tcn75a Microchip Technology Inc., tcn75a Datasheet - Page 22

• Manufacturer Part Number: tcn75a
• Description: 2-wire Serial Temperature Sensor
• Manufacturer: Microchip Technology Inc.

TCN75A
5.3.4.6
The fault queue feature can be used as a filter to lessen
the probability of spurious activation of the ALERT pin.
T
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, T
T
asserted as a comparator or an interrupt output.
This queue setting also applies for T
queues are selected, T
six consecutive conversions before ALERT is deas-
serted (Comparator mode) or before another interrupt
is asserted (Interrupt mode).
5.3.4.7
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 5-1 shows the T
corresponding resolution.
TABLE 5-1:
DS21935C-page 22
A
SET
must remain above T
Bits
for six consecutive conversions before ALERT is
10
12
11
9
Fault Queue
ΣΔ ADC Resolution
Resolution
RESOLUTION AND
CONVERSION TIME
0.0625
0.125
0.25
A
0.5
A
register conversion time for the
SET
must remain below T
for the consecutive num-
A
must be greater than
HYST
t
CONV
120 ms
240 ms
30 ms
60 ms
.
I
(typ.)
f six fault
HYST
for
5.4
The TCN75A has an internal Power-on Reset (POR)
circuit. If the power supply voltage V
to the 1.7V (typ.) threshold, the device resets the
registers to the power-up default settings.
Table 5-2 shows the power-up default summary.
TABLE 5-2:
At power-up, the TCN75A has an inherent 2 ms (typ.)
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
update the T
Register
CONFIG
Pointer
T
T
HYST
T
SET
Summary of Power-up Condition
A
A
register with valid temperature data.
POWER-UP DEFAULTS
(Hex)
0000
A000
9600
Data
00
00
© 2006 Microchip Technology Inc.
CONV
Continuous Conversion
Temperature register
Power-up Defaults
Comparator mode
Active-low Output
9-bit Resolution
for the TCN75A to
Fault Queue 1
DD
80°C
75°C
0°C
glitches down