SAPHBCTL.
EXCBIAS
SAPHBCTL.
PGABIAS
TxBias
0
1
SAPHBCTL.
CH0EBSW
SAPHMCNF.LPBE
from ASQ
TxBias
SAPHBCTL.
PGABSW
from ASQ
RxBias
to
SDHS
SDHSCTL6.
PGA_GAIN[5:0]
from
ASQ
SAPHICTL.
MUXCTL
SAPHICTL.
MUXSEL
1
0
TxBias
RxBias
SAPHICTL.
DUMEN
ASQ_acquisition
ASQ_adc_arming
SDHS_adc_arming
SDHS_acquisition
SAPHBCTL.CPDA
Charge
Pump
en
PGA
CH1_IN
CH0_IN
Tx
Bias
PPG or
PPG_A
ASQ
PHY
PVSS
PVCC
CH1_OUT
CH0_OUT
TR0
TR1
0
0
1
1
from ASQ
SAPHBCTL.
ASQBSW
0
1
from ASQ
0
0
1
1
SAPHMCNF.LPBE
SAPHBCTL.
ASQBSW
SAPHBCTL.
CH1EBSW
from ASQ
0
1
from ASQ
0
0
1
1
SAPHMCNF.LPBE
SAPHBCTL.
ASQBSW
0
1
0
0
1
1
from
ASQ
SAPHMCNF.LPBE
SAPHMCNF.CPEO
SAPHMCNF.
BIMP
Rx
Bias
SAPHMCNF.
BIMP
Ground centric signal
TxBias centric signal
RxBias centric signal
PVcc/4 centric signal
PVcc/2 centric signal
PVcc/4 + Bias centric
Dummy
Input
Physical Interface (PHY) Block
507
SLAU367P – October 2012 – Revised April 2020
Copyright © 2012–2020, Texas Instruments Incorporated
Sequencer for Acquisition, Programmable Pulse Generator, and Physical
Interface (SAPH, SAPH_A)
Table 21-2. Supply to the Rx Multiplexer
Register
Description
Recommended Data
Capture Time (Typical)
SAPHBCTL.CPDA = 0 (default)
The charge pump is automatically off when data capture begins.
<300 µs
SAPHBCTL.CPDA = 1
The charge pump remains on during data capture.
≥
300 µs
21.3.3.1 Tx Bias and Rx Bias
During a measurement sequence, bias voltages must be applied appropriately to the transmit signal and
receive signal. In auto mode, the entire measurement sequence including applying appropriate bias
voltages is fully controlled by the ASQ. In register mode, the application must apply the correct bias
voltages during a measurement sequence.
shows the two bias voltage sources, Tx bias and
Rx bias. The Tx bias must be applied to the output channel before generating excitation pulses. The Rx
bias must be applied to the input channel before capturing the input signal. A typical measurement
sequence is as follows [assuming that excitation (Tx) at CH0 and reception (Rx) at CH1]:
1. Before generating excitation pulses and stop pulses, apply the Tx bias to CH0_IN while CH0_OUT is
connected to GND through the SWG0 switch (see
and
NOTE: Apply Tx bias to CH0_IN while CH0_OUT is connected to GND through SWG0.
Figure 21-14. Before Excitation
2. Generate excitation pulses and stop pulses through CH0_OUT, and CH0_IN is connected to PGA
dummy load to meet the impedance-matching requirement. The pulses are driven to the transducer 0
(TR0) (see
).