19-2761; Rev 0; 1/03
IT
TION K
VALUA
E
BLE
AVAILA
Ultra-High-Efficiency White
LED Drivers
General Description
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
MAX1984/MAX1985/MAX1986
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.
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
Applications
PDAs and Hand-Held PCs
Cellular Phones
Digital Cameras
Pin Configurations
MODE
MODE
BITC
BITC
SEL
SEL
SEL
BITC
13
12 BITA
11 BITB
10 REF
9 SETI
5
LD2
6
LDG
7
LD3
8
LD4
BITA
BITA
TOP VIEW
MODE
15
IN
IN
20
OUT 1
LX 2
GND 3
LD1 4
LD2 5
6
LD3
19
18
17
16
15 BITB
14 REF
OUT 1
LX 2
GND 3
N.C. 4
LD1 5
20
19
18
17
16
15 BITB
14 REF
OUT 1
LX 2
16
14
MAX1984
13 SETI
12 LD8
11 LD7
MAX1985
13 SETI
12 N.C.
11 LD6
MAX1986
GND 3
LD1 4
7
LD4
8
LDG
9
LD5
10
LD6
6
LD2
7
LD3
8
LDG
9
LD4
10
LD5
4mm x 4mm
THIN QFN
4mm x 4mm
THIN QFN
4mm x 4mm
THIN QFN
________________________________________________________________
Maxim Integrated Products
IN
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.
Ultra-High-Efficiency White
LED Drivers
MAX1984/MAX1985/MAX1986
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 (V
OUT
+ 0.3V)
SETI, REF, MODE, SEL to GND ...................-0.3V to (V
IN
+ 0.3V)
Continuous Power Dissipation (T
A
= +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; V
IN
= 3.3V, SETI = BITA = BITB = BITC = SEL = IN, MODE = GND, C
OUT
= 4.7µF, C
REF
= 0.22µF,
T
A
= 0°C to +85°C,
unless otherwise noted. Typical values are at T
A
= +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
OUT Overvoltage Protection (OVP)
Threshold
INTERNAL MOSFET SWITCHES
N-Channel MOSFET On-Resistance
N-Channel MOSFET Leakage Current
P-Channel MOSFET On-Resistance
P-Channel MOSFET Leakage Current
N-Channel MOSFET Current Limit
CONTROL INPUTS
BITA, BITB, BITC Input Logic Low
Level
BITA, BITB, BITC Input Logic High
Level
MODE Input Logic Low Level
MODE Input Logic High Level
MODE, BITA, BITB, BITC Input Bias
Current
2.7V < V
IN
< 5.5V
2.7V < V
IN
< 5.5V
2.7V < V
IN
< 5.5V
2.7V < V
IN
< 5.5V
2.7V < V
IN
< 5.5V
V
IN
- 0.4
0.01
1
1.6
0.4
0.4
V
V
V
V
µA
I
LX
= 200mA
V
LX
= 5.5V, BITA = BITB = BITC = GND
I
LX
= 200mA
LX = GND, V
OUT
= 5.5V, BITA = BITB = BITC = GND
MAX1984
MAX1985
MAX1986
0.50
0.40
0.30
0.4
0.1
0.5
0.1
0.65
0.52
0.39
0.8
1
1
1
0.81
0.65
0.52
A
Ω
µA
Ω
µA
V
LD1
to V
LD8
= 50mV, OUT rising, 100mV typical
hysteresis
5.1
50mV typical hysteresis
BITA = BITB = BITC = IN, LD1 to LD8 = GND
BITA = BITB = BITC = GND
I
REF
= 0
2.7V < V
IN
< 5.5V
-1µA < I
REF
< +50µA
0.8
1.230
CONDITIONS
MIN
2.7
2.2
2.4
400
0.1
1.250
0.2
5
1
85
5.3
5.5
TYP
MAX
5.5
2.6
600
1
1.270
5
15
1.2
UNITS
V
V
µA
µA
V
mV
mV
MHz
%
V
2
_______________________________________________________________________________________
Ultra-High-Efficiency White
LED Drivers
ELECTRICAL CHARACTERISTICS (continued)
(Circuit of Figure 1; V
IN
= 3.3V, SETI = BITA = BITB = BITC = SEL = IN, MODE = GND, C
OUT
= 4.7µF, C
REF
= 0.22µF,
T
A
= 0°C to +85°C,
unless otherwise noted. Typical values are at T
A
= +25°C.)
PARAMETER
SEL Input Logic Low Level
SEL Input Logic Midlevel
SEL Input Logic High Level
SEL Input Bias Current
2.7V < V
IN
< 5.5V
2.7V < V
IN
< 5.5V
2.7V < V
IN
< 5.5V
SEL = GND, current out of the pin
SEL = IN, current into the pin
V
LD_
= 80mV, SETI = BITA = BITB = BITC = IN
V
LD
_ = 80mV, R
SETI
= 278kΩ ±0.1%, BITA = BITB =
BITC = IN
LD1 to LD8 Output Current
V
LD
_ = 80mV, R
SETI
= 1.8MΩ ±0.1%, BITA = BITB =
BITC = IN
V
LD_
= 80mV, R
SETI
= 597kΩ ±0.1%, BITA = BITB =
BITC = IN
V
LD1
= 1V, R
SETI
= 10kΩ, BITA = BITB = BITC = IN
SETI = GND
LD1 to LD8 Regulation Voltage
SETI High-Level Threshold
(18mA LED Default Current)
SETI Low-Level Threshold
(0.5mA LED Default Current)
SETI Output Current
OUTPUT CURRENT SOURCE
LD1 to LD8 On-Resistance
LD1 to LD8 Current-Source
Compliance
LD1 to LD8 Leakage Current
DIGITAL BRIGHTNESS CONTROL
2-Bit Control DAC LSB
3-Bit Control DAC LSB
DPWM BRIGHTNESS CONTROL
DPWM Input Supply Range
DPWM Shutdown Duty Cycle
MODE = BITC = IN
BITC = GND
2.3
3
5
5.5
7
V
%
MODE = SETI = BITB = IN, BITA = BITC = GND
(Note 2)
SETI = BITC = IN, MODE = BITA = BITB = GND
(Note 2)
26
7
33
14
39
21
%
%
V
LD_
= 50mV, V
OUT
= 3.5V
BITA = BITB = BITC = IN, 80mV < V
LD_
< 1V
(Note 1)
BITA = BITB = BITC = GND
3
0.3
0.01
4
5
1
Ω
%
µA
SETI = IN, I
LX
= 120mA (MAX1984),
110mA (MAX1985), 98mA (MAX1986)
2.7V < V
IN
< 5.5V
2.7V < V
IN
< 5.5V
SETI = GND
0.42
80
V
IN
- 0.4
50
40
70
125
100
16.5
22.5
12.5
16.5
18
25
14
18
26
0.50
100
0.60
120
mV
V
mV
µA
0.50
2.05
5
10
19.5
27.5
15.5
19.5
CONDITIONS
MIN
TYP
MAX
0.4
1.85
UNITS
V
V
V
µA
MAX1984/MAX1985/MAX1986
FULL-SCALE LED CURRENT ADJUSTMENT
mA
_______________________________________________________________________________________
3
Ultra-High-Efficiency White
LED Drivers
MAX1984/MAX1985/MAX1986
ELECTRICAL CHARACTERISTICS
(Circuit of Figure 1; V
IN
= 3.3V, SETI = BITA = BITB = BITC = SEL = IN, MODE = GND, C
OUT
= 4.7µF, C
REF
= 0.22µF,
T
A
= -40°C to
+85°C,
unless otherwise noted.) (Note 3)
PARAMETER
IN Supply Range
IN Undervoltage Lockout Threshold
IN Quiescent Current
REF Output Voltage
REF Line Regulation
REF Load Regulation
Oscillator Frequency
OUT Overvoltage Protection
Threshold
INTERNAL MOSFET SWITCHES
N-Channel MOSFET On-Resistance
P-Channel MOSFET On-Resistance
N-Channel MOSFET Current Limit
CONTROL INPUTS
BITA, BITB, BITC Input Logic Low
Level
BITA, BITB, BITC Input Logic High
Level
MODE Input Logic Low Level
MODE Input Logic High Level
SEL Input Logic Low Level
SEL Input Logic Midlevel
2.7V < V
IN
< 5.5V
2.7V < V
IN
< 5.5V
2.7V < V
IN
< 5.5V
2.7V < V
IN
< 5.5V
2.7V < V
IN
< 5.5V
2.7V < V
IN
< 5.5V
0.50
2.05
16
22
11.5
15.5
0.42
20
28
16.0
20.0
0.60
mA
V
IN
- 0.4
0.4
1.85
1.6
0.4
0.4
V
V
V
V
V
V
V
V
LD1
to V
LD8
= 50mV, OUT rising, 100mV typical
hysteresis
I
LX
= 200mA
I
LX
= 200mA
MAX1984
MAX1985
MAX1986
0.50
0.40
0.30
50mV typical hysteresis
BITA = BITB = BITC = IN, LD1 to LD8 = GND
I
REF
= 0
2.7V < V
IN
< 5.5V
-1µA < I
REF
< +50µA
0.8
5.1
1.230
CONDITIONS
MIN
2.7
2.2
TYP
MAX
5.5
2.6
600
1.270
5
15
1.2
5.5
UNITS
V
V
µA
V
mV
mV
MHz
V
0.8
1.0
0.81
0.65
0.52
Ω
Ω
A
SEL Input Logic High Level
2.7V < V
IN
< 5.5V
FULL-SCALE LED CURRENT ADJUSTMENT
V
LD
_ = 80mV, SETI = BITA = BITB = BITC = IN
V
LD
_ = 80mV, R
SETI
= 278kΩ ±1%, BITA = BITB =
BITC = IN
LD1 to LD8 Output Current
V
LD
_ = 80mV, R
SETI
= 1.8MΩ ±1%, BITA = BITB =
BITC = IN
V
LD_
= 80mV, R
SETI
= 697kΩ ±1%, BITA = BITB =
BITC = IN
SETI = GND
4
_______________________________________________________________________________________
Ultra-High-Efficiency White
LED Drivers
ELECTRICAL CHARACTERISTICS (continued)
(Circuit of Figure 1; V
IN
= 3.3V, SETI = BITA = BITB = BITC = SEL = IN, MODE = GND, C
OUT
= 4.7µF, C
REF
= 0.22µF,
T
A
= -40°C to
+85°C,
unless otherwise noted.) (Note 3)
PARAMETER
LD1 to LD8 Regulation Voltage
SETI High-Level Threshold
(18mA LED Default Current)
SETI Low-Level Threshold
(0.5mA LED Default Current)
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
3-Bit Control DAC LSB
DPWM BRIGHTNESS CONTROL
DPWM Input Supply Range
DPWM Shutdown Duty Cycle
MODE = BITC = IN
BITC = GND
2.3
3
5.5
7
V
%
I
LD_
= 25mA, V
OUT
= 3.5V
BITA = BITB = BITC = IN, 80mV < V
LD_
< 1V (Note 1)
4
8
Ω
%
CONDITIONS
SETI = IN, I
LX
= 120mA (MAX1984),
110mA (MAX1985), 98mA (MAX1986)
2.7V < V
IN
< 5.5V
2.7V < V
IN
< 5.5V
SETI = GND
MIN
80
V
IN
- 0.4
50
40
125
100
TYP
MAX
120
UNITS
mV
V
mV
µA
MAX1984/MAX1985/MAX1986
MODE = SETI = BITB = IN, BITA = BITC = GND
SETI = BITC = IN, MODE = BITA = BITB = GND
(Note 2)
26
7
39
21
%
%
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.
_______________________________________________________________________________________
5
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