AFE032 datasheet(20/77 Pages) TI1

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From Line-Coupling Circuit

To RX_PGA1 Input

RXPGA

Programmable

Filter

RX_PGA1

RX_PGA2_IN

RX_F_OUT

RX_PGA2_ OUT

RX_PGA1_IN

RX_PGA2

From line-coupling circuit

or passive band-pass filter.

To ADC input of MCU.

330 :

RXPGA

)

(

RXPGA

Inside the Device

RRXPGA2IN

RRXPGA1IN

1 k:

AFE032

SBOS669A – AUGUST 2013 – REVISED DECEMBER 2013

www.ti.com

The capacitors listed in Figure 14 should be rated to withstand the full AVDD power-supply voltage for CDAC and

PA_VS for CIN.

Rx Block

The Rx block consists of the Rx PGA1, Rx filter, and Rx PGA2. Both Rx PGA1 and Rx PGA2 are high-

performance programmable gain amplifiers that can be configured through the SPI interface.

Rx PGA1 can operate as either an attenuator or in gain. The Rx PGA1 gain steps are 0.125 V/V, 0.25 V/V, 0.5

V/V, 1 V/V, 2 V/V, 4 V/V, 8 V/V, 16 V/V, and 32 V/V. Gains are selectable with the RX_PGA1 gain bits (bits 7 to

4 in the REG_RXPGA_CFG register). Configuring the Rx PGA1 as an attenuator (at gains less than 1 V/V) is

useful for applications where large interference signals are present within the signal band. Attenuating the large

interference allows these signals to pass through the analog Rx signal chain without causing an overload; the

interference signal can then be processed and removed within the microprocessor as necessary. Similarly, if a

transmitter is located close to the receiver, gains less than 1 V/V may be needed.

The Rx PGA2 gain steps are 1 V/V, 4 V/V, and 16 V/V. Gains are selectable through the RX_PGA2 gain bits

(bits 3 to 1 in the REG_RXPGA_CFG register).

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

frequency is selectable between the CENELEC (bands A, B, C, or D), ARIB, or FCC modes. The LPF band

select bits (bits 6 to 4 of the REG_HPF/LPF_REG register) determine the cutoff frequency for the LPF. The HPF

band select bits (bits 1 and 2 of the REG_HPF/LPF_REG register) set up the cutoff frequency of the HPF.

Recommended connections for the Rx signal chain are shown in Figure 15.

(1) For capacitor value C1, f is the desired lower cutoff frequency and RRXPAG1IN is the input resistance of RX_PGA1.

(2) For capacitor value C2, f is the desired lower cutoff frequency and RRXPAG2IN is the input resistance of RX_PGA2.

Figure 15. Recommended Connections for Rx Signal Chain

Figure 16 shows, a fourth-order, passive band-pass filter that is optional but recommended for applications with

high performance needs. The external passive band-pass filter removes unwanted, out-of-band signals from the

signal path, and it prevents such signals from reaching the active internal filters within the device.

(1) For capacitor value C1, f is the desired lower cutoff frequency and RRXPGA1IN is the input resistance of RX_PGA1.

Figure 16. Passive Band-Pass Rx Filter

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