Rainbow Electronics DS1857 User Manual

DS1857

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 tem­perature-compensating bias voltages and currents in
control applications using minimal circuitry. The vari­able 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,

VCC, MON1, MON2)

♦ 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 0; 1/03

PART

PIN-PACKAGE

DS1857E-050

16 TSSOP

DS1857E-050/T&R

16 TSSOP
(Tape-and-Reel)

DS1857B-050

16 Ball CSBGA

A

TOP VIEW

B

C

D

1

16-BALL CSBGA (4mm x 4mm)

1.0mm PITCH

16 TSSOP

324

EXTTMP

A0WPENRHIZ

MON2MON1L0GND

H1V

CC

SCLA1

L1H0SDAA2

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

V

CC

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

V

CC

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.

V

CC

V

CC

VCC = 3.3V

4.7kΩ4.7kΩ

2-WIRE

INTERFACE

GROUND TO

DISABLE WRITE

PROTECT

Typical Operating Circuit

TEMP RANGE

-40°C to +95°C

-40°C to +95°C

-40°C to +95°C

DS1857

Dual Temperature-Controlled Resistors with
External Temperature Input and Monitors

2 _____________________________________________________________________

PARAMETER

SYMBOL

CONDITIONS MIN

TYP

MAX

UNITS

Supply Voltage V

CC

(Note 1) +3.0 5.5 V

Input Logic 1 (SDA, SCL, A2, A1, A0,
WPEN, RHIZ)

V

IH

(Note 2)

V

Input Logic 0 (SDA, SCL, A2, A1, A0,
WPEN, RHIZ)

V

IL

(Note 2) -0.3

V

Resistor Inputs (L0, L1, H0, H1) -0.3

V

Resistor Current I

RES

-3 +3 mA

ABSOLUTE MAXIMUM RATINGS

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.

Voltage on VCCRelative to Ground.......................-0.5V to +6.0V

Voltage on Inputs Relative

to Ground* ................................................-0.5V to V

CC

+ 0.5V

Voltage on Resistor Inputs Relative

to Ground* ................................................-0.5V to V

CC

+ 0.5V

Current into Resistors............................................................5mA

Operating Temperature Range ...........................-40°C to +95°C

Programming Temperature Range .........................0°C to +70°C

Storage Temperature Range .............................-55°C to +125°C

Soldering Temperature .......................................See IPC/JEDEC

J-STD-020A Specification

RECOMMENDED DC OPERATING CONDITIONS

(TA= -40°C to +95°C, unless otherwise noted.)

PARAMETER

CONDITIONS

UNITS

Supply Current I

CC

(Note 3) 1 2 mA

Input Leakage I

IL

-1 +1 µA

Input Current each I/O Pin 0.4 x V

CC

< V

I/O

< 0.9 x V

CC

µA

V

OL1

3mA sink current 0 0.4

Low-Level Output Voltage (SDA)

V

OL2

6mA sink current 0 0.6

V

Full-Scale Input (MON1, MON2) (Note 4)

V

Full-Scale VCC Monitor (Note 5)

V

I/O Capacitance C

I/O

10 pF

WPEN Pullup Resistor R

WPEN

40 65 100 kΩ

RHIZ Pullup Resistor R

RHIZ

40 65 100 kΩ

Digital Power-On Reset POD

2.2 V

Analog Power-On Reset POA

2.6 V

DC ELECTRICAL CHARACTERISTICS

(VCC= 3.0V to 5.5V, TA= -40°C to +95°C, unless otherwise noted.)

*Not to exceed 6.0V.

0.7 x Vcc VCC + 0.3

0.3 x V

VCC + 0.3

CC

SYMBOL

MIN TYP MAX

-10 +10

2.4875 2.5000 2.5125

6.5208 6.5536 6.5864

1.0

2.0

DS1857

Dual Temperature-Controlled Resistors with

External Temperature Input and Monitors

_____________________________________________________________________ 3

PARAMETER

SYMBOL

CONDITIONS

MIN

TYP

MAX

UNITS

EXTTMP Input Voltage

V

Conversion Resolution

625 µV

Conversion Accuracy

(Note 9)

mV

EXTERNAL TEMPERATURE

(VCC= 3.0V to 5.5V, TA= -40°C to +95°C, unless otherwise noted.)

PARAMETER

CONDITIONS

UNITS

Input Resolution

µV

Supply Resolution ∆V

CC

1.6 mV

Input/Supply Accuracy A

CC

% FS

(full scale)

Update Rate for MON1, MON2,
Temp, or V

CC

t

frame

20 30 ms

ANALOG VOLTAGE MONITORING

(VCC= 3.0V to 5.5V, TA= -40°C to +95°C, unless otherwise noted.)

PARAMETER

CONDITIONS

UNITS

Position 00h Resistance TA = +25°C

1.0

kΩ

Position FFh Resistance TA = +25°C 40 50 60 kΩ

Absolute Linearity (Note 6) -2 +2 LSB

Relative Linearity (Note 7) -1 +1 LSB

Temperature Coefficient (Note 8) 50

ppm/°C

High-Z Resistor Current I

RHIZ

R

HIZ

= V

CC

0.1 µA

ANALOG RESISTOR CHARACTERISTICS

(VCC= 3.0V to 5.5V, TA= -40°C to +95°C, unless otherwise noted.)

SYMBOL

SYMBOL

∆VMON 610

MIN TYP MAX

0.70

MIN TYP MAX

0.25 0.5

1.25

V

EXTTMP

∆V

EXTTMP

V

EXTTMP

1.779

12.8

DS1857

Dual Temperature-Controlled Resistors with
External Temperature Input and Monitors

4 _____________________________________________________________________

PARAMETER

CONDITIONS

UNITS

Fast mode (Note 10) 0 400

SCL Clock Frequency f

SCL

Standard mode (Note 10) 0 100

kHz

Fast mode (Note 10) 1.3

Bus Free Time Between STOP and
START Condition

t

BUF

Standard mode (Note 10) 4.7

µs

Fast mode (Notes 10, 11) 0.6

Hold Time (Repeated)
START Condition

Standard mode (Notes 10, 11) 4.0

µs

Fast mode (Note 10) 1.3

Low Period of SCL Clock t

LOW

Standard mode (Note 10) 4.7

µs

Fast mode (Note 10) 0.6

High Period of SCL Clock t

HIGH

Standard mode (Note 10) 4.0

µs

Fast mode (Notes 10, 12, 13) 0 0.9

Data Hold Time

Standard mode (Notes 10, 12, 13) 0

µs

Fast mode (Note 10)

Data Setup Time

Standard mode (Note 10)

ns

Fast mode (Note 10) 0.6

Start Setup Time

Standard mode (Note 10) 4.7

µs

Fast mode (Note 13)

300

Rise Time of Both SDA and SCL
Signals

t

F

Standard mode (Note 13)

ns

Fast mode (Note 13)

300

Fall Time of Both SDA and SCL
Signals

t

R

Standard mode (Note 13)

300

ns

Fast mode 0.6

Setup Time for STOP Condition

Standard mode 4.0

µs

Capacitive Load for Each Bus Line

C

B

(Note 13) 400 pF

EEPROM Write Time t

W

(Note 14) 10 ms

AC ELECTRICAL CHARACTERISTICS

(VCC= 3.0V to 5.5V, TA= -40°C to +95°C, unless otherwise noted.)

Note 1: All voltages are referenced to ground.

Note 2: I/O pins of fast-mode devices must not obstruct the SDA and SCL lines if V

CC

is switched off. The address inputs should be

connected to either V

CC

or GND depending on the desired address setting.

Note 3: SDA and SCL are connected to V

CC

and all other input signals are connected to well-defined logic levels.

Note 4: The maximum voltage the MON inputs will read is approximately 2.5V, even if the voltage on the inputs is greater than 2.5V.

Note 5: This voltage is defining the maximum range of the analog-to-digital converter and not the maximum V

CC

voltage.

Note 6: Absolute linearity is the difference of measured value from expected value at DAC position. The expected value is a

straight line from measured minimum position to measured maximum position.

Note 7: Relative linearity is the deviation of an LSB DAC setting change vs. the expected LSB change. The expected LSB change

is the slope of the straight line from measured minimum position to measured maximum position.

Note 8: See the Typical Operating Characteristics.

Note 9: The conversion accuracy does not include any error from the LM50.

Note 10: A fast-mode device can be used in a standard-mode system, but the requirement t

SU:DAT

> 250ns must then be met. This
is automatically the case if the device does not stretch the LOW period of the SCL signal. If such a device does stretch the
LOW period of the SCL signal, it must output the next data bit to the SDA line t

RMAX

+ t

SU:DAT

= 1000ns + 250ns = 1250ns

before the SCL line is released.

SYMBOL

MIN TYP MAX

t

HD:STA

t

HD:DAT

t

SU:DAT

t

SU:STA

t

SU:STO

100

250

20 + 0.1C

20 + 0.1C

20 + 0.1C

20 + 0.1C

B

B

B

B

1000

DS1857

Dual Temperature-Controlled Resistors with

External Temperature Input and Monitors

_____________________________________________________________________ 5

AC ELECTRICAL CHARACTERISTICS (continued)

(VCC= 3.0V to 5.5V, TA= -40°C to +95°C, unless otherwise noted.)

Note 11: After this period, the first clock pulse is generated.

Note 12: The maximum t

HD:DAT

only to has be met if the device does not stretch the LOW period (t

LOW

) of the SCL signal.

Note 13: A device must internally provide a hold time of at least 300ns for the SDA signal (see the V

IH MIN

of the SCL signal) in order

to bridge the undefined region of the falling edge of SCL.

Note 14: C

B

—total capacitance of one bus line, timing referenced to 0.9 x VCCand 0.1 x VCC.

Note 15: EEPROM write begins after a STOP condition occurs.

Typical Operating Characteristics

(VCC= 5.0V, TA= +25°C, unless otherwise noted.)

SUPPLY CURRENT vs. TEMPERATURE

DS1857 toc01

TEMPERATURE (°C)

SUPPLY CURRENT (µA)

806040200-20

540

580

620

660

700

500

-40 100

SUPPLY CURRENT vs. VOLTAGE

DS1857 toc02

VOLTAGE (V)

SUPPLY CURRENT (µA)

5.04.54.03.5

450

500

550

600

650

700

400

3.0 5.5

RESISTANCE vs. SETTING

DS1857 toc03

SETTING

RESISTANCE (kΩ)

25020015010050

10

20

30

40

50

60

0

0 300

ACTIVE SUPPLY CURRENT

vs. SCL FREQUENCY

DS1857 toc04

SCL FREQUENCY (kHz)

ACTIVE SUPPLY CURRENT (µA)

300200100

540

580

620

660

700

500

0 400

SDA = 5V

DS1857

Dual Temperature-Controlled Resistors with
External Temperature Input and Monitors

6 _____________________________________________________________________

Typical Operating Characteristics (continued)

(VCC= 5.0V, TA= +25°C, unless otherwise noted.)

RESISTOR 0 INL (LSB)

DS1857 toc05

POSITION

RESISTOR 0 INL (LSB)

225200150 17550 75 100 12525

-0.4

-0.3

-0.2

-0.1

0

0.1

0.2

0.3

0.4

0.5

-0.5
0 250

RESISTOR 0 DNL (LSB)

DS1857 toc06

RESISTOR 0 DNL (LSB)

-0.15

-0.05

0.05

0.15

0.25

-0.25

POSITION

225200150 17550 75 100 125250 250

RESISTOR 1 INL (LSB)

DS1857 toc07

POSITION

RESISTOR 1 INL (LSB)

225200150 17550 75 100 12525

-0.4

-0.3

-0.2

-0.1

0

0.1

0.2

0.3

0.4

0.5

-0.5
0 250

RESISTOR 1 DNL (LSB)

DS1857 toc08

RESISTOR 1 DNL (LSB)

-0.15

-0.05

0.05

0.15

0.25

-0.25

POSITION

225200150 17550 75 100 125250 250

EXTERNAL TEMP SENSOR VOLTAGE

vs. TEMPERATURE

DS1857 toc09

VOLTAGE (V)

TEMPERATURE (°C)

1.51.00.5

-20

0

20

40

60

80

100

120

140

-40

0 2.0

PPM vs. POSITION

DS1857 toc10

POSITION

ppm/°C

25020050 100 150

-10

40

90

140

190

240

290

340

-60

0 300

+25°C TO +85°C

+25°C TO -40°C

DS1857

Dual Temperature-Controlled Resistors with

External Temperature Input and Monitors

_____________________________________________________________________ 7

Detailed Description

The user can read the registers that monitor the VCC,
MON1, MON2, and temperature analog signals. After
each signal conversion, a corresponding bit is set that
can be monitored to verify that a conversion has
occurred. The signals also have alarm flags that notify
the user when the signals go above or below the user­defined value. Interrupts can also be set for each signal.

The position values of each resistor can be indepen­dently programmed. The user can assign a unique
value to each resistor for every 2°C increment over the

-40°C to +102°C range. Both resistors can also be put
in a high-impedance mode using the RHIZ pin.

An external temperature sense input, EXTTMP, con­verts an analog voltage into a digital value that repre­sents temperature. Its scale is defined by +10mV/°C
gain and +500mV offset at 0°C. This corresponds to the
characteristics of the LM50 temperature sensor. The
resistor look-up tables are stepped through according
to this temperature every 2°C from -40°C to +102°C.

PIN

BALL

NAME

FUNCTION

1B2SDA 2-Wire Serial Data Interface. This pin is for serial data transfer to and from the device.

2A2SCL 2-Wire Serial Clock Interface. The serial clock input is used to clock data into and out of the device.

3C3A0Address Input. The address input pins specify the 2-wire address of the device (when ADFIX = 0).

4A1A1Address Input. The address input pins specify the 2-wire address of the device (when ADFIX = 0).

5B1A2Address Input. The address input pins specify the 2-wire address of the device (when ADFIX = 0).

6C2

Write Protect Enable. The device is not write protected if WPEN is connected to ground. This pin has

an internal pullup (R

WPEN

) (See Table 6).

7C1

Supply Ground

8D1

Resistor Disable Input. When high, this signal places both resistors in an off state or high impedance
mode. When low, the resistors are on. This pin has an internal pullup (R

RHIZ

).

9D3

External Analog Input

10 D4

External Analog Input

11 C4

External Temperature Input. This analog signal is converted into a digital value that represents a

temperature. The digitized value indexes through the look-up tables.

12 D2 L0

Low-End Resistor 0 Terminal. It is not required that the low-end terminals be connected to a potential

less than the high-end terminal of the corresponding resistor. Voltage applied to any of the resistor

terminals cannot exceed the power-supply voltage, VCC, or go below ground.

13 B3 H0

High-End Resistor 0 Terminal. It is not required that the high-end terminals be connected to a

potential greater than the low-end terminal of the corresponding resistor. Voltage applied to any of the

resistor terminals cannot exceed the power-supply voltage, VCC, or go below ground.

14 B4 L1 Low-End Resistor 1 Terminal

15 A4 H1 High-End Resistor 1 Terminal.

16 A3 V

CC

Supply Voltage

Pin Descriptions

WPEN

GND

RHIZ

MON1

MON2

EXTTMP