LPC5411x All information provided in this document is subject to legal disclaimers. © NXP Semiconductors N.V. 2018. All rights reserved.
Product data sheet Rev. 2.1 — 9 May 2018 83 of 105
NXP Semiconductors
LPC5411x
32-bit ARM Cortex-M4/M0+ microcontroller
[1] Characterized through simulation. Not tested in production.
[2] The ADC default sampling time is 2.5 ADC clock cycles. To match a given analog source output
impedance, the sampling time can be extended by adding up to seven ADC clock cycles for a maximum
sampling time of 9.5 ADC clock cycles. See the TSAMP bits in the ADC CTRL register.
[3] Z
o
= analog source output impedance.
12.2.1 ADC input impedance
Figure 28 shows the ADC input impedance. In this figure:
• ADCx represents slow ADC input channels 6 to 11.
• ADCy represents fast ADC input channels 0 to 5.
• R
1
and R
sw
are the switch-on resistance on the ADC input channel.
• If fast channels (ADC inputs 0 to 5) are selected, the ADC input signal goes through
R
sw
to the sampling capacitor (C
ia
).
• If slow channels (ADC inputs 6 to 11) are selected, the ADC input signal goes through
R
1
+ R
sw
to the sampling capacitor (C
ia
).
• Typical values, R
1
= 487 , R
sw
= 278
• See Ta b l e 20 for C
io
.
• See Ta b l e 37 for C
ia
.
ADC inputs ADC_11 to ADC_6 (slow channels); ADC resolution = 10 bit
t
s
sampling time Z
o
< 0.05 kΩ
[3]
35 - - ns
0.05 kΩ Z
o
< 0.1 kΩ 38 - - ns
0.1 kΩ Z
o
< 0.2 kΩ 40 - - ns
0.2 kΩ Z
o
< 0.5 kΩ 46 - - ns
0.5 kΩ Z
o
< 1 kΩ 61 - - ns
1 kΩ Z
o
< 5 kΩ 86 - - ns
ADC inputs ADC_11 to ADC_6 (slow channels); ADC resolution = 8 bit
t
s
sampling time Z
o
< 0.05 kΩ
[3]
27 - - ns
0.05 kΩ Z
o
< 0.1 kΩ 29 - - ns
0.1 kΩ Z
o
< 0.2 kΩ 32 - - ns
0.2 kΩ Z
o
< 0.5 kΩ 36 - - ns
0.5 kΩ Z
o
< 1 kΩ 48 - - ns
1 kΩ Z
o
< 5 kΩ 69 - - ns
ADC inputs ADC_11 to ADC_6 (slow channels); ADC resolution = 6 bit
t
s
sampling time Z
o
< 0.05 kΩ
[3]
20 - - ns
0.05 kΩ Z
o
< 0.1 kΩ 22 - - ns
0.1 kΩ Z
o
< 0.2 kΩ 23 - - ns
0.2 kΩ Z
o
< 0.5 kΩ 26 - - ns
0.5 kΩ Z
o
< 1 kΩ 36 - - ns
1 kΩ Z
o
< 5 kΩ 51 - - ns
Table 38. ADC sampling times
…continued
[1]
T
amb
= -40
C to 85
C; 1.62 V
V
DDA
3.6 V; 1.62 V
V
DD
3.6 V
Symbol Parameter Conditions Min Typ Max Unit
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