MCP98243 datasheet(45/62 Pages) MICROCHIP

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DS22153C-page 45

MCP9843/98243

6.0

APPLICATIONS INFORMATION

6.1

Layout Considerations

The MCP9843/98243 device does not require any

additional components besides the master controller in

order to measure temperature. However, it is recom-

mended that a decoupling capacitor of 0.1 µF to 1 µF

be used between the VDD and GND pins. A high-

frequency ceramic capacitor is recommended. It is

necessary for the capacitor to be located as close as

possible to the power and ground pins of the device in

order to provide effective noise protection.

In addition, good PCB layout is key for better thermal

conduction from the PCB temperature to the sensor

die. For good temperature sensitivity, add a ground

layer under the device pins as shown in Figure 6-1.

6.2

Thermal Considerations

A potential for self-heating errors can exist if the

MCP9843/98243 SDA, SCLK and Event lines are

heavily loaded with pull-ups (high current). Typically,

the self-heating error is negligible because of the

relatively small current consumption of the MCP9843/

98243. A temperature accuracy error of approximately

0.5°C

could

result

from

self-heating

the

communication pins sink/source the maximum current

specified.

For example, if the Event output is loaded to maximum

IOL, Equation 6-1 can be used to determine the effect

of self-heating.

EQUATION 6-1:

EFFECT OF SELF-

HEATING

At room temperature (TA = +25°C) with maximum

IDD = 500 µA and VDD = 3.6V, the self-heating due to

power dissipation TΔ is 0.2°C for the DFN-8 package

and 0.5°C for the TSSOP-8 package.

FIGURE 6-1:

DFN Package Layout.

TΔ

OL_Event

OL_SDA

•

()

Where:

TΔ =TJ - TA

TJ = Junction Temperature

TA = Ambient Temperature

θJA = Package Thermal Resistance

VOL_Event, SDA = Event and SDA Output VOL

(0.4 Vmax)

IOL_Event, SDA = Event and SDA Output IOL

(3 mAmax)

GND

VDD

Event

SCL

SDA

EP9

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