_______________General Description

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.

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

♦♦ Power-Supply Transformer Driver for 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

______________Ordering Information

Transformer Driver for

Isolated RS-485 Interface

________________________________________________________________

Maxim Integrated Products

1

MAX253

D1

D2

FS

GND1

GND2

1

8

46

27

3

SD

FREQUENCY

SWITCH

C3

C1

C2

5V @ 200mA

OUTPUT

5V

ON / OFF

__________Typical Operating Circuit

19-0226; Rev 2; 4/10

For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642,

or visit Maxim’s website at www.maxim-ic.com.

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

MAX253ESA/V

-40°C to +85°C

8 SO

MAX253MJA

-55°C to +125°C

8 CERDIP**

*

Contact factory for dice specifications.

**

Contact factory for availability and processing to MIL-STD-883.

Devices are also available in a lead(Pb)-free/RoHS-compliant

package. Specify lead-free by adding a (+) to the part number

when ordering.

/V Denotes an automotive qualified part.

µMAX is a registered trademark of Maxim Integrated Products, Inc.