19-0372; Rev 4; 10/97
KIT
ATION
EVALU
E
BL
AVAILA
Isolated Transformer Driver
for PCMCIA Applications
____________________________Features
o
Transformer Driver for Ultra-Thin 5V-µs Transformers
o
Isolated DC-to-DC Power Supply for PCMCIA
Applications
o
450kHz Minimum Switching Frequency
o
Ultra-Low Input Supply Current Ripple
o
Single +5V or +3.3V Supply
o
5µW Low-Power Shutdown Mode
o
8-Pin SO and µMAX Packages
o
Low Output Ripple Permits Miniature Output
Capacitors
_______________General Description
The MAX845 provides an isolated power supply small
enough to fit in thin PCMCIA cards and space-sensitive
applications. It drives a low-profile center-tapped trans-
former primary from a 5V or 3.3V DC power supply. The
secondary can be wound to provide any isolated posi-
tive or negative voltage at powers up to 750mW.
The MAX845 consists of an oscillator followed by a tog-
gle flip-flop. The flip-flop generates two 50% duty-cycle
square waves, which are complementary at half the
oscillator frequency (450kHz, min). These two signals
drive the ground-referenced N-channel power switch-
es. Internal circuitry ensures break-before-make action
between the two switches.
A low-power shutdown disables both the switches and
the oscillator, reducing power consumption. An evalua-
tion kit (MAX845EVKIT-MM) is available to evaluate low-
profile 5V 40mA and 5V 100mA applications.
MAX845
________________________Applications
PCMCIA Modem Cards
Isolated Data Acquisition
Isolated Interface Power Supply
Noise-Immunity Communications Interface
Bridging Ground Differences
Medical Equipment
Process Control
Low-Power LAN Networks
_______________Ordering Information
PART
MAX845C/D
MAX845ESA
MAX845EUA
TEMP. RANGE
0°C to +70°C
-40°C to +85°C
-40°C to +85°C
PIN-PACKAGE
Dice*
8 SO
8 µMAX
*Contact factory for dice specifications.
__________Typical Operating Circuit
ON / OFF
4
SD
6
V
CC
D1
1
V
IN
5V
C1
CR1
OUTPUT
5V @ 150mA
___________________Pin Configuration
TOP VIEW
D1
C2
1
2
8
7
D2
GND2
V
CC
N.C.
MAX845
3
FREQUENCY
SELECT
FS
GND1
2
D2
GND2
7
CR2
8
T1
C3
GND1
FS
3
SD
4
MAX845
6
5
SO/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 ]
