Datasheet
HIGH AND LOW LIMIT REGISTERS
CONVERTER RESOLUTION (R1/R0)
TMP122-EP
SBOS454 – NOVEMBER 2008 ..........................................................................................................................................................................................
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Table 8. Fault Settings
F1 F0 CONSECUTIVE FAULTS
0 0 1
0 1 2
1 0 4
1 1 6
In Comparator Mode (TM1/TM0 = 0/0), the ALERT Pin of the TMP122 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 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 and a communication with the device has occurred after that point.
Operational modes are represented in Figure 8 . Table 9 and Table 10 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. TABLE IX. T
HIGH
Register.
All 13 bits for the Temperature, T
HIGH
, and T
LOW
registers are used in the comparisons for the ALERT function for
all converter 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.
Table 9. T
HIGH
Register
D15 D14 D13 D12 D11 D10 D9 D8 D7 D6 D5 D4 D3 D2 D1 D0
H12 H11 H10 H9 H8 H7 H6 H5 H4 H3 H2 H1 H0 1 1 0
Table 10. T
LOW
Register
D15 D14 D13 D12 D11 D10 D9 D8 D7 D6 D5 D4 D3 D2 D1 D0
L12 L11 L10 L9 L8 L7 L6 L5 L4 L3 L2 L1 L0 1 0 0
The Converter Resolution Bits control the resolution of the internal analog-to-digital (A/D) converter. This allows
the user to maximize efficiency by programming for higher resolution or faster conversion time. Table 11
identifies the resolution bits and the relationship between resolution and conversion time. The TMP122 has a
default resolution of 12 bits.
Table 11. Resolution
CONVERSION TIME
R1 R2 RESOLUTION
(TYPICAL)
0 0 9 bits (0.5 ° C) + sign 30 ms
0 1 10 bits (0.25 ° C) + sign 60 ms
1 0 11 bits (0.125 ° C) + sign 120 ms
1 1 12 bits (0.0625 ° C) + sign 240 ms
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