Document
19-0372; Rev 4; 10/97
KIT ATION EVALU E L B A AVAIL
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 transformer primary from a 5V or 3.3V DC power supply. The secondary can be wound to provide any isolated positive or negative voltage at powers up to 750mW. The MAX845 consists of an oscillator followed by a toggle 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 switches. 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 evaluation kit (MAX845EVKIT-MM) is available to evaluate lowprofile 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 VCC D1 1 VIN 5V C1 CR1 OUTPUT 5V @ 150mA
___________________Pin Configuration
TOP VIEW
D1 C2
1 2
8 7
D2 GND2 VCC 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.
Isolated Transformer Driver for PCMCIA Applications MAX845
ABSOLUTE MAXIMUM RATINGS
Supply Voltage (VCC) ...............................................-0.3V to +7V Control Input Voltage (SD, FS) ...................-0.3V to (VCC + 0.3V) Peak Output Switch Current (D1, D2) ......................................1A Output Switch Voltage (D1, D2) .............................................12V Average Output Switch Current (D1, D2) .........................200mA Continuous Power Dissipation (TA = +70°C) SO (derate 5.88mW/°C above +70°C) .........................471mW µMAX (derate 4.10mW/°C above +70°C) ....................330mW Operating Temperature Range ...