MAX1678 Datasheet, PDF (1/12 Pages) Maxim Integrated Products – 1-Cell to 2-Cell, Low-Noise, High-Efficiency, Step-Up DC-DC Converter

19-1381; Rev 0; 7/98
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1-Cell to 2-Cell, Low-Noise,
High-Efficiency, Step-Up DC-DC Converter
General Description
The MAX1678 is a high-efficiency, low-voltage, syn-
chronous-rectified, step-up DC-DC converter intended
for use in devices powered by 1 to 3-cell alkaline,
NiMH, or NiCd batteries or a 1-cell lithium battery. It
guarantees a 0.87V start-up voltage and features a low
37µA quiescent supply current.
The device includes a 1Ω, N-channel MOSFET power
switch, a synchronous rectifier that acts as the catch
diode, a reference, pulse-frequency-modulation (PFM)
control circuitry, and circuitry to reduce inductor ring-
ing—all in an ultra-small, 1.1mm-high µMAX package.
The output voltage is preset to 3.3V or can be adjusted
from +2V to +5.5V using only two resistors. Efficiencies
up to 90% are achieved for loads up to 50mA. The
device also features an independent undervoltage
comparator (PFI/PFO) and a logic-controlled 2µA shut-
down mode.
Features
o 0.87V Guaranteed Start-Up
o Up to 90% Efficiency
o Built-In Synchronous Rectifier (no external diode)
o Ultra-Small µMAX Package, 1.1mm High
o 37µA Quiescent Current (85µA from 1.5V battery)
o 2µA Logic-Controlled Shutdown
o Power-Fail Detector
o Dual Mode™ Output: Fixed 3.3V
Adjustable 2V to 5.5V
o 45mA Output Current at 3.3V for 1-Cell Input
o 90mA Output Current at 3.3V for 2-Cell Input
o Inductor-Damping Switch Suppresses EMI
Applications
Pagers
Remote Controls
Pointing Devices
Personal Medical Monitors
Single-Cell Battery-Powered Devices
Ordering Information
PART
MAX1678EUA
TEMP. RANGE
-40°C to +85°C
PIN-PACKAGE
8 µMAX
Note: To order these devices shipped in tape-and-reel, add a -T
to the part number.
Typical Operating Circuit
Pin Configuration
INPUT
0.87V TO V_OUT
ON
OFF
LOW-BATTERY
DETECTOR INPUT
LX
OUT
MAX1678
BATT
SHDN
PFI
GND
PFO
FB
OUTPUT
3.3V
LOW-BATTERY
DETECTOR OUTPUT
TOP VIEW
BATT 1
PFI 2
PFO 3
SHDN 4
MAX1678
µMAX
8 OUT
7 LX
6 GND
5 FB
Dual Mode is a trademark of Maxim Integrated Products.
________________________________________________________________ Maxim Integrated Products 1
For free samples & the latest literature: http://www.maxim-ic.com, or phone [phone].
For small orders, phone [phone] ext. 3468.