Cirrus Logic CDB5451A - Manual (Page 4)

CDB5451A
4 DS458DB3
2. HARDWARE
2.1 Evaluation Board Description
The CDB5451A board contains circuitry that will:
• Accept appropriate DC voltage levels from
the user’s +3V and/or +5V power supplies,
and direct this power to the VA+, VD+, VA-
and DGND pins of the CS5451A.
• Direct the six analog input signals to the six
input pairs of the CS5451A.
• Supply necessary voltage reference input
for the CS5451A’s VREFIN pin.
• Supply appropriate crystal/oscillator stimu-
lus to the CS5451A’s XIN pin.
• Direct the output driver signal from the
CS5451A’s charge-pump driver pin (CPD)
which is used produce the negative power
supply source for the CS5451A’s VA- pin.
• Provide a reset switch that allows the user to
set the CS5451A’s RESET pin from logic “1”
to logic “0”.
• Provide two DIP switches which allow the
user to set the logic levels on the CS5451A’s
GAIN and OWRS input pins.
• Detect and receive the data frame signal
and digital serial output data signals from
the CS5451A’s FSO and SDO pins, and
send this output data through the included
parallel cable, and up to user’s PC.
Several areas of blank proto-board space are pro-
vided so that, if desired, the user can interface their
own electronic sensor equipment onto the board.
The output from these sensors can be wired to the
six nearby analog input terminal block connectors,
which is then fed to the six analog input channels
of the CS5451A. Examples of such sensors would
include voltage and current transformers, shunt re-
sistors, and resistor divider networks.
The next section of this document describes the
various sections of the board. After this, operation
of the PC software is described in detail.
2.2 Power Supply Connections
The CDB5451A can be used in several different
power supply configurations. Table 1 shows the
various possible power connections with the re-
quired jumper settings. There are various +3 V
and +5 V options. The user must supply the +3V,
+5V, GND, and sometimes -2V voltage levels
needed to power the evaluation board.
2.2.1 Analog Power Supply
Referring to Figure 1, the A+ post supplies power
to the positive analog power input pin (VA+) of the
CS5451A. This post also supplies power to the
LT1004 voltage reference (D3) and the optional
+3V regulator (U5). If HDR9 is set to the “A-” set-
ting, the A- post can supply the required negative
voltage to the VA- pin of the CS5451A.
Note that the evaluation board contains the foot-
prints and connectivity which allows the user to in-
stall a LM317 voltage regulator (U5), which can be
used to create +3 V from a +5 V supply. This op-
tion is useful if the user wants to interface the eval-
uation board to another board that can only
operate from a +5V supply. With HDR17 set to
“+5V_IN”, one single +5 V supply can be used to
provide both the +5 V power to a microcontroller
and/or other devices, as well as +3 V for the
CDB5451A board. The included schematic dia-
gram shows the circuitry for the +5V regulator cir-
cuitry inside a box with dashed lines. These
components are not populated when the board is
shipped from the factory, but the user can install
these components if desired.
2.2.2 Digital Power Supply
The A+ post can be used to supply both the analog
power (to CS5451A VA+ pin) as well as the digital
power (to CS5451A VD+ pin). However if a sepa-
rate supply voltage is desired for the digital power
supply, the “VD+” banana connector post can be
used to independently supply a separate digital
power supply to the input of the CS5451A (VD+
pin), the 4.096 MHz oscillator (U1), and circuitry for
the parallel port interface. This is controlled by the
setting on HDR18.
The user should note that the CS5451A can oper-
ate with a digital supply voltage of either +3V or