Datasheet

C
3
C
4
R
2
R
3
L1
L2
From Line-Coupling
Circuit
C
1
1
2 fp R´ ´ ´
IN,PGA2
C =
2
Rx C1 Rx C2
330 W
To ADC
Input on MCU
LPF
PGA
PGA
See Note 2
Inside the AFE030
Rx_PGA1_OUT
Rx_F_IN
Rx_PGA1_
IN
Rx_PGA2_OUT
Rx_F_
OUT
PA_IN
C
2
1
2 fp R´ ´ ´
IN,PGA1
C =
1
See Note 1
Rx_C1 Rx_C2
See Note 3
AFE030
www.ti.com SBOS588A –DECEMBER 2011– REVISED DECEMBER 2011
The Rx PGA1, Rx Filter, and Rx PGA2 components have all inputs and outputs externally available to provide
maximum system design flexibility. Care should be taken when laying out the PCB traces from the inputs or
outputs to avoid excessive capacitive loading. Keeping the PCB capacitance from the inputs to ground, or
outputs to ground, below 100 pF is recommended.
Figure 34 shows the complete Rx signal path, including the optional passive passband filter.
(1) For capacitor value C1,f is the desired lower cutoff frequency and R
IN,PGA1
is the input resistance of Rx PGA1.
(2) For capacitor value C2,f is the desired lower cutoff frequency and R
IN,PGA2
is the input resistance of Rx PGA2.
(3) Refer to Table 3.
Figure 34. Complete Rx Signal Path (with Optional Bandpass Filter)
DAC Block
The DAC block consists only of the 10-bit DAC. The use of the DAC is recommended for best performance. The
serial interface is used to write directly to the DAC registers when the DAC pin (pin 7) is driven high. Placing the
DAC pin into a high state configures the SPI for direct serial interface to the DAC. Use the following sequence to
write to the DAC:
• Set CS low.
• Set the DAC pin (pin 7) high.
• Write a 10-bit word to DIN. The DAC register is left-justified and truncates more than 10 bits.
• CS high updates the DAC.
Copyright © 2011, Texas Instruments Incorporated 29
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