Texas Instruments Delfino TMS320F28374S, Manual

Page: 99 / 198

ADV
ANCEINFORMA
TION
TMS320F28377S, TMS320F28376S, TMS320F28375S, TMS320F28374S
www.ti.com SPRS881A – AUGUST 2014 – REVISED JUNE 2015
Table 5-46 shows the parasitic capacitance on each channel. Also note that enabling a comparator will
add approximately 1.4 pF of capacitance on positive comparator inputs and 2.5 pF of capacitance on
negative comparator inputs.
Table 5-46. Per-Channel Parasitic Capacitance
C
p
(pF)
ADC CHANNEL
COMPARATOR DISABLED COMPARATOR ENABLED
ADCINA0 12.9 N/A
ADCINA1 10.3 N/A
ADCINA2 5.9 7.3
ADCINA3 6.3 8.8
ADCINA4 5.9 7.3
ADCINA5 6.3 8.8
ADCINB0 117.0 N/A
ADCINB1 10.6 N/A
ADCINB2 5.9 7.3
ADCINB3 6.2 8.7
ADCINB4 5.2 N/A
ADCINB5 5.1 N/A
ADCINC2 5.5 6.9
ADCINC3 5.8 8.3
ADCINC4 5.0 6.4
ADCINC5 5.3 7.8
ADCIND0 5.3 6.7
ADCIND1 5.7 8.2
ADCIND2 5.3 6.7
ADCIND3 5.6 8.1
ADCIND4 4.3 N/A
ADCIND5 4.3 N/A
ADCIN14 8.6 10.0
ADCIN15 9.0 11.5
These input models should be used along with actual signal source impedance to determine the
acquisition window duration. See the "Choosing an Acquisition Window Duration" section of the
TMS320F2837xS Delfino Microcontrollers Technical Reference Manual ( SPRUHX5 ) for more information.
The user should analyze the ADC input setting assuming worst-case initial conditions on C
h
. This will
require assuming that C
h
could start the S+H window completely charged to V
REFHI
or completely
discharged to V
REFLO
. When the ADC transitions from an odd-numbered channel to an even-numbered
channel, or vice-versa, the actual initial voltage on C
h
will be close to being completely discharged to
V
REFLO
. For other transitions, the actually initial voltage on C
h
will be close to the voltage of the previously
converted channel.
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Specifications 99
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