MCP98244 datasheet(29/52 Pages) MICROCHIP

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 2012-2013 Microchip Technology Inc.

DS22327C-page 29

MCP98244

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 5-9 shows

the conditions that toggle the Event output.

If the device enters Shutdown mode with asserted

Event output, the output will deassert. It will remain

deasserted 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 de asserted by setting

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

Shutdown mode with asserted Event output, the output

will deassert. It will remain deasserted 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

reassert 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, the user must send

the Clear Interrupt command (bit 5 of CONFIG) for Event

output to deassert, when temperature drops below the

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

remains asserted (see Figure 5-9 for a graphical descrip-

tion). Switching from Interrupt mode to Comparator mode

also deasserts Event output.

This mode is designed for interrupt-driven microcontrol-

ler-based systems. The microcontroller receiving the

interrupt will have to acknowledge the interrupt by setting

bit 5 of CONFIG register from the MCP98244.

5.2.4

TEMPERATURE RESOLUTION

The MCP98244 device is capable of providing tem-

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

Resolution can selected using the Resolution register

(Register 5-8)

which

located

address

‘00001001’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 provides a 0.25°C resolution at

125 ms (max.). In order to prevent accidentally chang-

ing the resolution and exceeding the 125 ms conver-

sion time, the device must be in Shutdown mode to

change this register. The selected resolution can be

read by user using bit 4 and bit 3 of the Capability reg-

ister (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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