COMBOSOLAR datasheet(26/57 Pages) TI1

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· · ·

IN,PGA1

C =

From line coupling circuit

To Rx PGA1

See Note (1)

· · · IN,PGA2

C =

Rx C1

Rx C2

330 W

To ADC input on MCU

From line coupling circuit

or passive bandpass filter

LPF

PGA

Note (2)

Inside the AFE031

Rx_PGA1_OUT

Rx_F_IN

Rx_PGA1_

Rx_PGA2_

OUT

Rx_F_

OUT

RX_PGA2_IN

· · · IN,PGA1

C =

Note (1)

Rx_C1

Rx_C2

See Note (3)

AFE031

SBOS531D – AUGUST 2010 – REVISED MAY 2012

www.ti.com

The Rx Filter is a very low noise, unity-gain, fourth-order low-pass filter. The Rx Filter cutoff frequency is

selectable between CENELEC A or CENELEC B, C, and D modes. The Control1 Register bit location 3 setting

(CA CBCD) determines the cutoff frequency. Setting Control1 Register bit location 3 to '0' selects the CENELEC

A band; setting Control1 Register bit location 3 to '1' selects the CENELEC B, C, and D bands. Because the Rx

Filter is a very low noise analog filter, two external capacitors are required to properly configure the Rx Filter.

Table 3 shows the proper capacitance values for CENELEC A, B, C, and D bands. Capacitor Rx C1 is connected

between pin 24 and ground, and Rx C2 is connected between pin 23 and ground. For the capacitors shown, it is

recommended that these components be rated to withstand the full AVDD power-supply voltage

Table 3. Recommended External Capacitors Required for Rx Filter

FREQUENCY BAND

Rx C1, PIN 24

Rx C2, PIN 23

CUTOFF FREQUENCY (kHz)

CENELEC A

680 pF

CENELEC B, C, D

270 pF

560 pF

145

Figure 32 illustrates the recommended connections for the Rx signal chain.

(1)

For capacitor value C1, f is the desired lower cutoff frequency and RIN,PGA1 is the input resistance of Rx PGA1.

(2)

For capacitor value C2, f is the desired lower cutoff frequency and RIN,PGA2 is the input resistance of Rx PGA2.

(3)

Refer to Table 3.

Figure 32. Recommended Connections for Rx Signal Chain

As Figure 33 shows, a fourth-order passive passband filter is optional but recommended for applications where

high performance is required. The external passive passband filter removes any unwanted, out-of-band signals

from the signal path, and prevents them from reaching the active internal filters within the AFE031.

(1)

For capacitor value C, f is the desired lower cutoff frequency and RIN,PGA1 is the input resistance of Rx PGA1. Refer

to Table 3.

Figure 33. Passive Bandpass Rx Filter

Product Folder Link(s): AFE031

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