Evaluation Of The Programmable Gain Amplifier; Pga With S7 Open (Output Filter Usable); Pga With S7 Closed (Output Filter Not Usable) - Texas Instruments Piccolo F280049 controlCARD User Manual

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4.3 Evaluation of the Programmable Gain Amplifier (PGA)
When evaluating the PGA, the PGA_GND pin must be driven to the ground reference of the PGA_IN
signal. The PGA_GND signal may be provided using differential signaling through the HSEC fingers for
improved noise immunity, or the PGA_GND pin may be tied to the GND reference of the controlCARD
through a 0-Ω resistor (R55 in
HSEC_ADC-A2,B6,PGA1_IN
HSEC_PGA1_GND
The S7 switch bank provides the flexibility to either use the PGA output filter pin (PGAn_OF) for filtering
(S7 open in Figure
closed in Figure 4).
HSEC_ADC-A2,B6,PGA1_IN
HSEC_PGA1_GND
NOTE: The S7 closed implementation for PGA6 is different from the other PGAs. Instead of shorting
PGA6_OF and PGA6_IN, the PGA6_OF signal may be accessed from the HSEC connector
independently of the PGA6_IN signal.
NOTE: The PGA R
exposure to contention between the PGA_IN and PGA_OF pins may result in permanent
damage to the internal R
SPRUIC4C – July 2017 – Revised January 2019
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Figure 3) for simplicity.
Figure 3. PGA With S7 Open (Output Filter Usable)
S7
PGA1_IN
R37
0
C41
DNP
GND
PGA1_GND
R48
0
R55
DNP
GND
3) or for sampling the PGA input voltage directly by bypassing the internal PGA (S7
Figure 4. PGA With S7 Closed (Output Filter Not Usable)
S7
PGA1_IN
R37
0
C41
DNP
GND
PGA1_GND
R48
0
R55
DNP
GND
resistor should never be enabled while the S7 switch is closed. Prolonged
FILTER
resistor.
FILTER
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MCU_A_3V3 (VDDA)
+
PGA1
±
GND (VSS A)
R R
GND OUT
MCU_A_3V3 (VDDA)
+
PGA1
±
GND (VSS A)
R R
GND OUT
Piccolo F280049 controlCARD Information Guide
Special Notes
PGA1_OUT
R
FIL TE R
ADC
PGA1_OF
C34
330pF
GND
PGA1_OUT
R
FIL TE R
ADC
PGA1_OF
C34
330pF
GND
7