1.5°C SMBus Temperature Sensor in Miniature SOT-23
Datasheet
VDD
Ilow
Ibias
Ihigh
10-bit Output
Delta Vbe
Sample
&
1-bit
delta-sigma
Modulator
Digital
Averaging
Filter
Hold
Internal or
Remote Diode
Bias
Diode
Figure 4.2 Detailed Block Diagram
Figure 4.2 shows a detailed block diagram of the temperature measurement circuit. The EMC1001
incorporates switched capacitor technology that integrates the temperature diode ΔVBE from different
bias currents. The negative terminal, DN, for the temperature diode is internally biased with a forward
diode voltage referenced to ground.
The advantages of this architecture over Nyquist rate FLASH or SAR converters are superb linearity
and inherent noise immunity. The linearity can be directly attributed to the delta-sigma ADC single-bit
comparator while the noise immunity is achieved by the ~20ms integration time which translates to
50Hz input noise bandwidth.
4.2
Temperature Measurement Results and Data
The 10-bit temperature measurement results are stored in temperature value registers. Table 4.1
shows the two’s complement temperature data format with an LSB equivalent to 0.25°C.
Table 4.1 Temperature Data Format
VALID RANGE
–40°C TO 125°C
TEMPERATURE
TWO’S COMPLEMENT
-0.25°C
0.0°C
+0.25°C
+0.50°C
+0.75°C
+1°C
1111 1111 11 Note 4.1
0000 0000 00
0000 0000 01
0000 0000 10
0000 0000 11
0000 0001 00
+125°C
0111 1101 00 Note 4.2
Note 4.1 Temperature measurement returns 1100 0000 00 for all temperatures ≤ -64.00°C
Note 4.2 Temperature measurement returns 0111 1111 11 for all temperatures ≥ +127.75°C
The eight most significant bits are stored in the Temperature Value High Byte register and the two least
significant bits stored in the Temperature Value Low Byte register as outlined in Table 4.2. The six LSB
positions of the Temperature Value Low Byte register always read zero. In Table 4.2, the upper case
Revision 1.6 (01-29-07)
SMSC EMC1001
DATA1S0HEET
SMSC [ SMSC CORPORATION ]
