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EMC1201 View Datasheet(PDF) - SMSC -> Microchip

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EMC1201 Datasheet PDF : 0 Pages
Single/Dual Single-Wire Temp Sensor in SOT23-5 Using SMSC BudgetBusTMSensor Interface
Datasheet
VDD
Ihigh
Ilow
Ibias
fs
fs
fs
fs/2048
Internal or
Remote Diode
Bias
Diode
Delta Vbe
Sample
&
Hold
1-bit
Sigma
Delta
Modulator
Digital
Averaging
Filter
11-bit
Accurate
Conversion
3.1.1
Figure 3.2 Detailed Block Diagram of Temperature Monitor Architecture
Figure 3.2 shows a detailed block diagram of the temperature measurement circuit. As shown, the
EMC1201 and EMC1202 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.
EMC1202 Temperature Monitoring
The EMC1202, incorporates one internal diode and can monitor an additional temperature zone via
one external diode. An internal analog multiplexer switches between the internal and external diode.
Total conversion time for one internal and one external temperature reading is about 40ms. The
external diode 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 Figure 3.3:
3.2
to
DP
to
DN
Local Ground
to
to
DP
DP
to
to
DN
DN
Typical remote
substrate transistor
i.e. CPU substrate PNP
Typical remote
discrete PNP transistor
i.e. 2N3906
Typical remote
discrete NPN transistor
i.e. 2N3904
Figure 3.3 EMC1202 External Diode Examples
SMSC BudgetBus™ Sensor Interface
The EMC1201 and EMC1202 communicate with a host controller, such as the KBC1100, through the
proprietary single wire SMSC BudgetBus™ Sensor Interface known as BBUS. The BBUS is a single
SMSC EMC1201/EMC1202
7
DATASHEET
Revision 1.0 (06-14-06)
 

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