EMC1203 Standard Microsystems Corporation, EMC1203 Datasheet - Page 7

• Manufacturer Part Number: EMC1203
• Description: Triple/quad Single-wire Temp Sensor in Msop-8 Using SMSC Budgetbus Sensor Interface
• Manufacturer: Standard Microsystems Corporation

Triple/Quad Single-Wire Temp Sensor in MSOP-8 Using SMSC BudgetBus
Datasheet
SMSC EMC1203/EMC1204
3.1.1
3.1.2
or External
Internal
Figure 3.2
EMC1203 and EMC1204 incorporates switched capacitor technology that samples the temperature
diode voltage at two bias currents and holds the difference voltage. The sample frequency is 100kHz
and the current levels Ihigh and Ilow are 170uA and 10uA respectively.
The output of the switched capacitor sample and hold circuit interfaces to a single bit delta sigma
analog to digital converter. This ADC runs at 100kHz sample frequency and its output is digitally filtered
and averaged over 2048 samples effectively generating 11 bit accuracy.
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 digital averaging filter. The overall effective
bandwidth of the system is fs/2048 which translates to a 50Hz bandwidth at 100kHz sample rate.
Conversion time equals about 20ms per temperature monitor.
EMC1203 Temperature Monitoring
The EMC1203, incorporates one internal diode and can monitor two additional temperature zones with
two external diodes.An internal analog multiplexer switches between the internal and external diodes.
Total conversion time for one internal and two external temperature readings is about 60ms. The
external diodes can be either a CPU substrate diode or a discrete diode connected transistor like the
2N3904 or 2N3906. External diode connected transistors examples are shown in
EMC1204 Temperature Monitoring
The EMC1204, incorporates one internal diode and can monitor three external diodes. Total conversion
time for one internal and three external temperature reading is 80ms. An internal multiplexer switches
between internal and external diodes. The external thermal diode connected to DP1 and DN1 can
Diode
V
Figure 3.2 Detailed Block Diagram of Temperature Monitor Architecture
DD
i.e. CPU substrate PNP
I
substrate transistor
high
Typical remote
Local Ground
shows a detailed block diagram of the temperature measurement circuit. As shown, the
I
Figure 3.3 EMC1203 External Diode Examples
low
Diode
Bias
I
bias
DN
DP
to
to
Delta Vbe
Sample
discrete PNP transistor
Hold
DATASHEET
&
Typical remote
i.e. 2N3906
TM
5
Sensor Interface
Modulator
Sigma
Delta
1-bit
DP
DN
to
to
discrete NPN transistor
Typical remote
i.e. 2N3904
Averaging
Digital
Filter
11-bit Output
DP
DN
to
to
Revision 1.1 (06-12-06)
Figure
3.3: