Datasheet
6.1.4 Digital design
Ensure that all I/O pins cannot get pulled above VDD (Max I/O is VDD+0.3V).
CAUTION
Do not provide power to I/O pins prior to VDD, especially the
RESET_b pin.
• RESET_b pin
The RESET_b pin is an open-drain I/O pin that has an internal pullup resistor. An
external RC circuit is recommended to filter noise as shown in the following figure.
The resistor value must be in the range of 4.7 kΩ to 10 kΩ; the recommended
capacitance value is 0.1 μF. The RESET_b pin also has a selectable digital filter to
reject spurious noise.
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
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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 47. Reset circuit
When an external supervisor chip is connected to the RESET_b pin, a series
resistor must be used to avoid damaging the supervisor chip or the RESET_b pin,
as shown in the following figure. The series resistor value (RS below) must be in
the range of 100 Ω to 1 kΩ depending on the external reset chip drive strength. The
supervisor chip must have an active high, open-drain output.
Design considerations
126
Kinetis KL82 Microcontroller, Rev. 3, 08/2016
NXP Semiconductors