Slave Address

The slave address of the MAX6602 is 9Ah or 1001 101.

PC Board Layout

Follow these guidelines to reduce the measurement

error when measuring remote temperature:

1) Place the MAX6602 as close as is practical to the

remote diode. In noisy environments, such as a com-

puter motherboard, this distance can be 4in to 8in

(typ). This length can be increased if the worst noise

sources are avoided. Noise sources include CRTs,

clock generators, memory buses, and PCI buses.

2) Do not route the DXP-DXN lines next to the deflec-

tion coils of a CRT. Also, do not route the traces

across fast digital signals, which can easily intro-

duce +30°C error, even with good filtering.

3) Route the DXP and DXN traces in parallel and in

close proximity to each other. Each parallel pair of

traces should go to a remote diode. Route these

traces away from any higher voltage traces, such as

+12VDC. Leakage currents from PC board contami-

nation must be dealt with carefully since a 20M

Ω

leakage path from DXP to ground causes about

+1°C error. If high-voltage traces are unavoidable,

connect guard traces to GND on either side of the

DXP-DXN traces (Figure 5).

4) Route through as few vias and crossunders as possi-

ble to minimize copper/solder thermocouple effects.

5) Use wide traces when practical. 5-mil to 10-mil

traces are typical. Be aware of the effect of trace

resistance on temperature readings when using

long, narrow traces.

6) When the power supply is noisy, add a resistor (up

to 47

Twisted-Pair and Shielded Cables

Use a twisted-pair cable to connect the remote sensor

for remote-sensor distances longer than 8in or in very

noisy environments. Twisted-pair cable lengths can be

between 6ft and 12ft before noise introduces excessive

errors. For longer distances, the best solution is a

shielded twisted pair like that used for audio micro-

phones. For example, Belden #8451 works well for dis-

tances up to 100ft in a noisy environment. At the

device, connect the twisted pair to DXP and DXN and

the shield to GND. Leave the shield unconnected at the

remote sensor. For very long cable runs, the cable’s

parasitic capacitance often provides noise filtering, so

the 2200pF capacitor can often be removed or reduced

in value. Cable resistance also affects remote-sensor

accuracy. For every 1

Ω of series resistance, the error is

approximately +1/2°C.

Five-Channel Precision Temperature Monitor

16

______________________________________________________________________________________

5 mils to 10 mils

5 mils to 10 mils

5 mils to 10 mils

MINIMUM

5 mils to 10 mils

GND

DXP

DXN

GND

Figure 5. Recommended DXP-DXN PC Board Traces. The two

outer guard traces are recommended if high-voltage traces will

be near the DXN and DXP traces.