Datasheet

TMP122, TMP124
8
SBOS272B
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F1 F0 CONSECUTIVE FAULTS
00 1
01 2
10 4
11 6
TABLE VIII. Fault Settings of the TMP122 and TMP124.
THERMOSTAT MODE (TM1/TM0)
The Thermostat Mode bits of the TMP122/TMP124 indicate to
the device whether to operate in Comparator Mode, Interrupt
Mode or Interrupt Comparator Mode. For more information on
Comparator and Interrupt Mode, see text HIGH and LOW limit
registers. The bit assignments for thermostat mode are
described in Table VII. Power on default is comparator mode.
POLARITY (POL)
The Polarity Bit of the TMP122/TMP124 adjusts the polarity
of the ALERT pin output. By default, POL = 0 and the ALERT
pin will be active LOW, as shown in Figure 8. For POL = 1
the ALERT Pin will be active HIGH, and the state of the
ALERT Pin is inverted.
FAULT QUEUE (F1/F0)
A fault condition occurs when the measured temperature
exceeds the limits set in the T
HIGH
and T
LOW
registers. The
Fault Queue is provided to prevent a false alert due to
environmental noise and requires consecutive fault mea-
surements to trigger the alert function of the TMP122/TMP124.
Table VIII defines the number of consecutive faults required
to trigger a consecutive alert condition. Power-on default for
F1/F0 is 0/0.
HIGH AND LOW LIMIT REGISTERS
In Comparator Mode (TM1/TM0 = 0/0), the ALERT Pin of the
TMP122/TMP124 becomes active when the temperature
equals or exceeds the value in T
HIGH
and generates a
consecutive number of faults according to fault bits F1 and
F0. The ALERT pin will remain active until the temperature
falls below the indicated T
LOW
value for the same number of
faults.
In Interrupt Mode (TM1/TM0 = 0/1) the ALERT pin becomes
active when the temperature equals or exceeds T
HIGH
for a
consecutive number of fault conditions. The ALERT pin
remains active until a read operation of any register occurs.
The ALERT pin will also be cleared if the device is placed in
Shutdown Mode. Once the ALERT pin is cleared, it will only
become active again by the temperature falling below T
LOW
.
When the temperature falls below T
LOW
, the ALERT pin
becomes active and remains active until cleared by a read
operation of any register. Once the ALERT pin is cleared, the
above cycle will repeat with the ALERT pin becoming active
when the temperature equals or exceeds T
HIGH
.
In Interrupt/Comparator Mode (TM1/TM0 = 1/0), the ALERT
Pin of the TMP122/TMP124 becomes active when the tem-
perature equals or exceeds the value in T
HIGH
and generates
a consecutive number of faults according to fault bits F1 and
F0. The ALERT pin will remain active until the temperature
falls below the indicated T
LOW
value for the same number of
faults and a communication with the device has occurred
after that point.
Operational modes are represented in Figure 8. Tables IX
and X describe the format for the T
HIGH
and T
LOW
registers.
Power-up reset values for T
HIGH
and T
LOW
are: T
HIGH
= 80°C
and T
LOW
= 75°C. The format of the data for T
HIGH
and T
LOW
is the same as for the Temperature Register.
All 13 bits for the Temperature, T
HIGH
, and T
LOW
registers are
used in the comparisons for the ALERT function for all con-
verter resolutions. The three LSBs in T
HIGH
and T
LOW
can
affect the ALERT output even if the converter is configured for
9-bit resolution.
D15 D14 D13 D12 D11 D10 D9 D8
H12 H11 H10 H9 H8 H7 H6 H5
D7 D6 D5 D4 D3 D2 D1 D0
H4 H3 H2 H1 H0 1 1 0
TABLE IX. T
HIGH
Register.
D15 D14 D13 D12 D11 D10 D9 D8
L12 L11 L10 L9 L8 L7 L6 L5
D7 D6 D5 D4 D3 D2 D1 D0
L4 L3 L2 L1 L0 1 0 0
TABLE X. T
LOW
Register.
TM1 TM0 MODE OF OPERATION
0 0 Comparator Mode
0 1 Interrupt Mode
1 0 Interrupt Comparator Mode
11 —
TABLE VII. Mode Settings of the TMP122.
FIGURE 8. ALERT Output Transfer Function Diagrams.
Measured
Temperature
T
HIGH
T
LOW
TMP122/124 ALERT PIN
(Comparator Mode)
POL = 0
TMP122/124 ALERT PIN
(Interrupt Mode)
POL = 0
TMP122/124 ALERT PIN
(Interrupt/Comparator Mode)
POL = 0
Read Read
Time
Read