CS5484 datasheet(24/67 Pages) CIRRUS

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CS5484

DS981F3

5.5.1 Pulse Rate

Before configuring the PulseRate register, the full-scale

pulse rate needs to be calculated and the frequency

range needs to be specified through FREQ_RNG[3:0]

bits in the PulseWidth register. Refer to section 6.6.6

Pulse Output Width (PulseWidth) – Page 0, Address 8

on page 41. The FREQ_RNG[3:0] bits should be set to

b[0110]. For example, if a meter has the meter constant

of 1000imp/kWh, a maximum voltage (UMAX) of 240 V,

and a maximum current (IMAX) of 100A, the maximum

pulse rate is:

[1000x(240x100/1000)]/3600 = 6.6667Hz.

Assume the meter is calibrated with UMAX and IMAX,

and the Scale register contains the default value of 0.6.

After gain calibration, the power register value will be

0.36, which represents 240x100 = 24kW or 6.6667Hz

pulse output rate. The full-scale pulse rate is:

Fout = 6.6667/0.36 = 18.5185Hz.

The CS5484 pulse generation block behaves as

follows:

• The pulse rate generated by full-scale (1.0decimal)

power register is:

FOUT =(PulseRatex2000)/2FREQ_RNG

•The PulseRate register value is:

PulseRate = (FOUTx2FREQ_RNG)/2000

= (18.5186x64)/2000

= 0.5925952

= 0x4BDA29

5.5.2 Pulse Width

The PulseWidth register defines the Active-low time of

each energy pulse:

Active-low = 250µs+(PulseWidth/64000).

By default, the PulseWidth register value is 1, and the

Active-low time of each energy pulse is 265.6µs. Note

that the pulse width should never exceed the pulse

period.

5.6 Voltage Sag, Voltage Swell, and

Overcurrent Detection

Voltage sag detection is used to determine when the

voltage falls below a predetermined level for a specified

interval of time (duration). Voltage swell and overcurrent

detection determine when the voltage or current rises

above a predetermined level for the duration.

The duration is set by the value in the V1SagDUR

(V2SagDUR),

V1SwellDUR

(V2SwellDUR),

and

I1OverDUR (I2OverDUR) registers. Setting any of these

to zero (default) disables the detect feature for the given

channel. The value is in output word rate (OWR)

samples. The predetermined level is set by the values

the

V1SagLEVEL (V2SagLEVEL),

V1SwellDUR

(V2SwellDUR), and I1OverLEVEL (I2OverLEVEL) registers.

For each enabled input channel, the measured value is

rectified and compared to the associated level register.

Over the duration window, the number of samples

above and below the level are counted. If the number of

samples below the level exceeds the number of

samples above, a Status0 register bit V1SAG (V2SAG)

is set, indicating a sag condition. If the number of

samples above the level exceeds the number of

samples below, a Status0 register bit V1SWELL

(V2SWELL) or I1OVER (I2OVER) is set, indicating a

swell or overcurrent condition (see Figure 15).

Lev el

Du ra tio n

Figure 15. Sag, Swell, and Overcurrent Detect

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