Rainbow Electronics MAX868 - Manual

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General Description
The MAX868 inverting charge pump provides a low-cost
and compact means of generating a regulated negative
voltage up to -2 x V
IN from a positive input voltage
between 1.8V and 5.5V. It uses a pulse-frequency-
modulation (PFM) control scheme to generate the regulat-
ed negative output voltage. PFM operation is obtained
by gating the internal 450kHz oscillator on and off as
needed to maintain output voltage regulation. This
unique on-demand switching scheme gives the MAX868
excellent light-load efficiency without degrading its full-
load operation (up to 30mA), permitting smaller capaci-
tors to take advantage of the oscillator’s high switching
frequency.
The MAX868 requires no inductors; only four capacitors
are required to build a complete DC-DC converter.
Output voltage regulation is achieved by adding just two
resistors. The MAX868 comes in a 10-pin µMAX pack-
age, which is only 1.11mm high and occupies just half
the board area of a standard 8-pin SO.
________________________Applications
Small LCD Panels
Cell Phones
Cordless Phones
Camcorders
Handy-Terminals, PDAs
Medical Instruments
Battery-Operated Equipment
____________________________Features
♦ Regulated Negative Output Voltage
(up to -2 x V
IN )
♦ Ultra-Small, 10-Pin µMAX Package
♦ On-Demand Switching at up to 450kHz
♦ 30µA Quiescent Supply Current
♦ Requires Only Four Small External Capacitors
♦ 1.8V to 5.5V Input Voltage Range
♦ 0.1µA Logic-Controlled Shutdown
♦ Up to 30mA Output Current
MAX868
Regulated, Adjustable -2x
Inverting Charge Pump
________________________________________________________________ Maxim Integrated Products 1
1
2
3
4
5
10
9
8
7
6
FB
SHDN
C2+
IN PGND
C1-
OUT
GND
MAX868
µ
MAX
TOP VIEW
C2- C1+
Configuration
MAX868
C1+
IN
PGND
SHDN
GND
FB
OUT
0.1 µ F
1 µ F
2.2 µ F
V OUT = 0V TO -2 x V IN
V
IN
= 1.8V TO 5.5V
0.1 µ F
C1-
C2+
C2-
Typical Operating Circuit
19-1290; Rev 1; 2/98
PART
MAX868C/D
MAX868EUB -40°C to +85°C
0°C to +70°C
TEMP. RANGE PIN-PACKAGE
Dice*
10 µMAX
Ordering Information
* Dice are tested at T A = +25°C.