Datasheet

LPC11U2X All information provided in this document is subject to legal disclaimers. © NXP B.V. 2014. All rights reserved.
Product data sheet Rev. 2.3 — 27 March 2014 58 of 74
NXP Semiconductors
LPC11U2x
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 6
:
• The ADC input trace must be short and as close as possible to the LPC11U2x chip.
• Shield The ADC input traces from fast switching digital signals and noisy power
supply lines.
• The ADC and the digital core share the same power supply. Therefore, filter the power
supply line adequately.
• To improve the ADC performance in a noisy environment, put the device in Sleep
mode during the ADC conversion.