MCP9800/1/2/3

DS21909C-page 16

 2010 Microchip Technology Inc.

5.3.1

AMBIENT TEMPERATURE

The MCP9800/1/2/3 has a 16-bit read-only Ambient

Temperature register that contains 9-bit to 12-bit

temperature data. (0.5°C to 0.0625°C resolutions,

respectively). This data is formatted in two’s

complement. The bit assignments, as well as the

corresponding resolution, is shown in the register

assignment below.

The refresh rate of this register depends on the

selected ADC resolution. It takes 30 ms (typical) for

9-bit data and 240 ms (typical) for 12-bit data. Since

this register is double-buffered, the user can read the

register

while

the

MCP9800/1/2/3

performs

Analog-to-Digital conversion in the background. The

decimal code to ambient temperature conversion is

shown in Equation 5-2:

EQUATION 5-2:

T

A

Code

2

4

–



=

Where:

Code = MCP9800 output in decimal

REGISTER 5-2:

Upper Half:

R-0

R-0

R-0

R-0

R-0

R-0

R-0

R-0

Sign

bit 15

bit 8

Lower Half:

R-0

R-0

R-0

R-0

R-0

R-0

R-0

R-0

0

0

0

0

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

Note 1:

When the 0.5°C, 0.25°C or 0.125°C resolutions are selected, bit 6, bit 7 or bit 8 will remain clear <0>,

respectively.