cs5451a Cirrus Logic, Inc., cs5451a Datasheet - Page 8

• Manufacturer Part Number: cs5451a
• Description: Six-channel, Delta-sigma Analog-to-digital Converter
• Manufacturer: Cirrus Logic, Inc.

3. THEORY OF OPERATION
The CS5451A is a six-channel analog-to-digital convert-
er (ADC) followed by a serial interface that allows com-
munication with a target device. The analog inputs are
structured for 3-phase power meter applications, with
three dedicated voltage and current channels. Figure 2
illustrates the CS5451A typical inputs and power supply
connections.
The voltage-sensing element introduces a voltage
waveform on the voltage channel inputs VIN(1-3)± and
is subject to a fixed 1x gain amplifier. A fourth-order del-
ta-sigma modulator samples the amplified signal for dig-
itization.
Simultaneously, the current-sensing element introduces
a voltage waveform on the current channel input
8
V
I
PHASE
PHASE
+
Figure 2. Typical Connection Diagram
Reference
Optional
External
+3 V
1.2 V
-2 V
IIN(1-3)± and is subject to two selectable gains of the
programmable gain amplifier (PGA). The amplified sig-
nal is sampled by a fourth-order delta-sigma modulator
for digitization. Both converters sample at a rate of
XIN/8, the over-sampling provides a wide dynamic
range and simplified anti-alias filter design.
The decimating digital filters on all channels are Sinc
filters. The single bit data is passed to the low-pass dec-
imation filter and output at a fixed word rate. The deci-
mation rate is selectable for two output word rates.
The 16-bit output word is then transmitted via a master
serial data port. The six-channel data is multiplexed on
the serial data output and is preceded by a frame sync
signal.
VIN1-, VIN2-, or VIN3-
REFIN
IIN1+, IIN2+, or IIN3+
AGND
REFOUT
VIN1+, VIN2+, or VIN3+
IIN1-, IIN2-, or IIN3-
NOTE: Current input channels
VA+
VA-
actually measure voltage.
DGND
VD+
CS5451A
DS635F2
3