Rainbow-electronics DS1721 Manual do Utilizador descarregar pdf (Página 1)

1 of 16 111999

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 150 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

PIN DESCRIPTION

SDA - 2-Wire Serial Data Input/Output

SCL - 2-Wire Serial Clock

GND - Ground

OUT

- 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 1.2 s (MAX) to 150 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.

DS1721

2-Wire Digital Thermomete

and Thermostat

www.dalsemi.com

DS1721U

8-PIN µ-SOP

SDA

SCL

OUT

GND

1 8

2 7

DS1721S

8-Pin SOIC (150-mil)

SDA

SCL

OUT

GND

1 2 3 4 5 6 ... 15 16

Resumo do Conteúdo

Página 1

1 of 16 111999FEATURES Temperature measurements require noexternal components with ±1°C accuracy Measures temperatures from -55°C to+125°C; Fahren

Página 2 - OVERVIEW

DS172110 of 16SLAVE ADDRESSA control byte is the 1st byte received following the START condition from the master device. Thecontrol byte consists of a

Página 3

DS172111 of 16Stop Convert T [22h]This command stops temperature conversion. No further data is required. This command may be used tohalt a DS1721 in

Página 4 - OPERATION-Thermostat Control

DS172112 of 16SAMPLE COMMAND SEQUENCE Table 5Example: After power-up, initiates a temperature conversion, bus master reads temperatureBUS MASTERMODEDS

Página 5 - OPERATION-Programming

DS172113 of 16SAMPLE COMMAND SEQUENCE Table 6Example: Bus master programs the DS1721 for 11-bit conversions in the continuous mode with an activelow s

Página 6 - W bit in

DS172114 of 16ABSOLUTE MAXIMUM RATINGS*Voltage on VDD, Relative to Ground -0.3V to +7.0VVoltage on any other pin, Related to Ground -0.3V to +7.0VOper

Página 7 - 2-WIRE SERIAL DATA BUS

DS172115 of 16DC ELECTRICAL CHARACTERISTICS:DIGITAL THERMOMETER (-55°C to +125°C; 2.7V ≤ VDD ≤ 5.5V)PARAMETER SYMBOL CONDITION MIN TYP MAX UNITS NOTES

Página 8

DS172116 of 16NOTES:1. All voltages are referenced to ground.2. I/O pins of fast mode devices must not obstruct the SDA and SCL lines if VDD is swit

Página 9

DS17212 of 16DETAILED PIN DESCRIPTION Table 1PIN SYMBOL DESCRIPTION1SDAData input/output pin. For 2-wire serial communication port.2SCLClock input/out

Página 10

DS17213 of 16temperature falls below TL. Thus, any hysteresis can be realized for fan control without externalcomponents.Digital data is written to/re

Página 11 - DS1721 COMMAND SET Table 4

DS17214 of 16OPERATION-Measuring TemperatureThe core of DS1721 functionality is its direct-to-digital temperature sensor. The DS1721 measurestemperatu

Página 12

DS17215 of 16The active state for the totem-pole output is programmable by the user. The power-up default of theDS1721 has TH=80°C, TL=75°C, and the o

Página 13

DS17216 of 16R0, R1 = Thermometer Resolution Bits. Table 3 below defines the resolution of the digital thermometer,based on the settings of these two

Página 14

DS17217 of 16If the user does not wish to take advantage of the thermostat capabilities of the DS1721, the 24 bits can beused for general storage of s

Página 15

DS17218 of 16DATA TRANSFER ON 2-WIRE SERIAL BUS Figure 5Figure 6 details how data transfer is accomplished on the two-wire bus. Depending upon the sta

Página 16 - TIMING DIAGRAMS Figure 7

DS17219 of 162-WIRE SERIAL COMMUNICATION WITH DS1721 Figure 6