Dual Temperature-Controlled Resistors with

External Temperature Input and Monitors

______________________________________________ Maxim Integrated Products

1

For pricing delivery, and ordering information please contact Maxim/Dallas Direct! at

1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com.

General Description

The DS1857 dual temperature-controlled nonvolatile

(NV) variable resistors with external temperature input

and monitors consists of two 50kΩ 256-position linear

variable resistors, two analog monitor inputs (MON1,

MON2), and an external temperature sensor input. The

device provides an ideal method for setting and tem-

perature-compensating bias voltages and currents in

control applications using minimal circuitry. The vari-

able resistor settings are stored in EEPROM memory

and can be accessed over the 2-wire serial bus.

Applications

Optical Transceivers

Optical Transponders

Instrumentation and Industrial Controls

RF Power Amps

Diagnostic Monitoring

Features

♦ Four Total Monitored Channels (Temperature,

♦ Two External Analog Inputs (MON1, MON2)

♦ Interface to External Temperature Sensor (LM50)

♦ Two 50kΩ, Linear, 256-Position, Nonvolatile

Temperature-Controlled Variable Resistors

♦ Resistor Settings Changeable Every 2°C

♦ Access to Monitoring and ID Information

Configurable with Separate Device Addresses

♦ Resistor Disable (Open-Circuit) Function

♦ 2-Wire Serial Interface

♦ Three Address Lines for Multiple Devices

♦ Operates from a 3.3V or 5V Supply

♦ SFF-8472 Compatible

Ordering Information

Rev 1; 6/04

PART

TEMP RANGE

PIN-PACKAGE

DS1857E-050

-40°C to +95°C 16 TSSOP

DS1857E-050/T&R

-40°C to +95°C

16 TSSOP

(Tape-and-Reel)

DS1857B-050

-40°C to +95°C 16 Ball CSBGA

A

TOP VIEW

B

C

D

1

16-BALL CSBGA (4mm x 4mm)

1.0mm PITCH

16 TSSOP

3

24

EXTTMP

A0

WPEN

RHIZ

MON2

MON1

L0

GND

H1

SCL

A1

L1

H0

SDA

A2

DS1857

SDA

1

2

3

4

5

6

7

8

16

15

14

13

12

11

10

9

SCL

A0

A1

A2

WPEN

RHIZ

GND

H1

L1

H0

L0

EXTTMP

MON2

MON1

Pin Configurations

DS1857

SDA

1

2

3

4

5

6

7

8

16

0.1µF

15

14

13

12

11

10

9

SCL

A0**

A1**

A2**

WPEN

RHIZ

GND

H1

L1

H0

L0

EXTTMP

MON2

MON1

Tx DISABLE

TO EXTERNAL TEMPERATURE

SENSOR, SUCH AS LM50

DIAGNOSTIC

INPUTS

0 TO 2.5V FS

TO LASER BIAS

CONTROL

TO LASER MODULATION

CONTROL

DECOUPLING

CAP

Rx POWER*

Tx BIAS*

*Rx POWER AND Tx BIAS CAN BE ARBITRARILY

ASSIGNED TO THE MON INPUTS.

**ADDRESS INPUTS DETERMINE THE MAIN DEVICE 2-WIRE

SLAVE ADDRESS WHEN ADFIX = 0. THIS ADDRESS MUST BE

DIFFERENT THAN THE AUX DEVICE ADDRESS WHEN ADEN = 0.

4.7kΩ

4.7kΩ

2-WIRE

INTERFACE

GROUND TO

DISABLE WRITE

PROTECT

Typical Operating Circuit