EMC1046/47 EVB User Manual
SMSC EMC1046/47
Revision 1.0 (08-21-07)
7
3 Hardware Description
3.1
Introduction
The EVB-EMC1046/47 provides the means to demonstrate all of the EMC1046/47 features and to view
and modify registers. LEDs indicate status information and test points are included to monitor system
voltages with a user provided voltmeter or oscilloscope.
3.2
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.
3.2.1
Direct SMBus Connect Option
It is also possible to connect an external SMBus master to the EVB-EMC1046/47. A few jumper
settings are all that is required to drive the EMC1046/47 on the EVB:
n
Simply remove the jumpers on JP19 and connect the SMBus master to the SCL, SDA and 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.
3.3
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. These connections have been provided on P1. Consult the CPU
manufacturer’s datasheet for guidance on interfacing to the thermal diode. Refer to the schematic EVb-
EMC104647_SCH-7121-RevA.pdf for details on the EVB header connections.
3.4
Resistance Error Correction (REC)
External diode 1 on board the EVB-EMC1046/47 has a series resistance adjustment on the DN line.
Checking the REC (Resistance Error Correction) feature is accomplished by turning the resistor wheel
R1. With REC off, a significant temperature error will result. When the REC bit is set, the error will be
corrected for.
3.5
Power Source
This EVB requires only one USB connection to power the entire board. The USB-SMBus bridge
regulates the +5V USB power to +3.3V used by the EMC1046/47 and other EVB circuitry.
3.6
Test Points
Test points are provided for:
n
Ground
n
VDD supply pin
n
+3.3V power
n
+5V_USB power
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