's DRV output low, turning off the LED current. To turn the LED current on, the logic level at DIM must be at least 2.8V.
Applications Information
Selecting RSENSE to Set the LED Current The MAX16819/MAX16820 feature a programmable LED current using a resistor connected between IN and CSN. Use the following equation to calculate the sense resistor:
RSENSE () = 1 (VSNSHI + VSNSLO )(V ) 2 ILED (A )
(VIN - n x VLED ) x n x VLED x RSENSE
VIN x V x L
where n = number of LEDs, VLED = forward voltage drop of one LED, and V = (VSNSHI - VSNSLO). For proper component selection, please use the design tool available at: http://www.maxim-ic.com/MAX1681920-Tool.
HYSTERETIC MODE TSW = 1 fSW
ILED
I AVG. LED CURRENT
t
VDIM
t
Figure 1. Current Regulator Operation
_______________________________________________________________________________________ 7
2MHz High-Brightness LED Drivers with High-Side Current Sense and 5000:1 Dimming MAX16819/MAX16820
MOSFET Selection
The MAX16819/MAX16820's gate driver is capable of sourcing 0.5A and sinking 1A of current. MOSFET selection is based on the maximum input operating voltage VIN, output current ILED, and operating switching frequency. Choose a MOSFET that has a higher breakdown voltage than the maximum operation voltage, low R DS(ON), and low total charge for better efficiency. MOSFET threshold voltage must be adequate if operated at the low end of the input-voltage operating range.
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 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 MOSFET is on and the high current flows through IN--RSENSE-- LEDs--Inductor--MOSFET--GND. The other loop is formed when the MOSFET is off when the high current circulates through R SENSE --LEDs--Inductor--freewheeling diode. To minimize noise interaction, each loop area should be as small as possible. Place RSENSE as close as possible to the input filter and IN. For better noise immunity, a Kelvin connection is strongly recommended between CSN and RSENSE. Connect the exposed paddle to a large-area ground plane for improved power dissipation.
Freewheeling Diode Selection
The forward voltage of the freewheeling diode should be as low as possible for better efficiency. A Schottky diode is a good choice as long as the breakdown voltage is high enough to withstand the maximum operating voltage. The forward current rating of the diode must be at least equal to the maximum LED current.
LED Current Ripple
The LED current ripple is equal to the inductor current ripple. In cases when a lower LED current ripple is needed, a capacitor can be placed across the LED terminals.
Chip Information
PROCESS: BiCMOS
8
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2MHz High-Brightness LED Drivers with High-Side Current Sense and 5000:1 Dimming
Package Information
(The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information go to www.maxim-ic.com/packages.) 6, 8, &10L, DFN THIN.EPS
PACKAGE OUTLINE, 6,8,10 & 14L, TDFN, EXPOSED PAD, 3x3x0.80 mm
MAX16819/MAX16820
21-0137
H
1 2
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9
2MHz High-Brightness LED Drivers with High-Side Current Sense and 5000:1 Dimming MAX16819/MAX16820
Package Information (continued)
(The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information go to www.maxim-ic.com/packages.)
COMMON DIMENSIONS SYMBOL A D E A1 L k A2 MIN. 0.70 2.90 2.90 0.00 0.20 MAX. 0.80 3.10 3.10 0.05 0.40
PACKAGE VARIATIONS PKG. CODE T633-1 T633-2 T833-1 T833-2 T833-3 T1033-1 T1033-2 T1433-1 T1433-2 N 6 6 8 8 8 10 10 14 14 D2 1.500.10 1.500.10 1.500.10 1.500.10 1.500.10 1.500.10 1.500.10 1.700.10 1.700.10 E2 2.300.10 2.300.10 2.300.10 2.300.10 2.300.10 2.300.10 2.300.10 2.300.10 2.300.10 e 0.95 BSC 0.95 BSC 0.65 BSC 0.65 BSC 0.65 BSC 0.50 BSC 0.50 BSC 0.40 BSC 0.40 BSC JEDEC SPEC MO229 / WEEA MO229 / WEEA MO229 / WEEC MO229 / WEEC MO229 / WEEC MO229 / WEED-3 MO229 / WEED-3 ------b 0.400.05 0.400.05 0.300.05 0.300.05 0.300.05 0.250.05 0.250.05 0.200.05 0.200.05 [(N/2)-1] x e 1.90 REF 1.90 REF 1.95 REF 1.95 REF 1.95 REF 2.00 REF 2.00 REF 2.40 REF 2.40 REF
0.25 MIN. 0.20 REF.
PACKAGE OUTLINE, 6,8,10 & 14L, TDFN, EXPOSED PAD, 3x3x0.80 mm
-DRAWING NOT TO SCALE-
21-0137
H
2 2
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 (c) 2006 Maxim Integrated Products is a registered trademark of Maxim Integrated Products, Inc.

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