MCP98242-BESLASHST datasheet(28/52 Pages) MICROCHIP

28 / 52 page

MCP98242

DS21996C-page 28

5.2

SENSOR FEATURE DESCRIPTION

5.2.1

SHUTDOWN MODE

Shutdown

mode

disables

all

power-consuming

activities (including temperature sampling operations)

while leaving the serial interface active. This mode is

selected by setting bit 8 of CONFIG to ‘1’. In this mode,

the device consumes ISHDN. It remains in this mode

until bit 8 is cleared ‘0’ to enable Continuous

Conversion mode, or until power is recycled.

The Shutdown bit (bit 8) cannot be set to ‘1’ while bits

6 and 7 of CONFIG (Lock bits) are set to ‘1’. However,

it can be cleared ‘0’ or returned to Continuous

Conversion while locked.

In Shutdown mode, all registers can be read or written.

However, the serial bus activity increases the shutdown

current. In addition, if the device is shutdown while the

Event pin is asserted as active-low or deasserted

active-low (see Section 5.2.3.1 “Comparator Mode”),

the device will retain the active-low state. This

increases the shutdown current due to the additional

Event output pull-down current.

5.2.2

TEMPERATURE HYSTERESIS

(THYST)

A hysteresis of 0°C, 1.5°C, 3°C or 6°C can be selected

for the TUPPER, TLOWER and TCRIT temperate

boundaries using bits 10 and 9 of CONFIG. The

hysteresis applies for decreasing temperature only (hot

to cold), or as temperature drifts below the specified

limit.

The TUPPER, TLOWER and TCRIT boundary conditions

are described graphically in Figure 5-2.

5.2.3

EVENT OUTPUT CONFIGURATION

The Event output can be enabled using bit 3 of

CONFIG (Event output control bit) and can be

configured as either a comparator output or as Interrupt

Output mode using bit 0 of CONFIG (Event mode). The

polarity can also be specified as an active-high or

active-low using bit 1 of CONFIG (Event polarity).

When the ambient temperature increases above the

critical temperature limit, the Event output is forced to a

comparator output (regardless of bit 0 of CONFIG).

When the temperature drifts below the critical

temperature limit minus hysteresis, the Event output

automatically returns to the state specified by bit 0 of

CONFIG.

The status of the Event output can be read using bit 4

of CONFIG (Event status).

Bit 7 and 6 of the CONFIG register can be used to lock

the TUPPER, TLOWER and TCRIT registers. The bits

prevent false triggers at the Event output due to an

accidental rewrite to these registers.

The Event output can also be used as a critical

temperature output using bit 2 of CONFIG (critical

output only). When this feature is selected, the Event

output becomes a comparator output. In this mode, the

interrupt output configuration (bit 0 of CONFIG) is

ignored.

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 5-2 shows

the conditions that toggle the Event output.

If the device enters Shutdown mode with asserted

Event output, the output remains asserted during

Shutdown. The device must be operating in

Continuous Conversion mode for tCONV; the TA vs.

TUPPER, TLOWER and TCRIT boundary conditions need

to be satisfied in order for the Event output to deassert.

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. Note that when

switching from Comparator mode to Interrupt mode, it

is recommended to send interrupt clear command (set

bit 5) to reset the interrupt flag. Shutting down the

device will not reset or deassert the Event output. This

mode can not be selected when the Event output is

used as critical temperature output only, using bit 2 of

CONFIG. 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

MCP98242.

5.2.3.3

Temperature Resolution

The MCP98242 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 (maximum). 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.

MCP98242-BE/ST Datasheet(PDF) 28 Page - Microchip Technology

MCP98242-BE/ST Datasheet(HTML) 28 Page - Microchip Technology

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52

Datasheet Download

Link URL