Datasheet

ManualsBrandsMAXIM INTEGRATED ManualsPMICsDS1825U+

1 of 21 Rev 020105

FEATURES

§ Unique 1-Wire

Interface Requires Only One

Port Pin for Communication

§ Each Device has a Unique 64-Bit Serial Code

Stored in an On-Board ROM

§ Multidrop Capability Simplifies Distributed

Temperature-Sensing Applications

§ 4 Pin-Programmable Bits to Uniquely Identify

Up to 16 Sensor Locations on a Bus

§ Requires No External Components

§ Can be Powered from Data Line. Power Supply

Range: 3.0V to 3.7V

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

(-67°F to +257°F)

§ ±0.5°C Accuracy from -10°C to +85°C

§ Thermometer Resolution is User-Selectable

from 9 to 12 Bits

§ Converts Temperature to 12-Bit Digital Word in

750ms (max)

§ User-Definable (NV) Alarm Settings

§ Alarm Search Command Identifies and

Addresses Devices Whose Temperature is

Outside of Programmed Limits (Temperature

Alarm Condition)

§ Available in 8-Pin mSOP Package

§ Software Compatible with the DS1822

PIN ASSIGNMENT

PIN DESCRIPTION

GND - Ground

DQ - Data In/Out

N.C. - No Connect

- Power Supply Voltage

AD0 to AD3 - Address Pins

APPLICATIONS

Thermostatic Controls

Industrial Systems

Consumer Products

Thermometers

Thermally-Sensitive Systems

DESCRIPTION

The DS1825 digital thermometer provides 9 to 12-bit centigrade temperature measurements and has an alarm

function with NV user-programmable upper and lower trigger points. The DS1825 communicates over a 1-Wire bus

that by definition requires only one data line (and ground) for communication with a central microprocessor. It has

an operating temperature range of -55°C to +125°C and is accurate to ±0.5°C over the range of -10°C to +85°C. In

addition, the DS1825 can derive power directly from the data line (“parasite power”), eliminating the need for an

external power supply.

ORDERING INFORMATION

ORDERING NUMBER PACKAGE MARKING DESCRIPTION

DS1825U 1825 8-pin µSOP

DS1825U/T&R 1825 8-pin µSOP Tape-and-Reel

DS1825U+ 1825 (See Note 1)

8-pin mSOP, Lead Free

DS1825U+T&R 1825 (See Note 1) 8-pin µSOP Tape-and-Reel, Lead Free

Note 1: Additionally, a "+" symbol will be marked on the package.

DS1825

Programmable Resolution 1-Wire

Digital Thermometer With 4-Bit ID

www.maxim

ic.com

GND

N.C.

8-pin

SOP

(

DS1825U

)

DS1825

µSOP

(DS1825U)

1-Wire is a registered trademark of Dallas Semiconductor.

Summary of content (21 pages)

PAGE 1
DS1825 Programmable Resolution 1-Wire Digital Thermometer With 4-Bit ID www.maxim-ic.com FEATURES § § § § § § § § § § § § § § Unique 1-WireÒ Interface Requires Only One Port Pin for Communication Each Device has a Unique 64-Bit Serial Code Stored in an On-Board ROM Multidrop Capability Simplifies Distributed Temperature-Sensing Applications 4 Pin-Programmable Bits to Uniquely Identify Up to 16 Sensor Locations on a Bus Requires No External Components Can be Powered from Data Line. Power Supply Range: 3.
PAGE 2
DS1825 Programmable Resolution 1-Wire Digital Thermometer With 4-Bit ID DESCRIPTION (cont.) Each DS1825 has a unique 64-bit serial code, which allows multiple DS1825s to function on the same 1-Wire bus; thus, it is simple to use one microprocessor to control many DS1825s distributed over a large area. In addition, the 4-bit location address can be used to identify specific temperature sensors in the system without requiring a wide lookup table.
PAGE 3
DS1825 Programmable Resolution 1-Wire Digital Thermometer With 4-Bit ID AC ELECTRICAL CHARACTERISTICS: NV MEMORY (-55°C to +100°C; VDD = 3.0V to 3.
PAGE 4
DS1825 Programmable Resolution 1-Wire Digital Thermometer With 4-Bit ID OVERVIEW Figure 1 shows a block diagram of the DS1825, and pin descriptions are given in Table 1. The 64-bit ROM stores the device’s unique serial code. The scratchpad memory contains the 2-byte temperature register that stores the digital output from the temperature sensor. In addition, the scratchpad provides access to the 1-byte upper and lower alarm trigger registers (TH and TL), and the 1-byte configuration register.
PAGE 5
DS1825 Programmable Resolution 1-Wire Digital Thermometer With 4-Bit ID OPERATION¾MEASURING TEMPERATURE The core functionality of the DS1825 is its direct-to-digital temperature sensor. The resolution of the temperature sensor is user-configurable to 9, 10, 11, or 12 bits, corresponding to increments of 0.5°C, 0.25°C, 0.125°C, and 0.0625°C, respectively. The default resolution at power-up is 12-bit.
PAGE 6
DS1825 Programmable Resolution 1-Wire Digital Thermometer With 4-Bit ID Figure 3. TH AND TL REGISTER FORMAT bit 7 S bit 6 2 6 bit 5 2 5 bit 4 2 bit 3 5 2 5 bit 2 2 2 bit 1 2 1 bit 0 20 Only bits 11 through 4 of the temperature register are used in the TH and TL comparison since TH and TL are 8-bit registers. If the measured temperature is lower than or equal to TL or higher than or equal to TH, an alarm condition exists and an alarm flag is set inside the DS1825.
PAGE 7
DS1825 Programmable Resolution 1-Wire Digital Thermometer With 4-Bit ID Figure 4. SUPPLYING THE PARASITE-POWERED DS1825 DURING TEMPERATURE CONVERSIONS VPU DS1825 Microprocessor GND DQ VDD VPU 4.7K To Other 1-Wire Devices 1-Wire Bus Figure 5. POWERING THE DS1825 WITH AN EXTERNAL SUPPLY DS1825 VPU Microprocessor VDD (External Supply) GND DQ VDD 4.7K To Other 1-Wire Devices 1-Wire Bus 64-BIT LASERED ROM CODE Each DS1825 contains a unique 64-bit code (see Figure 6) stored in ROM.
PAGE 8
DS1825 Programmable Resolution 1-Wire Digital Thermometer With 4-Bit ID Byte 8 of the scratchpad is read-only and contains the cyclic redundancy check (CRC) code for bytes 0 through 7 of the scratchpad. The DS1825 generates this CRC using the method described in the CRC GENERATION section. Data is written to bytes 2, 3, and 4 of the scratchpad using the Write Scratchpad [4Eh] command; the data must be transmitted to the DS1825 starting with the least significant bit of byte 2.
PAGE 9
DS1825 Programmable Resolution 1-Wire Digital Thermometer With 4-Bit ID Table 4. THERMOMETER RESOLUTION CONFIGURATION R1 R0 Resolution 0 0 9-bit Max Conversion Time 93.75ms (tCONV/8) 0 1 10-bit 187.5ms (tCONV/4) 1 0 11-bit 375ms (tCONV/2) 1 1 12-bit 750ms (tCONV) CRC GENERATION th CRC bytes are provided as part of the DS1825’s 64-bit ROM code and in the 9 byte of the scratchpad memory.
PAGE 10
DS1825 Programmable Resolution 1-Wire Digital Thermometer With 4-Bit ID HARDWARE CONFIGURATION The 1-Wire bus has by definition only a single data line. Each device (master or slave) interfaces to the data line through an open-drain or 3-state port. This allows each device to “release” the data line when the device is not transmitting data so the bus is available for use by another device.
PAGE 11
DS1825 Programmable Resolution 1-Wire Digital Thermometer With 4-Bit ID SEARCH ROM [F0h] When a system is initially powered up, the master must identify the ROM codes of all slave devices on the bus, which allows the master to determine the number of slaves and their device types. The master learns the ROM codes through a process of elimination that requires the master to perform a Search ROM cycle (i.e.
PAGE 12
DS1825 Programmable Resolution 1-Wire Digital Thermometer With 4-Bit ID READ SCRATCHPAD [BEh] This command allows the master to read the contents of the scratchpad. The data transfer starts with the least th significant bit of byte 0 and continues through the scratchpad until the 9 byte (byte 8: CRC) is read. The master may issue a reset to terminate reading at any time if only part of the scratchpad data is needed.
PAGE 13
DS1825 Programmable Resolution 1-Wire Digital Thermometer With 4-Bit ID Figure 11.
PAGE 14
DS1825 Programmable Resolution 1-Wire Digital Thermometer With 4-Bit ID Figure 12.
PAGE 15
DS1825 Programmable Resolution 1-Wire Digital Thermometer With 4-Bit ID SUGGESTED PROCEDURE FOR BUILDING CROSS-REFERENCE TABLE This procedure uses the Search ROM command to find all DS1825s on the one-wire bus (16 maximum) and then reads each configuration register to match the ROMIDs to the hard-wired addresses.
PAGE 16
DS1825 Programmable Resolution 1-Wire Digital Thermometer With 4-Bit ID 1-Wire SIGNALING The DS1825 uses a strict 1-Wire communication protocol to insure data integrity. Several signal types are defined by this protocol: reset pulse, presence pulse, write 0, write 1, read 0, and read 1. All of these signals, with the exception of the presence pulse, are initiated by the bus master.
PAGE 17
DS1825 Programmable Resolution 1-Wire Digital Thermometer With 4-Bit ID Figure 15.
PAGE 18
DS1825 Programmable Resolution 1-Wire Digital Thermometer With 4-Bit ID Figure 16. DETAILED MASTER READ 1 TIMING VPU VIH of Master 1-WIRE BUS GND TINT > 1 ms TRC Master samples 15 ms Figure 17. RECOMMENDED MASTER READ 1 TIMING VPU VIH of Master 1-WIRE BUS GND Master samples TINT = TRC = small small 15 ms LINE TYPE LEGEND Bus master pulling low Resistor pullup DS1825 OPERATION EXAMPLE In this example there are multiple DS1825s on the bus and they are using parasite power.
PAGE 19
DS1825 Programmable Resolution 1-Wire Digital Thermometer With 4-Bit ID Figure 18. TYPICAL PERFORMANCE CURVE Error, Degrees Centigrade 1 +3σ 0 -3σ -1 -10 0 10 20 30 40 50 60 Temperature, Degrees Centigrade Figure 19.
PAGE 20
DS1825 Programmable Resolution 1-Wire Digital Thermometer With 4-Bit ID Figure 20. ADDRESS PROGRAMMING DIAGRAM, VDD POWERED 1-Wire Bus DQ VDD VDD GND AD0 AD1 AD2 AD3 Location 0 ADO = GND AD1 = GND AD2 = GND AD3 = GND VDD DQ VDD GND AD0 AD1 AD2 AD3 VDD DQ VDD GND AD0 AD1 AD2 AD3 VDD DQ VDD GND AD0 AD1 AD2 AD3 Note: AD0-AD3 cannot float, each pin must be tied to either VDD or GND.
PAGE 21
DS1825 Programmable Resolution 1-Wire Digital Thermometer With 4-Bit ID Figure 21. ADDRESS PROGRAMMING DIAGRAM, PARASITE POWERED 1-Wire Bus DQ VDD GND DQ VDD GND DQ VDD GND DQ VDD GND AD0 AD1 AD2 AD3 AD0 AD1 AD2 AD3 AD0 AD1 AD2 AD3 AD0 AD1 AD2 AD3 Note: AD0-AD3 cannot float, each pin must be tied to either VDD or GND.