DS1721U+ datasheet, PDF - EEWORLD Datasheet

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DS1721U+: DescriptionOn-board mounted temperature sensors Digital Thermometer & Thermostat; CategoryThe sensor Sensor/transducer; File Size255KB，17 Pages; ManufacturerMaxim; Websitehttps://www.maximintegrated.com/en.html; Environmental Compliance

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DS1721U+ Overview

On-board mounted temperature sensors Digital Thermometer & Thermostat

DS1721U+ Parametric

Parameter Name	Attribute value
Is it lead-free?	Lead free
Is it Rohs certified?	conform to
package instruction	TSSOP8,.19
Reach Compliance Code	compliant
ECCN code	EAR99
Factory Lead Time	6 weeks
Maximum accuracy (Celsius)	1 Cel
body width	3 mm
body height	1.1 mm
Body length or diameter	3 mm
shell	PLASTIC
JESD-609 code	e3
Installation features	SURFACE MOUNT
Number of digits	12
Number of terminals	8
Maximum working current	1.25 mA
Maximum operating temperature	125 °C
Minimum operating temperature	-55 °C
Output interface type	2-WIRE INTERFACE
Package body material	PLASTIC/EPOXY
Encapsulate equivalent code	TSSOP8,.19
Package Shape/Form	SQUARE
power supply	3/5 V
Sensor/Transducer Type	TEMPERATURE SENSOR,SWITCH/DIGITAL OUTPUT,SERIAL
Maximum supply voltage	5.5 V
Minimum supply voltage	2.7 V
surface mount	YES
Terminal surface	Matte Tin (Sn)
Termination type	SOLDER
Base Number Matches	1

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DS1721

2-Wire Digital Thermometer

and Thermostat

www.maxim-ic.com

FEATURES

Temperature measurements require no

external components with ±1°C accuracy

Measures temperatures from -55°C to

+125°C; Fahrenheit equivalent is -67°F to

+257°F

Temperature resolution is configurable from 9

to 12 (default) bits (0.5°C to 0.0625°C

resolution)

Maximum conversion time (9-bit resolution)

of 93.75 ms

Thermostatic settings are user-definable

Data is read/written via a 2-wire serial

interface (open drain I/O lines); 3-bit

addressability

Wide power supply range (2.7V - 5.5V)

Applications include personal computers,

cellular telephones, office equipment, or any

thermally sensitive system

8-pin, 150-mil SOIC package and 8-pin µSOP

package

PIN ASSIGNMENT

SDA

SCL

OUT

GND

SDA

SCL

OUT

GND

DS1721S

8-Pin SOIC (150-mil)

DS1721U

8-Pin µ-SOP

PIN DESCRIPTION

SDA

SCL

GND

OUT

- 2-Wire Serial Data Input/Output

- 2-Wire Serial Clock

- Ground

- Thermostat Output Signal

- Chip Address Input

- Power Supply Voltage (+5V)

DESCRIPTION

The DS1721 2-Wire Digital Thermometer and Thermostat provides 12-bit temperature readings, which

indicate the temperature of the device. Thermostatic settings and temperature readings are all

communicated to/from the DS1721 over a simple 2-wire serial interface. No additional components are

required; the device is truly a “temperature-to-digital” converter.

The DS1721 has three address bits that allow a user to multidrop up to eight sensors along the 2-wire bus,

greatly simplifying the bussing of distributed temperature sensing networks.

The thermal alarm output, T

OUT

, is active when the temperature of the device exceeds a user-defined

temperature TH. The output remains active until the temperature is equal to or below the user-defined

temperature TL, allowing for any hysteresis necessary. The active state of T

OUT

is configurable by the

user.

For applications that require faster conversion times, the user can adjust the readout resolution from 12 to

9 bits, effectively reducing the conversion time from 750ms (MAX) to 93.75 ms (MAX). This is

particularly useful in applications where temperature changes large magnitudes very rapidly.

Applications for DS1721 include personal computers/services, cellular telephones, office equipment, or

any microprocessor-based, thermally sensitive system.

1 of 17

110405

DS1721

OPERATION-Measuring Temperature

The core of DS1721 functionality is its direct-to-digital temperature sensor. The DS1721 measures

temperature through the use of an on-chip temperature measurement technique with an operation range

from -55°C to +125°C. The device can be configured to perform continuous conversions with the most

recent result being stored in the thermometer register. The device can also be configured to perform a

single conversion, store the result, and return to a standby mode. Regardless of the mode used, the digital

temperature is retrieved from the temperature register using the Read Temperature (AAh) command, as

described in detail in the “Command Set” section. The DS1721 power-up default has the sensor set to

automatically perform 12-bit conversions continuously once the Start Convert T (51h) command is

issued. Details on how to change the settings after power-up are contained in the “OPERATION-

Programming” section.

The resolution of the temperature conversion can be configured as 9, 10, 11, or 12 bits, with 12-bit

readings as the default state. This equates to a temperature resolution of 0.5°C, 0.25°C, 0.125°C, or

0.0625°C. Following each conversion thermal data is stored in the thermometer register in two’s

complement format; the information can be retrieved over the 2-wire interface by issuing a Read

Temperature (AAh) command. Table 2 describes the exact relationship of output data to measured

temperature. The table assumes the DS1721 is configured for 12-bit resolution; if the device is configured

in a lower resolution mode, insignificant bits will contain zeros. The data is transmitted serially over the

2-wire serial interface, MSb first. The MSb of the temperature register contains the “sign” (S) bit,

denoting whether the temperature is positive or negative. For Fahrenheit usage, a lookup table or

conversion routine must be used.

TEMPERATURE/DATA RELATIONSHIPS

Table 2

MSb

-1

-2

TEMP

+125°C

+25.0625°C

+10.125°C

+0.5°C

+0°C

-0.5°C

-10.125°C

-25.0625°C

-55°C

-3

(UNIT = °C)

-4

LSb

MSB

LSB

DIGITAL OUTPUT

(Binary)

0111 1101 0000 0000

0001 1001 0001 0000

0000 1010 0010 0000

0000 0000 1000 0000

0000 0000 0000 0000

1111 1111 1000 0000

1111 0101 1110 0000

1110 0110 1111 0000

1100 1001 0000 0000

DIGITAL OUTPUT

(Hex)

7D00h

1910h

0A20h

0080h

0000h

FF80h

F5E0h

E6F0h

C900h

OPERATION-Thermostat Control

In its operating mode, the DS1721 functions as a thermostat with programmable hysteresis, as shown in

Figure 2. The thermostat output updates as soon as a temperature conversion is complete. When the

DS1721’s temperature meets or exceeds the value stored in the high temperature trip register (TH), the

output becomes active, and will stay active until the temperature is equal to or below the temperature

stored in the low temperature trigger register (TL). In this way, any amount of hysteresis may be

obtained.

4 of 17

DS1721

The active state for the totem-pole output is programmable by the user. The power-up default of the

DS1721 has TH=80°C, TL=75°C, and the output state active high. Refer to the “OPERATION-

Programming” section for instructions in adjusting the thermostat setpoints and T

COM

active state.

THERMOSTAT OUTPUT OPERATION

Figure 2

OPERATION-Programming

There are two areas of interest in programming the DS1721: the Configuration/Status register and the

thermostat setpoints. All programming is done via the 2-wire interface using the protocols discussed in

the “Command Set” section.

Configuration/Status Register Programming

The configuration/status register is accessed via the Access Config (ACh) function command. Writing to

or reading from the register is determined by the R/

bit of the 2-wire control byte (See “2-wire Serial

Data Bus” section). Data is read from or written to the configuration register MSb first. The format of the

below along with the power-up state of the bit and its ability to be read or written to. The entire register is

volatile and will always power-up in the default state. Therefore, it is recommended that the user issue

any configuration programming commands immediately after power is cycled, before any other

commands are issued.

CONFIGURATION/STATUS REGISTER

Figure 3

DONE

MSb

POL

1SHOT

LSb

1SHOT

= Temperature Conversion Mode. If 1SHOT is "1", the DS1721 will perform and store one

temperature conversion upon reception of the Start Convert T (51h) command. If 1SHOT is "0", the

DS1721 will continuously perform temperature conversions and store the last completed result in the

Thermometer Register. The user has read/write access to the bit and the power-up default state is "0"

(continuous mode).

POL

= TCOM Polarity Bit. If POL is "1", the active state of the TCOM output will be high. A "0" stored

in this location sets the thermostat output to an active low state. The user has read/write access to the

POL bit, and the power-up default state is "1" (active high).

= Undefined. This bit is used internally by the DS1721. It will be a "0" at power-up and will change to

a "1" once the Start Convert T [51h] command is issued. This is a “Don’t Care” on a write; i.e. The

DS1721 will ignore writes to this location.

5 of 17

DS1721U+ Related Products

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Description	On-board mounted temperature sensors Digital Thermometer & Thermostat	Board Mount Temperature Sensors Digital Thermometer & Thermostat	Board Mount Temperature Sensors Digital Thermometer & Thermostat	Board Mount Temperature Sensors Digital Thermometer & Thermostat	On-board mounted temperature sensors Digital Thermometer & Thermostat	On-board mounted temperature sensors Digital Thermometer & Thermostat	On-board mounted temperature sensors Digital Thermometer & Thermostat
Is it lead-free?	Lead free	-	-	-	Lead free	Lead free	Lead free
Is it Rohs certified?	conform to	-	-	-	conform to	conform to	conform to
package instruction	TSSOP8,.19	-	-	-	SOP8,.25	SOP8,.25	TSSOP8,.19
Reach Compliance Code	compliant	-	-	-	compliant	compliant	compliant
ECCN code	EAR99	-	-	-	EAR99	EAR99	EAR99
Factory Lead Time	6 weeks	-	-	-	6 weeks	6 weeks	6 weeks
Maximum accuracy (Celsius)	1 Cel	-	-	-	1 Cel	1 Cel	1 Cel
body width	3 mm	-	-	-	3.91 mm	3.91 mm	3 mm
body height	1.1 mm	-	-	-	1.395 mm	1.395 mm	1.1 mm
Body length or diameter	3 mm	-	-	-	4.88 mm	4.88 mm	3 mm
shell	PLASTIC	-	-	-	PLASTIC	PLASTIC	PLASTIC
JESD-609 code	e3	-	-	-	e3	e3	e3
Installation features	SURFACE MOUNT	-	-	-	SURFACE MOUNT	SURFACE MOUNT	SURFACE MOUNT
Number of digits	12	-	-	-	12	12	12
Number of terminals	8	-	-	-	8	8	8
Maximum working current	1.25 mA	-	-	-	1.25 mA	1.25 mA	1.25 mA
Maximum operating temperature	125 °C	-	-	-	125 °C	125 °C	125 °C
Minimum operating temperature	-55 °C	-	-	-	-55 °C	-55 °C	-55 °C
Output interface type	2-WIRE INTERFACE	-	-	-	2-WIRE INTERFACE	2-WIRE INTERFACE	2-WIRE INTERFACE
Package body material	PLASTIC/EPOXY	-	-	-	PLASTIC/EPOXY	PLASTIC/EPOXY	PLASTIC/EPOXY
Encapsulate equivalent code	TSSOP8,.19	-	-	-	SOP8,.25	SOP8,.25	TSSOP8,.19
Package Shape/Form	SQUARE	-	-	-	RECTANGULAR	RECTANGULAR	SQUARE
power supply	3/5 V	-	-	-	3/5 V	3/5 V	3/5 V
Sensor/Transducer Type	TEMPERATURE SENSOR,SWITCH/DIGITAL OUTPUT,SERIAL	-	-	-	TEMPERATURE SENSOR,SWITCH/DIGITAL OUTPUT,SERIAL	TEMPERATURE SENSOR,SWITCH/DIGITAL OUTPUT,SERIAL	TEMPERATURE SENSOR,SWITCH/DIGITAL OUTPUT,SERIAL
Maximum supply voltage	5.5 V	-	-	-	5.5 V	5.5 V	5.5 V
Minimum supply voltage	2.7 V	-	-	-	2.7 V	2.7 V	2.7 V
surface mount	YES	-	-	-	YES	YES	YES
Terminal surface	Matte Tin (Sn)	-	-	-	Matte Tin (Sn)	Matte Tin (Sn)	Matte Tin (Sn)
Termination type	SOLDER	-	-	-	SOLDER	SOLDER	SOLDER
Base Number Matches	1	-	-	-	1	1	1

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