1°C Temperature Sensor with Beta Compensation
Datasheet
EMC1404
CPU
Host
DP1
DN1
Thermal
diode
SMCLK
Internal
Diode
SMDATA
SMBus
Interface
ALERT
DP2
DN2
Anti-parallel
diodes
THERM
Power Control
Figure 5.2 System Diagram for EMC1404
5.1
Modes of Operation
The EMC1403 and EMC1404 have two modes of operation.
Active (Run) - In this mode of operation, the ADC is converting on all temperature channels at the
programmed conversion rate. The temperature data is updated at the end of every conversion and
the limits are checked. In Active mode, writing to the one-shot register will do nothing.
Standby (Stop) - In this mode of operation, the majority of circuitry is powered down to reduce
supply current. The temperature data is not updated and the limits are not checked. In this mode
of operation, the SMBus is fully active and the part will return requested data. Writing to the one-
shot register will enable the device to update all temperature channels. Once all the channels are
updated, the device will return to the Standby mode.
5.1.1
5.1.2
Conversion Rates
The EMC1403 and EMC1404 may be configured for different conversion rates based on the system
requirements. The conversion rate is configured as described in Section 6.5. The default conversion
rate is 4 conversions per second. Other available conversion rates are shown in Table 6.6.
Dynamic Averaging
Dynamic averaging causes the EMC1403 and EMC1404 to measure the external diode channels for
an extended time based on the selected conversion rate. This functionality can be disabled for
increased power savings at the lower conversion rates (see Section 6.4). When dynamic averaging is
enabled, the device will automatically adjust the sampling and measurement time for the external diode
channels. This allows the device to average 2x or 16x longer than the normal 11 bit operation
(nominally 21ms per channel) 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 applies when a one-shot command is issued. The device will
perform the desired averaging during the one-shot operation according to the selected conversion rate.
When enabled, the dynamic averaging will affect the average supply current based on the chosen
conversion rate as shown in Table 5.1 for EMC1403.
Revision 1.16 (03-15-07)
SMSC EMC1403/EMC1404
DATA1S6HEET
SMSC [ SMSC CORPORATION ]
