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V
S
R
S
V
I
R
I
V
C
C
I
V = Input voltage at pin Ax
V = External source voltage
R = External source resistance
R = Internal MUX-on input resistance
C = Input capacitance
V = Capacitance-charging voltage
I
S
S
I
I
C
C
= Parasitic capacitance, internal
C
= Parasitic capacitance, external
pint
Pext
MSP430
C
pint
C
pext
ADC10_B Operation
16.2.5.3 Sample Timing Considerations
When SAMPCON = 0, all Ax inputs are high impedance. When SAMPCON = 1, the selected Ax input can
be modeled as an RC low-pass filter during the sampling time t
sample
(see
). An internal MUX-on
input resistance R
I
(see device specific datasheet) in series with capacitor C
I
(see device specific
datasheet) is seen by the source. The capacitor C
I
voltage V
C
must be charged to within one-half LSB of
the source voltage V
S
for an accurate 10-bit conversion.
Figure 16-5. Analog Input Equivalent Circuit
The resistance of the source R
S
and R
I
affect t
sample
. See the device specific datasheet for the t
sample
limits.
16.2.6 Conversion Result
The conversion result is accessible using the
register independently of the conversion mode
selected by the user. When a conversion result is written to ADC10MEM0, the ADC10IFG0 is set.
16.2.7 ADC10_B Conversion Modes
The ADC10_B has four operating modes selected by the CONSEQx bits (see
Table 16-1. Conversion Mode Summary
ADC10CONSEQx
Mode
Operation
00
Single-channel single-conversion
A single channel is converted once.
01
Sequence-of-channels
A sequence of channels is converted once.
10
Repeat-single-channel
A single channel is converted repeatedly.
11
Repeat-sequence-of-channels
A sequence of channels is converted repeatedly.
439
SLAU272C – May 2011 – Revised November 2013
ADC10_B Module
Copyright © 2011–2013, Texas Instruments Incorporated