19-1290; Rev 1; 2/98
Regulated, Adjustable -2x
Inverting Charge Pump
MAX868
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.
____________________________Features
o
Regulated Negative Output Voltage
(up to -2 x V
IN
)
o
Ultra-Small, 10-Pin µMAX Package
o
On-Demand Switching at up to 450kHz
o
30µA Quiescent Supply Current
o
Requires Only Four Small External Capacitors
o
1.8V to 5.5V Input Voltage Range
o
0.1µA Logic-Controlled Shutdown
o
Up to 30mA Output Current
Ordering Information
PART
TEMP. RANGE
PIN-PACKAGE
Dice*
10 µMAX
MAX868C/D
0°C to +70°C
MAX868EUB
-40°C to +85°C
*Dice
are tested at T
A
= +25°C.
________________________Applications
Small LCD Panels
Cell Phones
Cordless Phones
Camcorders
Handy-Terminals, PDAs
Medical Instruments
Battery-Operated Equipment
Typical Operating Circuit
Configuration
V
IN
= 1.8V TO 5.5V
1µF
TOP VIEW
SHDN
IN
MAX868
GND
1
OUT
C1-
PGND
C1+
2
3
4
5
10
FB
9
SHDN
C2+
IN
C2-
C2+
0.1µF
C2-
PGND
GND
2.2µF
OUT
C1+
0.1µF
C1-
V
OUT
= 0V TO -2 x V
IN
FB
MAX868
8
7
6
µMAX
________________________________________________________________
Maxim Integrated Products
1
For free samples & the latest literature: http://www.maxim-ic.com, or phone 1-800-998-8800.
For small orders, phone 408-737-7600 ext. 3468.
MAXIM [ MAXIM INTEGRATED PRODUCTS ]
