MCP98243 datasheet(33/62 Pages) MICROCHIP

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DS22153C-page 33

MCP9843/98243

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 5-12 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. If the inter-

rupt clear bit (Bit 5) is never set, then the Event output will

re-assert after the first temperature conversion.

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 5-12 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 MCP9843/98243.

5.2.4

TEMPERATURE RESOLUTION

The MCP9843/98243 device is capable of providing a

temperature data with 0.5°C to 0.0625°C resolution.

The Resolution can selected using the Resolution

‘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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