Datasheet
2010 Microchip Technology Inc. DS21935D-page 25
TCN75A
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.
T
A
must remain above T
SET
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, T
A
must be
greater than T
SET
for six consecutive conversions
before ALERT is asserted as a comparator or an inter-
rupt output.
This queue setting also applies for T
HYST
. If six fault
queues are selected, T
A
must remain below T
HYST
for
six consecutive conversions before ALERT is
deasserted (Comparator mode) or before another
interrupt is asserted (Interrupt mode).
5.3.4.7 ADC Resolution
The TCN75A provides access to select the ADC
resolution from 9-bit to 12-bit (0.5°C to 0.0625°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 T
A
register conversion time for the
corresponding resolution.
TABLE 5-3: RESOLUTION AND
CONVERSION TIME
5.4 Summary of Power-up Condition
The TCN75A has an internal Power-on Reset (POR)
circuit. If the power supply voltage V
DD
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: POWER-UP DEFAULTS
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 t
CONV
for the TCN75A
to update the T
A
register with valid temperature data.
Bits Resolution t
CONV
(typical)
90.5 30ms
10 0.25 60 ms
11 0.125 120 ms
12 0.0625 240 ms
Register
Data
(Hex)
Power-up Defaults
T
A
0000 0°C
T
SET
A000 80°C
T
HYST
9600 75°C
Pointer 00 Temperature register
CONFIG 00
Continuous Conversion
Comparator mode
Active-low Output
Fault Queue 1
9-bit Resolution