Cirrus Logic CRD5463PM - Manual (Page 4)

CRD5463PM
4 DS805RD2
2.3 Current Sensor
The AC load current must be converted into a low-level voltage signal before being applied to the CS5463.
A shunt resistor is a very common choice for current sensing in power monitoring applications because it
is inexpensive, small, linear, and normally doesn't introduce phase shift.
Figure 4. CRD5463PM Shunt Resistor Current Sensor
Benefiting from its 50x gain amplifier and the low noise level on the current channel, the CS5463 can ac-
commodate the ultra low-value shunt to achieve both low power dissipation at high current and high ac-
curacy at low current.
The shunt resistance is determined by the maximum peak load current (I
peak
) and the CS5463 current
channel’s maximum input range. With the 50x PGA setting, the maximum input range of the CS5463’s
current channel is 50 mVp. Therefore, the Rshunt is chosen to satisfy the equation:
The power rating of the shunt should be at least twice the actual power dissipation of the shunt with the
maximum continuous load current.
To measure the maximum of 15 A RMS and 23 A peak load current, the CRD5463PM uses a 2 m
Ω, 1.5 W
shunt resistor as the current sensor.
2.4 CS5463 Power Measurement IC
The power measurement device CS5463 is on the daughter board. The CS5463 is an integrated power
measurement device which combines two
ΔΣ analog-to-digital converter, power calculation engine and a
serial interface on a single chip. The sensed line voltage and load current are first converted into 24-bit
instantaneous values. The powerful on-chip DSP calculates voltage and current RMS values, active pow-
er, reactive power, apparent power, power factor, etc.
All these measurement values are available in specifically addressed 24-bit registers which can be ac-
cessed through SPI interface.
For more detailed information of the CS5463, please refer to the CS5463 datasheet.
http://www.cirrus.com/en/pubs/proDatasheet/CS5463_F2.pdf
I
R
Shunt
Vout Rshunt I Vout
× =
mVp Rshunt Ipeak 50
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