MCP98243 datasheet(33/62 Pages) MICROCHIP

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DS22153B-page 33

MCP98243

5.2.3.1

Comparator Mode

Comparator mode is selected using bit 0 of CONFIG. In

this mode, the Event output is asserted as active-high

or active-low using bit 1 of CONFIG. Figure 5-13 shows

the conditions that toggle the Event output.

If the device enters Shutdown mode with asserted

Event output, the output will de-assert. It will remain de-

asserted until the device enters Continuous Conver-

sion mode and after the first temperature conversion is

completed, tCONV. After the initial temperature conver-

sion, TA must satisfy the TUPPER or TLOWER boundary

conditions in order for Event output to be asserted.

Comparator mode is useful for thermostat-type

applications, such as turning on a cooling fan or

triggering a system shutdown when the temperature

exceeds a safe operating range.

5.2.3.2

Interrupt Mode

In the Interrupt mode, the Event output is asserted as

active-high or active-low (depending on the polarity

configuration) when TA drifts above or below TUPPER

and TLOWER limits. The output is deasserted by setting

bit 5 (Interrupt Clear) of CONFIG. If the device enters

Shutdown mode with asserted Event output, the output

will de-assert. It will remain de-asserted until the device

enters Continuous Conversion mode and after the first

temperature conversion is completed, tCONV. After the

initial temperature conversion, TA must cross the TUPPER

or TLOWER boundary conditions in order for Event output

to be asserted.

In addition, if TA >= TCRIT the Event output is forced as

Comparator mode and asserts until TA < TCRIT - THYST.

While the Event output is asserted, user must send Clear

Interrupt command (bit 5 of CONFIG) for Event output to

de-assert, when temperature drops below the critical

limit, TA < TCRIT - THYST. Otherwise, Event output

remains asserted (see Figure 5-13 for graphical descrip-

tion). Switching from Interrupt mode to Comparator mode

also de-asserts Event output.

This mode is designed for interrupt driven microcontroller

based systems. The microcontroller receiving the

interrupt will have to acknowledge the interrupt by setting

bit 5 of CONFIG register from the MCP98243.

5.2.4

TEMPERATURE RESOLUTION

The MCP98243 is capable of providing a temperature

data with 0.5°C to 0.0625°C resolution. The Resolution

can selected using the Resolution register (Register 5-

8) which is located in address ‘00001000’b. This

address location is not specified in JEDEC Standard

JC42.4. However, it provides additional flexibility while

being functionally compatible with JC42.4 and provide

a 0.25°C resolution at 125 ms (max.). The selected

resolution can be read by user using bit 4 and bit 3 of

the Capability register (Register 5-2). A 0.25°C

resolution is set as POR default by factory.

TABLE 5-2:

TEMPERATURE

CONVERSION TIME

Resolution

tCONV

(ms)

Samples/sec

(typical)

0.5°C

0.25°C

(Power-up default)

0.125°C

130

0.0625°C

260

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