CS5460 View Datasheet(PDF) - Cirrus Logic
Part Name
Description
MFG CO.
CS5460 Datasheet PDF : 34 Pages
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CS5460
pedance than the voltage channel. These imped-
ance specs are given at the beginning of this data
sheet (see the specification titled “Effective Input
Impedance” for the voltage and current channels).
For example, the differential input impedance in
the current channel is spec’d to be 30 kOhm. As
the user increases the value of RPI to provide for
more and more common-mode surge protection,
the voltage drop across the external protection re-
sistor increases, and it divides the input signal
down more and more. This in turn reduces the dy-
namic range of the signals that are ultimately pre-
sented to the CS5460’s inputs. As an example,
suppose that the user creates a current-sensor con-
figuration that provides a differential voltage of
150mV (RMS) across shunt resistor RS at maxi-
mum line-current level. However, the user has set
RPI to 500 Ohms. This means that when there is
150mV across the shunt resistor (RS), the voltage
across the IIN+ and IIN- inputs is actually 150mV
* [ 30K / (500 + 30K)] = ~148mV (RMS). We see
that this has decreased the maximum signal input
level. To avoid this voltage division, the user
should first consider the input protection that is go-
ing to be necessary, and then calculate the sensor
gains such that the drop across the protection resis-
tors is taken into account.
Typical values for these components are RPI = 500
Ohm, CPI = 0.02uF, CPV = 0.002uF and if neces-
sary, RPV = 5 KOhm.
5.7 PCB Layout
The CS5460 should be placed entirely over an ana-
log ground plane with both the VA- and DGND
pins of the device connected to the analog plane.
Place the analog-digital plane split immediately ad-
jacent to the digital portion of the chip.
Note:
See the CDB5460 data sheet for suggested
layout details and Applications Note 18 for
more detailed layout guidelines. Before
layout, please call for our Free Schematic
Review Service.
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DS279PP5
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