CS5466 Ver la hoja de datos (PDF) - Cirrus Logic

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componentes Descripción

Fabricante

CS5466

Low-cost Power/Energy IC with Pulse Output

Cirrus Logic 

CS5466

4th Order

IIN± PGA

∆Σ

Sinc3 IIR

HPF

Modulator

Digital Filter

Current Channel

2nd Order

VIN± 10x

∆Σ

Sinc3 IIR

HPF

Modulator

Digital Filter

Voltage Channel

FREQ[2:0]

IGAIN[1:0]

HPF

Config

N=400

xΣ

N

Energy-to-

Pulse Rate

Converter

E1

E2

FOUT

NEG

Figure 2. Data Flow

4. THEORY OF OPERATION

The CS5466 is a dual-channel analog-to-digital convert-

er (ADC) followed by a computation engine that per-

forms an energy-to-pulse conversion. The flow diagram

for the two data paths is depicted in Figure 2. The ana-

log inputs are structured with two dedicated channels,

voltage and current, then optimized to simplify interfac-

ing to sensing elements.

The voltage-sensing element introduces a voltage

waveform on the voltage channel input VIN± and is sub-

ject to a fixed 10x gain amplifier. A second-order delta-

sigma modulator samples the amplified signal for digiti-

zation.

Simultaneously, the current sensing element introduces

a voltage waveform on the current channel input IIN±

and is subject to four programmable gains. The ampli-

fied signal is sampled by a fourth-order delta-sigma

modulator for digitization. Both converters sample at a

rate of MCLK / 8. The over-sampling provides a wide

dynamic range and simplified anti-alias filter design.

4.1 Digital Filters

The decimating digital filters on both channels are Sinc3

filters followed by fourth-order IIR filters. The single-bit

data is passed to the low-pass decimation filter and out-

put at a fixed word rate. The output word is passed to

the IIR filter to compensate for the magnitude roll-off of

the low-pass filtering operation.

An optional digital high-pass filter (HPF in Figure 2) re-

moves any DC component from the selected signal

path. By removing the DC component from the voltage

or current channel, any DC content will also be removed

from the calculated average active (real) power as well.

4.2 Active Power Computation

The instantaneous voltage and current data samples

are multiplied to obtain the instantaneous power. The

product is then averaged over 400 conversions to com-

pute the active power value used to drive pulse outputs

E1, E2, and FOUT. Output pulse rate of E1 and E2 can

be set to one of four frequencies to directly drive a step-

per motor or a electromechanical counter or interface to

a microcontroller or infrared LED. The alternating output

pulses of E1 and E2 allows for use with low-cost elec-

tromechanical counters.

Output FOUT provides a uniform pulse stream that is

proportional to the active power and is designed for sys-

tem calibration. The FREQ[2:0] inputs set the output

pulse rate of E1, E2, and FOUT. See ”Energy Pulse

Outputs” on page 11. for more details.

10

DS659F1

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