Maxim MAX16805 Eeprom-programmable, high-voltage, 350ma led drivers with led current foldback Datasheet

19-0625; Rev 1; 1/07
KIT
ATION
EVALU
E
L
B
A
AVAIL
EEPROM-Programmable, High-Voltage,
350mA LED Drivers with LED Current Foldback
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
♦ EEPROM or I2C Dynamically Programmable:
♦
♦
♦
♦
♦
♦
♦
♦
LED Current Foldback for High Input Voltage
LED Current Reference
LED Current Thermal Foldback (MAX16806)
On-Board 200Hz Ramp Generator Eliminates the
Need for µC PWM Signal
Flexible Analog or PWM Control for PWM or
Theater Dimming
Wetting Current and Debounce for Momentary
Switch (MAX16806)
5.5V to 40V Input with Up to 39V Output Capability
35mA to 350mA Adjustable LED Current
Waveshaping Minimizes EMI During Dimming
Output Short-Circuit and Overtemperature
Protection
-40°C to +125°C Operating Temperature Range
Ordering Information
PART
Applications
Automotive Interior: Map, Dome, and Courtesy
Lighting
TEMP RANGE
PIN
PACKAGE
PKG
CODE
MAX16805ATP+ -40°C to +125°C 20 TQFN-EP** T2055M-5
MAX16806ATP+ -40°C to +125°C 20 TQFN-EP** T2055M-5
+Denotes lead-free package.
Automotive Exterior:
Rear Combination Light (RCL)
Daytime Running Light (DRL)
Adaptive Front Light
**EP = Exposed pad.
Pin Configurations appear at end of data sheet.
Emergency Vehicle Warning Lights
Navigation and Marine Indicators
Typical Operating Circuits
+5.5V TO +40V
OUT
0.1μF
SCL
SERIAL DATA
SDA
MAX16805
LEDs
OUT
EN
V5
+5V REG
0.1μF
LEDs
VCC
MAX16806
CS+
V5
IN
0.1μF
V5
0.1μF
SERIAL CLOCK
V5
+5V REG
EN
ILED
+5.5V TO +40V
ILED
IN
MAX6613† OUT
CS+
TFP/SCL
RSENSE
RSENSE
GND
TFN/SDA
CS-
CSSW
DIM
PWM DIMMING
DIM
GND
ANALOG CONTROL PWM DIMMING
†MAX6613 THERMAL SENSOR IS OPTIONAL.
GND
PWM CONTROL DIMMING
________________________________________________________________ Maxim Integrated Products
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.
1
MAX16805/MAX16806
General Description
MAX16805/MAX16806
EEPROM-Programmable, High-Voltage, 350mA
LED Drivers with LED Current Foldback
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/µs
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 = +70°C)
20-Pin Thin QFN (derate 34.5mW/°C above +70°C)....2758.6mW
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
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 = 0.1µF, IV5 = 0, CS- = GND, RSENSE = 0.56Ω, VDIM = 4V, DGND = GND, TFP/SCL = 5V, TFN/SDA = 0V,
SW = CFD = Open, TA = TJ = -40°C to +125°C, unless otherwise noted. Typical values are at TA = +25°C.) (Note 1)
PARAMETER
Supply Voltage Range
Ground Current
Shutdown Supply Current
Guaranteed Output Current
SYMBOL
(Note 2)
IG
ILOAD = 350mA
VEN ≤ 0.3V
ISHDN
IOUT
MIN
TYP
MAX
UNITS
40
V
2.5
4.5
mA
12
40
5.5
RSENSE = 0.55Ω
350
ΔVDO
µA
mA
35mA < IOUT < 350mA, RSENSE tolerance
not included
Output Current Accuracy
Dropout Voltage (Note 3)
CONDITIONS
VIN
3.0
IOUT = 350mA, 12V < VIN < 40V
0.4
1.2
IOUT = 350mA, 6.5V < VIN < 12V
0.5
1.5
Output Current Slew Rate
(External PWM Signal at DIM)
Current rising, DIM rising to 4V
17
Current falling, DIM falling to 0.6V
17
Short-Circuit Current
VOUT = 0V
600
%
V
mA/µs
mA
ENABLE INPUT
EN Input Current
IEN
EN Input-Voltage High
VIH
EN Input-Voltage Low
VIL
Enable Turn-On Time
tON
100
2.8
V
0.6
EN rising edge to 90% of OUT
nA
225
V
µs
5V REGULATOR
Output Voltage Regulation
(MAX16806)
0 < IV5 < 0.5mA,
SW = GND
V5
6.5V < VIN < 40V
4.9
5.1
5.3
V
0 < IV5 < 2mA,
SW = open
4.9
5.1
5.3
0 < IV5 < 2mA, 6.5V < VIN < 40V
4.9
5.1
5.3
V
VSENSE = [VCS+ - VCS-], Binning
Adjustment register at factory default
(0x0F)
192
198
204
mV
Input Current (CS+)
VCS+ = 210mV
12
Input Current (CS-)
VCS+ = 210mV
Output Voltage Regulation
(MAX16805)
V5
CURRENT SENSE
Regulated RSENSE Voltage
2
VRSNS
_______________________________________________________________________________________
µA
-75
µA
EEPROM-Programmable, High-Voltage, 350mA
LED Drivers with LED Current Foldback
(VIN = VEN = 12V, CV5 = 0.1µF, IV5 = 0, CS- = GND, RSENSE = 0.56Ω, VDIM = 4V, DGND = GND, TFP/SCL = 5V, TFN/SDA = 0V,
SW = CFD = Open, TA = TJ = -40°C to +125°C, unless otherwise noted. Typical values are at TA = +25°C.) (Note 1)
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
Minimum Regulated VSENSE
Programming Range
VSENSE(MIN)
99.4
103
106.6
Maximum Regulated VSENSE
Programming Range
VSENSE(MAX)
192
198
204
Regulated VSENSE Default
Voltage
VSENSE(DEF)
UNITS
mV
Binning Adjustment register at factory
default (0x0F)
198
mV
EXTERNAL PWM DIMMING INPUT
DIM Input Current
0.5
µA
Turn-On Time
tON
After DIM rising to 4V (Note 4)
28
52
µs
Turn-Off Time
tOFF
After DIM falling to 0.6V (Note 4)
19
38
µs
335
354
THERMAL FOLDBACK (MAX16806 with MAX6613)
Maximum Thermal Foldback
Knee Point Programming Range
TFKNEE(MAX)
326
mV
Minimum Thermal Foldback Knee
Point Programming Range
TFKNEE(MIN)
Minimum Thermal Foldback
Temperature Programming Range
TF(MIN)
+60
Maximum Thermal Foldback
Temperature Programming Range
TF(MAX)
+135
1143
1174
1213
°C
Thermal Foldback Default
Threshold Temperature
VTH
Thermal Foldback Default
Threshold Voltage
TFVTH
Thermal Foldback Knee Point register at
factory default (0x00)
+60
°C
1.174
V
Minimum Thermal Foldback Slope
TFSL(MIN)
3.88
4
4.12
V/V
Maximum Thermal Foldback Slope
TFSL(MAX)
15.52
16
16.48
V/V
Thermal Foldback Slope Gain register at
factory default (0x03)
Thermal Foldback Default Slope
TFP/SCL (SCL for MAX16805)
Voltage Compliance Range
VTFP
TFN/SDA (SDA for MAX16805)
Voltage Compliance Range
VTFN
Minimum Thermal Foldback
Clamp Current Reduction Range
TFC(MIN)
4
V/V
I2C interface active
-0.3
V5
Remote thermal sensor active
+0.3
V5
-0.3
V5
+25oC ≤ TA ≤ +125oC
40
V
V
%
_______________________________________________________________________________________
3
MAX16805/MAX16806
ELECTRICAL CHARACTERISTICS (continued)
MAX16805/MAX16806
EEPROM-Programmable, High-Voltage, 350mA
LED Drivers with LED Current Foldback
ELECTRICAL CHARACTERISTICS (continued)
(VIN = VEN = 12V, CV5 = 0.1µF, IV5 = 0, CS- = GND, RSENSE = 0.56Ω, VDIM = 4V, DGND = GND, TFP/SCL = 5V, TFN/SDA = 0V,
SW = CFD = Open, TA = TJ = -40°C to +125°C, unless otherwise noted. Typical values are at TA = +25°C.) (Note 1)
PARAMETER
SYMBOL
Maximum Thermal Foldback
Clamp Current Reduction Range
TFC(MAX)
Default Thermal Foldback Clamp
Current Reduction Range
TFDEF
CONDITIONS
MIN
TYP
MAX
UNITS
+25oC ≤ TA ≤ +125oC
100
%
Thermal Foldback Clamp register at
factory default (0x07),
+25oC ≤ TA ≤ +125oC
40
%
+155
°C
+23
°C
THERMAL PROTECTION
Thermal Shutdown Temperature
TJ(SHDN)
Thermal Shutdown Hysteresis
LED CURRENT FOLDBACK
Minimum Input LED Current
Foldback Range
VCFD(MIN)
11.4
V
Maximum Input LED Current
Foldback Range
VCFD(MAX)
16.4
V
LED Current Foldback Threshold register
at factory default (0x00)
16.4
V
VIN > 11V, CFD register bit 3 = 0
0.71
VIN > 11V, CFD register bit 3 = 1
0.355
LED Current Foldback Default
Level
VCFD
LED Current Foldback Voltage
Step Size
V/step
INTERNAL RAMP GENERATOR
Internal RAMP Frequency
External Sync Frequency Range
fRAMP
176
fDIM
80
200
External Sync Voltage Low
External Sync Voltage High
Hz
Hz
0.4
V
2.8
VDIM = 0V
Output Current Duty Cycle
224
2000
IDC
V
0
VDIM > (VRAMP + 0.4V) (MAX16806),
VDIM > +3.3V (MAX16805)
%
100
Minimum Ramp Peak
Programming Range
VRAMP(MIN)
1.49
1.55
1.60
V
Maximum Ramp Peak
Programming Range
VRAMP(MAX)
2.77
2.88
3.00
V
Ramp Peak register at factory default
(0x07)
Ramp Peak Default Voltage
Ramp Offset Voltage
2.88
V
210
mV
MOMENTARY SWITCH INTERFACE (SW) (MAX16806)
SW Pullup Current
ISW
VSW = 0V
1
SW Input-Voltage High
VIH
ISW = 100µA
4
SW Input-Voltage Low
VIL
3
mA
V
0.4
V
Minimum Pulse Width
120
ms
Minimum Debounce Time
40
ms
4
_______________________________________________________________________________________
EEPROM-Programmable, High-Voltage, 350mA
LED Drivers with LED Current Foldback
(VIN = VEN = 12V, CV5 = 0.1µF, IV5 = 0, CS- = GND, RSENSE = 0.56Ω, VDIM = 4V, DGND = GND, TFP/SCL = 5V, TFN/SDA = 0V,
SW = CFD = Open, TA = TJ = -40°C to +125°C, unless otherwise noted. Typical values are at TA = +25°C.) (Note 1)
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
VIN Voltage for EEPROM
Programming
20
22
24
V
EEPROM Data-Retention Time
10
EEPROM
Years
I2C DIGITAL INPUTS (TFP/SCL, TFN/SDA) (Note 5)
Logic Input-Voltage High
VIH
Logic Input-Voltage Low
VIL
2.8
V
0.8
Input Capacitance
5
SDA Output Voltage Low
VOL
ISINK = 3mA
V
pF
0.4
V
400
kHz
I2C INTERFACE TIMING (Figure 1)
Serial Clock Frequency
fSCL
Bus Free Time Between STOP
and START Condition
tBUF
1.3
µs
START Condition Hold Time
tHD:STA
0.6
µs
Clock Low Period
tLOW
1.3
µs
Clock High Period
tHIGH
0.6
µs
tSU:STA
0.6
µs
Repeat START Condition Setup
Time
Data Hold Time
tHD:DAT
Data Setup Time
tSU:DAT
Receive SCL/SDA Rise Time
tF
STOP Condition Setup Time
tSU:STO
Transmit SDA Fall Time
0
0.9
µs
300
ns
100
ns
tR
Receive SCL/SDA Fall Time
Pulse Width of Spike Suppressed
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
250
0.6
tSP
50
ISINK < 6mA, CB ≤ 400pF (Note 6)
ns
µs
ns
250
ns
Note 1: All devices 100% production tested at TJ = +25°C. 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 = 0.56Ω 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). ΔVDO = 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 13Ω 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.
_______________________________________________________________________________________
5
MAX16805/MAX16806
ELECTRICAL CHARACTERISTICS (continued)
Typical Operating Characteristics
(VIN = 12V, VEN = VIN, CV5 = 0.1µF, IV5 = 0, CS- = GND, RSENSE = 0.56Ω, connect OUT to CS+, VDIM = 4V, SW = VFD = open,
VTFP/SC = 5V, VTFN/SD = GND, DGND = GND. TA = +25°C, unless otherwise noted.)
300
250
ILOAD = 200mA
200
150
0.203
0.202
0.201
0.200
0.199
0.198
ILOAD = 100mA
100
350
IOUT = 350mA
300
250
200
150
IOUT = 100mA
100
0.197
ILOAD = 35mA
50
50
0.196
0
0.195
0
0
2
4
6
8
10
12
20 50 80 110 140 170 200 230 260 290 320 350
TEMPERATURE (°C)
OUTPUT CURRENT (mA)
INPUT VOLTAGE (V)
DROPOUT VOLTAGE
vs. TEMPERATURE
+5V REGULATOR OUTPUT
vs. TEMPERATURE
+5V REGULATOR OUTPUT
vs. INPUT VOLTAGE
0.7
0.6
0.5
0.4
0.3
0.2
5.10
ILOAD = 2mA
5.05
16
MAX16805 toc06
MAX16805 toc05
NO LOAD
ILOAD = 1mA
5.15
14
5.20
+5V REGULATOR OUTPUT (V)
0.8
5.20
+5V REGULATOR OUTPUT (V)
VIN = 12V
ILOAD = 350mA
0.9
MAX16805 toc04
-40 -25 -10 5 20 35 50 65 80 95 110 125
1.0
DROPOUT VOLTAGE (V)
MAX16805 toc02
350
VIN = 12V
0.204
400
OUTPUT CURRENT (mA)
ILOAD = 350mA
(VCS+ - VCS-) (V)
OUTPUT CURRENT (mA)
400
OUTPUT CURRENT vs. INPUT VOLTAGE
(VCS+ - VCS-) vs. OUTPUT CURRENT
0.205
MAX16805 toc01
450
MAX16805 toc03
OUTPUT CURRENT
vs. TEMPERATURE
NO LOAD
5.15
5.10
ILOAD = 1mA
ILOAD = 2mA
5.05
0.1
0
5.00
5.00
20
25
35
INPUT VOLTAGE (V)
(VCS+ - VCS-) vs. IV5
200Hz DIMMED OPERATION
VIN = 20V
20
VIN = 12V
MAX16805 toc08
VIN = 12
0.2005
(VCS+ - VCS-) (V)
VIN = 40V
40
MAX16805 toc09
0.2010
VDIM
2V/div
0.2000
0V
ILOAD = 350mA
VIN = 12V
DIM PULSED AT
200Hz (1% DUTY
CYCLE)
0.1995
0.1990
VIN = 6.5V
ILOAD
200mA/div
0A
0.1985
5
0.1980
0
-40 -25 -10 5 20 35 50 65 80 95 110 125
TEMPERATURE (°C)
6
30
TEMPERATURE (°C)
25
10
15
TEMPERATURE (°C)
30
15
10
-40 -25 -10 5 20 35 50 65 80 95 110 125
MAX16805 toc07
35
5
-40 -25 -10 5 20 35 50 65 80 95 110 125
SHUTDOWN CURRENT
vs. TEMPERATURE
SHUTDOWN CURRENT (μA)
MAX16805/MAX16806
EEPROM-Programmable, High-Voltage, 350mA
LED Drivers with LED Current Foldback
0
1
2
3
4
5
6
7
8
20μs/div
IV5 (mA)
_______________________________________________________________________________________
EEPROM-Programmable, High-Voltage, 350mA
LED Drivers with LED Current Foldback
MAX16805 toc11
120
VDIM
2V/div
VDIM
2V/div
0V
0V
ILED
200mA/div
ILED
200mA/div
0A
0A
MAX16805 toc12
DIM PULSED AT
200Hz
OUTPUT CURRENT DUTY CYCLE (%)
MAX16805 toc10
DIM PULSED AT
200Hz
OUTPUT CURRENT DUTY CYCLE
vs. ANALOG DIM VOLTAGE
LED CURRENT RISE TIME (EXPANDED)
LED CURRENT FALL TIME (EXPANDED)
VIN = 12V
RAMP REGISTER = 0x07
CFD = GND
TFP = 5V
TFN = GND
100
80
60
40
20
0
0
20μs/div
20μs/div
1
2
3
4
VDIM (V)
LED CURRENT
THRESHOLD REGISTER = (0x07)
100
80
BIT3 = 1
60
40
BIT3 = 0
20
LED CURRENT
THRESHOLD REGISTER = (0x00)
100
80
BIT3 = 1
60
40
BIT3 = 0
20
0
0
0
2
4
6
10 12 14 16 18 20
8
0
5
10
15
20
25
INPUT VOLTAGE (V)
INPUT VOLTAGE (V)
OUTPUT CLAMP
vs. THERMAL FOLDBACK SLOPE
OUTPUT RESPONSE TO SW INPUT
30
MAX16805 toc16
MAX16805 toc15
45
THERMAL SLOPE = 4V/V
40
35
OUTPUT CLAMP (%)
120
OUTPUT CURRENT DUTY CYCLE (%)
MAX16805 toc13
OUTPUT CURRENT DUTY CYCLE (%)
120
MAX16805 toc14
OUTPUT CURRENT
DUTY CYCLE vs. INPUT VOLTAGE
OUTPUT CURRENT
DUTY CYCLE vs. INPUT VOLTAGE
VSW
5V/div
THERMAL SLOPE = 4V/V
30
DEBOUNCE
TIME
DEBOUNCE
TIME
THERMAL SLOPE = 8V/V
25
THERMAL SLOPE = 12V/V
20
VSENSE
200mV/div
15
THERMAL
KNEE = +60°C
10
5
THERMAL FOLDBACK
CLAMP LEVEL = 40%
0
0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
1.6
40ms/div
VTFN (V)
_______________________________________________________________________________________
7
MAX16805/MAX16806
Typical Operating Characteristics (continued)
(VIN = 12V, VEN = VIN, CV5 = 0.1µF, IV5 = 0, CS- = GND, RSENSE = 0.56Ω, connect OUT to CS+, VDIM = 4V, SW = VFD = open,
VTFP/SC = 5V, VTFN/SD = GND, DGND = GND. TA = +25°C, unless otherwise noted.)
EEPROM-Programmable, High-Voltage, 350mA
LED Drivers with LED Current Foldback
MAX16805/MAX16806
Pin Description
PIN
8
MAX16805
MAX16806
1, 20
1, 20
NAME
OUT
FUNCTION
Current Regulated Output. Connect pins 1 and 20.
Input Supply. Bypass IN with a 0.1µF (min) capacitor to GND. Connect pins 2
and 3.
2, 3
2, 3
IN
4
4
CFD
5
5
DGND
6
—
SCL
I2C Serial Clock Input
7
—
SDA
I2C Serial-Data Input/Output
8, 10, 16
8, 10,16
GND
Ground
9, 11, 18
9, 18
N.C.
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.
No Connection. Leave unconnected (internal connection).
5V Regulated Output. Connect a 0.1µF capacitor from V5 to GND. Connect pin
12 to 15.
12, 15
12, 15
V5
13
13
CS+
Positive Input of the Internal Differential Amplifier. Connect the current-sense
resistor between CS+ and CS- to program the output current level.
14
14
CS-
Negative Input of the Internal Differential Amplifier. Connect the current-sense
resistor between CS- and CS+ to program the output current level.
17
17
DIM
Dimming Input. See the Dimming Input (DIM) section.
19
19
EN
Enable Input. Drive EN high to enable the output and the 5V regulator.
—
11
SW
Momentary Switch Interface. See the Momentary Switch Interface (SW) section.
—
6
TFP/SCL
Thermal Foldback Positive Input/I2C Serial Clock Input. See the Thermal Sensor
Inputs/I2C Interface (TFP/SCL and TFN/SDA) section.
—
7
TFN/SDA
Thermal Foldback Negative Input/I2C Serial-Data Input/Output. See the Thermal
Sensor Inputs/I2C Interface (TFP/SCL and TFN/SDA) section.
EP
EP
EP
Exposed Pad. Connect to the ground plane for improved power dissipation. Do
not use as a ground connection for the part.
_______________________________________________________________________________________
EEPROM-Programmable, High-Voltage, 350mA
LED Drivers with LED Current Foldback
V5
IN
IN
REGULATOR
1.25V
TRIMMED
BANDGAP
EN
I_REG
OUT
MAX16805
MAX16806
DIM
GND
DIFFERENTIAL
SENSE
AMPLIFIER
THERMAL
SHUTDOWN
CS+
CS-
IN
CURRENT
FOLDBACK
CFD
EEPROM
210mV
200Hz RAMP
GENERATOR
MUX
AND
LOGIC
SW
(N.C.)
POR
REFERENCE
GENERATOR
V5
V5
EEPROM
AND SERIAL
INTERFACE
PULSE
DETECTOR
TRIMMED
BANDGAP
THERMAL
FOLDBACK*
TFP/SCL TFN/SDA
(SDA)
(SCL)
*NOT PART OF THE MAX16805
( ) MAX16805
_______________________________________________________________________________________
9
MAX16805/MAX16806
Functional Diagram
MAX16805/MAX16806
EEPROM-Programmable, High-Voltage, 350mA
LED Drivers with LED Current Foldback
SDA
tBUF
tHD:STA
tLOW
tR
tSP
tF
SCL
tHD:STA
tSU:STA
tHIGH
P
tSU:DAT
STOP
tSU:STO
START
tHD:DAT
REPEATED
START
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.
10
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
______________________________________________________________________________________
EEPROM-Programmable, High-Voltage, 350mA
LED Drivers with LED Current Foldback
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. When the thermal sensor
is not used, connect TFP/SCL and TFN/SDA through
50kΩ resistors to V5 and GND, respectively.
The MAX16805 does not offer dual-function inputs. SCL
and SDA are used only to communicate with the
MAX16805 through the I2C interface.
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.
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 = +155°C (typ), the
internal thermal protection circuitry turns off the pass
device. The MAX16805/MAX16806 recover from thermal shutdown once the junction temperature drops by
+23°C (typ). This feature allows self-protection by thermally cycling in the event of a short-circuit or overload
condition.
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
VIN
IN
OUT
EN
V5
+5V REG
THEATER
DIMMING
SIGNAL
LEDs
0.1μF
MAX16805
MAX16806
CS+
RSENSE
CS-
DIM
GND
Figure 2. Theater Dimming Light
SDA
SCL
S
P
START
CONDITION
STOP
CONDITION
Figure 3. I2C Communication Start and Stop Conditions
up to 400kHz. The master (typically a microcontroller)
initiates data transfer on the bus and generates SCL.
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).
______________________________________________________________________________________
11
MAX16805/MAX16806
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
EEPROM-Programmable, High-Voltage, 350mA
LED Drivers with LED Current Foldback
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).
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
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.
Table 1. Slave Address
WRITE ADDRESS (HEX)
READ ADDRESS (HEX)
0xEE
0xEF
SDA
SCL
DATA STABLE, CHANGE OF DATA
DATA VALID
ALLOWED
Figure 4. Bit Transfer
NOT ACKNOWLEDGE
START
SDA
ACKNOWLEDGE
SCL
1
2
9
8
Figure 5. Acknowledge
SDA
START
SCL
A7
A6
A5
A4
A3
A2
A1
RW
ACK
2
3
4
5
6
7
8
9
MSB
1
Figure 6. Slave Address
12
______________________________________________________________________________________
EEPROM-Programmable, High-Voltage, 350mA
LED Drivers with LED Current Foldback
Table 2. Registers Address
REGISTER
ADDRESS
NO. OF BITS/
REGISTER
Binning Adjustment
0x00
4
Ramp Peak
0x01
3
LED Current Foldback
Threshold (LED_CFT)
0x02
4
Thermal Foldback Knee Point
0x03
4
Thermal Foldback Slope
Gain
0x04
2
Thermal Foldback Clamp
Level
0x05
3
EEPROM Content Transfer
0x06
—
EEPROM Program Enable
0x08
—
Password Register
0xFF
—
REGISTER NAME
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
0
SLAVE ADDRESS
S
COMMAND BYTE
A
A
P
ACKNOWLEDGE FROM
MAX16805/MAX16806
RW
Figure 7. Command Byte Received
ACKNOWLEDGE FROM
MAX16805/MAX16806
S
0
SLAVE ADDRESS
ACKNOWLEDGE FROM
MAX16805/MAX16806
A
RW
COMMAND BYTE
ACKNOWLEDGE FROM
MAX16805/MAX16806
A
DATA BYTE
A
P
1 BYTE
Figure 8. Command and a Single Data Byte Received
______________________________________________________________________________________
13
MAX16805/MAX16806
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
EEPROM-Programmable, High-Voltage, 350mA
LED Drivers with LED Current Foldback
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 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.
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.
Table 3. Binning Adjustment
Table 4. Ramp Peak Value
Ramp Peak Register (0x01), MAX16806
REGULATION
VOLTAGE (mV)
BIT 3
BIT 2
BIT 1
BIT 0
HEX
RAMP END
POINT (V)
BIT 2
BIT 1
BIT 0
HEX
103.0
0
0
0
0
(0x00)
1.55
0
0
0
(0x00)
0
0
1
(0x01)
109.0
0
0
0
1
(0x01)
1.74
115.4
0
0
1
0
(0x02)
1.93
0
1
0
(0x02)
121.8
0
0
1
1
(0x03)
2.12
0
1
1
(0x03)
(0x04)
2.32
1
0
0
(0x04)
(0x05)
2.51
1
0
1
(0x05)
1
1
0
(0x06)
1
1
1
(0x07)
128.2
134.6
14
0
0
1
1
0
0
0
1
141.0
0
1
1
0
(0x06)
2.70
147.4
0
1
1
1
(0x07)
2.88
153.7
1
0
0
0
(0x08)
160.1
1
0
0
1
(0x09)
166.5
1
0
1
0
(0x0A)
173.0
1
0
1
1
(0x0B)
179.3
1
1
0
0
(0x0C)
185.7
1
1
0
1
(0x0D)
192.1
1
1
1
0
(0x0E)
198.0
1
1
1
1
(0x0F)
Table 5. LED Current Foldback Threshold
CURRENT
FOLDBACK
THRESHOLD (V)
BIT 2
BIT 1
BIT 0
HEX
16.4
0
0
0
(0x00)
15.7
0
0
1
(0x01)
15.0
0
1
0
(0x02)
14.3
0
1
1
(0x03)
13.5
1
0
0
(0x04)
12.8
1
0
1
(0x05)
12.1
1
1
0
(0x06)
11.4
1
1
1
(0x07)
______________________________________________________________________________________
EEPROM-Programmable, High-Voltage, 350mA
LED Drivers with LED Current Foldback
Thermal Foldback Slope Gain Register
(0x04), 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 +60°C.
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.
Table 6. Thermal Foldback Knee
THERMAL FOLDBACK
KNEE POINT (°C)
(MAX6613)
THERMAL FOLDBACK
KNEE POINT (mV)
BIT 3
BIT 2
BIT 1
BIT 0
HEX
60
1174
0
0
0
0
(0x00)
65
1118
0
0
0
1
(0x01)
70
1062
0
0
1
0
(0x02)
75
1006
0
0
1
1
(0x03)
80
950
0
1
0
0
(0x04)
85
894
0
1
0
1
(0x05)
90
838
0
1
1
0
(0x06)
96
782
0
1
1
1
(0x07)
101
726
1
0
0
0
(0x08)
106
670
1
0
0
1
(0x09)
111
615
1
0
1
0
(0x0A)
116
559
1
0
1
1
(0x0B)
121
503
1
1
0
0
(0x0C)
126
447
1
1
0
1
(0x0D)
131
391
1
1
1
0
(0x0E)
136
335
1
1
1
1
(0x0F)
Table 7. Thermal Foldback Slope Gain
THERMAL FOLDBACK
SLOPE GAIN (V/V)
BIT 1
BIT 0
HEX
16
0
0
(0x00)
12
0
1
(0x01)
8
1
0
(0x02)
4
1
1
(0x03)
______________________________________________________________________________________
15
MAX16805/MAX16806
Thermal Foldback Knee Point (TFK)
Register (0x03), MAX16806
MAX16805/MAX16806
EEPROM-Programmable, High-Voltage, 350mA
LED Drivers with LED Current Foldback
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%.
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 (%)
BIT 2
BIT 1
BIT 0
HEX
100
0
0
0
(0x00)
91
0
0
1
(0x01)
83
0
1
0
(0x02)
74
0
1
1
(0x03)
66
1
0
0
(0x04)
57
1
0
1
(0x05)
49
1
1
0
(0x06)
40
1
1
1
(0x07)
16
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) + ΔVDO(MAX)
where VFT(MAX) is the total forward voltage of all series
connected LEDs and ΔVDO(MAX) is the maximum drop
output voltage.
______________________________________________________________________________________
EEPROM-Programmable, High-Voltage, 350mA
LED Drivers with LED Current Foldback
V5
CS-
CS+
V5
N.C.
V5
CS-
CS+
V5
SW
TOP VIEW
15
14
13
12
11
15
14
13
12
11
GND 16
10
GND
GND 16
10
GND
DIM 17
9
N.C.
DIM 17
9
N.C.
8
GND
N.C. 18
8
GND
7
SDA
EN 19
7
TFN/SDA
6
SCL
OUT 20
6
TFP/SCL
2
3
4
5
1
CFD
DGND
OUT
THIN QFN
2
3
4
5
DGND
1
IN
+
IN
+
OUT
OUT 20
CFD
EN 19
MAX16806
IN
MAX16805
IN
N.C. 18
THIN QFN
Chip Information
PROCESS: BiCMOS-DMOS
______________________________________________________________________________________
17
MAX16805/MAX16806
Pin Configurations
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.)
QFN THIN.EPS
MAX16805/MAX16806
EEPROM-Programmable, High-Voltage, 350mA
LED Drivers with LED Current Foldback
18
______________________________________________________________________________________
EEPROM-Programmable, High-Voltage, 350mA
LED Drivers with LED Current Foldback
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
© 2007 Maxim Integrated Products
is a registered trademark of Maxim Integrated Products, Inc.
MAX16805/MAX16806
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.)
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