19-1219; Rev 1; 6/97
AN
N KIT M
LUATIO ABLE
EVA
AVAIL
UAL
28V, Low-Power, High-Voltage,
Boost or Inverting DC-DC Converter
____________________________Features
o
Internal, 500mA, 28V N-Channel Switch
(No External FET Required)
o
Generates Positive or Negative Output Voltages
o
80µA Supply Current
o
1µA Max Shutdown Current
o
Up to 300kHz Switching Frequency
o
Adjustable Current Limit Allows Use of Small,
Inexpensive Inductors
o
8-Pin SO Package
_______________General Description
The MAX629 low-power DC-DC converter features an
internal N-channel MOSFET switch and programmable
current limiting. It is designed to supply positive or neg-
ative bias voltages up to ±28V from input voltages in
the 0.8V to V
OUT
range, and can be configured for
boost, flyback, and SEPIC topologies.
The MAX629’s current-limited pulse-frequency-modula-
tion (PFM) control scheme provides high efficiency over
a wide range of load conditions. An internal, 0.5A N-
channel MOSFET switch reduces the total part count,
and a high switching frequency (up to 300kHz) allows
for tiny surface-mount magnetics.
The MAX629’s combination of low supply current, logic-
controlled shutdown, small package, and tiny external
components makes it an extremely compact and effi-
cient high-voltage biasing solution that’s ideal for bat-
tery-powered applications. The MAX629 is available in
an 8-pin SO package.
MAX629
______________Ordering Information
PART
MAX629C/D
MAX629ESA
TEMP. RANGE
0°C to +70°C
-40°C to +85°C
PIN-PACKAGE
Dice*
8 SO
________________________Applications
Positive or Negative LCD Bias Generators
High-Efficiency DC-DC Boost Converters
Varactor Tuning Diode Bias
Palmtop Computers
2-Cell and 3-Cell Battery-Powered Applications
*Dice
are tested at T
A
= +25°C, DC parameters only.
Note:
To order tape-and-reel shipping, add “-T” to the end of
the part number.
Pin Configuration appears at end of data sheet.
___________________________________________________Typical Operating Circuit
V
IN
+2.7V
TO +5.5V
V
OUT
28V
V
IN
+2.7V
TO +5.5V
V
CC
SHDN
ISET
POL
FB
LX
V
CC
SHDN
ISET
POL
LX
-V
OUT
-28V
MAX629
REF
GND
MAX629
FB
REF
GND
POSITIVE OUTPUT VOLTAGE
NEGATIVE OUTPUT VOLTAGE
________________________________________________________________
Maxim Integrated Products
1
For free samples & the latest literature: http://www.maxim-ic.com, or phone 1-800-998-8800
MAXIM [ MAXIM INTEGRATED PRODUCTS ]
