MAX1984 Datasheet, PDF (1/17 Pages) Maxim Integrated Products – Ultra-High-Efficiency White LED Drivers

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
11 LD7
6 7 8 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.