DS1822 DS1822 Econo 1-Wire Digital Thermometer BENEFITS AND FEATURES PIN ASSIGNMENT Unique 1-Wire Interface Requires Only One DALLAS Port Pin for Communications NC 1 8 NC 1822 o Can Be Powered from Data Line NC 2 7 NC o Power-Supply Range is 3.0V to 5.5V 1 2 3 V 3 6 NC Reduced Component Count with Integrated DD Temperature Sensor and Interface DQ 4 5 GND o Requires No External Components o Measures temperatures from -55C to 8-Pin 150mil SO +125C (-67F to +257F) (DS1822Z) o 2.0C Accuracy from -10C to +85C o Thermometer Resolution is User-Selectable from 9 to 12 Bits o Converts Temperature to 12-Bit Digital Word in 750ms (max) Simplifies Distributed Temperature Sensing with Multidrop Capability 1 2 3 o Each Device Has a Unique 64-Bit Serial Code Stored in an On-Board Device (BOTTOM VIEW) o Flexible, User-Definable Nonvolatile TO-92 (NV) Alarm Settings with Alarm Search (DS1822) Command Identifies Devices with Temperatures Outside Programmed Limits PIN DESCRIPTION o Software compatible with the DS18B20 GND - Ground Applications Include Thermostatic Controls, DQ - Data In/Out Industrial Systems, Consumer Products, V - Power Supply Voltage DD Thermometers, or Any Thermally Sensitive NC - No Connect System DESCRIPTION The DS1822 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 DS1822 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 55C to +125C and is accurate to 2.0C over the range of 10C to +85C. In addition, the DS1822 can derive power directly from the data line (parasite power), eliminating the need for an external power supply. Each DS1822 has a unique 64-bit serial code, which allows multiple DS1822s to function on the 1-Wire bus thus, it is simple to use one microprocessor to control many DS1822s distributed over a large area. Applications that can benefit from this feature include HVAC environmental controls, temperature monitoring systems inside buildings, equipment or machinery, and process monitoring and control systems. 1-Wire is a registered trademark of Maxim Integrated Products, 1 of 21 042815 Inc. GND DQ V DDDS1822 ORDER INFORMATION ORDERING PACKAGE DESCRIPTION NUMBER MARKING DS1822 1822 DS1822 in 3-pin TO92 DS1822/T&R 1822 DS1822 in 3-pin TO92, 2000 Piece Tape-and-Reel DS1822+ 1822 (See Note) DS1822 in Lead-Free 3-pin TO92 DS1822+T&R 1822 (See Note) DS1822 in Lead-Free 3-pin TO92, 2000 Piece Tape-and- Reel DS1822Z DS1822 DS1822 in 150 mil 8-pin SO DS1822Z/T&R DS1822 DS1822 in 150 mil 8-pin SO, 2500 Piece Tape-and-Reel DS1822Z+ DS1822 (See Note) DS1822 in Lead-Free 150 mil 8-pin SO DS1822Z+T&R DS1822 (See Note) DS1822 in Lead-Free 150 mil 8-pin SO, 2500 Piece Tape-and-Reel Note: A + symbol will also be marked on the package. DETAILED PIN DESCRIPTIONS Table 1 8-PIN SO* TO-92 SYMBOL DESCRIPTION 5 1 GND Ground. 4 2 DQ Data Input/Output pin. Open-drain 1-Wire interface pin. Also provides power to the device when used in parasite power mode (see Parasite Power section). 3 3 V Optional V pin. V must be grounded for operation in DD DD DD parasite power mode. *All pins not specified in this table are No Connect pins. OVERVIEW Figure 1 shows a block diagram of the DS1822, and pin descriptions are given in Table 1. The 64-bit ROM stores the devices 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 (T and T ), and the 1-byte configuration H L register. The configuration register allows the user to set the resolution of the temperature-to-digital conversion to 9, 10, 11, or 12 bits. The T , T and configuration registers are NV (EEPROM), so they will H L retain data when the device is powered down. The DS1822 uses Dallas exclusive 1-Wire bus protocol that implements bus communication using one control signal. The control line requires a weak pullup resistor since all devices are linked to the bus via a 3-state or open-drain port (the DQ pin in the case of the DS1822). In this bus system, the microprocessor (the master device) identifies and addresses devices on the bus using each devices unique 64-bit code. Because each device has a unique code, the number of devices that can be addressed on one bus is virtually unlimited. The 1-Wire bus protocol, including detailed explanations of the commands and time slots, is covered in the 1-WIRE BUS SYSTEM section of this data sheet. Another feature of the DS1822 is the ability to operate without an external power supply. Power is instead supplied through the 1-Wire pullup resistor via the DQ pin when the bus is high. The high bus signal also charges an internal capacitor (C ), which then supplies power to the device when the bus is low. This PP method of deriving power from the 1-Wire bus is referred to as parasite power. As an alternative, the DS1822 may also be powered by an external supply on V . DD 2 of 21