MAX845 Datasheet, PDF (1/16 Pages) Maxim Integrated Products – Isolated Transformer Driver for PCMCIA Applications

19-0372; Rev 4; 10/97
EVAALVUAAILTAIOBNLEKIT
Isolated Transformer Driver
for PCMCIA Applications
_______________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.
________________________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
____________________________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
_______________Ordering Information
PART
TEMP. RANGE
MAX845C/D
0°C to +70°C
MAX845ESA
-40°C to +85°C
MAX845EUA
-40°C to +85°C
*Contact factory for dice specifications.
PIN-PACKAGE
Dice*
8 SO
8 µMAX
__________Typical Operating Circuit ^{___________________Pin Configuration}
ON / OFF
V_IN 5V
4
6
SD
V_CC
1
D1
C1
CR1
MAX845
3
FS
FREQUENCY
8
D2
T1
SELECT _{GND1 GND2}
2
7
CR2
OUTPUT
5V @ 150mA
C2
C3
TOP VIEW
D1 ₁
GND1 2
FS 3
SD 4
MAX845
8 D2
7 GND2
6 VCC
5 N.C.
SO/µMAX
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