1°C Triple Temperature Sensor with Beta Compensation and Hotter of Two Zones
Datasheet
3.3.2
Dynamic Averaging
The EMC1043 temperature channels support a new feature that measures the external diode channels
for an extended time based on the selected conversion rate. This functionality can be disabled as
described in Section 4.5 for increased power savings at the lower conversion rates. When Dynamic
Averaging is enabled, the device will automatically adjust the sampling and measurement time for both
external diode channels. This allows the device to average 2x or 4x longer than the normal 11 bit
operation 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 on the
temperature measurement.
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.
The Dynamic Averaging will affect the average supply current based on the chosen conversion rate
as shown in Table 3.1.
Table 3.1 Supply Current vs. Conversion Rate and ADC Averaging Factor
ADC AVERAGING FACTOR
4X
2X
(MAX_RES = 1)
(DA_n = 0)
(MAX_RES = 0)
(DA_n = 0)
1X
CONVERSION RATE
(DA_n = 1)
1 / sec
2 / sec
4 / sec
8 / sec
16 / sec
190uA
132uA
205uA
350uA
640uA
N/A
105uA
315uA
580uA
N/A
150uA
235uA
405uA
750uA
N/A
3.4
Temperature Monitors
In general, thermal diode temperature measurements are based on the change in forward bias voltage
of a diode when operated at two different currents. This ΔVBE is then proportional to absolute
temperature as shown in the following equation:
where:
k = Boltzmann’s constant
⎛
⎞
IHIGH
ηkT
q
T = absolute temperature in Kelvin
q = electron charge
[1]
⎜
⎜
⎟
⎟
ΔVBE = VBE _ HIGH −VBE _ LOW
=
ln
ILOW
⎝
⎠
η = diode ideality factor
SMSC EMC1043
Revision 1.37 (09-05-06)
DATA1S3HEET
SMSC [ SMSC CORPORATION ]
