AFE030 datasheet(34/58 Pages) TI1

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Time (s)

E_Tx_Out

E_Tx_In

E_Tx_Clk

3.3

100

10k

100k

10M

100M

Frequency (Hz)

High-pass cutoff determined by:

EXT

where:

= Input resistance of ERx = 78 k

= External capacitance

EXT

AFE030

SBOS588A

– DECEMBER 2011 – REVISED DECEMBER 2011

www.ti.com

ETx and ERx Blocks

The AFE030 contains a two-wire transmitter block, ETx, and a two-wire receiver block, ERx. These blocks

support communications that use amplitude shift keying (ASK) with on-off keying (OOK) modulation.

The ETx block is a gated driver that allows for transmission of a carrier input signal and modulating input signal.

For typical applications, a 50-kHz square wave carrier signal is applied to E_Tx_Clk while the modulating signal

is applied to E_Tx_In. The output (E_Tx_Out) is then in a high-impedance state when E_Tx_In is '1'. Figure 42

shows the relationship between E_Tx_Clk, E_Tx_In, and E_Tx_Out.

Figure 42. ETx Block Transfer Function

The ERx Block consists of a low-pass analog filter configured in an inverting gain of

–4.5 db. This block, along

with an external capacitor, can be used to create a passband filter response as shown in Figure 43.

Figure 43. ERx Block Frequency Response

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