PAC1921
HIGH-SIDE CURRENT/POWER SENSOR
EVALUATION BOARD USER’S GUIDE
2015 Microchip Technology Inc.
DS50002376A-page 21
Chapter 3. Hardware Description
3.1
INTRODUCTION
The PAC1921 High-Side Current/Power Sensor Evaluation Board provides the means
to evaluate features, and to view and modify registers. There are two modes for using
the evaluation board:
• Demo mode: Monitors an on-board power source
• Sys mode: Monitors an external power source
LEDs indicate status information and test points are included to monitor system
voltages with a user-provided voltmeter or oscilloscope.
The PAC1921 device is an SMBus-compliant, high-side current/power monitor in a
10-pin, 3 mm x 3 mm DFN package. For details regarding the PAC1921 device, refer
to the
“PAC1921 Data Sheet”
(DS20005293).
3.1.1
Power Source
The board requires only one Universal Serial Bus (USB) connection to power the
board. USB bus voltage is provided to the on-board test power sources and the
USB-to-SMBus bridge. The evaluation board circuitry uses the on-board regulator to
regulate the +5V USB power to +3.3V.
3.2
USB-TO-SMBus BRIDGE
The USB-to-SMBus is based on the MCP2221 USB-to-I
2
C™ protocol converter, which
provides the interface between the USB and the SMBus. Power is sourced to the
microcontroller 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 PAC1921 High-Side
Current/Power Sensor Evaluation Board. A few modifications to the board are
required, as explained below:
• Remove the jumpers on J13 and connect the SMBus master to the
SMBus_DATA, SMBus_CLK and #READ/INT pins, as well as an external supply
for +3.3V. Note that a return is also provided on this header for convenience
(GND).
• The +3.3V can be supplied by the SMBus bridge by leaving the +3.3V jumper in
place and retaining the USB connection.
