EMC1422_12 Datasheet, PDF (16/41 Pages) SMSC Corporation – 1°C Temperature Sensor with Hardware Thermal Shutdown

1°C Temperature Sensor with Hardware Thermal Shutdown
Datasheet
while still maintaining the selected conversion rate. The benefits of dynamic averaging are improved
noise rejection due to the longer integration time as well as less random variation of the temperature
measurement.
When enabled, the dynamic averaging will affect the average supply current based on the chosen
conversion rate as shown in Table 5.1 for the EMC1422.
Table 5.1 Supply Current vs. Conversion Rate for EMC1422
CONVERSION RATE
1 / sec
2 / sec
4 / sec (default)
8 / sec
16 / sec
32 / sec
64 / sec
AVERAGE SUPPLY CURRENT
ENABLED
(DEFAULT)
660uA
930uA
950uA
1010uA
1020uA
1050uA
1100uA
DISABLED
430uA
475uA
510uA
630uA
775uA
1050uA
1100uA
AVERAGING FACTOR (BASED ON
11-BIT OPERATION)
ENABLED
(DEFAULT)
16x
16x
8x
4x
2x
1x
0.5x
DISABLED
1x
1x
1x
1x
1x
1x
0.5x
5.1
SYS_SHDN Output
The SYS_SHDN output is asserted independently of the ALERT output and cannot be masked. If the
External Diode temperature exceeds the Hardware Thermal Shutdown Limit for the programmed
number of consecutive measurements, then the SYS_SHDN pin is asserted.
The Hardware Thermal Shutdown Limit is defined at power-up via the pull-up resistors on the
SYS_SHDN and ALERT pins as shown in Table 5.2. This limit cannot be modified or masked via
software.
In addition to External Diode channel triggering the SYS_SHDN pin when the measured temperature
exceeds to the Hardware Thermal Shutdown Limit, each of the measurement channels can be
configured to assert the SYS_SHDN pin when they exceed the corresponding THERM Limit.
When the SYS_SHDN pin is asserted, it will not release until the External Diode temperature drops
below the Hardware Thermal Shutdown Limit minus 10°C and all other measured temperatures drop
below the THERM Limit minus the THERM Hysteresis value (when linked to SYS_SHDN).
Figure 5.2 shows a block diagram of the interaction between the input channels and the SYS_SHDN
pin.
Revision 2.0 (08-10-12)
16
DATASHEET
SMSC EMC1422