Datasheet

AFE4490
SBAS602F –DECEMBER 2012–REVISED OCTOBER 2013 www.ti.com
R
G
values with various gain settings are listed in Table 2.
Table 2. R
G
Values
R
G
(dB) GAIN (kΩ)
0 (x1) 100
3.5 (x1.5) 150
6 (x2) 200
9.5 (x3) 300
12 (x4) 400
Receiver Control Signals
LED2 sample phase (S
LED2
): When this signal is high, the amplifier output corresponds to the LED2 on-time.
The amplifier output is filtered and sampled into capacitor C
LED2
. To avoid settling effects resulting from the LED
or cable, program S
LED2
to start after the LED turns on. This settling delay is programmable.
Ambient sample phase (S
LED2_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 C
LED2_amb
.
LED1 sample phase (S
LED1
): When this signal is high, the amplifier output corresponds to the LED1 on-time.
The amplifier output is filtered and sampled into capacitor C
LED1
. To avoid settling effects resulting from the LED
or cable, program S
LED1
to start after the LED turns on. This settling delay is programmable.
Ambient sample phase (S
LED1_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 C
LED1_amb
.
LED2 convert phase (CONV
LED2
): When this signal is high, the voltage sampled on C
LED2
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 (CONV
LED2_amb
, CONV
LED1_amb
): When this signal is high, the voltage sampled on
C
LED2_amb
(or C
LED1_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 (CONV
LED1
): When this signal is high, the voltage sampled on C
LED1
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 57 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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