CDB5461 Datasheet, PDF (4/27 Pages) Cirrus Logic – Evaluation Board and Software

CDB5461
1. HARDWARE
1.1 Introduction
The CDB5461 evaluation board provides a
quick means of evaluating the CS5461 Power
Meter IC. The CDB5461 evaluation board’s
analog section operates from a single +5V
power supply. The evaluation board interfaces
the CS5461 to an IBM^® compatible PC via an
RS-232 interface. Additional analysis software
provides easy access to the internal registers
of the CS5461, and provides a means to mea-
sure and display the performance in the time
and frequency domains.
1.2 Evaluation Board Overview
The board is partitioned into two main sec-
tions: analog and digital. The analog section
consists of the CS5461 and a precision volt-
age reference. The digital section consists of
the 8051 microcontroller, 32 Kilobytes of
SRAM, the hardware test switches, the reset
circuitry, and the RS-232 interface. The board
also has a user friendly power supply connec-
tion.
1.2.1 Analog Section
The CS5461 is designed to accurately mea-
sure and calculate: Energy, Instantaneous
Power, I_RMS, and V_RMS while operating from a
4.096 MHz crystal. As shown in Figure 9,
there are four BNC connectors (J6, J7, J8, J9)
provided for converter input connections. A
Shunt Sensor or Current Transformer can be
connected to the converter’s current inputs via
J9 (IIN+) and J8 (IIN-). A voltage divider can
be connected to the converter’s voltage input
via J6 (VIN+) and J7 (VIN-). A simple RC net-
work filters the sensor’s output to reduce any
interference picked up by the input leads. The
3 dB corner of the filter is approximately
50 kHz differential and common mode.
The evaluation board provides three voltage
reference options: On-chip, On-board, and Ex-
ternal, as shown in Figure 9. Table 1 illustrates
the options available. With J18’s jumpers in
position REFOUT, the CS5461’s on-chip refer-
ence provides 2.5V. With J18’s jumpers in po-
sition LT1019, the LT1019 provides 2.5V (the
LT1019 was chosen for its low drift, typically
5 ppm/°C). If needed R29 can be populated
and use to dial-in a specific reference voltage
just above or below 2.5V. By setting J18’s
jumpers to position REF+, VREFIN will be set
to the external voltage at J26’s REF+ and VA-
inputs.
Reference
LT1019
Description
Selects on board
LT1019 Reference
(5ppm/°C)
REF+
Selects external
reference
J18
O O LT1019
O O REF+
O O REFOUT
O O LT1019
O O REF+
O O REFOUT
REFOUT
Selects the reference
supplied by CS5461
O O LT1019
O O REF+
O O REFOUT
Table 1. Reference Selection
The CS5461 serial interfaces are SPI^TM and
Microwire^TM compatible. The interface control
lines (CS, SDI, SDO, and SCLK) are connect-
ed to the 8051 microcontroller via Port 1. To in-
terface an external microcontroller, these
control lines are also connected to J19 (Head-
er 19). However to accomplish this, the evalu-
ation board must be modified in one of three
ways: 1) cut the interface control traces going
to the microcontroller, 2) remove resistors 24,
23, 22, and 21, or 3) remove the microcontrol-
ler.
4