November 2004

7

MIC281

MIC281

Micrel

Slave Address

The MIC281 will only respond to its own unique slave ad-

dress. A match between the MIC281’s address and the

address specified in the serial bit stream must be made to

initiate communication. The MIC281’s slave address is fixed

at the time of manufacture. Eight different slave addresses

are available as determined by the part number. See Table

2 below and the Ordering Information table.

Part Number

Slave Address

MIC281-0BM6

MIC281-1BM6

MIC281-2BM6

MIC281-3BM6

MIC281-4BM6

MIC281-5BM6

MIC281-6BM6

MIC281-7BM6

Table 2. MIC281 Slave Addresses

Temperature Data Format

Theleast-significantbitofthetemperatureregisterrepresents

one degree Centigrade. The values are in a two’s comple-

ment format, wherein the most significant bit (D7) represents

the sign: zero for positive temperatures and one for negative

temperatures. Table 3 shows examples of the data format

used by the MIC281 for temperatures.

Temperature

Binary

Hex

+127°C

0111 1111

7F

+125°C

0111 1101

7D

+25°C

0001 1001

19

+1°C

0000 0001

01

0°C

0000 0000

00

–1°C

1111 1111

FF

–25°C

1110 0111

E7

–125°C

1000 0011

83

–128°C

1000 0000

80

Table 3. Digital Temperature Format

Diode Faults

The MIC281 is designed to respond in a failsafe manner to

diode faults. If an internal or external fault occurs in the tem-

perature sensing circuitry, such as T1 being open or shorted

maximum full-scale value, +127°C. Note that diode faults will

notbedetecteduntilthefirstA/Dconversioncycleiscompleted

following power-up or exiting shutdown mode.

Shutdown Mode

Setting the shutdown bit in the configuration register will

cause the MIC281 to cease operation. The A/D converter will

registers will be affected by entering shutdown mode. The

last temperature reading will persist in the TEMP register.