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• There is a 0.1 µF low-ESR capacitor from V
REFH
to V
REFL
.
• There is a 0.1 µF low-ESR capacitor from V
DDA
to V
SSA
.
• If inductive isolation is used from the primary supply, an additional 1 µF capacitor is
placed from V
DDA
to V
SSA
.
• V
SSA
(and V
REFL
, if connected) is connected to V
SS
at a quiet point in the ground
plane.
• Operate the MCU in wait or Stop3 mode before initiating (hardware triggered
conversions) or immediately after initiating (hardware or software triggered
conversions) the ADC conversion.
• For software triggered conversions, immediately follow the write to ADC_SC1
with a wait instruction or stop instruction.
• For Stop3 mode operation, select ADACK as the clock source. Operation in
Stop3 reduces V
DD
noise but increases effective conversion time due to stop
recovery.
• There is no I/O switching, input or output, on the MCU during the conversion.
There are some situations where external system activity causes radiated or conducted
noise emissions or excessive V
DD
noise is coupled into the ADC. In these situations, or
when the MCU cannot be placed in wait or Stop3 or I/O activity cannot be halted, these
recommended actions may reduce the effect of noise on the accuracy:
• Place a 0.01 µF capacitor (C
AS
) on the selected input channel to V
REFL
or V
SSA
(this
improves noise issues, but affects the sample rate based on the external analog source
resistance).
• Average the result by converting the analog input many times in succession and
dividing the sum of the results. Four samples are required to eliminate the effect of a
1LSB, one-time error.
• Reduce the effect of synchronous noise by operating off the asynchronous clock
(ADACK) and averaging. Noise that is synchronous to ADCK cannot be averaged
out.
Application information
MC9S08PA4 Reference Manual, Rev. 5, 08/2017
324
NXP Semiconductors
Содержание MC9S08PA4
Страница 1: ...MC9S08PA4 Reference Manual Supports MC9S08PA4 Document Number MC9S08PA4RM Rev 5 08 2017 ...
Страница 2: ...MC9S08PA4 Reference Manual Rev 5 08 2017 2 NXP Semiconductors ...
Страница 22: ...MC9S08PA4 Reference Manual Rev 5 08 2017 22 NXP Semiconductors ...
Страница 28: ...System clock distribution MC9S08PA4 Reference Manual Rev 5 08 2017 28 NXP Semiconductors ...
Страница 150: ...Port data registers MC9S08PA4 Reference Manual Rev 5 08 2017 150 NXP Semiconductors ...
Страница 196: ...Human machine interfaces HMI MC9S08PA4 Reference Manual Rev 5 08 2017 196 NXP Semiconductors ...
Страница 224: ...Instruction Set Summary MC9S08PA4 Reference Manual Rev 5 08 2017 224 NXP Semiconductors ...
Страница 232: ...Functional Description MC9S08PA4 Reference Manual Rev 5 08 2017 232 NXP Semiconductors ...
Страница 258: ...FTM Interrupts MC9S08PA4 Reference Manual Rev 5 08 2017 258 NXP Semiconductors ...
Страница 268: ...Initialization application information MC9S08PA4 Reference Manual Rev 5 08 2017 268 NXP Semiconductors ...
Страница 294: ...Functional description MC9S08PA4 Reference Manual Rev 5 08 2017 294 NXP Semiconductors ...
Страница 370: ...Memory map and register description MC9S08PA4 Reference Manual Rev 5 08 2017 370 NXP Semiconductors ...
Страница 398: ...Resets MC9S08PA4 Reference Manual Rev 5 08 2017 398 NXP Semiconductors ...
Страница 400: ...MC9S08PA4 Reference Manual Rev 5 08 2017 400 NXP Semiconductors ...