UM11029
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© NXP Semiconductors N.V. 2017. All rights reserved.
User manual
Rev. 1.0 — 16 June 2017
443 of 515
NXP Semiconductors
UM11029
Chapter 26: LPC84x 12-bit Analog-to-Digital Converter (ADC)
26.5 General description
The ADC controller provides great flexibility in launching and controlling sequences of A/D
conversions using the associated 12-bit, successive approximation A/D converter. A/D
conversion sequences can be initiated under software control or in response to a selected
hardware trigger. The ADC supports eight hardware triggers.
Once the triggers are set up (software and hardware triggers can be mixed), the ADC runs
through the pre-defined conversion sequence, converting a sample whenever a trigger
signal arrives, until the sequence is disabled.
The ADC controller uses the system clock as a bus clock. The ADC clock is derived from
the system clock. A programmable divider is included to scale the system clock to the
maximum ADC clock rate of 30 MHz. The ADC clock drives the successive approximation
process.
A fully accurate conversion requires 25 of these ADC clocks.
Fig 61. ADC block diagram
0
1
2
3
4
7
CONVERSION
TRIGGER
DATA
REGISTERS
THRESHOLD
COMPARE
CHANNEL
and
SEQUENCE
CONTROL
ADC_THCMP_IRQ
sequence B
complete IRQ
data overrun IRQ
ADC_[0:11]
start
conversion
channel
select
ANALOG-to-
DIGITAL
CONVERTER
channel 0:11
12
ADC
ADC
result
PININT_IRQ0
PININT_IRQ1
SCT_OUT3
SCT_OUT4
T0_MAT3
ARM_TXEV
sequence A
complete IRQ
ADC_SEQB_IRQ
ADC_OVR_IRQ
ADC_SEQA_IRQ
5
COMP0_OUT
GPIO_INT_BMAT
6