EVB-EMC2101 User Manual
Revision 1.5 (12-13-06)
SMSC EMC2101
8
3.2
EMC2101
The EMC2101 is an SMBus temperature sensor with 1 internal and 1 external sensor in an 8 pin
MSOP and 8 pin SOIC package. Communications with the EMC2101 sensor is via the SMBus.
3.3
USB to SMBus Bridge
The USB to SMBus bridge is based on an 8051 micro controller with integrated USB and SMBus
interfaces as well as internal flash and RAM. During EVB manufacture, firmware is loaded into the
bridge that provides the interface between the USB and the SMBus. Power is sourced to the micro
controller from the USB interface for device power and communication.
3.3.1
Direct SMBus Connect Option
It is also possible to connect an external SMBus master to the EMC2101 EVB. A few jumper settings
are all that is required to drive the EMC2101:
n
Simply remove the jumpers on JP6 and connect the SMBus master to the SCL, SDA and ALERT
pins, as well as an external supply for +3.3V.
n
The +3.3V can be supplied by the SMBus bridge by leaving the +3.3V jumper in place and retaining
the USB connection.
3.4
Connecting to Remote Diodes
This EVB is populated with jumpers to connect to an external diode or CPU/GPU. If connecting to a
CPU’s thermal diode, it is necessary to provide a common ground. Also, it is usually necessary to bias
the appropriate CPU Vcc plane above this common ground to avoid forward-biasing the ESD diodes
with the temperature sensor signals. Test point TP3, 8, 10, or 11 provides a ground connection. Consult
the CPU manufacturer’s datasheet for guidance on interfacing to the thermal diode. Refer to the
schematic EVB-EMC2101 SCH-7069-REVB1.pdf for details on the EVB header connections.
3.5
Resistance Error Correction (REC)
The remote diode DN signal path has a 100 ohm series resistor to demonstrate the EMC2101’s REC
feature. The resistor may be effectively removed from the circuit by installing a jumper on JP7 or JP13
(-R diode). See
for details on the REC jumper settings.
3.6
Power Source
This EVB requires only a USB cable. The USB-SMBus bridge regulates the +5V USB power to +3.3V
used by the EMC2101 and other EVB ciruitry such as the fan and resistive heater.
3.7
Test Points
Test points are provided for:
n
Ground
n
+3.3V power
n
+5V_USB power
n
FAN pin output
n
ALERT output
n
TACH for 3 wire fan (included)
