MAX868 Datasheet, PDF (1/12 Pages) Maxim Integrated Products – Regulated, Adjustable -2x Inverting Charge Pump

19-1290; Rev 1; 2/98
Regulated, Adjustable -2x
Inverting Charge Pump
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
Configuration
TOP VIEW
____________________________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
MAX868C/D
0°C to +70°C
MAX868EUB
-40°C to +85°C
*Dice are tested at T_A = +25°C.
PIN-PACKAGE
Dice*
10 µMAX
Typical Operating Circuit
V_IN = 1.8V TO 5.5V
1µF
SHDN IN
GND 1
OUT 2
C1- 3
PGND 4
C1+ 5
MAX868
µMAX
10 FB
9 SHDN
8 C2+
7 IN
6 C2-
0.1µF
0.1µF
MAX868
C1+
FB
C1-
C2+
OUT
C2-
PGND GND
V_OUT = 0V TO -2 x V_IN
2.2µF
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