Datasheet

LPC11U1X All information provided in this document is subject to legal disclaimers. © NXP Semiconductors N.V. 2014. All rights reserved.
Product data sheet Rev. 2.2 — 11 March 2014 58 of 72
NXP Semiconductors
LPC11U1x
32-bit ARM Cortex-M0 microcontroller
Under nominal operating condition V
DD
= 3.3 V and with the maximum sampling
frequency fs = 400 kHz, the parameters assume the following values:
C
ia
= 1 pF (max)
R
mux
= 2 kΩ (max)
R
sw
= 1.3 kΩ (max)
C
io
= 7.1 pF (max)
The effective input impedance with these parameters is R
in
= 308 kΩ.
11.7 ADC usage notes
The following guidelines show how to increase the performance of the ADC in a noisy
environment beyond the ADC specifications listed in Table 7
:
• The ADC input trace must be short and as close as possible to the LPC11U1x chip.
• The ADC input traces must be shielded from fast switching digital signals and noisy
power supply lines.
• Because the ADC and the digital core share the same power supply, the power supply
line must be adequately filtered.
• To improve the ADC performance in a very noisy environment, put the device in Sleep
mode during the ADC conversion.