EVB-EMC1001 SMSC, EVB-EMC1001 Datasheet - Page 5

• Manufacturer Part Number: EVB-EMC1001
• Description: MCU, MPU & DSP Development Tools Evaluation Board
• Manufacturer: SMSC

Specifications of EVB-EMC1001

• Processor To Be Evaluated: EMC1001
• Interface Type: USB
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

EVB-EMC1001 User Manual
3 Circuit Description
3.1
3.2
3.3
3.4
3.5
3.6
3.7
SMSC EMC1001
Introduction
EMC1001
USB to SMBus Bridge
Power Source
Fan Drive Circuit
System Interrupts / LEDs
Direct SMBus Connect Option
The EMC1001 EVB provides the means to demonstrate EMC1001 features and to view and modify
registers. LED Indicators and test points are included to show status information and a fan driver circuit
linearly drives a 5V fan to 3 different speeds based on programmable temperature limits.
The EMC1001 is an SMBus temperature sensor in a 6 pin SOT23 package. The EMC1001 has 2
programmable outputs,
temperatures exceed programmed limits.
The USB to SMBus bridge is based on an 8051 microcontroller 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 SMBus and the USB driver. Power is sourced to the
MCU from the USB interface.
This demo board derives +5V power from the USB port. The bridge microcontroller has an internal
voltage regulator that supplies +3.3V to the EMC1001 and other EVB circuits.
The fan drive circuit linearly drives a 5V, 2-wire fan. Three different drive voltages are possible with
the resistor values used on this EVB, 0, 2.4 and 4.1V. If R6 is populated with an 820 ohm resistor, the
fan drive voltages will be approximately 2.4, 3.2. and 4.1V. Other fan drive voltage combinations can
be achieved by varying R3, R4 and R6. R3 and R4 are located on the top side of the PCB next to
transistor Q1. R6 is on the bottom side of the PCB directly opposite Q1.
Note: Full fan ON cannot be achieved with this circuit due to transistor voltage drop.
The fan drive voltage is set by controlling Q1’s base and emitter voltages. When neither the
Alert/Therm2
the base and emitter voltages are high and the fan will be OFF. When the
asserted low, the base voltage is set by the resistor divider R3/R4. Asserting the
will turn the transistor fully ON, resulting in the maximum fan drive voltage for this circuit, which is
approximately 4.1V.
The
Alert (red) status The
RegMan application.
It is also possible to connect an external SMBus master to the EMC1001 EVB. A few modifications to
the circuit are required:
n
Cut 3 traces connecting JP4 pins 3-4, 5-6 and 7-8 on the bottom side of the PCB. This will
disconnect the USB bridge from the SMBus. The pullup resistors for the SMBus SDA, SCL and
Alert/Therm2
SMBus Master.
Alert/Therm2
or
Addr
signals are also disconnected so external pullups will need to be supplied by the
and
/
Therm
Therm
Alert/Therm2
Alert/Therm2
outputs are asserted low, no current flows through Q1’s base terminal so
outputs each have a dual-color LED to indicate the Normal (green) and
line is also routed to the USB bridge to provide Alert status to the
and
5
Addr
/
Therm
, which may be configured to assert when
Alert/Therm2
Addr
Revision 1.1 (12-14-06)
/
Therm
output low
output is