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19-2761; Rev 0; 1/03
EVAALVUAAILTAIOBNLEKIT
Ultra-High-Efficiency White
LED Drivers
General Description
The MAX1984/MAX1985/MAX1986 are white light-emit-
ting diode (LED) drivers that use individual regulators to
control the current of up to eight LEDs. A high-efficiency
step-up regulator generates just enough voltage to keep
all the current regulators in regulation. A versatile dim-
ming interface accommodates analog, digitally adjusted
pulse-width modulation (DPWM), or parallel control.
The individual current regulators allow good current
matching between LEDs. Open or shorted LEDs cannot
affect the performance of other LEDs.
The step-up regulator achieves high efficiency by using
synchronous rectification. The internal N-channel switch
and P-channel synchronous rectifier eliminate the need
for external MOSFETs and diodes. The 1MHz switching
frequency allows the use of low-profile inductors and
ceramic capacitors.
The brightness can be easily adjusted using a multi-
mode dimming interface, which allows brightness control
through a DPWM signal, a 2- or 3-bit parallel control
interface, or an analog signal. The DPWM signal can be
connected directly to the control pin without the need for
an external RC filter if its frequency is 10kHz or above.
The MAX1984 drives up to eight LEDs, the MAX1985
drives up to six LEDs, and the MAX1986 drives up to
four LEDs. Each device has an LED select pin (SEL)
that allows one subset, the other subset, or all LEDs to
be illuminated. All three devices are available in a
4mm 4mm thin QFN package.
Applications
PDAs and Hand-Held PCs
Cellular Phones
Digital Cameras
Features
o Synchronous Step-Up Regulator
Achieves >95% Efficiency
Internal Switch and Synchronous Rectifier
Eliminates External MOSFETs and Diodes
1MHz Fixed Frequency Minimizes Component
Sizes
o Up to 90% Total LED Efficiency
o Accurate LED Current Matching (8% max)
o Adjustable Maximum LED Current
o Multimode Dimming Control
Digital Pulse-Width Modulation Control
2-Bit Parallel Control
3-Bit Parallel Control
Analog Control
o Selectively Enable LEDs
o Open-LED Detection
o Unique 0.5mA LED Test Mode
o 2.7V to 5.5V Input Supply Range
o Small 4mm x 4mm 20-Pin Thin QFN Package
Ordering Information
PART
MAX1984ETP
MAX1985ETP
MAX1986ETE
TEMP RANGE
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
PIN-PACKAGE
20 Thin QFN
20 Thin QFN
16 Thin QFN
NO. OF
LEDs
8
6
4
Pin Configurations
TOP VIEW
20 19 18 17 16
OUT 1
15 BITB
LX 2
14 REF
GND 3
LD1 4
MAX1984
13 SETI
12 LD8
LD2 5
6
78
11 LD7
9 10
20 19 18 17 16
OUT 1
15 BITB
LX 2
14 REF
GND 3
N.C. 4
MAX1985
13 SETI
12 N.C.
LD1 5
11 LD6
6 7 8 9 10
OUT 1
LX 2
GND 3
LD1 4
16 15 14 13
MAX1986
5 678
12 BITA
11 BITB
10 REF
9 SETI
4mm x 4mm
THIN QFN
4mm x 4mm
THIN QFN
4mm x 4mm
THIN QFN
________________________________________________________________ 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.

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Ultra-High-Efficiency White
LED Drivers
ABSOLUTE MAXIMUM RATINGS
OUT, IN, BITA, BITB, BITC, LD1, LD2, LD3, LD4,
LD5, LD6, LD7, LD8 to GND ................................-0.3V to +6V
LDG to GND........................................................................±0.3V
LX to GND ................................................-0.3V to (VOUT + 0.3V)
SETI, REF, MODE, SEL to GND ...................-0.3V to (VIN + 0.3V)
Continuous Power Dissipation (TA = +70°C)
16-Pin Thin QFN (derate 16.9mW/°C above +70°C) ...1349mW
20-Pin Thin QFN (derate 16.9mW/°C above +70°C) ...1349mW
Operating Temperature Range ...........................-40°C to +85°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
(Circuit of Figure 1; VIN = 3.3V, SETI = BITA = BITB = BITC = SEL = IN, MODE = GND, COUT = 4.7µF, CREF = 0.22µF, TA = 0°C to +85°C,
unless otherwise noted. Typical values are at TA = +25°C.)
PARAMETER
IN Supply Range
IN Undervoltage Lockout Threshold
IN Quiescent Current
IN Shutdown Current
REF Output Voltage
REF Line Regulation
REF Load Regulation
Oscillator Frequency
Oscillator Maximum Duty Cycle
CONDITIONS
50mV typical hysteresis
BITA = BITB = BITC = IN, LD1 to LD8 = GND
BITA = BITB = BITC = GND
IREF = 0
2.7V < VIN < 5.5V
-1µA < IREF < +50µA
MIN
2.7
2.2
1.230
0.8
TYP
2.4
400
0.1
1.250
0.2
5
1
85
MAX
5.5
2.6
600
1
1.270
5
15
1.2
UNITS
V
V
µA
µA
V
mV
mV
MHz
%
OUT Overvoltage Protection (OVP)
Threshold
VLD1 to VLD8 = 50mV, OUT rising, 100mV typical
hysteresis
5.1 5.3 5.5
V
INTERNAL MOSFET SWITCHES
N-Channel MOSFET On-Resistance ILX = 200mA
0.4 0.8
N-Channel MOSFET Leakage Current VLX = 5.5V, BITA = BITB = BITC = GND
0.1 1
P-Channel MOSFET On-Resistance ILX = 200mA
P-Channel MOSFET Leakage Current LX = GND, VOUT = 5.5V, BITA = BITB = BITC = GND
0.5 1
0.1 1
MAX1984
0.50 0.65 0.81
N-Channel MOSFET Current Limit
MAX1985
0.40 0.52 0.65
MAX1986
0.30 0.39 0.52
CONTROL INPUTS
µA
µA
A
BITA, BITB, BITC Input Logic Low
Level
2.7V < VIN < 5.5V
0.4 V
BITA, BITB, BITC Input Logic High
Level
2.7V < VIN < 5.5V
1.6 V
MODE Input Logic Low Level
MODE Input Logic High Level
MODE, BITA, BITB, BITC Input Bias
Current
2.7V < VIN < 5.5V
2.7V < VIN < 5.5V
2.7V < VIN < 5.5V
VIN - 0.4
0.01
0.4
1
V
V
µA
2 _______________________________________________________________________________________

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Ultra-High-Efficiency White
LED Drivers
ELECTRICAL CHARACTERISTICS (continued)
(Circuit of Figure 1; VIN = 3.3V, SETI = BITA = BITB = BITC = SEL = IN, MODE = GND, COUT = 4.7µF, CREF = 0.22µF, TA = 0°C to +85°C,
unless otherwise noted. Typical values are at TA = +25°C.)
PARAMETER
CONDITIONS
MIN TYP MAX UNITS
SEL Input Logic Low Level
SEL Input Logic Midlevel
2.7V < VIN < 5.5V
2.7V < VIN < 5.5V
0.50
0.4 V
1.85 V
SEL Input Logic High Level
SEL Input Bias Current
2.7V < VIN < 5.5V
SEL = GND, current out of the pin
SEL = IN, current into the pin
2.05
V
5
µA
10
FULL-SCALE LED CURRENT ADJUSTMENT
VLD_ = 80mV, SETI = BITA = BITB = BITC = IN
16.5 18 19.5
VLD_ = 80mV, RSETI = 278k±0.1%, BITA = BITB =
22.5
25
27.5
BITC = IN
LD1 to LD8 Output Current
VLD_ = 80mV, RSETI = 1.8M±0.1%, BITA = BITB =
BITC = IN
VLD_ = 80mV, RSETI = 597k±0.1%, BITA = BITB =
BITC = IN
VLD1 = 1V, RSETI = 10k, BITA = BITB = BITC = IN
SETI = GND
12.5
16.5
0.42
14
18
26
0.50
15.5
19.5
0.60
mA
LD1 to LD8 Regulation Voltage
SETI = IN, ILX = 120mA (MAX1984),
110mA (MAX1985), 98mA (MAX1986)
80 100 120 mV
SETI High-Level Threshold
(18mA LED Default Current)
2.7V < VIN < 5.5V
VIN - 0.4
V
SETI Low-Level Threshold
(0.5mA LED Default Current)
2.7V < VIN < 5.5V
50 125 mV
SETI Output Current
OUTPUT CURRENT SOURCE
LD1 to LD8 On-Resistance
LD1 to LD8 Current-Source
Compliance
SETI = GND
VLD_ = 50mV, VOUT = 3.5V
BITA = BITB = BITC = IN, 80mV < VLD_ < 1V
(Note 1)
40 70 100 µA
34
0.3 5
%
LD1 to LD8 Leakage Current
BITA = BITB = BITC = GND
DIGITAL BRIGHTNESS CONTROL
0.01 1
µA
2-Bit Control DAC LSB
MODE = SETI = BITB = IN, BITA = BITC = GND
(Note 2)
26 33 39
%
3-Bit Control DAC LSB
SETI = BITC = IN, MODE = BITA = BITB = GND
(Note 2)
7 14 21 %
DPWM BRIGHTNESS CONTROL
DPWM Input Supply Range
DPWM Shutdown Duty Cycle
MODE = BITC = IN
BITC = GND
2.3 5.5 V
357%
_______________________________________________________________________________________ 3

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Ultra-High-Efficiency White
LED Drivers
ELECTRICAL CHARACTERISTICS
(Circuit of Figure 1; VIN = 3.3V, SETI = BITA = BITB = BITC = SEL = IN, MODE = GND, COUT = 4.7µF, CREF = 0.22µF, TA = -40°C to
+85°C, unless otherwise noted.) (Note 3)
PARAMETER
IN Supply Range
CONDITIONS
MIN TYP MAX UNITS
2.7 5.5 V
IN Undervoltage Lockout Threshold 50mV typical hysteresis
2.2 2.6 V
IN Quiescent Current
REF Output Voltage
REF Line Regulation
REF Load Regulation
Oscillator Frequency
BITA = BITB = BITC = IN, LD1 to LD8 = GND
IREF = 0
2.7V < VIN < 5.5V
-1µA < IREF < +50µA
OUT Overvoltage Protection
Threshold
INTERNAL MOSFET SWITCHES
N-Channel MOSFET On-Resistance
P-Channel MOSFET On-Resistance
N-Channel MOSFET Current Limit
CONTROL INPUTS
VLD1 to VLD8 = 50mV, OUT rising, 100mV typical
hysteresis
ILX = 200mA
ILX = 200mA
MAX1984
MAX1985
MAX1986
BITA, BITB, BITC Input Logic Low
Level
2.7V < VIN < 5.5V
BITA, BITB, BITC Input Logic High
Level
2.7V < VIN < 5.5V
MODE Input Logic Low Level
2.7V < VIN < 5.5V
MODE Input Logic High Level
2.7V < VIN < 5.5V
SEL Input Logic Low Level
2.7V < VIN < 5.5V
SEL Input Logic Midlevel
2.7V < VIN < 5.5V
SEL Input Logic High Level
2.7V < VIN < 5.5V
FULL-SCALE LED CURRENT ADJUSTMENT
VLD_ = 80mV, SETI = BITA = BITB = BITC = IN
VLD_ = 80mV, RSETI = 278k±1%, BITA = BITB =
BITC = IN
LD1 to LD8 Output Current
VLD_ = 80mV, RSETI = 1.8M±1%, BITA = BITB =
BITC = IN
VLD_ = 80mV, RSETI = 697k±1%, BITA = BITB =
BITC = IN
SETI = GND
1.230
0.8
5.1
0.50
0.40
0.30
1.6
VIN - 0.4
0.50
2.05
16
22
11.5
15.5
0.42
600
1.270
5
15
1.2
5.5
µA
V
mV
mV
MHz
V
0.8
1.0
0.81
0.65
0.52
A
0.4
0.4
0.4
1.85
20
28
16.0
20.0
0.60
V
V
V
V
V
V
V
mA
4 _______________________________________________________________________________________

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Ultra-High-Efficiency White
LED Drivers
ELECTRICAL CHARACTERISTICS (continued)
(Circuit of Figure 1; VIN = 3.3V, SETI = BITA = BITB = BITC = SEL = IN, MODE = GND, COUT = 4.7µF, CREF = 0.22µF, TA = -40°C to
+85°C, unless otherwise noted.) (Note 3)
PARAMETER
LD1 to LD8 Regulation Voltage
SETI High-Level Threshold
(18mA LED Default Current)
CONDITIONS
SETI = IN, ILX = 120mA (MAX1984),
110mA (MAX1985), 98mA (MAX1986)
2.7V < VIN < 5.5V
MIN TYP MAX UNITS
80 120 mV
VIN - 0.4
V
SETI Low-Level Threshold
(0.5mA LED Default Current)
2.7V < VIN < 5.5V
SETI Output Current
OUTPUT CURRENT SOURCE
LD1 to LD8 On-Resistance
LD1 to LD8 Current-Source
Compliance
DIGITAL BRIGHTNESS CONTROL
2-Bit Control DAC LSB
SETI = GND
ILD_ = 25mA, VOUT = 3.5V
BITA = BITB = BITC = IN, 80mV < VLD_ < 1V (Note 1)
MODE = SETI = BITB = IN, BITA = BITC = GND
3-Bit Control DAC LSB
SETI = BITC = IN, MODE = BITA = BITB = GND
(Note 2)
DPWM BRIGHTNESS CONTROL
DPWM Input Supply Range
DPWM Shutdown Duty Cycle
MODE = BITC = IN
BITC = GND
Note 1: Current variation is caused by the current source voltage changes.
Note 2: Measurement is with respect to 100% of the programmed LED output current.
Note 3: Specifications to -40°C are guaranteed by design, not production tested.
50
40
26
7
2.3
3
125 mV
100 µA
4
8%
39 %
21 %
5.5 V
7%
_______________________________________________________________________________________ 5