© 2006 Microchip Technology Inc.

DS21935C-page 13

TCN75A

5.3.1

AMBIENT TEMPERATURE

The TCN75A 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,

respecively). 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 (typ.) for 9-bit

data and 240 ms (typ.) for 12-bit data. Since this

register is double-buffered, the user can read the

register while the TCN75A performs Analog-to-Digital

conversion in the background. The decimal code to

ambient

temperature

conversion

is

shown

in

Equation 5-2:

EQUATION 5-2:

Code 2

4

–

×

=

Where:

Code = TCN75A 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.