MAX845EUA+ Analog Devices

MAX845 19-0372 Rev 4 10/97 Isolated Transformer Driver for PCMCIA Applications General Description Features The MAX845 provides an isolated power supply small Transformer Driver for Ultra-Thin 5V-s Transformers enough to fit in thin PCMCIA cards and space-sensitive Isolated DC-to-DC Power Supply for PCMCIA applications. It drives a low-profile center-tapped trans- Applications former primary from a 5V or 3.3V DC power supply. The secondary can be wound to provide any isolated posi- 450kHz Minimum Switching Frequency tive or negative voltage at powers up to 750mW. Ultra-Low Input Supply Current Ripple The MAX845 consists of an oscillator followed by a tog- gle flip-flop. The flip-flop generates two 50% duty-cycle Single +5V or +3.3V Supply square waves, which are complementary at half the 5W Low-Power Shutdown Mode oscillator frequency (450kHz, min). These two signals drive the ground-referenced N-channel power switch- 8-Pin SO and MAX Packages es. Internal circuitry ensures break-before-make action Low Output Ripple Permits Miniature Output between the two switches. Capacitors 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 Ordering Information PCMCIA Modem Cards PART TEMP. RANGE PIN-PACKAGE Isolated Data Acquisition MAX845C/D 0C to +70C Dice* Isolated Interface Power Supply MAX845ESA -40C to +85C 8 SO Noise-Immunity Communications Interface MAX845EUA -40C to +85C 8 MAX Bridging Ground Differences *Contact factory for dice specifications. Medical Equipment Process Control Low-Power LAN Networks Pin Configuration Typical Operating Circuit V IN 5V TOP VIEW ON / OFF C1 46 OUTPUT CR1 SD V 5V 150mA CC 1 D1 D1 1 8 D2 C2 GND1 2 7 GND2 MAX845 MAX845 FS 3 6 V CC 3 8 FS D2 SD 4 T1 5 N.C. FREQUENCY C3 SELECT GND1 GND2 27 SO/MAX CR2 Maxim Integrated Products 1 For free samples & the latest literature: Isolated Transformer Driver for PCMCIA Applications ABSOLUTE MAXIMUM RATINGS Supply Voltage (V ) ...............................................-0.3V to +7V Operating Temperature Range ...........................-40C to +85C CC Control Input Voltage (SD, FS) ...................-0.3V to (V + 0.3V) Storage Temperature Range .............................-65C to +160C CC Peak Output Switch Current (D1, D2)......................................1A Junction Temperature......................................................+150C Output Switch Voltage (D1, D2).............................................12V Lead Temperature (soldering, 10sec) .............................+300C Average Output Switch Current (D1, D2) .........................200mA Continuous Power Dissipation (T = +70C) A SO (derate 5.88mW/C above +70C).........................471mW MAX (derate 4.10mW/C above +70C) ....................330mW Stresses beyond those listed under Absolute Maximum Ratings may cause permanent damage to the device. These are stress ratings only, and functional operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability. ELECTRICAL CHARACTERISTICS (V = 5V 10%, T = T to T , unless otherwise noted. Typical values are at T = +25C.) CC A MIN MAX A PARAMETER CONDITIONS MIN TYP MAX UNITS Switch On-Resistance D1, D2 100mA 1.5 4.0 FS = V = 4.5V 450 675 900 CC FS = V = 5.5V 550 860 1100 CC Switch Frequency kHz FS = 0V, V = 4.5V 500 CC FS = 0V, V = 5.5V 575 CC Operating Supply Current (Note 1) No load, SD = 0V, FS = V 1.1 5.0 mA CC Shutdown Supply Current (Note 2) SD = V 0.4 A CC High 2.4 Shutdown Input Threshold V Low 0.8 Shutdown Input Leakage Current 10 pA High 2.4 FS Input Threshold V Low 0.8 FS = 0V 50 FS Input Current A FS = V 10 CC Minimum Start-Up Voltage 2.5 2.2 V Note 1: Operating supply current is the current used by the MAX845 only. Load current is not included. Note 2: Shutdown supply current includes output switch leakage currents. 2 MAX845