Datasheet AD7814 (Analog Devices) - 7

AD7814 AD7814* 8051* AD7814* ADSP-21xx* SCLK P3.1 SCLK SCK DOUT P3.0 DOUT DR DIN P1.2 DIN DT CS P1.3 CS RFS TFS *ADDITIONAL PINS OMITTED FOR CLARITY
Figure 4. AD7814 to 8051 Interface
*ADDITIONAL PINS OMITTED FOR CLARITY AD7814 to PIC16C6x/7x Interface
Figure 6. AD7814 to ADSP-21xx Interface Figure 5 shows an interface circuit between the AD7814 and the PIC16C6x/7x microcontroller. The PIC16C6x/7x synchronous
MOUNTING THE AD7814
serial port (SSP) is configured as an SPI master with the clock The AD7814 can be used for surface or air temperature sensing polarity bit set to a logic one. In this mode, the serial clock line applications. If the device is cemented to a surface with ther- of the PIC16C6x/7x idles high between data transfers. Data is mally conductive adhesive, the die temperature will be within transferred to and from the AD7814 in two 8-bit serial data about 0.1°C of the surface temperature, thanks to the device’s operations. In the example shown, port line RA1 is being used low power consumption. Care should be taken to insulate the to generate the CS for the AD7814. back and leads of the device from the air, if the ambient air temperature is different from the surface temperature being measured.
AD7814* PIC16C6x/7x*
The ground pin provides the best thermal path to the die, so the
SCLK SCK
temperature of the die will be close to that of the printed circuit
DOUT SDO
ground track. Care should be taken to ensure that this is in good
DIN SDI
thermal contact with the surface being measured.
CS RA1
As with any IC, the AD7814 and its associated wiring and cir- cuits must be kept free from moisture to prevent leakage and
*ADDITIONAL PINS OMITTED FOR CLARITY
corrosion, particularly in cold conditions where condensation is Figure 5. AD7814 to PIC16C6x/7x Interface more likely to occur. Water-resistant varnishes and conformal coatings can be used for protection. The small size of the
AD7814 to ADSP-21xx Interface
Figure 6 shows an interface between the AD7814 and the AD7814 package allows it to be mounted inside sealed metal ADSP-21xx DSP processor. To ensure correct operation of the probes, which provide a safe environment for the device. interface, the SPORT control register should be set up as follows:
SUPPLY DECOUPLING
TFSW = RFSW = 1, Alternate Framing The AD7814 should be decoupled with a 0.1 µF ceramic INVRFS = INVTFS = 1, Active Low Framing Signal capacitor between VDD and GND. This is particularly important DTYPE = 00, Right Justify Data if the AD7814 is mounted remotely from the power supply. SLEN = 1111, 16-Bit Data Words ISCLK = 1, Internal Serial Clock
1.0
TFSR = RFS = 1, Frame Every Word IRFS = 0, RFS Configured As Input
0.8
ITFS = 1, TFS Configured As Output The interface requires an inverter between the SCLK line of the
0.6
ADSP-21xx and the SCLK input of the AD7814. The ADSP-
0.4
21xx has the TFS and RFS of the SPORT tied together with TFS set as an output and RFS set as an input. The DSP operates
0.2
in alternate framing mode and the SPORT control register is set up as described earlier.
TEMPERATURE ERROR 0 –0.2 –0.4 –55 –40 0 25 40 85 100 120 TEMPERATURE –
ⴗ
C
Figure 7. Typical Temperature Error REV. E –7– Document Outline FEATURES FUNCTIONAL BLOCK DIAGRAM GENERAL DESCRIPTION PRODUCT HIGHLIGHTS SPECIFICATIONS TIMING CHARACTERISTICS ABSOLUTE MAXIMUM RATINGS ORDERING GUIDE PIN FUNCTION DESCRIPTIONS PIN CONFIGURATIONS CIRCUIT INFORMATION CONVERTER DETAILS TEMPERATURE VALUE REGISTER SERIAL INTERFACE Read Operation Write Operation MICROPROCESSOR INTERFACING AD7814 to MC68HC11 Interface AD7814 to 8051 Interface AD7814 to PIC16C6x/7x Interface AD7814 to ADSP-21xx Interface MOUNTING THE AD7814 SUPPLY DECOUPLING OUTLINE DIMENSIONS Revision History