LPC540xx
NXP Semiconductors
32-bit ARM Cortex-M4 microcontroller
Table 53. ADC sampling times[1] …continued
-40 C Tamb <= 85 C; 1.71 V VDDA 3.6 V; 1.71 V VDD 3.6 V
Symbol
Parameter
Conditions
Min
Typ
Max
Unit
ADC inputs ADC_11 to ADC_6 (slow channels); ADC resolution = 10 bit
[3]
[3]
[3]
ts
sampling time
Zo < 0.05 kΩ
35
38
40
46
61
86
-
-
-
-
-
-
-
-
-
-
-
-
ns
ns
ns
ns
ns
ns
0.05 kΩ <= Zo < 0.1 kΩ
0.1 kΩ <= Zo < 0.2 kΩ
0.2 kΩ <= Zo < 0.5 kΩ
0.5 kΩ <= Zo < 1 kΩ
1 kΩ <= Zo < 5 kΩ
ADC inputs ADC_11 to ADC_6 (slow channels); ADC resolution = 8 bit
ts
sampling time
Zo < 0.05 kΩ
27
29
32
36
48
69
-
-
-
-
-
-
-
-
-
-
-
-
ns
ns
ns
ns
ns
ns
0.05 kΩ <= Zo < 0.1 kΩ
0.1 kΩ <= Zo < 0.2 kΩ
0.2 kΩ <= Zo < 0.5 kΩ
0.5 kΩ <= Zo < 1 kΩ
1 kΩ <= Zo < 5 kΩ
ADC inputs ADC_11 to ADC_6 (slow channels); ADC resolution = 6 bit
ts
sampling time
Zo < 0.05 kΩ
20
22
23
26
36
51
-
-
-
-
-
-
-
-
-
-
-
-
ns
ns
ns
ns
ns
ns
0.05 kΩ <= Zo < 0.1 kΩ
0.1 kΩ <= Zo < 0.2 kΩ
0.2 kΩ <= Zo < 0.5 kΩ
0.5 kΩ <= Zo < 1 kΩ
1 kΩ <= Zo < 5 kΩ
[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] Zo = analog source output impedance.
[4] For VDD 2.5 V, add one additional clock cycle to the values in Table 53.
12.2.1 ADC input impedance
Figure 42 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.
• R1 and Rsw 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 (Cia).
• If slow channels (ADC inputs 6 to 11) are selected, the ADC input signal goes through
R1 + Rsw to the sampling capacitor (Cia).
• Typical values, R1 = 487 , Rsw = 278
• See Table 20 for Cio.
• See Table 52 for Cia.
LPC540xx
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© NXP Semiconductors N.V. 2018. All rights reserved.
Product data sheet
Rev. 1.8 — 22 June 2018
141 of 168
NXP [ NXP ]
