Rainbow Electronics DS1631 User Manual

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SC

SDA

SC

SDA

DS1631

±0.5°C Accuracy Digital Thermomete

and Thermostat

FEATURES

§ Temperature measurements require no

external components

§ Measures temperatures from -55°C to +125°C

(-67°F to +257°F)

§ ±0.5°C accuracy over a range of 0°C to

+70°C

§ Output resolution is user-selectable to 9, 10,

11, or 12 bits

§ Wide power-supply range (2.7V to 5.5V)

§ Converts temperature to digital word in

750ms (max)

§ Multidrop capability simplifies distributed

temperature-sensing applications

§ Thermostatic settings are user-definable and

nonvolatile (NV)

§ Data is read/written through a 2-wire serial

interface (SDA and SCL pins)

§ Applications include thermostatic controls,

industrial systems, consumer products,
thermometers, or any thermally sensitive
system

§ Available in 8-pin SO (150mil) and mSOP

packages

PIN ASSIGNMENT

DS1631Z

7

6

T

OUT

GND

2

L

3

DS1631Z—8-pin SO (150mil)

D1631

7

6

T

OUT

GND

2

L

3

DS1631U—mSOP

PIN DESCRIPTION

SDA - Open-Drain Data I/O
SCL - Clock Input
T
GND - Ground
V
A
A
A

- Thermostat Output

OUT

- Power Supply (2.7V to 5.5V)

DD

- Address Input

0

- Address Input

1

- Address Input

2

V

DD

A

0

A

1

A

2

V

DD

A

0

A

1

A

2

DESCRIPTION

The DS1631 digital thermometer and thermostat provides 9-, 10-, 11-, or 12-bit digital temperature
readings over a range of -55°C to +125°C. The thermometer accuracy is ±0.5°C from 0°C to +70°C with

3.0V £ V
The thermostat output (T
thermostat trip point (T

£ 5.5V. The thermostat provides custom hysteresis with user-defined trip points (TH and TL).

DD

) becomes active when the temperature of the device exceeds the upper

OUT

), and remains active until the temperature drops below the lower thermostat trip

H

point (TL).

The T

and TL registers and thermometer configuration settings are stored in NV EEPROM so the

H

DS1631 can be programmed prior to installation. Communication with the DS1631 is achieved through a
standard 2-wire serial interface.

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DETAILED PIN DESCRIPTION Table 1

A

A

A1A2A

0

OU

PIN SYMBOL DESCRIPTION

1SDAData input/output pin for 2-wire serial communication port. Open drain.
2SCLClock input pin for 2-wire serial communication port.
3T

OUT

4 GND
5A
6A
7A

2

1

0

Thermostat output pin. Push-pull.
Ground pin.
Address input pin.
Address input pin.
Address input pin.

8VDDSupply Voltage. 2.7V to 5.5V input power pin.

DS1631 FUNCTIONAL BLOCK DIAGRAM Figure 1

DS1631

V

GND

SCL

SD

ADDRESS

AND

I/O CONTROL

CONFIGURATION REGISTER

ND CONTROL LOGIC

TEMPERATURE SENSOR

TH REGISTER

REGISTER

T

L

DIGITAL

COMPARATOR/LOGIC

DS1631 REGISTER SUMMARY Table 2

REGISTER

NAME

Temperature (Read Only) 2 bytes SRAM Measured temperature in two’s complement

T

H

T

L

Configuration (Read/

USER

ACCESS

(Read/
Write)

(Read/
Write)

Write, but
some bits are
Read Only—

see Table 5)

SIZE MEMORY

TYPE

REGISTER CONTENTS

AND POWER-UP/POR STATE

format.
Power-up/POR state: -60ºC (1100 0100
0000 0000)

2 bytes EEPROM Upper alarm trip point in two’s complement

format.
Power-up/POR state: user defined.

2 bytes EEPROM Lower alarm trip point in two’s

complement format.
Power-up/POR state: user defined.

1 byte SRAM and

EEPROM

Configuration and status information.
Unsigned data.
6 MSbs = SRAM
2 LSbs (POL and 1SHOT bits) = EEPROM
Power-up/POR state: 100011XX (XX =
User defined)

T

T

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DS1631

OVERVIEW

The DS1631 measures temperature using a bandgap-based temperature sensor. A delta-sigma analog-to­digital converter (ADC) converts the measured temperature to a 9-, 10-, 11-, or 12-bit (user-selectable)
digital value that is calibrated in degrees centigrade; for Fahrenheit applications a lookup table or
conversion routine must be used. The DS1631 also provides thermostat capability with user­programmable NV trip-point registers. Communication with the DS1631 is achieved through a standard
2-wire serial interface.

Detailed DS1631 pin descriptions are provided in Table 1 and user-accessible registers are summarized in
Table 2.

Note: The DS1631 is software- and pin-compatible with DS1621. This compatibility covers all
functions/commands described in the DS1621 data sheet including access to the Count_Remain and
Count_Per_C registers for high-resolution temperature calculations based on the legacy dual-oscillator
architecture. Refer to Application Note 176 Using the DS1631 in DS1621 Applications for more
information.

OPERATION—MEASURING TEMPERATURE

The DS1631 can be programmed to take continuous temperature measurements (continuous conversion
mode) or to take single temperature measurements on command (one-shot mode). The measurement
mode is programmed through the 1SHOT bit in the configuration register: 1SHOT = 1—one-shot mode;
1SHOT = 0—continuous conversion mode. The 1SHOT bit is stored in NV EEPROM, so it can be
programmed prior to installation if desired. In continuous conversion mode, when a Start Convert T
command is issued, the DS1631 will perform consecutive temperature measurements until a Stop Convert
T command is issued. In one-shot mode, the Start Convert T command causes one temperature
measurement to be taken, then the DS1631 returns to a low-power idle state. One-shot mode is
recommended for use in power-sensitive applications.

The resolution of the DS1631 digital temperature data is user-configurable to 9, 10, 11, or 12 bits,
corresponding to temperature increments of 0.5°C, 0.25°C, 0.125°C, and 0.0625°C, respectively. The
default resolution at power-up is 12 bits, and it can be changed through the R0 and R1 bits in the
configuration register as explained in the CONFIGURATION REGISTER section of this data sheet. Note
that the conversion time doubles for each additional bit of resolution.

After each temperature measurement and analog-to-digital conversion, the DS1631 stores the temperature
as a 16-bit two’s complement number in the 2-byte temperature register (see Figure 2). The sign bit (S)
indicates if the temperature is positive or negative: for positive numbers S = 0 and for negative numbers S
= 1. The Read Temperature command provides user access to the temperature register.

Bits 3 through 0 of the temperature register are hardwired to 0. When the DS1631 is configured for 12-bit
resolution, the 12 MSbs (bits 15 through 4) of the temperature register will contain temperature data. For
11-bit resolution, the 11 MSbs (bits 15 through 5) of the temperature register will contain data, and bit 4
will read out as 0. Likewise, for 10-bit resolution, the 10 MSbs (bits 15 through 6) will contain data, and
for 9-bit the 9 MSbs (bits 15 through 7) will contain data, and all unused LSbs will contain 0s. Table 3
gives examples of 12-bit resolution digital output data and the corresponding temperatures.

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TEMPERATURE, TH, and TL REGISTER FORMAT Figure 2

bit 15 bit 14 bit 13 bit 12 bit 11 bit 10 bit 9 bit 8

MS Byte

LS Byte

S2

bit 7 bit 6 bit 5 bit 4 bit 3 bit 2 bit 1 bit 0

-1

2

6

-2

2

5

2

-3

2

4

2

-4

2

3

2

2

2

1

2

0000

12-BIT RESOLUTION TEMPERATURE/DATA RELATIONSHIP Table 3

DS1631

0

2

TEMPERATURE

(°C)

DIGITAL OUTPUT

(BINARY)

DIGITAL OUTPUT

(HEX)

[phone] 0000 7D00h

+25.0625 0001 1001 0001 0000 1910h

+10.125 0000 1010 0010 0000 0A20h

+0.5 0000 0000 1000 0000 0080h

0 0000 0000 0000 0000 0000h

-0.5 1111 1111 1000 0000 FF80h

-10.125 1111 0101 1110 0000 F5E0h

-25.0625 1110 0110 1111 0000 E6F0h

-55 1100 1001 0000 0000 C900h

OPERATION—THERMOSTAT FUNCTION

The DS1631 thermostat output (T
updated value until the next conversion completes. T
defined upper and lower trip points. When the measured temperature meets or exceeds the value stored in
the upper trip-point register (TH), T
below the value stored in the lower trip-point register (TL) (see Figure 3). This allows the user to program
any amount of hysteresis into the output response. The active state of T
the polarity bit (POL) in the configuration register: POL = 1—T
active low.

) is updated after every temperature conversion, and remains at the

OUT

is activated and deactivated based on user-

OUT

will become active and stay active until the temperature falls

OUT

is user-programmable through

OUT

is active high; POL = 0—T

OUT

OUT

is

The user-defined values in the T

and TL registers (see Figure 2) must be in two’s complement format

H

with the MSb (bit 15) containing the sign bit (S). The resolution of the TH and TL values is determined by
the R0 and R1 bits in the configuration register (see Table 4), so the TH and TL resolution will match the
output temperature resolution. For example, for 10-bit resolution bits 5 through 0 of the TH and T
registers will read out as 0 (even if 1s are written to these bits), and the converted temperature will be
compared to the 10 MSbs of TH and TL.

The TH and TL registers and the POL bit are stored in EEPROM; therefore, they are NV and can be
programmed prior to installation of the DS1631. Writing to and reading from the T

, TL, and

H

configuration registers is achieved using the Access TH, Access TL, and Access Config commands.

Another thermostat feature is the temperature high and low flags (THF and TLF) in the configuration
register. These bits provide a record of whether the temperature has been greater than TH or less than T
at anytime since the DS1631 was powered up. If the temperature ever exceeds the TH register value, the
THF bit in the configuration register will be set to 1, and if the temperature ever falls below the T

value,

L

the TLF bit in the configuration register will be set to 1. Once THF and/or TLF has been set, it will
remain set until over-written with a 0 by the user or until the power is cycled.

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L

L

THERMOSTAT OUTPUT OPERATION Figure 3

b

b

b

b

b

b

g

DS1631

Lo

ic 1

Logic 0

POL=1 (T

T

L

is active high)

OUT

T

OUT

T

H

Temp

CONFIGURATION REGISTER

The configuration register allows the user to program various DS1631 options such as conversion
resolution, T

polarity, and operating mode. It also provides information to the user about conversion

OUT

status, EEPROM activity, and thermostat activity. The configuration register is arranged as shown in
Figure 4 and detailed descriptions of each bit are provided in Table 5. This register can be read from and
written to using the Access Config command. Note that the POL and 1SHOT bits are stored in EEPROM
and all other configuration register bits are SRAM.

CONFIGURATION REGISTER Figure 4

MSb

it 6

it 5

it 4

it 3

it 2

it 1 LSb

DONE THF TLF NVB R1 R0 POL* 1SHOT*

*NV (EEPROM)

RESOLUTION CONFIGURATION Table 4

R1 R0 RESOLUTION CONVERSION

0 0 9-bit 93.75ms

0 1 10-bit 187.5ms

1 0 11-bit 375ms

1 1 12-bit 750ms

START, STOP, AND ACK SIGNALS Figure 5

SDA

SCL

TIME (MAX)

START

Condition

5 of 14

ACK (or NACK)

From Receiver

STOP

Condition