Programmable Resolution 1-Wire Digital Thermometer

www.DataSheet4U.com 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: 3.0V 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 VDD DQ N.C. GND 1 8 AD3 AD2 AD1 AD0 2 7 DS1825 3 6 8-pin mSOP (DS1825U) 5 4 µSOP (DS1825U) PIN DESCRIPTION GND DQ N.C. VDD AD0 to AD3 - Ground - Data In/Out - No Connect - Power Supply Voltage - Address Pins APPLICATIONS 1-Wire is a registered trademark of Dallas Semiconductor. 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. 1 of 21 Rev 020105 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. 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. ABSOLUTE MAXIMUM RATINGS* Voltage on Any Pin Relative to Ground Operating Temperature Range Storage Temperature Range Solder Dip Temperature (10s) Reflow Oven Temperature -0.5V to +6.0V -55°C to +125°C -55°C to +125°C +260°C +220°C These are stress ratings only and functional operation of the device at these or any other conditions above those indicated in the operation sections of this specification is not implied. Exposure to absolute maximum rating conditions for extended periods of time may affect reliability. DC ELECTRICAL CHARACTERISTICS PARAMETER Supply Voltage Pullup Supply Voltage Thermometer Error Programming Resistor: AD0-AD3 DQ Input Logic Low DQ Input Logic High SYMBOL VDD VPU tERR RPGM VIL(DQ) Local Power VIH(DQ) Parasite Power Sink Current Standby Current Active Current DQ Input Current Drift IL IDDS IDD IDQ VI/O = 0.4V VDD = 3.7V CONDITION Local Power Parasite Power Local Power -10°C to +85°C -55°C to +125°C MIN +3.0 +3.0 +3.0 (-55°C to +125°C; VDD= 3.0V to 3.7V) TYP MAX +3.7 +3.7 VDD ±0.5 ±2 10 +0.7 The lower of 3.7 or VDD + 0.3 500 0.65 5 ±0.2 1000 1.5 UNITS V V °C °C kW V V NOTES 1 1, 2 3 12 1, 4, 5 1, 6 0 -0.3 +2.2 +3.0 4.0 mA nA mA µA °C 1 7, 8 9 10 11 NOTES: 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. All voltages are referenced to ground. The Pullup Supply Voltage specification assumes that the pullup device is ideal, and therefore the high level of the pullup is equal to VPU. In order to meet the VIH spec of the DS1825, the actual supply rail for the strong pullup transistor must include margin for the voltage drop across the transistor when it is turned on; thus: VPU_ACTUAL = VPU_IDEAL + VTRANSISTOR. See typical performance curve in Figure 18 Logic low voltages are specified at a sink current of 4mA. To guarantee a presence pulse under low voltage parasite power conditions, VILMAX may have to be reduced to as low as 0.5V. Logic high voltages are specified at a source current of 1mA. Standby current specified up to 70°C. Standby current typically is 3mA at 125°C. To minimize IDDS, DQ should be within the following ranges: GND £ DQ £ GND + 0.3V or VDD - 0.3V £ DQ £ VDD. Active current refers to supply current during active temperature conversions or EEPROM writes. DQ line is high (“hi-Z” state). Drift data is based on a 1000 hour stress test at 125°C. Inputs AD0-AD3 must be tied either High or Low. A "Low" is a connection to the GND terminal. A "High" connection varies with usage of the DS1825. When connected as a parasite powered sensor, a connection to DQ is considered a High. When powered through the VDD pin, a connection to VDD is a High. If left floating, the input values are indeterminate and may be either logical "0" or logical "1." See Figures 20 and 21 for details. When optional programming resistors are used, their maximum values are 10,000W. 2 of 21 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 3.7V) PARAMETER NV Write Cycle Time EEPROM Writes EEPROM Data Retention SYMBOL twr NEEWR tEEDR CONDITION MIN 50k 10 TYP 2 MAX 10 -55°C to +55°C -55°C to +55°C UNITS ms writes years AC ELECTRICAL CHARACTERISTICS PARAMETER Temperature Conversion Time Time to Strong Pullup On Time Slot Recovery Time Write 0 Low Time Write 1 Low Time Read Data Valid Reset Time High Reset Time Low Presence Detect High Presence Detect Low Capacitance: DQ Capacitance: AD0-AD3 SYMBOL tCONV tSPON tSLOT tREC tLOW0 tLOW1 tRDV tRSTH tRSTL tPDHIGH tPDLOW CIN/OUT CIN_AD CONDITION 9-bit resolution 10-bit resolution 11-bit resolution 12-bit resolution Start Convert T Command Issued (-55°C to +125°C; VDD = 3.0V to 3.7V) MIN TYP MAX 93.75 187.5 375 750 10 120 120 15 15 60 240 25 50 UNITS ms ms ms ms µs µs µs µs µs µs µs µs µs µs pF pF NOTES 1 1 1 1 1 1 1 1 1 1 1, 2 1 1 60 1 60 1 480 480 15 60 NOTES: 1. 2. Refer to timing diagrams in Figure 18. Under parasite power, if tRSTL > 960ms, a power on reset may occur. Table 1. DETAILED PIN DESCRIPTIONS PIN 4 2 DQ 1 5 6 7 8 3 VDD AD0 AD1 AD2 AD3 N.C. SYMBOL GND Ground. 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.) Optional VDD pin. VDD must be grounded for operation in parasite power mode. Location Address Input Pin LSB Location Address Input Pin Location Address Input Pin Location Address Input Pin MSB No Connection DESCRIPTION 3 of 21 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. The configuration register allows the user to set the resolution of the temperature-to-digital conversion to 9, 10, 11, or 12 bits. It is also used for the hardwired address programmed by the AD0-AD3 pins. The TH, TL, and configuration registers are NV (EEPROM), so they will retain data when the device is powered down. The DS1825 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 through a 3-state or open-drain port (the DQ pin in the case of the DS1825). In this bus system, the microprocessor (the master device) identifies and addresses devices on the bus using each device’s 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 DS1825 is the ability to operate without an external power supply. Power is instead supplied through the 1-Wire pullup resistor through the DQ pin when the bus is high. The high bus signal also charges an internal capacitor (CPP), which then supplies power to the device when the bus is low. This method of deriving power from the 1-Wire bus is referred to as “parasite power.” As an alternative, the DS1825 can also be powered by an external supply on VDD. Figure 1. DS1825 BLOCK DIAGRAM VPULLUP 4.7k Memory Control Logic DQ Parasite Power Circuit GND Cpp 64-Bit ROM And 1-wire Port VDD Power Supply Sense S C R A T C P A D 16-bit Temp Reg 8-bit TH Register 8-bit TL Register 8-bit CRC Gen 8-bit Config. Reg Address Pin Input Latch AD0-AD3 4 of 21 DS1825 Programmable Resolution 1-Wire Digital Thermometer With 4-Bit ID OPERATION¾MEASURING TEMPERATURE The core functionality of the DS1825 is its dir