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UM10850
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© NXP B.V. 2016. All rights reserved.
User manual
Rev. 2.4 — 13 September 2016
361 of 464
NXP Semiconductors
UM10850
Chapter 25: LPC5410x 12-bit ADC controller (ADC0)
25.4 Pin description
The ADC can measure the voltage on any of the input signals on the analog input
channel. Digital signals must be disconnected from the ADC input pins when the ADC
function is to be used by setting DIGIMODE = 0 on those pins in the related IOCON
registers.
Warning:
If the ADC is used, signal levels on analog input pins must not be above the
level of V
DDA
at any time. Otherwise, ADC readings will be invalid. If the ADC is not used
in an application, then the pins associated with ADC inputs can be used as digital I/O pins.
The ADC pin triggers are movable (digital) functions. To use external pin triggers for ADC
conversions, assign the pin triggers to a pin via IOCON. In addition to assigning the pin
triggers to a pin, they must also be selected in the conversion sequence registers for each
ADC conversion sequence defined.
The V
REFP
and V
REFN
pins provide a positive and negative reference voltage input. The
result of the conversion is (4095 x input voltage V
IN
)/(V
REFP
- V
REFN
). The result of an
input voltage below V
REFN
is 0, and the result of an input voltage above V
REFP
is 4095
(0xFFF).
Analog Power and Ground should typically be the same voltages as V
DD
and V
SS
, but
should be isolated to minimize noise and error. If the ADC is not used, V
DDA
and V
REFP
should be tied to V
DD
, and V
SSA
and V
REFN
should be tied to V
SS
.
Recommended IOCON settings are shown in
Table 412. ADC common supply and reference pins
Pin
Description
VDDA
Analog supply voltage. V
REFP
must not exceed the voltage level on V
DDA
. This pin should be tied to V
DD
(not left floating) if the ADC is not used.
Remark:
The supply voltage V
DD
must be equal or lower than V
DDA
.
VSSA
Analog ground. This pin should be tied to V
SS
(not left floating) if the ADC is not used.
VREFP
Positive reference voltage. To operate the ADC within specifications at the maximum sampling rate, ensure
that V
REFP
= V
DDA
. This pin should be tied to V
DD
(not left floating) if the ADC is not used.
Remark:
Remark: Note that V
REFP
is internally connected (not separately pinned) with V
DDA
for some
packages/part numbers.
VREFN
Negative reference voltage. The voltage level should typically be equal Vss and Vssa.This pin should be
tied to V
SS
(not left floating) if the ADC is not used.
Remark:
Note that V
REFN
is internally connected (not separately pinned) with V
SSA
for some packages/part
numbers.
Table 413. ADC0 pin description
Function
Connect to
Description
ADC0_0
PIO0_29
Analog input channel 0.
ADC0_1
PIO0_30
Analog input channel 1.
ADC0_2
PIO0_31
Analog input channel 2.
ADC0_3
PIO1_0
Analog input channel 3.
ADC0_4
PIO1_1
Analog input channel 4.
ADC0_5
PIO1_2
Analog input channel 5.