MAX253 Datasheet, PDF (1/16 Pages) Maxim Integrated Products – Transformer Driver for Isolated RS-485 Interface

19-0226; Rev 0; 1/94
Transformer Driver for
Isolated RS-485 Interface
_______________General Description
The MAX253 is a monolithic oscillator/power-driver,
specifically designed to provide isolated power for an
isolated RS-485 or RS-232 data interface. It
drives a center-tapped transformer primary from a 5V
or 3.3V DC power supply. The secondary can be
wound to provide any isolated voltage needed at power
levels up to 1W.
The MAX253 consists of a CMOS oscillator driving a
pair of N-channel power switches. The oscillator runs
at double the output frequency, driving a toggle flip-flop
to ensure 50% duty cycle to each of the switches.
Internal delays are arranged to ensure break-before-
make action between the two switches.
The SD pin puts the entire device into a low-power
shutdown state, disabling both the power switches and
oscillator.
________________________Applications
Isolated RS-485/RS-232 Power-Supply
Transformer Driver
High Noise-Immunity Communications Interface
Isolated and/or High-Voltage Power Supplies
Bridge Ground Differentials
Medical Equipment
Process Control
____________________________Features
o Power-Supply Transformer Driver for Isolated
RS-485/RS-232 Data-Interface Applications
o Single +5V or +3.3V Supply
o Low-Current Shutdown Mode: 0.4µA
o Pin-Selectable Frequency: 350kHz or 200kHz
o 8-Pin DIP, SO, and µMAX Packages
______________Ordering Information
PART
TEMP. RANGE
PIN-PACKAGE
MAX253CPA
0°C to +70°C
8 Plastic DIP
MAX253CSA
0°C to +70°C
8 SO
MAX253CUA
0°C to +70°C
8 µMAX
MAX253C/D
0°C to +70°C
Dice*
MAX253EPA
-40°C to +85°C
8 Plastic DIP
MAX253ESA
-40°C to +85°C
8 SO
MAX253EUA
-40°C to +85°C
8 µMAX
MAX253MJA
-55°C to +125°C 8 CERDIP**
* Contact factory for dice specifications.
**Contact factory for availability and processing to MIL-STD-883.
__________Typical Operating Circuit
ON / OFF
VIN 5V
4
6
SD
VCC
1
D1
MAX253
3
FREQUENCY
SWITCH
FS
GND1
2
8
D2
GND2
7
C1
OUTPUT
5V @ 200mA
C3
C2
__________________Pin Configuration
TOP VIEW
D1 ₁
GND1 2
FS 3
SD 4
MAX253
8 D2
7 GND2
6 VCC
5 N.C.
DIP/SO/µMAX
________________________________________________________________ Maxim Integrated Products 1
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