AFE4490 datasheet(21/69 Pages) TI

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AFE4400

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SBAS601D – DECEMBER 2012 – REVISED MAY 2013

Receiver Control Signals

LED2 sample phase (SLED2): When this signal is high, the amplifier output corresponds to the LED2 on-time.

The amplifier output is filtered and sampled into capacitor CLED2. To avoid settling effects resulting from the LED

or cable, program SLED2 to start after the LED turns on. This settling delay is programmable.

Ambient sample phase (SLED2_amb): When this signal is high, the amplifier output corresponds to the LED2 off-

time and can be used to estimate the ambient signal (for the LED2 phase). The amplifier output is filtered and

sampled into capacitor CLED2_amb.

LED1 sample phase (SLED1): When this signal is high, the amplifier output corresponds to the LED1 on-time.

The amplifier output is filtered and sampled into capacitor CLED1. To avoid settling effects resulting from the LED

or cable, program SLED1 to start after the LED turns on. This settling delay is programmable.

Ambient sample phase (SLED1_amb): When this signal is high, the amplifier output corresponds to the LED1 off-

time and can be used to estimate the ambient signal (for the LED1 phase). The amplifier output is filtered and

sampled into capacitor CLED1_amb.

LED2 convert phase (CONVLED2): When this signal is high, the voltage sampled on CLED2 is buffered and

applied to the ADC for conversion. The conversion time duration is always 25% of the pulse repetition period. At

the end of the conversion, the ADC provides a single digital code corresponding to the LED2 sample.

Ambient convert phases (CONVLED2_amb, CONVLED1_amb): When this signal is high, the voltage sampled on

CLED2_amb (or CLED1_amb) is buffered and applied to the ADC for conversion. The conversion time duration is

always 25% of the pulse repetition period. At the end of the conversion, the ADC provides a single digital code

corresponding to the ambient sample.

LED1 convert phase (CONVLED1): When this signal is high, the voltage sampled on CLED1 is buffered and

applied to the ADC for conversion. The conversion time duration is always 25% of the pulse repetition period. At

the end of the conversion, the ADC provides a single digital code corresponding to the LED1 sample.

Receiver Timing

See Figure 36 for a timing diagram detailing the control signals related to the LED on-time, Rx sample time, and

the ADC conversion times for each channel.

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