CDB5460A Datasheet, PDF (5/28 Pages) Cirrus Logic – Evaluation Board and Software

CDB5460A
1. HARDWARE
1.1 Introduction
The CDB5460A evaluation board provides a quick
means of evaluating the CS5460A Power Meter IC.
The CDB5460A evaluation board’s analog section
operates from either a single +5 V or dual ±2.5 V
power supply. The evaluation board interfaces the
CS5460A to an IBM^TM compatible PC via an RS-
232 interface. To accomplish this, the board comes
equipped with an 80C51 microcontroller and a 9-
pin RS-232 cable which physically interfaces the
evaluation board to the PC. Additionally, analysis
software provides easy access to the internal regis-
ters of the CS5460A, and provides a means to dis-
play the performance in the time domain or
frequency domain.
1.2 Evaluation Board Overview
The board is partitioned into two main sections: an-
alog and digital. The analog section consists of the
CS5460A and a precision voltage reference. The
digital section consists of the 80C51 microcontrol-
ler, 32 Kilobytes of SRAM, the hardware test
switches, the reset circuitry, and the RS-232 inter-
face. The board also has a user friendly power sup-
ply connection.
1.2.1 Analog Section
The CS5460A is designed to accurately measure
and calculate: Energy, Instantaneous Power, I_RMS,
and V_RMS while operating from a 4.096 MHz crys-
tal. As shown in Figure 9 there are four BNC con-
nectors (J6, J7, J8, J9) provided for converter input
connections. A Shunt Sensor or Current Trans-
former can be connected to the converter’s current
inputs via J9 (IIN+) and J8 (IIN-). A voltage divid-
er can be connected to the converter’s voltage input
via J6 (VIN+) and J7 (VIN-). Note, a simple RC
network filters the sensor’s output to reduce any in-
terference picked up by the input leads. The 3 dB
corner of the filter is approximately 50 KHz differ-
ential and common mode.
The evaluation board provides three voltage refer-
ence options, on-chip, on-board and external, as
shown in Figure 9. Table 1 illustrates the options
available. With J18’s jumpers in position RE-
FOUT, the on-chip reference provides 2.5 volts.
With J18’s jumpers in position LT1019, the
LT1019 provides 2.5 volts (the LT1019 was chosen
for its low drift, typically 5 ppm/°C). By setting
J18’s jumpers to position REF+, the user can sup-
ply an external voltage reference to J26’s REF+
and VA- inputs. Application Note 4 on the web
(http://www.cirrus.com/products//pubs.html) de-
tails various voltage references.
Reference
LT1019
REF+
Description
Selects on board
LT1019 Reference
(5ppm/°C)
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 CS5460A
O O LT1019
O O REF+
O O REFOUT
Table 1. Reference Selection
The CS5460A serial interfaces are SPI^TM and Mi-
crowire^TM compatible. The interface control lines
(CS, SDI, SDO, and SCLK) are connected to the
80C51 microcontroller via Port 1. To interface an
external microcontroller, these control lines are
also connected to J19 (Header 19). However to ac-
complish this, the evaluation board must be modi-
fied in one of three ways: 1) cut the interface
control traces going to the microcontroller, 2) re-
move resistors 24, 23, 22, and 21, or 3) remove the
microcontroller.
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