Q32M210 Datasheet, PDF (40/50 Pages) ON Semiconductor – Precision Mixed-Signal 32-bit Microcontroller SPI/SQI interface.

ALT0
ALT0
Select
off
A0_IN0
off
A0_IN1
off
A0_IN2
ALT1
ALT1
Select
off
A0_IN3
off
A0_IN4
off
A0_IN5
off
A0_IN6
off
A0_IN7
Q32M210
A0_IN
A0_OUTA
A0_OUTB
off
off
A0
− ^VBATA
+ _VSS
A0_REF
A1_OUTA
off
A0_OUT
to PGA input MUX
A1_OUTB
off
A1_IN
A1
− ^VBATA
+ _VSS
A1_REF
A2_OUTA
off
A1_OUT
to PGA input MUX
A2_OUTB
off
A2_IN
A2
− ^VBATA
+ _VSS
A2_REF
Figure 26. Sensor Interface
A2_OUT
to PGA input MUX
The external sensor interface consists of multiplexers,
opamps, and switches.
The device contains an 8:1 analog MUX which allows up
to eight sensors to be connected to the negative terminal of
opamp A0. The inputs to the MUX are A0_IN0 through
A0_IN7. The device contains two alternate multiplexers
ALT0 and ALT1. ALT0 is a 3:1 analog MUX allowing
A0_IN0 through A0_IN2 to be connected to the ALT0 pin.
ALT1 is a 5:1 analog MUX allow A0_IN3 through A0_IN7
to be connected to the ALT1 pin. When signals are
connected to ALT0 or ALT1, they may also optionally be
connected to the negative terminal of opamp A0.
The MUXs feature low−impedance paths for connected
channels and high isolation of unconnected channels. The
switches are implemented using specialized transistors
ensuring ultra low leakage into the signal path from the
power supplies, voltage references, and other system blocks.
The three on−chip opamps A0, A1, and A2 support a
nominal common−mode input range from 0 V to VBATA –
0.7 V. The output swings to a maximum of VBATA−50 mV.
The opamps are designed to have a very high power supply
rejection ratio and are thus able to reject variations in the
battery supply. This allows for a low noise interface to the
sensor which is effectively isolated from any voltage ripple
or spikes that may appear on the power supply.
The opamps support feedback resistors up to 5 MW in a
transimpedance (TIA) configuration without compromising
stability.
The device contains four single−pole single−throw
(SPST) switches. When the switch is closed the resulting
channel features very low impedance allowing for nearly
transparent routing of voltage and current signals. The
voltage headroom for the channel is related to the analog
supply voltage, VBATA. The SPSTs are designed to avoid
trapped charge when the switch state changes from closed to
open.
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