MCP9801 datasheet(15/30 Pages) MICROCHIP

15 / 30 page

 2004 Microchip Technology Inc.

DS21909B-page 15

MCP9800/1/2/3

4.3.4.6

Fault Queue

The fault queue feature can be used as a filter to lessen

the probability of spurious activation of the ALERT pin.

TA must remain above TSET for the consecutive num-

ber of conversion cycles selected using the Fault

Queue bits. Bit 3 and bit 4 of CONFIG can be used to

select up to six fault queue cycles. For example, if six

fault queues are selected, TA must be greater than

TSET for six consecutive conversions before ALERT is

asserted as a comparator or an interrupt output.

This queue setting also applies for THYST. TA must

remain below THYST for six consecutive conversions

before ALERT is deasserted (comparator mode) or

before another interrupt is asserted (interrupt mode).

4.3.4.7

Σ∆ ADC Resolution

The MCP9800/1/2/3 provides access to select the ADC

resolution from 9-bit to 12-bit using bit 6 and bit 5 of the

CONFIG register. The user can gain better insight into

the

trends

and

characteristics

the

ambient

temperature by using a finer resolution. Increasing the

resolution

also

reduces

the

quantization

error.

Figure 2-4 shows accuracy versus resolution.

Table 4-1 shows the TA register conversion time for the

corresponding resolution.

TABLE 4-1:

RESOLUTION AND

CONVERSION TIME

4.4

Summary of Power-up Default

The MCP9800/1/2/3 has an internal Power-on Reset

(POR) circuit. If the power supply voltage VDD glitches

down to the 1.7V (typ.) threshold, the device resets the

registers to the power-up default settings.

Table 4-2 shows the power-up default summary.

TABLE 4-2:

POWER-UP DEFAULTS

Bits

Resolution

°C/Bit (typ.)

Conversion time

tCONV ms (typ.)

90.5

0.25

0.125

120

0.0625

240

Data

(Hex)

Power-up Defaults

0000

0°C

TSET

A000

80°C

THYST

9600

75°C

Pointer

Temperature register

CONFIG

Continuous Conversion

Comparator mode

Active-Low Output

Fault Queue 1

9-bit Resolution

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