(PDF) MAX845 Datasheet PDF | Maxim





MAX845 Datasheet PDF

Part Number MAX845
Description Isolated Transformer Driver for PCMCIA Applications
Manufacture Maxim
Total Page 16 Pages
PDF Download Download MAX845 Datasheet PDF

Features: Datasheet pdf 19-0372; Rev 4; 10/97 KIT ATION EVALU E L B A AVAIL Isolated Transformer Driv er for PCMCIA Applications ____________ ________________Features o Transformer Driver for Ultra-Thin 5V-µs Transforme rs o Isolated DC-to-DC Power Supply for PCMCIA Applications o 450kHz Minimum S witching Frequency o Ultra-Low Input Su pply Current Ripple o Single +5V or +3. 3V Supply o 5µW Low-Power Shutdown Mod e o 8-Pin SO and µMAX Packages o Low O utput Ripple Permits Miniature Output C apacitors _______________General Descr iption The MAX845 provides an isolated power supply small enough to fit in thi n PCMCIA cards and space-sensitive appl ications. It drives a low-profile cente r-tapped transformer primary from a 5V or 3.3V DC power supply. The secondary can be wound to provide any isolated po sitive or negative voltage at powers up to 750mW. The MAX845 consists of an os cillator followed by a toggle flip-flop . The flip-flop generates two 50% duty- cycle square waves, which are complementary at half the oscillator.

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MAX845 datasheet
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
VIN 5V
46
SD VCC 1
D1
C1
CR1
MAX845
3
FREQUENCY
SELECT
FS
GND1
2
8
D2
GND2
7
T1
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
________________________________________________________________ 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.

MAX845 datasheet
Isolated Transformer Driver
for PCMCIA Applications
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 ...........................-40°C to +85°C
Storage Temperature Range .............................-65°C to +160°C
Junction Temperature ......................................................+150°C
Lead Temperature (soldering, 10sec) .............................+300°C
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
(VCC = 5V ±10%, TA = TMIN to TMAX, unless otherwise noted. Typical values are at TA = +25°C.)
PARAMETER
Switch On-Resistance
Switch Frequency
Operating Supply Current (Note 1)
Shutdown Supply Current (Note 2)
Shutdown Input Threshold
Shutdown Input Leakage Current
FS Input Threshold
FS Input Current
Minimum Start-Up Voltage
CONDITIONS
D1, D2; 100mA
FS = VCC = 4.5V
FS = VCC = 5.5V
FS = 0V, VCC = 4.5V
FS = 0V, VCC = 5.5V
No load, SD = 0V, FS = VCC
SD = VCC
High
Low
High
Low
FS = 0V
FS = VCC
MIN TYP MAX UNITS
1.5 4.0
450 675 900
550 860 1100
kHz
500
575
1.1 5.0 mA
0.4 µA
2.4
V
0.8
10 pA
2.4
V
0.8
50
µA
10
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 _______________________________________________________________________________________




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