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19-0625; Rev 0; 8/06
EEPROM-Programmable, High-Voltage, 350mA LED Drivers with LED Current Foldback
General Description
The MAX16805/MAX16806 LED drivers eliminate the need for microcontrollers or switch-mode converters for automotive interior dome, map, and courtesy light applications. An EEPROM-programmable LED currentsense reference simplifies production by using one sense resistor to set the LED current for all LED bins. A dual-mode DIM pin and an on-board 200Hz ramp generator allow for PWM dimming with an analog or PWM control signal. The analog control signal at dimming input DIM allows for the "theater dimming" effect to be implemented. Fast turn-on/-off times ensure a widerange PWM operation, while waveshaping circuitry minimizes EMI. EEPROM-programmable LED current foldback makes it possible to operate at a high input voltage, while saving the cost and space associated with having a large heatsink. The MAX16806 works with an external thermal sensor to maintain maximum LED junction temperature by folding back the LED current. The thermal foldback temperature knee and slope are EEPROM programmable. The MAX16806 SW pin supplies necessary wetting current to a momentary switch.
Features
o EEPROM or I2C* Dynamically Programmable: LED Current Foldback for High Input Voltage LED Current Reference LED Current Thermal Foldback (MAX16806) o On-Board 200Hz Ramp Generator Eliminates the Need for C PWM Signal o Flexible Analog or PWM Control for PWM or Theater Dimming o Wetting Current and Debounce for Momentary Switch (MAX16806) o 5.5V to 40V Input with Up to 39V Output Capability o 35mA to 350mA Adjustable LED Current o Waveshaping Minimizes EMI During Dimming o Output Short-Circuit and Overtemperature Protection o -40C to +125C Operating Temperature Range
MAX16805/MAX16806
Ordering Information
PART TEMP RANGE PIN PACKAGE PKG CODE
Applications
Automotive Interior: Map, Dome, and Courtesy Lighting Automotive Exterior: Rear Combination Light (RCL) Daytime Running Light (DRL) Adaptive Front Light Emergency Vehicle Warning Lights Navigation and Marine Indicators
MAX16805ATP+ -40C to +125C 20 TQFN-EP** T2055M-5 MAX16806ATP+ -40C to +125C 20 TQFN-EP** T2055M-5
+Denotes lead-free package. **EP = Exposed pad.
Pin Configurations appear at end of data sheet.
*Purchase of I2C components from Maxim Integrated Products, Inc. or one of its sublicensed Associated Companies, conveys a license under the Philips I2C Patent Rights to use these components in an I2C system, provided that the system conforms to the I2C Standard Specification as defined by Philips.
Typical Operating Circuits
+5.5V TO +40V IN 0.1F EN SERIAL CLOCK SERIAL DATA V5 CSDIM PWM DIMMING GND DIM GND SW SCL SDA V5 0.1F LEDs VCC OUT +5V REG V5 0.1F EN V5 0.1F LEDs ILED +5.5V TO +40V IN OUT +5V REG ILED
MAX16805
CS+ RSENSE
MAX16806 MAX6613 OUT
GND TFP/SCL
CS+ RSENSE
TFN/SDA CS-
ANALOG CONTROL PWM DIMMING
MAX6613 THERMAL SENSOR IS OPTIONAL.
PWM CONTROL DIMMING
________________________________________________________________ Maxim Integrated Products
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EEPROM-Programmable, High-Voltage, 350mA LED Drivers with LED Current Foldback MAX16805/MAX16806
ABSOLUTE MAXIMUM RATINGS
IN to GND ...............................................................-0.3V to +45V DIM, OUT, EN to GND ................................-0.3V to (VIN + 0.3V) IN Slew Rate (20V < VIN < 45V) ...................................250mV/s SDA, SCL (MAX16805), TFN/SDA, TFP/SCL (MAX16806) to GND...............................-0.3V to +6V CFD, CS+, V5 to GND ..............................................-0.3V to +6V DGND and CS- to GND.........................................-0.3V to +0.3V OUT Short Circuited to GND Duration (VIN < +16V)..........1 hour Maximum Current Into Any Pin (except IN and OUT) ......20mA Continuous Power Dissipation (TA = +70C) 20-Pin Thin QFN (derate 34.5mW/C above +70C)....2758.6mW Operating Temperature Range .........................-40C to +125C Junction Temperature ......................................................+150C Storage Temperature Range .............................-65C to +150C Lead Temperature (soldering, 10s) .................................+300C
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 = VEN = 12V, CV5 = 0.1F, IV5 = 0, CS- = GND, RSENSE = 0.56, VDIM = 4V, DGND = GND, TFP/SCL = 5V, TFN/SDA = 0V, SW = CFD = Open, TA = TJ = -40C to +125C, unless otherwise noted. Typical values are at TA = +25C.) (Note 1)
PARAMETER Supply Voltage Range Ground Current Shutdown Supply Current Guaranteed Output Current Output Current Accuracy Dropout Voltage (Note 3) Output Current Slew Rate (External PWM Signal at DIM) Short-Circuit Current ENABLE INPUT EN Input Current EN Input-Voltage High EN Input-Voltage Low Enable Turn-On Time 5V REGULATOR Output Voltage Regulation (MAX16806) 0 < IV5 < 0.5mA, SW = GND V5 6.5V < VIN < 40V 0 < IV5 < 2mA, SW = open 4.9 4.9 4.9 5.1 5.1 5.1 5.3 V 5.3 5.3 V IEN VIH VIL tON EN rising edge to 90% of OUT 225 2.8 0.6 100 nA V V s VDO SYMBOL VIN IG ISHDN IOUT (Note 2) ILOAD = 350mA VEN 0.3V RSENSE = 0.55 35mA < IOUT < 350mA, RSENSE tolerance not included IOUT = 350mA, 12V < VIN < 40V IOUT = 350mA, 6.5V < VIN < 12V Current rising, DIM rising to 4V Current falling, DIM falling to 0.6V VOUT = 0V 0.4 0.5 17 17 600 350 3.0 1.2 1.5 CONDITIONS MIN 5.5 2.5 12 TYP MAX 40 4.5 40 UNITS V mA A mA % V mA/s mA
Output Voltage Regulation (MAX16805) CURRENT SENSE Regulated RSENSE Voltage Input Current (CS+) Input Current (CS-)
V5
0 < IV5 < 2mA, 6.5V < VIN < 40V
VRSNS
VSENSE = [VCS+ - VCS-], Binning Adjustment register at factory default (0x0F) VCS+ = 210mV VCS+ = 210mV
192 12
198
204
mV A
-75
A
2
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EEPROM-Programmable, High-Voltage, 350mA LED Drivers with LED Current Foldback
ELECTRICAL CHARACTERISTICS (continued)
(VIN = VEN = 12V, CV5 = 0.1F, IV5 = 0, CS- = GND, RSENSE = 0.56, VDIM = 4V, DGND = GND, TFP/SCL = 5V, TFN/SDA = 0V, SW = CFD = Open, TA = TJ = -40C to +125C, unless otherwise noted. Typical values are at TA = +25C.) (Note 1)
PARAMETER Minimum Regulated VSENSE Programming Range Maximum Regulated VSENSE Programming Range Regulated VSENSE Default Voltage EXTERNAL PWM DIMMING INPUT DIM Input Current Turn-On Time Turn-Off Time Maximum Thermal Foldback Knee Point Programming Range Minimum Thermal Foldback Knee Point Programming Range Minimum Thermal Foldback Temperature Programming Range Maximum Thermal Foldback Temperature Programming Range Thermal Foldback Default Threshold Temperature Thermal Foldback Default Threshold Voltage Minimum Thermal Foldback Slope Maximum Thermal Foldback Slope Thermal Foldback Default Slope TFP/SCL (SCL for MAX16805) Voltage Compliance Range TFN/SDA (SDA for MAX16805) Voltage Compliance Range Minimum Thermal Foldback Clamp Current Reduction Range VTFP VTFN TFC(MIN) +25oC TA +125oC tON tOFF After DIM rising to 4V (Note 4) After DIM falling to 0.6V (Note 4) 28 19 0.5 52 38 A s s SYMBOL VSENSE(MIN) VSENSE(MAX) VSENSE(DEF) Binning Adjustment register at factory default (0x0F) CONDITIONS MIN 99.4 192 TYP 103 198 198 MAX 106.6 mV 204 mV UNITS
MAX16805/MAX16806
THERMAL FOLDBACK (MAX16806 with MAX6613) TFKNEE(MAX) TFKNEE(MIN) TF(MIN) TF(MAX) VTH TFVTH TFSL(MIN) TFSL(MAX) Thermal Foldback Slope Gain register at factory default (0x03) I C interface active Remote thermal sensor active
2
326 1143
335 1174 +60
354 mV 1213
C +135 Thermal Foldback Knee Point register at factory default (0x00) +60 1.174 3.88 15.52 4 16 4 -0.3 +0.3 -0.3 40 V5 V5 V5 4.12 16.48 C V V/V V/V V/V V V %
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EEPROM-Programmable, High-Voltage, 350mA LED Drivers with LED Current Foldback MAX16805/MAX16806
ELECTRICAL CHARACTERISTICS (continued)
(VIN = VEN = 12V, CV5 = 0.1F, IV5 = 0, CS- = GND, RSENSE = 0.56, VDIM = 4V, DGND = GND, TFP/SCL = 5V, TFN/SDA = 0V, SW = CFD = Open, TA = TJ = -40C to +125C, unless otherwise noted. Typical values are at TA = +25C.) (Note 1)
PARAMETER Maximum Thermal Foldback Clamp Current Reduction Range Default Thermal Foldback Clamp Current Reduction Range THERMAL PROTECTION Thermal Shutdown Temperature Thermal Shutdown Hysteresis LED CURRENT FOLDBACK Minimum Input LED Current Foldback Range Maximum Input LED Current Foldback Range LED Current Foldback Default Level LED Current Foldback Voltage Step Size INTERNAL RAMP GENERATOR Internal RAMP Frequency External Sync Frequency Range External Sync Voltage Low External Sync Voltage High VDIM = 0V Output Current Duty Cycle Minimum Ramp Peak Programming Range Maximum Ramp Peak Programming Range Ramp Peak Default Voltage Ramp Offset Voltage MOMENTARY SWITCH INTERFACE (SW) (MAX16806) SW Pullup Current SW Input-Voltage High SW Input-Voltage Low Minimum Pulse Width Minimum Debounce Time ISW VIH VIL 120 40 VSW = 0V ISW = 100A 1 4 0.4 3 mA V V ms ms IDC VDIM > (VRAMP + 0.4V) (MAX16806), VDIM > +3.3V (MAX16805) 1.49 2.77 Ramp Peak register at factory default (0x07) 2.8 0 100 1.55 2.88 2.88 210 1.60 3.00 % fRAMP fDIM 176 80 200 224 2000 0.4 Hz Hz V V VCFD(MIN) VCFD(MAX) VCFD LED Current Foldback Threshold register at factory default (0x00) VIN > 11V, CFD register bit 3 = 0 VIN > 11V, CFD register bit 3 = 1 11.4 16.4 16.4 0.71 0.355 V V V V/step TJ(SHDN) +155 +23 C C SYMBOL TFC(MAX) CONDITIONS +25oC TA +125oC Thermal Foldback Clamp register at factory default (0x07), +25oC TA +125oC MIN TYP 100 MAX UNITS %
TFDEF
40
%
VRAMP(MIN) VRAMP(MAX)
V V V mV
4
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EEPROM-Programmable, High-Voltage, 350mA LED Drivers with LED Current Foldback
ELECTRICAL CHARACTERISTICS (continued)
(VIN = VEN = 12V, CV5 = 0.1F, IV5 = 0, CS- = GND, RSENSE = 0.56, VDIM = 4V, DGND = GND, TFP/SCL = 5V, TFN/SDA = 0V, SW = CFD = Open, TA = TJ = -40C to +125C, unless otherwise noted. Typical values are at TA = +25C.) (Note 1)
PARAMETER EEPROM VIN Voltage for EEPROM Programming EEPROM Data-Retention Time I2C DIGITAL INPUTS (TFP/SCL, TFN/SDA) (Note 5) Logic Input-Voltage High Logic Input-Voltage Low Input Capacitance SDA Output Voltage Low I2C INTERFACE TIMING (Figure 1) Serial Clock Frequency Bus Free Time Between STOP and START Condition START Condition Hold Time Clock Low Period Clock High Period Repeat START Condition Setup Time fSCL tBUF tHD:STA tLOW tHIGH tSU:STA A master device must provide a hold time of at least 300ns for the SDA signal (referred to VIL of the SCL signal) in order to bridge the undefined region of SCL's falling edge 1.3 0.6 1.3 0.6 0.6 400 kHz s s s s s VOL ISINK = 3mA VIH VIL 5 0.4 2.8 0.8 V V pF V 20 10 22 24 V Years SYMBOL CONDITIONS MIN TYP MAX UNITS
MAX16805/MAX16806
Data Hold Time
tHD:DAT
0
0.9
s
Data Setup Time Receive SCL/SDA Rise Time Receive SCL/SDA Fall Time STOP Condition Setup Time Pulse Width of Spike Suppressed Transmit SDA Fall Time
tSU:DAT tR tF tSU:STO tSP ISINK < 6mA, CB 400pF (Note 6)
100 300 250 0.6 50 250
ns ns ns s ns ns
Note 1: All devices 100% production tested at TJ = +25C. Limits over the operating temperature range are guaranteed by design. Note 2: Resistors were added from OUT to CS+ to aid with the power dissipation during testing. Note 3: Dropout is measured as follows: Connect a resistor from OUT to CS+. Connect RSENSE = 0.56 from CS+ to CS-. Set VIN = VOUT +3V (record VOUT as VOUT1). Reduce VIN until VOUT = 0.97 x VOUT1 (record as VIN2 and VOUT2). VDO = VIN2 - VOUT2. Note 4: tON time includes the delay and the rise time needed for IOUT to reach 90% of its final value. tOFF time is the time needed for IOUT to drop below 10%. See the Typical Operating Characteristics. tON and tOFF are tested with 13 from OUT to CS+. Note 5: TPF/SCL (SCL for MAX16805) and TPN/SDA (SDA for the MAX16805) are I2C interface compatible only when the MAX16805/MAX16806 are the only parts on the bus for production programming. Note 6: CB is the total bus capacitance.
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EEPROM-Programmable, High-Voltage, 350mA LED Drivers with LED Current Foldback MAX16805/MAX16806
Typical Operating Characteristics
(VIN = 12V, VEN = VIN, CV5 = 0.1F, IV5 = 0, CS- = GND, RSENSE = 0.56, connect OUT to CS+, VDIM = 4V, SW = VFD = open, VTFP/SC = 5V, VTFN/SD = GND, DGND = GND. TA = +25C, unless otherwise noted.)
OUTPUT CURRENT vs. TEMPERATURE
MAX16805 toc01
(VCS+ - VCS-) vs. OUTPUT CURRENT
0.204 0.203 (VCS+ - VCS-) (V) 0.202 0.201 0.200 0.199 0.198 0.197 VIN = 12V
MAX16805 toc02
OUTPUT CURRENT vs. INPUT VOLTAGE
350 OUTPUT CURRENT (mA) 300 250 200 150 IOUT = 100mA 100 50 0 0 2 4 6 8 10 12 14 16
MAX16805 toc03
450 400 OUTPUT CURRENT (mA) 350 300 250 ILOAD = 200mA 200 150 100 50 0 ILOAD = 35mA ILOAD = 100mA ILOAD = 350mA
0.205
400 IOUT = 350mA
0.196 0.195 20 50 80 110 140 170 200 230 260 290 320 350 OUTPUT CURRENT (mA)
-40 -25 -10 5 20 35 50 65 80 95 110 125 TEMPERATURE (C)
INPUT VOLTAGE (V)
DROPOUT VOLTAGE vs. TEMPERATURE
MAX16805 toc04
+5V REGULATOR OUTPUT vs. TEMPERATURE
MAX16805 toc05
+5V REGULATOR OUTPUT vs. INPUT VOLTAGE
MAX16805 toc06
1.0 0.9 0.8 DROPOUT VOLTAGE (V) 0.7 0.6 0.5 0.4 0.3 0.2 0.1 0 VIN = 12V ILOAD = 350mA
5.20 NO LOAD 5.15 ILOAD = 1mA
5.20 NO LOAD 5.15
+5V REGULATOR OUTPUT (V)
+5V REGULATOR OUTPUT (V)
5.10 ILOAD = 2mA 5.05
5.10 ILOAD = 2mA 5.05 ILOAD = 1mA
5.00 -40 -25 -10 5 20 35 50 65 80 95 110 125 TEMPERATURE (C) -40 -25 -10 5 20 35 50 65 80 95 110 125 TEMPERATURE (C)
5.00 5 10 15 20 25 30 35 40 INPUT VOLTAGE (V)
SHUTDOWN CURRENT vs. TEMPERATURE
MAX16805 toc07
(VCS+ - VCS-) vs. IV5
VIN = 12
MAX16805 toc08
200Hz DIMMED OPERATION
MAX16805 toc09
0.2010 0.2005 (VCS+ - VCS-) (V) 0.2000 0.1995 0.1990 0.1985
35 SHUTDOWN CURRENT (A) 30 25 20 15 10 5 0
VIN = 40V
VDIM 2V/div 0V ILOAD = 350mA VIN = 12V DIM PULSED AT 200Hz (1% DUTY CYCLE)
VIN = 20V VIN = 12V VIN = 6.5V
ILOAD 200mA/div 0A
0.1980 -40 -25 -10 5 20 35 50 65 80 95 110 125 TEMPERATURE (C) 0 1 2 3 4 IV5 (mA) 5 6 7 8 20s/div
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EEPROM-Programmable, High-Voltage, 350mA LED Drivers with LED Current Foldback
Typical Operating Characteristics (continued)
(VIN = 12V, VEN = VIN, CV5 = 0.1F, IV5 = 0, CS- = GND, RSENSE = 0.56, connect OUT to CS+, VDIM = 4V, SW = VFD = open, VTFP/SC = 5V, VTFN/SD = GND, DGND = GND. TA = +25C, unless otherwise noted.)
OUTPUT CURRENT DUTY CYCLE vs. ANALOG DIM VOLTAGE
OUTPUT CURRENT DUTY CYCLE (%) VIN = 12V RAMP REGISTER = 0x07 CFD = GND TFP = 5V TFN = GND
MAX16805 toc12
MAX16805/MAX16806
LED CURRENT FALL TIME (EXPANDED)
MAX16805 toc10
LED CURRENT RISE TIME (EXPANDED)
MAX16805 toc11
120 VDIM 2V/div 0V 100 80 60 40 20 0
DIM PULSED AT 200Hz
DIM PULSED AT 200Hz VDIM 2V/div 0V
ILED 200mA/div 0A
ILED 200mA/div 0A
20s/div
20s/div
0
1
2 VDIM (V)
3
4
OUTPUT CURRENT DUTY CYCLE vs. INPUT VOLTAGE
MAX16805 toc13
OUTPUT CURRENT DUTY CYCLE vs. INPUT VOLTAGE
OUTPUT CURRENT DUTY CYCLE (%) LED CURRENT THRESHOLD REGISTER = (0x00)
MAX16805 toc14
120 OUTPUT CURRENT DUTY CYCLE (%) 100 80 60 40
120 100 80
LED CURRENT THRESHOLD REGISTER = (0x07)
BIT3 = 1
BIT3 = 1 60 40 20 0 BIT3 = 0
BIT3 = 0 20 0 0 2 4 6 8 10 12 14 16 18 20 INPUT VOLTAGE (V)
0
5
10
15
20
25
30
INPUT VOLTAGE (V)
OUTPUT CLAMP vs. THERMAL FOLDBACK SLOPE
THERMAL SLOPE = 4V/V
OUTPUT RESPONSE TO SW INPUT
MAX16805 toc16 MAX16805 toc15
45 40 35 OUTPUT CLAMP (%)
THERMAL SLOPE = 4V/V
30 25 20 15 10 5 0 0 0.2 0.4 0.6 0.8 VTFN (V) 1.0 1.2 1.4 1.6 40ms/div
THERMAL FOLDBACK CLAMP LEVEL = 40% THERMAL KNEE = +60C THERMAL SLOPE = 8V/V THERMAL SLOPE = 12V/V
DEBOUNCE TIME DEBOUNCE TIME
VSW 5V/div
VSENSE 200mV/div
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EEPROM-Programmable, High-Voltage, 350mA LED Drivers with LED Current Foldback MAX16805/MAX16806
Pin Description
PIN MAX16805 1, 20 2, 3 MAX16806 1, 20 2, 3 NAME OUT IN FUNCTION Current Regulated Output. Connect pins 1 and 20. Input Supply. Bypass IN with a 0.1F (min) capacitor to GND. Connect pins 2 and 3. LED Current Foldback Dimming Enable Input. Leave CFD unconnected to enable the current foldback dimming function. Drive CFD low to disable the LED current foldback dimming function. Digital Ground. Connect to GND. I2C Serial Clock Input I2C Serial-Data Input/Output Ground No Connection. Leave unconnected (internal connection). 5V Regulated Output. Connect a 0.1F capacitor from V5 to GND. Connect pin 12 to 15. Positive Input of the Internal Differential Amplifier. Connect the current-sense resistor between CS+ and CS- to program the output current level. Negative Input of the Internal Differential Amplifier. Connect the current-sense resistor between CS- and CS+ to program the output current level. Dimming Input. See the Dimming Input (DIM) section. Enable Input. Drive EN high to enable the output and the 5V regulator. Momentary Switch Interface. See the Momentary Switch Interface (SW) section. Thermal Foldback Positive Input/I2C Serial Clock Input. See the Thermal Sensor Inputs/I2C Interface (TFP/SCL and TFN/SDA) section. Thermal Foldback Negative Input/I2C Serial-Data Input/Output. See the Thermal Sensor Inputs/I2C Interface (TFP/SCL and TFN/SDA) section. Exposed Pad. Connect to the ground plane for improved power dissipation. Do not use as a ground connection for the part.
4 5 6 7 8, 10, 16 9, 11, 18 12, 15 13 14 17 19 -- -- -- EP
4 5 -- -- 8, 10,16 9, 18 12, 15 13 14 17 19 11 6 7 EP
CFD DGND SCL SDA GND N.C. V5 CS+ CSDIM EN SW TFP/SCL TFN/SDA EP
8
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EEPROM-Programmable, High-Voltage, 350mA LED Drivers with LED Current Foldback
Functional Diagram
IN V5
MAX16805/MAX16806
IN REGULATOR TRIMMED BANDGAP 1.25V I_REG
EN
DIM GND
MAX16805 MAX16806
THERMAL SHUTDOWN DIFFERENTIAL SENSE AMPLIFIER
OUT CS+ CS-
IN
CFD
CURRENT FOLDBACK EEPROM 210mV 200Hz RAMP GENERATOR
MUX AND LOGIC
SW (N.C.) PULSE DETECTOR
POR
V5
REFERENCE GENERATOR
V5
EEPROM AND SERIAL INTERFACE
TRIMMED BANDGAP THERMAL FOLDBACK*
TFP/SCL TFN/SDA (SDA) (SCL)
*NOT PART OF THE MAX16805 ( ) MAX16805
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EEPROM-Programmable, High-Voltage, 350mA LED Drivers with LED Current Foldback MAX16805/MAX16806
SDA
tBUF tLOW tR tF
tHD:STA
tSP
SCL tHD:STA STOP START tHD:DAT tHIGH tSU:DAT REPEATED START tSU:STA tSU:STO P
Figure 1. I2C Serial Interface Timing Diagram
Detailed Description
The MAX16805/MAX16806 are constant-current regulators that provide up to 350mA of current to one or more strings of high-brightness LEDs. A wide operating input voltage range of 5.5V to 40V makes the devices ideal for automotive applications. The MAX16805/MAX16806 feature the I2C interface that allows communication with the internal dynamic registers and EEPROM. Dynamic registers control the MAX16805/MAX16806 functions and can be updated in real time through the I2C interface. See Table 2 for register addresses. Turning off the input voltage clears the dynamic register contents. To save settings, store them into the EEPROM. The MAX16805/MAX16806 load the stored settings into the dynamic registers at power-up. In addition, during normal operation a write command to the EEPROM Content Transfer register loads the stored settings into the dynamic register. Information stored can be transferred into dynamic registers after issuing a "write" command to the EEPROM Content Transfer register. The MAX16805/MAX16806's 5V regulator (V5) provides up to 2mA of current to external circuitry. However, the MAX16806's 5V regulator can deliver 2mA of output current only when the momentary switch is not used. When the momentary switch is active, the MAX16806 achieves up to 0.5mA of current. In addition, the MAX16805/MAX16806 feature thermal and output shortcircuit protection. The wide operating voltage range helps protect the device against large transients up to 45V such as those found in load dump situations.
The MAX16805/MAX16806 use a feedback loop to control the output current. The differential voltage across the sense resistor is compared to a fixed reference voltage and the error is amplified to serve as the drive to the internal pass device, see the Functional Diagram. The MAX16805/MAX16806 offer a programmable LED current reference using the Binning Adjustment register. These devices are current controllers internally optimized for driving the impedance range expected from 1 to 10 (or more) high-brightness LEDs.
Dimming Input (DIM)
The MAX16805/MAX16806's dimming input operates with either an analog or PWM control signal. If the pulse detector detects three edges of a PWM signal with a frequency range between 80Hz to 2kHz, the MAX16805/MAX16806 synchronize to external PWM input signal and pulse-width-modulate the LED current. If an analog control signal is applied to DIM, the MAX16805/MAX16806 compare the DC input to an internally generated 200Hz ramp to pulse-width-modulate the LED current. The maximum peak value of the 200Hz ramp can be programmed using the Ramp Peak register. This allows the LED current to be adjusted through the I2C interface from 50% (typ) to 100% in real time when VDIM is 1.54V. The output current duty cycle is adjustable from 0% to 100% (0.21V < VDIM < 3.1V). Use the following formula to calculate the output current duty cycle: Duty cycle = (VDIM - 0.21V) / VRAMP
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EEPROM-Programmable, High-Voltage, 350mA LED Drivers with LED Current Foldback
The dimming feature can be used for LED brightness adjustment (see the Typical Operating Circuits) and theater dimming. If the external PWM signal is used, theater dimming can be achieved by varying the PWM duty cycle. Figure 2 shows a simple circuit that implements theater dimming with a DC input signal.
MAX16805/MAX16806
VIN
IN
OUT +5V REG V5 LEDs 0.1F
EN
Thermal Sensor Inputs/I2C Interface (TFP/SCL and TFN/SDA)
The MAX16806 features dual-function inputs, TFP/SCL and TFN/SDA. In programming mode, TFP/SCL and TFN/SDA serve as the I2C serial communication interface. TFP/SCL and TFN/SDA also serve as inputs for analog signals generated by an external temperature sensor such as the MAX6613. The MAX16805 does not offer dual-function inputs. SCL and SDA are used only to communicate with the MAX16805 through the I2C interface.
THEATER DIMMING SIGNAL
MAX16805 MAX16806
CS+
RSENSE DIM GND CS-
Momentary Switch Interface (SW)
The MAX16806 offers a momentary switch (SW) that overrides the analog dimming signal by latching the output current to 100% duty cycle. The MAX16806 does not override external PWM signal at DIM or dimming caused by thermal or LED current foldback. To latch the output current into a 100% duty cycle, press SW once. To restore the initial duty cycle determined by the DC level at DIM, press SW again. The MAX16806 provides a minimum of 1mA of wetting current to the momentary switch.
Figure 2. Theater Dimming Light
SDA
SCL S START CONDITION P STOP CONDITION
Overtemperature Protection
The MAX16805/MAX16806 enter a thermal shutdown in the event of overheating. This typically occurs in overload or output short-circuit conditions. When the junction temperature exceeds T J = +155C (typ), the internal thermal protection circuitry turns off the pass device. The MAX16805/MAX16806 recover from thermal shutdown once the junction temperature drops by +23C (typ). This feature allows self-protection by thermally cycling in the event of a short-circuit or overload condition.
Figure 3. I2C Communication Start and Stop Conditions
Start and Stop Conditions
Both SCL and SDA remain high when the interface is not busy. A master controller signals the beginning of a transmission with a START condition by transitioning SDA from high to low while SCL is high. The master controller issues a STOP condition by transitioning the SDA from low to high while SCL is high, when it finishes communicating with the slave. The bus is then free for another transmission (Figure 3).
Digital Interface
The MAX16805/MAX16806 feature an I2C, 2-wire serial interface consisting of a bidirectional serial data line (SDA) and a serial clock line (SCL). SDA and SCL facilitate bidirectional communication between the MAX16805/MAX16806 and the master device at rates up to 400kHz. The master (typically a microcontroller) initiates data transfer on the bus and generates SCL.
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EEPROM-Programmable, High-Voltage, 350mA LED Drivers with LED Current Foldback MAX16805/MAX16806
Bit Transfer
One data bit is transferred during each clock pulse. The data on the SDA line must remain stable while SCL is high (Figure 4). clock pulse, and the recipient pulls down SDA during the acknowledge clock pulse, so the SDA line remains stable low during the high period of the clock pulse.
Slave Address
The MAX16805/MAX16806 have a 7-bit-long slave address (Figure 6, Table 1). The 8th bit following the 7bit slave address is the R/W bit. Set the R/W bit low for a write command and high for a read command.
Acknowledge
The acknowledge bit is a clocked 9th bit that the recipient uses to handshake receipt each byte of data (Figure 5). Therefore, each byte effectively transferred requires 9 bits. The master controller generates the 9th
Table 1. Slave Address
WRITE ADDRESS (HEX)
SDA
READ ADDRESS (HEX) 0xEF
0xEE
SCL
DATA STABLE, CHANGE OF DATA DATA VALID ALLOWED
Figure 4. Bit Transfer
START SDA NOT ACKNOWLEDGE
ACKNOWLEDGE
SCL
1
2
8
9
Figure 5. Acknowledge
SDA
A7
A6
A5
A4
A3
A2
A1
RW
ACK
START SCL
MSB 1 2
3
4
5
6
7
8
9
Figure 6. Slave Address
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EEPROM-Programmable, High-Voltage, 350mA LED Drivers with LED Current Foldback
Message Format
Write to the MAX16805/MAX16806 by transmitting the device's slave address with R/W, 8th bit set to zero followed by at least 1 byte of information (Figure 7). The first byte of information is the command byte. The bytes received after the command byte are the data bytes. The first data byte goes into the internal register as selected by the command byte (Figure 8). If there is more than one data byte, the MAX16805/MAX16806 auto-increment to the next register address locations to write the subsequent data bytes. The MAX16805/ MAX16806 auto-increment up to the register address 0x05, EEPROM Content Transfer register. A read operation is performed as follows: After the START condition (S), a 7-bit slave ID is sent followed by an 8th bit (R/W) set to zero. A register address is then sent to specify the address location from which the read has to take place. To complete a read operation, the master needs to generate a repeated START (Sr) followed by the 7-bit slave ID but with the 8th bit (R/W) set to "1" this time indicating a read operation. On the other hand, a read operation can be performed by sending in the 7-bit slave ID followed by
MAX16805/MAX16806
Table 2. Registers Address
REGISTER NAME Binning Adjustment Ramp Peak LED Current Foldback Threshold (LED_CFT) Thermal Foldback Knee Point Thermal Foldback Slope Gain Thermal Foldback Clamp Level EEPROM Content Transfer EEPROM Program Enable Password Register REGISTER ADDRESS 0x00 0x01 0x02 0x03 0x04 0x05 0x06 0x08 0xFF NO. OF BITS/ REGISTER 4 3 4 4 2 3 -- -- --
an 8th bit (R/W) set to "1" if the current address location happens to be the address location from which data needs to be read.
ACKNOWLEDGE FROM MAX16805/MAX16806
S
SLAVE ADDRESS
0
A
COMMAND BYTE
A
P
RW
ACKNOWLEDGE FROM MAX16805/MAX16806
Figure 7. Command Byte Received
ACKNOWLEDGE FROM MAX16805/MAX16806
ACKNOWLEDGE FROM MAX16805/MAX16806
S
SLAVE ADDRESS
0
A
COMMAND BYTE
A
DATA BYTE
A
P
RW
ACKNOWLEDGE FROM MAX16805/MAX16806
1 BYTE
Figure 8. Command and a Single Data Byte Received
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13
EEPROM-Programmable, High-Voltage, 350mA LED Drivers with LED Current Foldback MAX16805/MAX16806
Binning Adjustment Register (0x00)
The Binning Adjustment register is a 4-bit register that sets the differential regulation voltage reference between CS+ and CS-. Only the first 4 bits of the data byte update the Binning Adjustment register. The remaining 4 bits are ignored. See Table 3. The factorydefault register value is 198mV.
LED Current Foldback Threshold (LED_CFT) Register (0x02)
LED_CFT is a 4-bit register that sets the threshold for the onset of the LED current foldback operation. Only the first 3 bits of the data byte program the LED_CFT register. Bit 3, not shown in Table 5, sets the LED current foldback range. The MAX16805/MAX16806 start dimming the LED current when the input voltage exceeds the LED current foldback threshold. For bit 3 = 0, the dimming range is 1.2 times the programmed ramp peak voltage. For bit 3 = 1, the dimming range is 2.4 times the programmed ramp peak. To disable the LED current foldback feature of the MAX16805/MAX16806 connect CFT to GND. The factory-default register value is 16V.
Ramp Peak Register (0x01), MAX16806
The Ramp Peak register is a 3-bit register that sets the maximum peak value of an internally 200Hz generated ramp. The ramp signal can be programmed for a peak value of 1.55V to 2.88V. Only the first 3 bits of the data byte update the Ramp Peak register. The remaining 5 bits are ignored (see Table 4). The factory-default register value is 2.88V.
Table 3. Binning Adjustment
REGULATION VOLTAGE (mV) 103.0 109.0 115.4 121.8 128.2 134.6 141.0 147.4 153.7 160.1 166.5 173.0 179.3 185.7 192.1 198.0 BIT 3 0 0 0 0 0 0 0 0 1 1 1 1 1 1 1 1 BIT 2 0 0 0 0 1 1 1 1 0 0 0 0 1 1 1 1 BIT 1 0 0 1 1 0 0 1 1 0 0 1 1 0 0 1 1 BIT 0 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 HEX (0x00) (0x01) (0x02) (0x03) (0x04) (0x05) (0x06) (0x07) (0x08) (0x09) (0x0A) (0x0B) (0x0C) (0x0D) (0x0E) (0x0F)
Table 4. Ramp Peak Value
RAMP END POINT (V) 1.55 1.74 1.93 2.12 2.32 2.51 2.70 2.88 BIT 2 0 0 0 0 1 1 1 1 BIT 1 0 0 1 1 0 0 1 1 BIT 0 0 1 0 1 0 1 0 1 HEX (0x00) (0x01) (0x02) (0x03) (0x04) (0x05) (0x06) (0x07)
Table 5. LED Current Foldback Threshold
CURRENT FOLDBACK THRESHOLD (V) 16.4 15.7 15.0 14.3 13.5 12.8 12.1 11.4 BIT 2 0 0 0 0 1 1 1 1 BIT 1 0 0 1 1 0 0 1 1 BIT 0 0 1 0 1 0 1 0 1 HEX (0x00) (0x01) (0x02) (0x03) (0x04) (0x05) (0x06) (0x07)
14
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EEPROM-Programmable, High-Voltage, 350mA LED Drivers with LED Current Foldback
Thermal Foldback Knee Point (TFK) Register (0x03), MAX16806
The TFK register is a 4-bit register that sets the thermal knee. Only the first 4 bits of the data byte program the TFK register. The remaining 4 bits are ignored (see Table 6). The MAX16806 initiates dimming once the differential voltage between TFP/SCL and TFN/SDA drops below the programmed thermal foldback knee. The factory-default register value is 1.174V, which corresponds to the MAX6613 thermal sensor output to +60C.
Thermal Foldback Slope Gain Register (0x04), MAX16806
Thermal Foldback Slope Gain register is a 2-bit register that sets the gain after the thermal foldback knee. Only the first 2 bits of the data byte program the Thermal Foldback Slope Gain register. The remaining 6 bits are ignored (see Table 7). The factory-default register value is 4V/V.
MAX16805/MAX16806
Table 6. Thermal Foldback Knee
THERMAL FOLDBACK KNEE POINT (C) (MAX6613) 60 65 70 75 80 85 90 96 101 106 111 116 121 126 131 136 THERMAL FOLDBACK KNEE POINT (mV) 1174 1118 1062 1006 950 894 838 782 726 670 615 559 503 447 391 335 BIT 3 0 0 0 0 0 0 0 0 1 1 1 1 1 1 1 1 BIT 2 0 0 0 0 1 1 1 1 0 0 0 0 1 1 1 1 BIT 1 0 0 1 1 0 0 1 1 0 0 1 1 0 0 1 1 BIT 0 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 HEX (0x00) (0x01) (0x02) (0x03) (0x04) (0x05) (0x06) (0x07) (0x08) (0x09) (0x0A) (0x0B) (0x0C) (0x0D) (0x0E) (0x0F)
Table 7. Thermal Foldback Slope Gain
THERMAL FOLDBACK SLOPE GAIN (V/V) 16 12 8 4 BIT 1 0 0 1 1 BIT 0 0 1 0 1 HEX (0x00) (0x01) (0x02) (0x03)
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15
EEPROM-Programmable, High-Voltage, 350mA LED Drivers with LED Current Foldback MAX16805/MAX16806
Thermal Foldback Clamp Level Register (0x05), MAX16806
Thermal Foldback Clamp Level is a 3-bit register that sets the minimum percentage of the LED current. Only the first 3 bits of the data byte program the Thermal Foldback Clamp Level register. The remaining 5 bits are ignored. See Table 8. The factory-default register value is 40%.
Applications Information
Programming the LED Current The MAX16805/MAX16806 use a sense resistor across CS+ and CS- to set the LED current. The differential sense amplifier connected across R SENSE provides ground-loop immunity and low-frequency noise rejection. The LED current is given by the equation below: ILED = VSENSE / RSENSE V SENSE is programmable from 103mV to 198mV using I2C. Programming EEPROM Set VIN to 22V before initiating the EEPROM programming. The MAX16805/MAX16806 use dynamic registers to program the EEPROM. Once the desired dynamic registers have been updated with a setting, write the data byte (0xCA) to the Password register (0xFF). The data byte (0xCA) enables the EEPROM programming mode. Any other data byte except the (0xCA) disables the EEPROM programming mode. To transfer data from dynamic registers to the EEPROM, write to EEPROM Program Enable register (0x08). Input Voltage Considerations For proper operation, the minimum input voltage must always be: VIN(MIN) > VSENSE + VFT(MAX) + VDO(MAX) where VFT(MAX) is the total forward voltage of all series connected LEDs and VDO(MAX) is the maximum drop output voltage.
EEPROM Content Transfer Register (0x06)
The MAX16805/MAX16806 use the EEPROM Content Transfer register to transfer data from the EEPROM to the dynamic registers. A write command issued to this register transfers data from the EEPROM to the dynamic registers. Data bytes written to the EEPROM Content Transfer register do not have any significance. At power-up, the EEPROM content is automatically loaded into the dynamic registers.
EEPROM Program Enable Register (0x08)
The EEPROM Program Enable register enables the EEPROM for programming. Write to the EEPROM Programming Enable register to initiate the EEPROM programming cycle. Data written to the register does not have any significance, however, it must be issued following a write command [(0xFF), (0xCA)] to the Password register.
Table 8. Thermal Foldback Clamp Level
THERMAL FOLDBACK CLAMP LEVEL (%) 100 91 83 74 66 57 49 40 BIT 2 0 0 0 0 1 1 1 1 BIT 1 0 0 1 1 0 0 1 1 BIT 0 0 1 0 1 0 1 0 1 HEX (0x00) (0x01) (0x02) (0x03) (0x04) (0x05) (0x06) (0x07)
16
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EEPROM-Programmable, High-Voltage, 350mA LED Drivers with LED Current Foldback
Pin Configurations
N.C. CS+ CS+ CSCS-
MAX16805/MAX16806
15
14
13
12
11
15
14
13
12
GND 16 DIM 17 N.C. 18 EN 19 OUT 20 +
10 9
GND N.C. GND SDA SCL
SW 11
TOP VIEW
V5
V5
V5
V5
GND 16 DIM 17 N.C. 18 EN 19 OUT 20 +
10 9
GND N.C. GND TFN/SDA TFP/SCL
MAX16805
8 7 6
MAX16806
8 7 6
1 OUT
2 IN
3 IN
4 CFD
5 DGND
1 OUT
2 IN
3 IN
4 CFD
5 DGND
THIN QFN
THIN QFN
Chip Information
PROCESS: BiCMOS-DMOS
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17
EEPROM-Programmable, High-Voltage, 350mA LED Drivers with LED Current Foldback MAX16805/MAX16806
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.)
18
______________________________________________________________________________________
QFN THIN.EPS
EEPROM-Programmable, High-Voltage, 350mA LED Drivers with LED Current Foldback
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.)
MAX16805/MAX16806
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.
Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 ____________________ 19
(c) 2006 Maxim Integrated Products is a registered trademark of Maxim Integrated Products, Inc.

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