TCN75A_1 Datasheet, PDF(25/40 Page) Microchip Technology

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TCN75A_1 Datasheet, PDF (25/40 Pages) Microchip Technology – 2-Wire Serial Temperature Sensor

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FIGURE 5-7:

Alert Output.

5.3.4.6 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

number of conversion cycles selected using the Fault

Queue bits. Bit 3 and bit 4 of the CONFIG register 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 inter-

rupt output.

This queue setting also applies for THYST. If six fault

queues are selected, TA must remain below THYST for

six consecutive conversions before ALERT is

deasserted (Comparator mode) or before another

interrupt is asserted (Interrupt mode).

5.3.4.7 ïï ADC Resolution

The TCN75A provides access to select the ADC

resolution from 9-bit to 12-bit (0.5Â°C to 0.0625Â°C

resolution) using bit 6 and bit 5 of the CONFIG register.

The user can gain better insight into the trends and

characteristics of the ambient temperature by using a

finer resolution. Increasing the resolution also reduces

the quantization error. Figure 2-3 shows accuracy

versus resolution.

Table 5-3 shows the TA register conversion time for the

corresponding resolution.

TABLE 5-3:

Bits

RESOLUTION AND

CONVERSION TIME

Resolution

0.5

0.25

0.125

0.0625

tCONV (typical)

30 ms

60 ms

120 ms

240 ms

TCN75A

5.4 Summary of Power-up Condition

The TCN75A has an internal Power-on Reset (POR)

circuit. If the power supply voltage VDD glitches down

to the 1.7V (typical) threshold, the device resets the

registers to the power-up default settings.

Table 5-4 shows the power-up default summary.

TABLE 5-4:

TSET

THYST

Pointer

CONFIG

POWER-UP DEFAULTS

Data

(Hex)

0000

A000

9600

Power-up Defaults

0Â°C

80Â°C

75Â°C

Temperature register

Continuous Conversion

Comparator mode

Active-low Output

Fault Queue 1

9-bit Resolution

At power-up, the TCN75A has an inherent 2 ms

(typical) power-up delay before updating the registers

with default values and start a conversion cycle. This

delay reduces register corruption due to unsettled

power. After power-up, it takes tCONV for the TCN75A

to update the TA register with valid temperature data.

ï£ 2010 Microchip Technology Inc.

DS21935D-page 25

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