MCP9844 datasheet(16/44 Pages) MICROCHIP

16 / 44 page

MCP9844

DS20005192A-page 16

 2013 Microchip Technology Inc.

5.1.2

SENSOR CONFIGURATION

The MCP9844 device has a 16-bit Configuration regis-

ter (CONFIG) that allows the user to set various func-

tions for a robust temperature monitoring system. Bits

10 through 0 are used to select the event output bound-

ary hysteresis, device Shutdown or Low-Power mode,

temperature boundary and critical temperature lock,

and temperature event output enable/disable. In addi-

tion, the user can select the event output condition (out-

put set for TUPPER and TLOWER temperature boundary

or TCRIT only), read event output status and set event

output polarity and mode (Comparator Output or

Interrupt Output mode).

The temperature hysteresis bits 10 and 9 can be used

to prevent output

chatter when the ambient

temperature gradually changes beyond the user

specified temperature boundary (see Section 5.2.2

“Temperature Hysteresis (THYST)”). The Continuous

Conversion or Shutdown mode is selected using bit 8.

In Shutdown mode, the band gap temperature sensor

circuit stops converting temperature and the Ambient

Temperature

(TA) holds the previous

successfully

converted

temperature

data

(see

Section 5.2.1 “Shutdown Mode”

). Bits 7 and 6 are

used to lock the user-specified boundaries TUPPER,

TLOWER and TCRIT to prevent an accidental rewrite.

Bits 5 through 0 are used to configure the temperature

Event output pin. All functions are described in

Configuration”

CONFIGURATION REGISTER (CONFIG)

 ADDRESS ‘0000 0001’b

U-0

R/W-0

——

—

THYST

SHDN

bit 15

bit 8

R/W-0

R-0

R/W-0

Crit. Lock

Win. Lock

Int. Clear

Event Stat.

Event Cnt.

Event Sel.

Event Pol.

Event Mod.

bit 7

bit 0

Legend:

R = Readable bit

W = Writable bit

U = Unimplemented bit, read as ‘0’

-n = Value at POR

‘1’ = Bit is set

‘0’ = Bit is cleared

x = Bit is unknown

bit 15-11

Unimplemented:

Read as ‘0’

bit 10-9

TUPPER and TLOWER Limit Hysteresis (THYST):

= 0°C (power-up default)

= 1.5°C

= 3.0°C

= 6.0°C

(Refer to Section 5.2.3 “Event Output Configuration”)

This bit can not be altered when either of the lock bits are set (bit 6 and bit 7).

This bit can be programmed in Shutdown mode.

bit 8

Shutdown Mode (SHDN):

Continuous Conversion (power-up default)

Shutdown (Low-Power mode)

In shutdown, all power-consuming activities are disabled, though all registers can be written to or read.

Event output will de-assert.

This bit cannot be set ‘1’ when either of the lock bits is set (bit 6 and bit 7). However, it can be cleared

‘0’ for Continuous Conversion while locked (Refer to Section 5.2.1 “Shutdown Mode”).

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