MCP98242-BESLASHST datasheet(23/52 Pages) MICROCHIP

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DS21996C-page 23

MCP98242

5.1.4

AMBIENT TEMPERATURE

The MCP98242 uses a band gap temperature sensor

circuit to output analog voltage proportional to absolute

temperature. An internal

ΔΣ ADC is used to convert the

analog voltage to a digital word. The converter

resolution is set to 0.25 °C + sign (11-bit data). The

digital word is loaded to a 16-bit read-only Ambient

Temperature register

(TA) that contains 11-bit

temperature data in two’s complement format.

The TA register bits (bits 12 thru 0) are double-buffered.

Therefore, the user can access the register while, in the

background, the MCP98242 performs an analog-to-

digital conversion. The temperature data from the

ΔΣ

ADC is loaded in parallel to the TA register at tCONV

refresh rate.

The TA magnitude in decimal to ambient temperature

conversion is shown in Equation 5-1:

EQUATION 5-1:

DECIMAL CODE TO

TEMPERATURE

CONVERSION

In addition, the TA register uses three bits (bits 15, 14

and 13) to reflect the Event pin state. This allows the

user to identify the cause of the Event output trigger

(see Section 5.2.3 “Event Output Configuration”);

bit 15 is set to ‘1’ if TA is greater than or equal to TCRIT,

bit 14 is set to ‘1’ if TA is greater than TUPPER and bit 13

is set to ‘1’ if TA is less than TLOWER.

The TA register bit assignment and boundary

conditions are described in Register 5-5.

Code 2

–

Where:

TA = Ambient Temperature (°C)

Code = MCP98242 temperature output

magnitude in decimal (bits 0-11)

AMBIENT TEMPERATURE REGISTER (TA) → ADDRESS ‘0000 0101’b

R-0

TA vs. TCRIT TA vs. TUPPER TA vs. TLOWER

SIGN

27 °C

26 °C

25 °C

24 °C

bit 15

bit 8

R-0

23 °C

22 °C

21 °C

20 °C

2-1 °C

2-2 °C

—

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

TA vs. TCRIT (1) Bit:

0 =TA < TCRIT

1 =TA ≥ TCRIT

bit 14

TA vs. TUPPER (1) Bit:

0 =TA ≤ TUPPER

1 =TA > TUPPER

bit 13

TA vs. TLOWER (1) Bit:

0 =TA ≥ TLOWER

1 =TA < TLOWER

bit 12

SIGN Bit:

0 =TA ≥ 0°C

1 =TA < 0°C

bit 11-2

Ambient Temperature (TA) Bits:

10-bit Ambient Temperature data in two’s complement format.

bit 1-0

TA: Data in 2’s complement format. Depending on the status of the Resolution Register (Register 5-8),

these bits may display 2-3°C (0.125°C) and 2-4°C (0.0625°C), respectively.

Note 1: Not affected by the status of the Event output configuration (bits 5 to 0 of CONFIG), Register 5-3.

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