Transformer Driver for Isolated RS-485 Interface
Transformer Driver for
Isolated RS-485 Interface MAX253 General Description Benefits and Features The MAX253 monolithic oscillator/power-driver is
specifically designed to provide isolated power for an
isolated RS-485 or RS-232 data interface. The device
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. • Simple Power-Supply Transformer Driver Design for 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 flipflop to ensure 50% duty cycle to each of the switches.
Internal delays are arranged to ensure break-beforemake action between the two switches. Isolated RS-485/RS-232 Data-Interface Applications
• Single 5V or 3.3V Supply
• Low-Current Shutdown Mode: 0.4µA
• Pin-Selectable Frequency: 350kHz or 200kHz
• 8-Pin DIP, SO, and µMAX® Packages Take Minimal
Board Space Ordering Information
PART
MAX253CPA TEMP RANGE
0°C to +70°C PIN-PACKAGE
8 Plastic DIP The SD pin puts the entire device into a low-power
shutdown state, disabling both the power switches and
oscillator. MAX253CSA 0°C to +70°C 8 SO MAX253CUA 0°C to +70°C 8 µMAX MAX253C/D 0°C to +70°C Dice* Applications MAX253EPA -40°C to +85°C 8 Plastic DIP MAX253ESA -40°C to +85°C 8 SO MAX253ESA/V -40°C to +85°C 8 SO MAX253MJA -55°C to +125°C 8 CERDIP** Isolated RS-485/RS-232 Power-Supply
Transformer Driver …
