CS5461A

16

DS661F2

INT pin will become active if the DRDY bit is unmasked

in the Mask Register. When these bits are set, they

must be cleared (logic 0) by the user before they can be

asserted again.

If the Cycle Count Register (N) is set to 1, all output cal-

culations are instantaneous, and DRDY, like CRDY, will

indicate when instantaneous measurements are fin-

ished. Some calculations are inhibited when the cycle

count is less than 2.

5.4 Energy Pulse Output

The CS5461A provides three output pins for energy reg-

istration. The E1 and E2 pins provide a simple interface

which energy can be registered. These pins are de-

signed to directly connect to a stepper motor or electro-

mechanical counter. E1 and E2 pins can be set to one

of four pulse output formats, Normal, Alternate, Stepper

Motor, or Mechanical Counter. Table 2 defines the

pulse output format, which is controlled by bits ALT in

the Configuration Register, and MECH and STEP in the

Control Register.

The E3 pin is designated for system calibration, the

pulse rate can be selected to reach a frequency of

512 kHz.

The pulse output frequency of E1 and E2 is directly pro-

portional to the active power calculated from the input

signals. To calculate the output frequency on E1 and

E2, the following transfer function can be utilized:

With MCLK = 4.096 MHz, PF = 1, and default settings,

the pulses will have an average frequency equal to the

the input signals applied to the voltage and current

channels cause full-scale readings in the instantaneous

voltage and current registers. When MCLK/K is not

equal to 4.096 MHz, the user should scale the

by

a

factor

of

4.096 MHz/(MCLK/K) to get the actual pulse rate out-

put.

5.4.1 Normal Format

The Normal format is the default. Figure 3 illustrates the

output format on pins E1 and E2. The E1 pin outputs ac-

tive-low pulses with a frequency proportional to the ac-

tive power. The E2 pin is the energy direction indicator.

Positive energy is represented by a pulse on the E1 pin

while the E2 pin remains high. Negative energy is rep-

resented by synchronous pulses on both the E1 pin and

the E2 pin.

quency on output pin E1, when full-scale input signals

are applied to the voltage and current channels. The

maximum

pulse

frequency

from

the

E1

pin

ALT

STEP

MECH

FORMAT

000

Normal

0

X

1

Mechanical Counter

0

1

0

Stepper Motor

1

X

1

Alternate Pulse

Table 2. E1 and E2 Pulse Output Format

VIN = rms voltage across VIN+ and VIN- [V]

VGAIN = Voltage channel gain

IIN = rms voltage across IIN+ and IIN- [V]

IGAIN = Current channel gain

PF = Power Factor

PulseRateE1,2 = Maximum frequency on E1 and E2 [Hz]

VREFIN = Voltage at VREFIN pin [V]

FREQ

E

VIN

VGAIN

×

IIN

×

IGAIN

PF

×

PulseRateE

12

,

×

×

VREFIN

2

------------------------------------------------------------------------------------------------------------------------------------------------

=

E1

P o s itiv e E nergy B u rs t

N e g a tiv e E nergy B u rs t

. . .

. . .

. . .

. . .

E2

t

du r

Figure 3. Normal Format on pulse outputs E1 and E2