MAX32600 User’s Guide
Analog Front End
8.3 ADC
to +V
REF
/2. Setting the
field to 1 indicates a range of -V
REF
to +V
REF
.
Note
There are instances, however, when the signal-to-noise ratio (SNR) can be improved by using differential input mode with unipolar signal conditioning.
For example, if V
REF
= 2.0V and AIN0+ is used to measure a signal between 2.0 to 2.5V, unipolar mode and single-ended input mode are not valid
because the reference is out of range. A valid measurement can be taken if AIN0- is DC biased at 2.0V and unipolar and differential modes are
enabled. A PGA gain of 4X would give a full-scale result.
8.3.4.4
Input Multiplexer
The Input Mux controls which analog input (or pair of inputs when operating in differential input mode) is routed to the PGA (or directly to the ADC when the PGA
is set to bypass mode). There are 16 external analog inputs, which can be used as single-ended inputs or as differential pairs. Any mixture of single-ended and
differential is also supported. When used in single-ended mode, the negative input of the PGA and/or ADC is internally connected to V
AGND
.
In addition to the external analog inputs, there are several different internal analog inputs and input pairs available for selection. These include:
•
±
V
DDA3
: Enables measurement of a voltage that is greater than the reference voltage. The input voltage must still be
≤
V
DDA3
.
• Internal temperature sensor, V
BE
, and resistor taps.
• Op amp outputs: OUTA, OUTB, OUTC, and OUTD.
• INA+
• V
REFDAC
and V
REFADC
output buffers
• (V
DDA3ADC
)/4
• Internal Temperature Sensor (TMON)
• scm_or
• sno_or
Note
All internal Input Mux connections (such as OUTA, INA+) should only be used with signal frequencies less than 10kHz, otherwise THD and SINAD
could be adversely affected.
Input Mux Selection
The fields
and
select the analog input to be used and, when appropriate, whether single-ended or differ-
ential mode will be used. The following table describes all input possibilities; "X" in this table represents a "don’t care" value.
ADC Input Mux Selection Table
Rev.1.3 April 2015
Maxim Integrated
Page 410
