AD7314

AD7314 Low Voltage, 10-Bit Digital Temperature Sensor in 8-Lead MSOP Data Sheet (REV. A)

Document overview

• Manufacturer or author: Analog Devices, Inc.
• PDF pages: 8

Technical content

a AD7314 Information furnished by Analog Devices is believed to be accurate and reliable. However, no responsibility is assumed by Analog Devices for its use, nor for any infringements of patents or other rights of third parties that may result from its use. No license is granted by implication or otherwise under any patent or patent rights of Analog Devices. Trademarks and registered trademarks are the property of their respective owners. Tel: 781/329-4700 www.analog.com Fax: 781/326-8703 © 2003 Analog Devices, Inc. All rights reserved. REV. A Low Voltage, 10-Bit Digital Temperature Sensor in 8-Lead MSOP FUNCTIONAL BLOCK DIAGRAM AD7314 BAND GAP TEMPERATURE SENSOR SERIAL BUS INTERFACE GND ID VDD CE SCLK SDI SDO 10-BIT ANALOG-TO-DIGITAL CONVERTER TEMPERATURE VALUE REGISTER

FEATURES

10-Bit Temperature-to-Digital Converter –35/H11543C to +85 /H11543C Operating Temperature Range /H115502/H11543C Accuracy SPI ® and DSP Compatible Serial Interface Shutdown Mode Space-Saving MSOP Package

APPLICATIONS

The AD7314 is a complete temperature monitoring system in an 8-lead MSOP package. It contains a band gap temperature sensor and 10-bit ADC to monitor and digitize the temperature reading to a resolution of 0.25 ∞C. The AD7314 has a flexible serial interface that allows easy interfacing to most microcontrollers. The interface is compat- ible with SPI, QSPI™, and MICROWIRE™ protocols and is also compatible with DSPs. The part features a standby mode that is controlled via the serial interface. The AD7314’s low supply current and SPI compatible interface make it ideal for a variety of applications, including personal computers, office equipment, and domestic appliances. PRODUCT HIGHLIGHTS 1. The AD7314 has an on-chip temperature sensor that allows an accurate measurement of the ambient temperature. The measurable temperature range is –35 ∞C to +85∞C, with a ±2∞C temperature accuracy. 2. Supply voltage of 2.65 V to 5.5 V. 3. Space-saving 8-lead MSOP package. 4. 10-bit temperature reading to 0.25 ∞C resolution. 5. The AD7314 features a standby mode that reduces the current consumption to 1 mA max.

REV. A–2– AD7314–SPECIFICATIONS*(TA = TMIN to TMAX, VDD = 2.65 V to 5.5 V, unless otherwise noted.) Parameter Min Typ Max Unit Test Conditions/Comments TEMPERATURE SENSOR AND ADC Accuracy ±2.0 ∞CT A = –35∞C to +85∞C. VDD = 2.65 V to 2.9 V ±1.0 ∞CT A = –35∞C to +85∞C. VDD = 3 V to 5.5 V Resolution 10 Bits Update Rate, tR 400 ms Temperature Conversion Time 25 ms SUPPLIES Supply Voltage 2.65 5.5 V For Specified Performance Supply Current Normal Mode (Inactive) 250 300 mA Part Not Converting, VDD = 2.65 V to 2.9 V 275 mA Part Not Converting, VDD = 3 V to 5.5 V Normal Mode (Active) 1 mA Part Converting, V DD = 2.65 V to 2.9 V 1.2 mA Part Converting, V DD = 3 V to 5.5 V Shutdown Mode 1 mAV DD = 2.65 V to 2.9 V 1 mAV DD = 3 V to 5.5 V Power Dissipation 860 mWV DD = 2.65 V. Using Normal Mode (Auto Conversion) Power Dissipation V DD = 2.65 V. Using Shutdown Mode

1 SPS 3 mW

10 SPS 3.3 mW

100 SPS 6 mW

Input High Voltage, V IH 1.85 V V DD = 2.65 V to 2.9 V Input Low Voltage, V IL 0.53 V V DD = 2.65 V to 2.9 V Input High Voltage, V IH 2.4 V V DD = 3 V to 5.5 V Input Low Voltage, V IL 0.8 V V DD = 3 V to 5.5 V Input Current, IIN ±1 mAV IN = 0 V to VDD Input Capacitance, CIN 10 pF All Digital Inputs DIGITAL OUTPUT Output High Voltage, V OH 2.4 V I SOURCE = ISINK = 200 mA Output Low Voltage, V OL 0.4 V I OL = 200 mA Output Capacitance, C OUT 50 pF *All specifications apply for –35 ∞C to +85∞C, unless otherwise noted. Specifications subject to change without notice. TIMING CHARACTERISTICS1, 2 Parameter Limit Unit Comments t1 0 ns min CE to SCLK Setup Time t2 50 ns min SCLK High Pulse Width t3 50 ns min SCLK Low Pulse Width 4 35 ns max Data Access Time after SCLK Rising Edge t5 20 ns min Data Setup Time prior to SCLK Falling Edge t6 0 ns min Data Hold Time after SCLK Falling Edge t7 0 ns min CE to SCLK Hold Time 4 40 ns max CE to SDO High Impedance NOTES 1Guaranteed by design and characterization, not production tested. 2All input signals are specified with tr = tf = 5 ns (10% to 90% of V DD) and are timed from a voltage level of 1.6 V. 3All specifications apply for –35 ∞C to +85∞C, unless otherwise noted. 4Measured with the load circuit of Figure 2. Specifications subject to change without notice. (TA 3 = TMIN to TMAX, VDD = 2.65 V to 5.5 V, unless otherwise noted. See Figure 1.)

REV. A AD7314 –4– PIN FUNCTION DESCRIPTIONS Pin No. Mnemonic Description 1N CN o Connect. 2C EC hip Enable Input. The device is selected when this input is high. The SCLK input is disabled when this pin is low. 3 SCLK Serial Clock Input. This is the clock input for the serial port. The serial clock is used to clock data out of the temperature value register of the AD7314 and also to clock data into the control register on the part. 4 GND Analog and Digital Ground. 5S DO Serial Data Output. Logic output. Data is clocked out of the temperature value register at this pin. 6 SDI Serial Data Input. Serial data to be loaded to the parts’s control register is provided on this input. 7I D Identification. This pin can be used by a master device to identify the AD7314 in an SPI bus system. This pin has an internal pull-down resistor of 1 k W. 8V DD Positive Supply Voltage, 2.65 V to 5.5 V. PIN CONFIGURATION 8-Lead MSOP TOP VIEW (Not to Scale) NC = NO CONNECT NC SDO CE SCLK GND SDI V DD AD7314 ID

REV. A AD7314 –5– CIRCUIT INFORMATION The AD7314 is a 10-bit digital temperature sensor. The part houses an on-chip temperature sensor, a 10-bit A/D converter, and reference and serial interface logic functions in an MSOP package. The A/D converter section consists of a conventional successive approximation co nverter based around a capacitor DAC. The parts are capable of running on a 2.65 V to 5.5 V power supply. The on-chip temperature sensor allows an accurate measurement of the ambient device tem perature to be made. The working measurement range of the AD7314 is –35 ∞C to +85∞C. CONVERTER DETAILS The conversion clock for the part is internally generated so no external clock is required except when reading from and writing to the serial port. In normal mode, an internal clock oscillator runs the automatic conversion sequence. A conversion is initi- ated every 400 ms. At this time, the part wakes up and performs a temperature conversion. This temperature conversion typically takes 25 ms, at which time the part automatically shuts down. The result of the most recent temperature conversion is avail- able in the serial output register at any time. The AD7314 can be placed in a shutdown mode, via the control register, in which case the on-chip oscillator is shut down and no further conversions are initiated until the AD7314 is taken out of shut- down mode. The conversion result from the last conversion prior to shutdown can still be read from the AD7314 even when it is in shutdown mode. In the automatic conversion mode, every time a read or write operation takes place, the internal clock oscillator is restarted at the end of the read or write operation. The result of the conver- sion is available, typically 25 ms later. Similarly, when the part is taken out of shutdown mode, the internal clock oscillator is restarted and the conversion result is available, typically 25 ms later. Reading from the device again before conversion is com- plete will provide the same set of data. Temperature Value Register The temperature value register is a read-only register that stores the temperature reading from the ADC in 10-bit twos comple- ment format. The temperature data format is shown in Table I. This shows the full theoretical range of the ADC from –128∞C to +127∞C, but in practice the temperature measurement range is limited to the operating temperature range of the device (–35∞C to +85 ∞C). Table I. Temperature Data Format Digital Output Temperature (/H11543C) DB9 . . . DB0 –128 10 0000 0000 –125 10 0000 1100 –100 10 0111 0000 –75 10 1101 0100 –50 11 0011 1000 –25 11 1001 1100 –0.25 11 1111 1111 0 00 0000 0000 0.25 00 0000 0001 10 00 0010 1000 25 00 0110 0100 50 00 1100 1000 75 01 0010 1100 100 01 1001 0000 125 01 1111 0100 127 01 1111 1100 Serial Interface The serial interface on the AD7314 consists of four wires, CE, SCLK, SDI, and SDO. The interface can be operated in 3-wire mode with SDI tied to ground, in which case the interface has read-only capability, with data being read from the data register via the SDO line. The SDI line is used to write the part into standby mode, if required. The CE line is used to select the device when more than one device is connected to the serial clock and data lines. To ensure that the serial port is reset prop- erly after power-up, the CE must be at a logic low before the first serial port access. The serial clock is active only when CE is high. For correct data synchronization, it is important that the CE be low when the serial port is not being accessed. The part operates in a slave mode and requires an externally applied serial clock to the SCLK input to access data from the data register. The serial interface on the AD7314 is designed to allow the part to be interfaced to systems that provide a serial clock that is synchronized to the serial data, such as the 80C51, 87C51, 68HC11, 68HC05, and PIC16Cxx microcontrollers as well as DSP processors. A read operation from the AD7314 accesses data from the temperature value register while a write op eration to the part writes data to the control register. Input data is not loaded into the control register until the rising edge of the 15th SCLK cycle. Data on the SDI line is latched in on the falling edge of the serial clock while data is updated on the SDO line on the rising edge of the serial clock. Read Operation Figure 3 shows the interface diagram for a serial read from the AD7314. The CE line enables the SCLK input. A leading zero and 10 bits of data are transferred during a read operation. Read operations occur during streams of 16 clock pulses. Output data is updated on the rising edge of SCLK. The serial data is accessed in a number of bytes if 10 bits of data are being read. At the end of the read operation, the SDO line remains in the state of the last bit of data clocked out of the AD7314 until CE returns low, at which time the SDO line goes into three-state.

REV. A–8– C02414–0–10/03(A) AD7314 8-Lead Mini Small Outline Package [MSOP] (RM-8) Dimensions shown in millimeters 0.80 0.60 0.40 8/H11543 0/H11543 4.90 BSC PIN 1

0.65 BSC

3.00 BSC SEATING PLANE 0.15 0.00 0.38 0.22

1.10 MAX

3.00 BSC COPLANARITY 0.10 0.23 0.08 COMPLIANT TO JEDEC STANDARDS MO-187AA

Revision History

10/03—Data Sheet changed from REV. 0 to REV. A. OUTLINE DIMENSIONS