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PSoC™ 6

Kawa
Level 1
First question asked Welcome!
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I don't know how to connect the VREF pin(49pin).
Should I connect a capacitor?
If so, how much capacity should I connect?

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Vasanth
Moderator
Moderator 500 solutions authored First question asked 1000 replies posted
Moderator

Hi,

In case you are using an ADC please check the SAR REF section in the architecture TRM.

SARREF generates VDDA and VDDA/2 voltages. In addition, it can take in a 1.2-V bandgap reference from AREF (see the
Analog Reference Block chapter on page 502 for details) or an external VREF connected to a dedicated pin (see the device datasheet for details). External VREF value should be between 1-V and VDDA.The external VREF pin is also used to bypass the internal references. The VREF_SEL bitfield in the SAR_CTRL register can be used to select which one of these references is connected to the SAR ADC.The internal references, 1.2 V from bandgap and VDDA/2, are buffered with the reference buffer. This reference may be routed to the external VREF pin where a capacitor can be used to filter noise that may exist on the reference.

Reference buffer startup time varies with different bypass capacitor size. Table 39-4 lists two common values for the bypass capacitor and its startup time specification. If reference selection is changed between scans or when scanning after device low-power modes in which the ADC is not active (see the Device Power Modes chapter on page 198), make sure the reference buffer is settled before the SAR ADC starts sampling.

Vasanth_0-1642480524854.png

 

Best Regards,
Vasanth

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Vasanth
Moderator
Moderator 500 solutions authored First question asked 1000 replies posted
Moderator

Hi,

In case you are using an ADC please check the SAR REF section in the architecture TRM.

SARREF generates VDDA and VDDA/2 voltages. In addition, it can take in a 1.2-V bandgap reference from AREF (see the
Analog Reference Block chapter on page 502 for details) or an external VREF connected to a dedicated pin (see the device datasheet for details). External VREF value should be between 1-V and VDDA.The external VREF pin is also used to bypass the internal references. The VREF_SEL bitfield in the SAR_CTRL register can be used to select which one of these references is connected to the SAR ADC.The internal references, 1.2 V from bandgap and VDDA/2, are buffered with the reference buffer. This reference may be routed to the external VREF pin where a capacitor can be used to filter noise that may exist on the reference.

Reference buffer startup time varies with different bypass capacitor size. Table 39-4 lists two common values for the bypass capacitor and its startup time specification. If reference selection is changed between scans or when scanning after device low-power modes in which the ADC is not active (see the Device Power Modes chapter on page 198), make sure the reference buffer is settled before the SAR ADC starts sampling.

Vasanth_0-1642480524854.png

 

Best Regards,
Vasanth

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