19-2761; Rev 0; 1/03
Ultra-High-Efficiency White
LED Drivers
General Description
Features
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.
ꢀ Synchronous Step-Up Regulator
Achieves >95% Efficiency
Internal Switch and Synchronous Rectifier
Eliminates External MOSFETs and Diodes
1MHz Fixed Frequency Minimizes Component
Sizes
ꢀ Up to 90% Total LED Efficiency
The individual current regulators allow good current
matching between LEDs. Open or shorted LEDs cannot
affect the performance of other LEDs.
ꢀ Accurate LED Current Matching (8% max)
ꢀ Adjustable Maximum LED Current
ꢀ Multimode Dimming Control
Digital Pulse-Width Modulation Control
2-Bit Parallel Control
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.
3-Bit Parallel Control
Analog Control
ꢀ Selectively Enable LEDs
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.
ꢀ Open-LED Detection
ꢀ Unique 0.5mA LED Test Mode
ꢀ 2.7V to 5.5V Input Supply Range
ꢀ Small 4mm x 4mm 20-Pin Thin QFN Package
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
NO. OF
LEDs
PART
TEMP RANGE PIN-PACKAGE
MAX1984ETP
MAX1985ETP
MAX1986ETE
-40°C to +85°C 20 Thin QFN
-40°C to +85°C 20 Thin QFN
-40°C to +85°C 16 Thin QFN
8
6
4
Applications
PDAs and Hand-Held PCs
Cellular Phones
Digital Cameras
Pin Configurations
TOP VIEW
20
19
18
17
16
20
19
18
17
16
16
15
14
13
OUT
LX
1
2
3
4
5
15 BITB
14 REF
13 SETI
12 LD8
11 LD7
OUT
LX
1
2
3
4
5
15 BITB
14 REF
13 SETI
12 N.C.
11 LD6
OUT
LX
1
2
3
4
12 BITA
11 BITB
10 REF
GND
LD1
LD2
GND
N.C.
LD1
MAX1984
MAX1985
MAX1986
GND
LD1
9
SETI
6
7
8
9
10
6
7
8
9
10
5
6
7
8
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.