ADT7316ARQZ1 View Datasheet(PDF) - Analog Devices

Part Name

Description

MFG CO.

ADT7316ARQZ1

±0.5°C Accurate Digital Temperature Sensor and Quad Voltage Output 12-/10-/8-Bit DACs

Analog Devices 

LAYOUT CONSIDERATIONS

Digital boards can be electrically noisy environments, and

care must be taken to protect the analog inputs from noise,

particularly when measuring the very small voltages from a

remote diode sensor. Take the following precautions:

• Place the ADT7316/ADT7317/ADT7318 as close as

possible to the remote sensing diode. Provided that the

worst noise sources, such as clock generators, data/address

buses, and CRTs are avoided, this distance can be 4 inches

to 8 inches.

• Route the D+ and D− tracks close together, in parallel, with

grounded guard tracks on each side. Provide a ground

plane under the tracks if possible.

• Use wide tracks to minimize inductance and reduce noise

pickup. A 10 mil track minimum width and spacing is

recommended.

GND

D+

D–

GND

10 MIL

10 MIL

10 MIL

10 MIL

10 MIL

10 MIL

10 MIL

Figure 61. Arrangement of Signal Tracks

ADT7316/ADT7317/ADT7318

• Try to minimize the number of copper/solder joints, which

can cause thermocouple effects. Where copper/ solder joints

are used, make sure that they are in both the D+ and D−

paths and at the same temperature. Thermocouple effects

should not be a major problem as 1°C corresponds to about

240 μV, and thermocouple voltages are about 3 μV/°C of

the temperature difference. Unless there are two thermo-

couples with a big temperature differential between them,

thermocouple voltages should be much less than 200 mV.

• Place 0.1 μF bypass and 2200 pF input filter capacitors

close to the ADT7316/ADT7317/ADT7318.

• If the distance to the remote sensor is more than 8 inches,

the use of the twisted pair cable is recommended. This

works for distances from 6 feet to 12 feet.

• For really long distances (up to 100 feet), use shielded twisted

pair, such as Belden #8451 microphone cable. Connect the

twisted pair to D+ and D− and the shield to GND close to

the ADT7316/ADT7317/ADT7318. Leave the remote end

of the shield unconnected to avoid ground loops.

• Because the measurement technique uses switched current

sources, excessive cable and/or filter capacitance can affect

the measurement. When using long cables, the filter capacitor

may be reduced or removed.

Cable resistance can also introduce errors. Series resistance

of 1 Ω introduces about 0.5°C error.

Rev. B | Page 41 of 44

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