Datasheet
• Take special care to minimize noise levels on the VREFH/VREFL inputs. An
option is to use the internal reference voltage (output 1.2 V typically) as the ADC
reference.
• VDDIO_E, which is dedicated to powering PORTE, must be powered after VDD
and must be greater than or equal to VDD voltage.
6.1.3 Analog design
Each ADC input must have an RC filter as shown in the following figure. The
maximum value of R must be RAS max if fast sampling and high resolution are
required. The value of C must be chosen to ensure that the RC time constant is very
small compared to the sample period.
MCU
ADCx
C
R
Input signal
1
2
1
2
Figure 45. RC circuit for ADC input
High voltage measurement circuits require voltage division, current limiting, and
over-voltage protection as shown the following figure. The voltage divider formed by
R1 – R4 must yield a voltage less than or equal to VREFH. The current must be
limited to less than the injection current limit. Since the ADC pins do not have diodes
to VDD, external clamp diodes must be included to protect against transient over-
voltages.
5
5
4
4
3
3
2
2
1
1
D D
C C
B B
A A
EXTAL XTAL
OSCILLATOR
EXTAL XTAL
OSCILLATOR
EXTAL XTAL
OSCILLATOR
EXTAL XTAL
OSCILLATOR
EXTAL XTAL
OSCILLATOR
EXTAL XTAL
OSCILLATOR
MCU
ADCx
MCU
ADCx
MCU
RESET_b
MCU
NMI_b
MCU
RESET_b
Supervisor Chip
OUT
Active high,
open drain
RESET_b
SWD_DIO
SWD_CLK
Analog input
High voltage input
RESET_b
VDD
VDD
VDD
VDD
VDD
VDD
Drawing Title:
Size Document Number Rev
Date: Sheet
of
Page Title:
ICAP Classification: FCP: FIUO: PUBI:
SCH-XXXXX PDF: SPF-XXXXX X
<Title>
C
Friday, February 06, 2015
<PageTitle>
1 1
___ ___
X
Drawing Title:
Size Document Number Rev
Date: Sheet
of
Page Title:
ICAP Classification: FCP: FIUO: PUBI:
SCH-XXXXX PDF: SPF-XXXXX X
<Title>
C
Friday, February 06, 2015
<PageTitle>
1 1
___ ___
X
Drawing Title:
Size Document Number Rev
Date: Sheet
of
Page Title:
ICAP Classification: FCP: FIUO: PUBI:
SCH-XXXXX PDF: SPF-XXXXX X
<Title>
C
Friday, February 06, 2015
<PageTitle>
1 1
___ ___
X
R
1 2
0.1uF
12
R5
1 2
Cx
12
0.1uF
12
RESONATOR
1 3
2
Cy
12
Cx
12
CRYSTAL
21
J1
HDR_5X2
1 2
3 4
65
7
8
9 10
Cy
12
10k
12
10k
12
R4
12
CRYSTAL
21
0.1uF
12
10k
12
CRYSTAL
21
R1
1 2
R3
1 2
C
12
RESONATOR
1 3
2
R2
1 2
10k
12
10k
12
RF
1 2
RS
12
BAT54SW
1 2
3
RS
12
RS
12
C
12
RF
1 2
RS
1 2
RF
1 2
CRYSTAL
21
Figure 46. High voltage measurement with an ADC input
Design considerations
Kinetis KL82 Microcontroller, Rev. 3, 08/2016
125
NXP Semiconductors