MAXIM MAX16822A/MAX16822B Manual
Contents
1. do 3 g8cc89LXVMW Vcc89LXVIMW MAX16822A MAX16822B 2MHz High Brightness LED Drivers with Integrated MOSFET and High Side Current Sense Typical Operating Characteristics continued VIN 48V Cvcc 1uF RSENSE 0 629 L 220uH connected between IN and CS Typical values are at TA 25 C MAX16822A toc06 ke nad 200mA div 0 VDIM 5V div 200mA div 0 VDIM 5V div 0 MAX16822A toc10 0 125 unless otherwise noted NORMALIZED QUIESCENT CURRENT PWM DIMMING vs VIN vs VIN AT 200Hz DUTY CYCLE 10 1 10 z 500 3 T mM 8 _ 400 E i 1 05 pa Se EE 350 E i S 1 00 250 Z i a i i 5 15 t 0 950 S gt 100 i 5 F VpiM 0V i 0 90 0 5 10 15 20 25 30 35 40 45 50 55 60 65 15 20 25 30 35 40 45 50 55 60 65 1ms div Vin V Vin V PWM DIMMING PWM DIMMING AT 200Hz DUTY CYCLE 90 AT 20kHz DUTY CYCLE 90 MAX16822A toc07 MAX16822A toc08 lLED 200mA div 5V div i ees Bee 0 i 1 H 1ms div 10us div LED CURRENT ILED vs VTEMP 1 vs TEMPERATURE 500 8 0 5 450 400 04 350 300 03 amp 250 2 200 02 eid2. M TION KIT ALUA E AVAILABL MAKII me MHz High Brightness LED Drivers with Integrated MOSFET and High Side Current Sense General Description 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 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 sens ing 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 dim ming The MAX16822A allows 1096 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 volt age from TEMP t
3. 150 100 04 50 Vin 48V 0 0 0 04 08 12 16 20 24 28 40 25 10 5 20 35 50 65 80 951 VrewP 1 TEMPERATURE MAXIM 2MHz High Brightness LED Drivers with Integrated MOSFET and High Side Current Sense Typical Operating Characteristics continued VIN VpiM 48V Cvcc 1uF RSENSE 0 629 L 220uH connected between IN and CS Typical values are at TA 25 C unless otherwise noted LXRDSON vs TEMPERATURE VIN 65V MAX16822A toc11 0 8 Vin 48V LXnpsoN 0 5 04 40 25 10 5 20 35 50 65 80 95 110 125 TEMPERATURE C ITEMP I vs TEMPERATURE 30 0 295 5 29 2 285 280 a 275 E von 26 5 26 25 5 Vin 48V 25 40 25 10 5 20 35 50 65 80 95 110 125 TEMPERATURE C Pin Description FUNCTION Current Sense Input Connect a resistor between IN and CS to program the LED current Positive Supply Voltage Input Bypass with a 1uF or higher value capacitor to GND Ground PGND Power Ground LX 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 01 capacitor to GND if thermal foldback or analog dimming is used See the Thermal Foldback section for more details Detailed Description
4. 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 and deliver up to 350mA of output current A high side current sense resistor sets the output current and a dedicated PWM 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 exter nal components while delivering LED current with 3 accuracy using a 1 sense resistor See Figure 1 for an internal block diagram g8cc89LXVMW Vcc89LXVIW 16822 16822 2MHz High Brightness LED Drivers with Integrated MOSFET and High Side Current Sense el MAXIM CC REGULATOR MAX16822A ANA MAX16822B GATE 0 85 65V CURRENT SENSE DRIVER DMOS SWITCH COMPARATOR BANDGAP REFERENCE UVLO COMPARATOR DIM BUFFER THERMAL FOLDBACK VFTBON_THR E COMPARATOR 2N Figure 1 Internal Block Diagram 6 MAXIM 2MHz High Brightness LED Drivers with Integrated MOSFET and High Side Current Sense 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 MAX1
5. 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 MAKLM 2MHz High Brightness LED Drivers with Integrated MOSFET and High Side Current Sense Pin Configuration TOP VIEW AVLAZCLA Chip Information PROCESS BiCMOS Package Information For the latest package outline information go to www maxim ic com packages PACKAGE CODE DOCUMENT NO s g8cc89LXVMW Vcc89LXVIW 2MHz High Brightness LED Drivers with Integrated MOSFET and High Side Current Sense Revision History REVISION REVISION PAGES NUMBER DATE DESCRIPTION CHANGED 1 5 08 Initial release 6 08 Updated Ordering Information table to release MAX16822B MAX16822A MAX16822B 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 2008 Maxim Integrated Products MAXIM is registered trademark of Maxim Integrated Products Inc
6. 6822A 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 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 Analog Dimming The MAX16822A MAX16822B offer an analog dimming feature that reduces the output current when the volt age at TEMP 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 and ground or by a voltage on a resistor connected across TEMP and ground induced by an internal current source of 250A 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 Lep A x i 7 ON where VTFB ON 2V 0 75 are obtained from the Electrical Characteristics table and VAp is the voltage at TEMP 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 o
7. HB LEDs RsENSE TEMP I MAXIM boi MAX16822A MAX16822B D OPTIONAL Maxim Integrated Products 1 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 g8cc89LXVMW Vcc89LXVIMW MAX16822A MAX16822B 2MHz High Brightness LED Drivers with Integrated MOSFET and High Side Current Sense ABSOLUTE MAXIMUM RATINGS IN CS LX DIM ROS ER agn tertiis TEMP 1 to GND PGND to GND Maximum Current into Any Pin except IN LX and Continuous Power Dissipation TA 70 C 8 SO derate 7 4mW C above 70 C Note 1 Package thermal resistances were obtained using the method described in J 0 3V to 70V Junction to Ambient Thermal Resistance Ja Note 1 186 C W 0 3V to 6V Pin to PiniESD RANGS 2 5kV 0 3V to 0 3V Operating Temperature Range 40 C to 125 C 0 3V to 0 3V JUNCTION Temperature eiiie recte ten tpi 150 Storage Temperature Range 65 C to 150 C 20mA Lead Temperature Soldering 105 300 Hue 588 2mW EDEC 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 Max
8. imum 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 PARAMETER CONDITIONS 24V VpIM VIN TA TJ 40 C to 125 C unless otherwise noted Typical values are at TA 25 C SYMBOL MAX UNITS Input Voltage Range Ground Current VIN No switching 65 V mA Supply Current lt 0 6V 12V pA UNDERVOLTAGE LOCKOUT UVLO Undervoltage Lockout Undervoltage Lockout Hysteresis Vos VIN 100mV VIN rising from 4V until VLX lt 0 5VIN Vcs VIN 100mV falling from 6 5V until VLX gt 0 5VIN SENSE COMPARATOR Sense Voltage Threshold High VSNSHI AX16822A VIN Vcs rising from 140mV until Vi x gt 0 5VIN AX16822B VIN Vcs rising from 140mV until Vi x gt O 5VIN Sense Voltage Threshold Low Propagation Delay to Output High 16822 V il VLX lt O 5VIN Vcs falling from 260mV AX16822B VI il VLX lt O 5VIN Vcs falling from 260mV ing edge of VIN Vcs from 140mV to 260mv to VLx O 5VIN Propagation Delay to Output Low CS Input Current Rising edge of Vcs ViN from 260mv to 140mV t
9. n the NTC thermis tor thermally attached to the LEDs and electrically connected between TEMP and ground drops below the internal 2V threshold limit 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 equa tion below to calculate the value of this resistor 1 V V XV Rsewse 9 M SNSHI VSNSLO 2 LED A where VSNSHI is the sense voltage threshold high and VSNSLO 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 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 ipe GINESEILED STN gp PISENSE VN X AV xL where n is the number of LEDs Vi Ep is the forward voltage drop of 1 LED and AV 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 U
10. o GND TEMP 1 also sources 25 to a negative temperature coefficient NTC thermistor con nected between TEMP 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 pro tection that turns off the LX driver when the junction temperature exceeds 165 The MAX16822A MAX16822B operate over the 40 C to 125 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 Pin Configuration appears at end of data sheet MAKIM Features High Efficiency Solution 6 5V to 65V Input Voltage Range On Board 65V 0 850 Power MOSFET Hysteretic Control Up to 2MHz Switching Frequency 3 LED Current Accuracy 9 9 9 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 9 9 9 9 9 9 9 40 C to 125 C Operating Temperature Range Ordering Information PART TEMP RANGE MAX16822AASA 40 C to 125 C 8 SO MAX16822BASA 40 C to 125 C 8 SO Denotes a lead free ROHS compliant package PIN PACKAGE Typical Application Circuit
11. o VL x lt 0 5VIN VIN Vos 200mV MAXIM 2MHz High Brightness LED Drivers with Integrated MOSFET and High Side Current Sense ELECTRICAL CHARACTERISTICS continued VIN 24V VIN TA TJ 40 C to 125 unless otherwise noted Typical values are at TA 25 PARAMETER SYMBOL CONDITIONS INTERNAL MOSFET 24V Vcs 23 9V 350mA VpIM 6 0V Vcs 5 9V 350mA Drain to Source Resistance M OV 65V DIM INPUT DIM Input Voltage High Vcs 100mV DIM Input Voltage Low CS VIN 100mV DIM Turn On Time M rising edge to lt 0 5VIN DIM Input Leakage M VIN DIM Input Leakage M OV THERMAL SHUTDOWN Thermal Shutdown Threshold Temperature rising Thermal Shutdown Threshold Hsysteresis THERMAL FOLDBACK Thermal Foldback Enable Threshold Voltage VTFBON_THR VDIM 5V Thermal Foldback Slope FBsioPE VDIM 5V TEMP Output Bias Current ITEMP I Typical Operating Characteristics VIN VpiM 48V Cvcc 1uF RSENSE 0 629 L 220uH connected between IN and CS Typical values are at TA 25 C unless otherwise noted EFFICIENCY DUTY CYCLE FREQUENCY vs VIN vs VIN 9 LEDs 11 LEDs13 LEI 7 LEDs 16822 toc02 16822 toc03 EFFICIENCY 96 DUTY CYCLE 96 FREQUENCY kHz gt om oc Rocco x
12. se the following formula to calculate an approximate inductor value and use the closest standard value MN M gp x nM gp x RsENSE Vin x AV x L approx For component selection use the MAX16822A B Design Tool available at www maximic com MAX16822 software g8cc89LXVMW Vcc89LXVIW 16822 16822 2MHz High Brightness LED Drivers with Integrated MOSFET and High Side Current Sense HYSTERETIC MODE Figure 2 Current Hegulator 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 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
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MAXIM MAX16822A/MAX16822B Manual