Datasheet

C
LPF
MCU
PGA
PA
1
2 f 22 kp W
· · ·
C =
Note (3)
Tx_F_OUT
Tx_PGA_
IN
Tx_F_IN1
PA_OUT1
PA_OUT2
Tx_PGA_
OUT
Tx_F_IN2
PA_IN
C
C
GPIO
Note (1)
Inside the AFE031
510 W 510 W
Note (2)
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
GPIO
Note (1)
43 kW
43 kW
AFE031
SBOS531D –AUGUST 2010–REVISED MAY 2012 www.ti.com
(1) When using both Tx Filter inputs, use 43-kΩ resistors to match the input resistance for best frequency response.
(2) For capacitor value C, f is the desired lower cutoff frequency and 22 kΩ is the PA input resistance.
Figure 29. Recommended Tx Signal Chain Connections in PWM Mode Using Two PWM Signals
In PWM mode, there is inherently more distortion from the PWM signal than from the internal DAC. To achieve
the best results in PWM mode, add passive RC filters to increase the low-pass filtering. Figure 30 and Figure 31
illustrate the recommended locations of these RC filters.
(1) Leave unused Tx Filter input unconnected.
(2) Refer to Table 2.
(3) For capacitor value C, f is the desired lower cutoff frequency and 22 kΩ is the PA input resistance.
Figure 30. Recommended Tx Signal Chain Connections in PWM Mode
Using One PWM Signal and Additional RC Filters
24 Copyright © 2010–2012, Texas Instruments Incorporated
Product Folder Link(s): AFE031