CS5466 datasheet(11/16 Pages) CIRRUS

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CS5466

FUNCTIONAL DESCRIPTION

5.1

Analog Inputs

The CS5466 is equipped with two fully differential input

channels. The inputs VIN

± and IIN± are designated as

the voltage and current channel inputs, respectively.

The full-scale differential input voltage for the current

and voltage channel is

±250 mVP.

5.1.1

Voltage Channel

The output of the line voltage resistive divider or trans-

former is connected to the VIN+ and VIN- input pins of

the CS5466. The voltage channel is equipped with a

10x fixed gain amplifier. The full-scale signal level that

can be applied to the voltage channel is

±250 mV. If the

input signal is a sine wave the maximum RMS voltage

is:

which is approximately 70.7% of maximum peak volt-

age.

5.1.2

Current Channel

The output of the current sense resistor or transformer

is connected to the IIN+ and IIN- input pins of the

CS5466. To accommodate different current sensing de-

vices the current channel incorporates a Programmable

Gain Amplifier (PGA) that can be set to one of four input

ranges. Input pins IGAIN1 and IGAIN0 (See Table 1)

define the PGA’s four gain selections and correspond-

ing maximum input signal level.

For example if IGAIN1=IGAIN0=0, the current channel’s

PGA gain is set to 10x. If the input signals are pure si-

nusoids with zero phase shift, the maximum peak differ-

ential signal on the current or voltage channel is

±250 mVP. The input signal levels are approximately

70.7% of maximum peak voltage producing a full scale

energy pulse registration equal to 50% of absolute max-

imum energy pulse registration. This will be discussed

further in Section 5.3.

5.2

High-Pass Filter

By removing the offset from either channel, no error

component will be generated at dc when computing the

average real power. Input pin HPF defines the three op-

tions;

– High-Pass Filter (HPF) is disabled when pin

HPF is connected high.

– HPF is enabled in the voltage channel when

pin HPF is connected low.

– HPF is enabled in the current channel when pin

HPF is connected to pin FOUT.

5.3

Energy Pulse Outputs

The CS5466 provides three output pins for energy reg-

istration. The E1 and E2 pins provide a simple interface

from which energy can be registered. These pins are

designed to directly connect to a stepper motor or elec-

tromechanical counter. The pulse rate on the E1 and E2

pins are in the range of 0 to 4 Hz and all frequency set-

tings are optimized to be used with standard meter con-

stants. The FOUT pin is designated for system

calibration, the pulse rate can be selected to reach a fre-

quency of 8000 Hz.

5.3.1

Pulse Output Format.

The CS5466 produces alternating pulses on E1 and E2.

This pulse format is designed to drive a stepper motor.

Each pin produces active low pulses with a minimum

pulse width of 250 ms when MCLK = 4.096 MHz. Refer

to CS5466 Switching Characteristics on page 8 for tim-

ing parameters.

The FOUT pin issues active high pulses. The pulse

width is equal to 90 ms (typical), unless the period falls

below 180 ms. At this time the pulses will be equal to

half the period. In mode 3 (FREQ2:0 = 3), the pulse

width of all FOUT pulses is typically 20

µs regardless of

the pulse rate (MCLK = 4.096 MHz).

5.3.2

Selecting Frequency of E1 and E2

The pulse rate on E1 and E2 can be set to one of four

frequency ranges. Input pins FREQ1 and FREQ0 (See

Table 2) determine the maximum frequency on E1 and

E2 for pure sinusoidal inputs with zero phase shift. As

shown in Figure 1 on page 8, the frequency of E2 is

equal to the frequency of E1 with active low alternating

pulses.

As discussed in Section 5.1.2, the maximum frequency

on the E1 and E2 output pins is equal to the selected fre-

quency in Table 2 if the maximum peak differential sig-

nal applied to both channels is a sine wave with zero

phase shift.

IGAIN1

IGAIN0

Maximum Input

Range

±250mV

10x

±50mV

50x

±25mV

100x

±16.67mV

150x

Table 1. Current Channel PGA Setting

250mV

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

176.78mV

RMS

≅

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