Dual Channel 1°C Temperature Sensor with Beta Compensation and 1.8V SMBus Communications
Datasheet
Revision 1.0 (07-11-13) 22 SMSC EMC1182
DATASHEET
APPLICATION NOTE: When monitoring a substrate transistor or CPU diode and beta compensation is enabled, the
Ideality Factor should not be adjusted. Beta Compensation automatically corrects for most
ideality errors.
5.7 Diode Faults
The EMC1182 detects an open on the DP and DN pins, and a short across the DP and DN pins. For
each temperature measurement made, the device checks for a diode fault on the external diode
channel(s). When a diode fault is detected, the
ALERT / THERM2 pin asserts (unless masked, see
Section 5.8) and the temperature data reads 00h in the MSB and LSB registers (note: the low limit will
not be checked). A diode fault is defined as one of the following: an open between DP and DN, a short
from V
DD
to DP, or a short from V
DD
to DN.
If a short occurs across DP and DN or a short occurs from DP to GND, the low limit status bit is set
and the ALERT / THERM2 pin asserts (unless masked). This condition is indistinguishable from a
temperature measurement of 0.000°C (-64°C in extended range) resulting in temperature data of 00h
in the MSB and LSB registers.
If a short from DN to GND occurs (with a diode connected), temperature measurements will continue
as normal with no alerts.
5.8 Consecutive Alerts
The EMC1182 contains multiple consecutive alert counters. One set of counters applies to the ALERT
/ THERM2 pin and the second set of counters applies to the THERM pin. Each temperature
measurement channel has a separate consecutive alert counter for each of the
ALERT / THERM2 and
THERM pins. All counters are user programmable and determine the number of consecutive
measurements that a temperature channel(s) must be out-of-limit or reporting a diode fault before the
corresponding pin is asserted.
See Section 6.11, "Consecutive ALERT Register 22h" for more details on the consecutive alert
function.
5.9 Digital Filter
To reduce the effect of noise and temperature spikes on the reported temperature, the External Diode
channel uses a programmable digital filter. This filter can be configured as Level 1, Level 2, or Disabled
(default) (see Section 6.14). The typical filter performance is shown in Figure 5.4 and Figure 5.5.
