CS5490 datasheet(20/57 Pages) CIRRUS

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CS5490

DS982F3

After reset, the energy pulse generation block is

disabled (DOMODE[3:0] = Hi-Z). To output a desired

energy pulse to a DO pin, it is necessary to follow the

steps below:

1. Write to register PulseWidth (page 0, address 8) to

select the energy pulse width and pulse frequency

range.

2. Write to register PulseRate (page 18, address 28) to

select the energy pulse rate.

3. Write to register PulseCtrl (page 0, address 9) to

select the input to the energy pulse generation block.

4. Write ‘1’ to bit EPG_ON of register Config1 (page 0,

address 1) to enable the energy pulse generation

block.

5. Wait at least 0.1s.

6. Write bits DOMODE[3:0] of register Config1 to select

DO to output pulses from the energy pulse

generation block.

7. Send DSP instruction (0xD5) to begin continuous

conversion.

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. For example, if a meter

has the meter constant of 1000imp/kWh, a maximum

voltage (UMAX) of 240V, 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 240 x 100 = 24kW or 6.6667Hz

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

Fout = 6.6667/0.36 = 18.5185Hz.

Refer to section 6.6.6 Pulse Output Width (PulseWidth)

– Page 0, Address 8 on page 36. The FREQ_RNG[3:0]

bits should be set to b[0110].

PSUM Sign

QSUM Sign

P Sign

Q Sign

Reserved

V Crossing

I Crossing

DO_OD

(Config1)

(PulseCtrl) EPGIN[3:0]

DOMODE[3:0]

(Config1)

Hi-Z

Interrupt

PSUM

QSUM

SSUM

PAVG

QAVG

PULSE RATE

EPG_ON

(Config1)

MCLK

(PulseWidth) PW[7:0]

(PulseWidth) FREQ_RNG[3:0]

0000

0001

0010

0011

0100

0101

0110

0111

1000

0000

0001

0010

0011

0100

0101

0110

0111

1000

1001

1010

1011

1100

1101

1110

1111

Reserved

Figure 10. Energy Pulse Generation and Digital Output Control

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