MCP98243 datasheet(32/62 Pages) MICROCHIP

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MCP9843/98243

DS22153C-page 32

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.

If the device is shutdown while the Event pin is

asserted, then the Event output will be de-asserted

during shutdown. It will remain de-asserted until the

device is enabled for normal operation. Once the

device is enabled it takes tCONV before the device

re-asserts the Event output.

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 hysteresis bits can not be changed if either of the

lock bits, bits 6 and 7 of CONFIG, are set to ‘1’.

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 active-high output is selected, a pull-down

resistor is requried on the Event pin. When active-low

output is selected, a pull-up resistor is required on the

Event

pin, see Figure 5-10 and Figure 5-11 for

graphical circuit description. These configurations are

designed to serve processors with Low-to-High or

High-to-Low edge triggered inputs. With these

configurations, when the Event output De-asserts,

power will not be dissipated across the pull-up or

pull-down resistors.

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.

FIGURE 5-10:

Active-High Event Output

Configuration.

FIGURE 5-11:

Active-Low Event Output

Configuration.

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

of CONFIG (Event status). This bit can not be set to ‘1’

in shutdown mode.

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.

MCP9843/98243

Event Output

RPD

VDD

MCP9843/98243

Event Output

RPU

VDD

MCP98243 Datasheet(PDF) 32 Page - Microchip Technology

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