Datasheet

LPF
MCU
PGA
PA
1
2 f 22 kp W
· · ·
C =
Note (2)
Inside the AFE031
Tx_F_OUT
Tx_PGA_
IN
Tx_F_IN1
PA_OUT1
PA_OUT2
Tx_PGA_
OUT
Tx_F_IN2
PA_IN
C
GPIO
Note (1)
DAC PGA
LPF
PA
SPI
MCU
1
2 f 22 kp W· · ·
C =
Note (1)
Inside the AFE031
Tx_PGA_IN
Tx_PGA_
OUT
Tx_F_
IN1
PA_OUT1
PA_OUT2
SCLK
DIN
DOUT
CS
Tx_F_
OUT
Tx_F_
IN2
PA_IN
C
AFE031
www.ti.com SBOS531D –AUGUST 2010–REVISED MAY 2012
The proper connections for the Tx signal path for DAC mode operation are shown in Figure 27. Operating in
DAC mode results in the lowest distortion signal injected onto the ac mains. No additional external filtering
components are required to meet CENELEC requirements for A, B, C or D bands when operating in DAC mode.
(1) For capacitor value C, f is the desired lower cutoff frequency and 22 kΩ is the PA input resistance.
Figure 27. Recommended Tx Signal Chain Connections Using DAC Mode
In PWM mode (where pin 7 is a logical '0' and Enable1 Register bit location 5 is a logical '0'), the microprocessor
general-purpose input/output (GPIO) can be connected directly to either one of the Tx Filter inputs; the unused
input should remain unconnected. A lower distortion PWM signal generated from two PWM signals shifted in
phase by 90 degrees can be also be input to the Tx Filter through the use of both inputs. Figure 28 and
Figure 29 show the proper connections for single PWM and dual PWM operating modes, respectively.
(1) Leave unused Tx Filter input unconnected.
(2) For capacitor value C, f is the desired lower cutoff frequency and 22 kΩ is the PA input resistance.
Figure 28. Recommended Tx Signal Chain Connections in PWM Mode Using One PWM Signal
Copyright © 2010–2012, Texas Instruments Incorporated 23
Product Folder Link(s): AFE031