Component - Voltage Reference V1.70

PSoC® Creator™ Component Datasheet
Voltage Reference (Vref)
1.70
Features
 Precision voltage reference for analog blocks
 Routable bandgap generated voltage references: 0.256 V, 1.024 V
 Routable voltage supplies: Vdda, Vssa, Vccd, Vddd, Vbat, System-Wide Reference
General Description
The Voltage Reference (Vref) component allows you to provide a stable precision reference
voltage for the analog resources in your design. Each component instance represents a physical
analog reference source in the PSoC device. Depending on the allowed routing options available
for your intended analog peripheral, you may choose from a list of supported reference voltages.
The on-chip voltage reference uses a curvature compensated voltage bandgap with a resistor
divider to generate reference voltages of 1.024 V and 0.256 V. The method achieves a fixed DC
voltage reference that remains stable and agnostic to temperature and supply voltage variations.
You may also use the Vref component to route a voltage supply to your design, as long as the
path is valid.
Notes


The on-chip voltage reference is not intended to source or sink current. If the intended
usage is to drive a signal, then buffer the Vref signal with an Opamp component.
Every Vref is associated with an analog resource. To enable a Vref, the associated
resource must be enabled. All Vrefs default their AutoEnable parameter to true. Since
auto-enable Vrefs automatically enable the associated analog resource, all Vrefs are
automatically enabled by default.
When to Use a Vref
Use Vref components for threshold detectors, reference inputs to analog-to-digital converters,
comparators, and programmable gain amplifiers. They can also be used whenever you need a
known voltage.
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Document Number: 002-10643 Rev. **
Revised March 17, 2016
Voltage Reference (Vref)
PSoC® Creator™ Component Datasheet
Input/Output Connections
The Vref component has a single output terminal that provides access to the selected voltage
reference.
Component Parameters
Drag a Vref onto your design and double click it to open the Configure dialog.
Basic Tab
VRef Name
Defines the Vref source:

1.024 V (Default) – Produced using bandgap generator. Most widely supported voltage
reference for analog peripherals.



Vssa (GND) – Internal Vssa voltage.

Vdda (HiZ) – The Vdda voltage reference is provided with a resistive divider and so has
high impedance. (Cannot be used in the design if a Vref component instance with Vdda/2
exists since they share the same source.)
0.256 V – Produced using bandgap generator. Supported in select analog peripherals.
Vdda/2 – Derived from Vdda (HiZ) using a resistive divider. (Cannot be used in the design
if a Vref component instance with Vdda (HiZ) exists, since they share the same source).
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Document Number: 002-10643 Rev. **
PSoC® Creator™ Component Datasheet





Voltage Reference (Vref)
Vccd – Special 1.8-V reference that is only available as a source for SIO pins.
Vddd – Internal Vddd voltage. Cannot be used in design if Vbat or Vdda are used.
Vbat – Internal Vbat voltage. Cannot be used in design if Vddd or Vdda are used.
Vdda – Internal Vdda voltage. Cannot be used in design if Vddd or Vbat are used.
System-Wide Reference – Design-wide voltage reference derived from the programmable
reference block. Not available for PSoC 3 or PSoC 5LP devices.
Advanced Tab
AutoEnable
When AutoEnable is set to true (Default), Vref is enabled automatically when the device is
initialized and the static analog routes are established. This parameter applies to the 1.024 V
and 0.256 V options for connections that are not dedicated to analog peripherals.
When a 1.024 V or 0.256 V Vref is connected to intended analog block connections such as the
comparator, the device automatically enables the Vref when the connected components are
enabled. AutoEnable is not necessary in these cases.
If the intended use of the Vref component is to connect to a non-dedicated block, then it is
necessary for the dedicated block for that voltage reference to be consumed and powered in
order to power the voltage reference.
Document Number: 002-10643 Rev. **
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PSoC® Creator™ Component Datasheet
Voltage Reference (Vref)
Notes


Vref components that require AutoEnable set to true have reduced routing capability
because specific analog routing resources are required to supply the auto-enable Vref.
If AutoEnable is set to false, then you will need to enable the associated analog
peripheral (e.g. comparator, DAC) to be able to use that particular Vref source. Refer to
the Analog tab of the Design Wide Resources file to view the analog routing in your
design.
Functional Description
The Vref component provides an analog voltage reference in your design by using one of the
available voltage references. Connection to this particular voltage reference is through a single
terminal. Depending on the source and available routing, the Vref component may be shared
among several components.
Placement
For a design project, the list of available voltage references is determined by what is available
from the selected family or device.
Note If using the Vref component in a library project, make the implementation device specific to
be able to see the available reference sources.
The table below shows the list of supported voltage references for the dedicated analog blocks.
All analog block reference sources are buffered by a low-power 5uA high accuracy buffer. You
may use the table as a guide to determine the relationship between the voltage reference and
the associated analog block.
Note If your design requires routing the voltage reference to destinations that are not meant for
the dedicated analog block terminal, then additional resources may be used / needed.
Note Refer to the Analog tab of the Design Wide Resources editor to see the resource usage
and analog routing in your design.
Analog block
Reference
Comparator
1.024 V
To Comparator negative inputs.
0.256 V
To Comparator negative inputs.
Opamp
1.024 V
To Opamp positive inputs.
SC/CT
1.024 V
To SC/CT block positive and negative inputs. For example, PGA and TIA
components.
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Description
Document Number: 002-10643 Rev. **
PSoC® Creator™ Component Datasheet
Voltage Reference (Vref)
Analog block
Reference
Description
DAC
0.256 V
Reference voltage for DAC during VDAC mode operation.
DeltaSig ADC
1.024 V
Reference voltage to Delta Sigma Modulator. This voltage is additionally buffered in
the DSM block by a 10 uA buffer.
The following table is a summary of routing resource used to connect voltage supplies in your
design as voltage references.
Route source
ABUSL0
Internal
Pin
Reference
Description
Vdda (HiZ)
All analog blocks connected to the analog local bus ABUSL0 can get this voltage.
Cannot be used if Vdda/2 is also used in the design via ABUSL0.
Vdda/2
All analog blocks connected to the analog local bus ABUSL0 can get this voltage.
Cannot be used if Vdda (HiZ) is also used in the design via ABUSL0.
Vccd
Uses the device Vccd source as voltage reference for the SIO pin.
Vssa
Uses the internal device ground as reference.
Vddd
Connects to the Vddd pin
Vbat
Connects to the Vbat pin (Passes through internal LPF).
Vdda
Connects to the Vdda pin.
System-Wide Reference
The System-Wide Reference is based on the dedicated programmable reference hardware block
in the silicon (not available for PSoC 3 or PSoC 5LP devices).
The System-Wide Reference provides an adjustable, stable reference voltage for the analog
resources in your design. It could be based on either Vdda or the Bandgap voltage in 1/16
increments. This reference may be connected to any high impedance input, such as the input to
an opamp or comparator. It cannot be routed to a GPIO unless it is buffered with an opamp.
Refer to the System Editor of the Design-Wide Resources (<project>.cydwr) file to see/adjust the
configuration of the System-Wide Reference in your design.
You can also tune the Design-Wide Resources settings using System APIs. For more details,
refer to device System Reference Guide.
Document Number: 002-10643 Rev. **
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Voltage Reference (Vref)
PSoC® Creator™ Component Datasheet
AutoEnable Vref Connecting to an Amux Switchable Connection
An auto-enable 1.024 V or a 0.256 V Vref component must be by itself when connected to an
Amux switchable connection. This restriction is introduced so the analog routine can handle the
auto-enable Vref feature without ambiguities.
For example, in order for Design 1 to work it must be converted as shown in Design2.
Note If you choose to set the AutoEnable parameter of the Vref component to false, this
restriction does not apply. However it is likely that you will need to manually enable the
associated analog block to supply power to the voltage reference.
Low Power Mode
In low power mode, Vssa (GND) and Vdda (HiZ) are the only two Vref options available.
Resources
When AutoEnable is enabled for a non-dedicated analog signal, the bandgap generated Vref
(1.024 V and 0.256 V) consumes the associated analog block (e.g. a comparator). This is a
necessary step in order to control the power setting of the voltage reference. Hence the analog
block will no longer be available as a resource to be used in your design.
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Document Number: 002-10643 Rev. **
PSoC® Creator™ Component Datasheet
Voltage Reference (Vref)
DC and AC Electrical Characteristics
The following values indicate expected performance based on initial characterization data. Note
that the 1.024 V voltage reference calibrations were performed for the buffered ADC_DelSig
reference.
Voltage Reference Specifications
Parameter
Vref
Description
1.024V Vref = 1.024 [1]
Conditions
Min
Initial trimming, 25 °C
Typ
Max
1.024
Units
V
(+/- 0.5%)
–
–
30
ppm/°C
Long term drift
–
100
–
ppm/Khr
Thermal cycling drift (stability) [2]
–
100
–
Ppm
Vdda/2 resistor division ratio
accuracy
-1%
–
+1%
DC Offset (process variation)
–
0
3.5
Temperature drift [2]
Rvdda
Box method
%
mV
1
Although the +/-0.1% error is true for the output of the buffered Delsig reference, it is not true for any of the
1.024 V Vref components that a user places. These voltages can easily be off by +/-0.5% or more.
2
Based on device characterization (Not production tested).
Document Number: 002-10643 Rev. **
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PSoC® Creator™ Component Datasheet
Voltage Reference (Vref)
Component Changes
This section lists the major changes in the component from the previous version.
Version
1.70
Description of Changes
Added System-Wide Reference to the Vref
sources.
Reason for Changes / Impact
PSoC Analog Coprocessor device support.
Edited datasheet to add note about the
1.024 V reference error.
1.60.a
Expanded Functional Description section
Added placement details and analog block relationship
Updated DC and AC electrical characteristics
Added Rvdda
Miscellaneous datasheet updates
General cleanup and added clarifying information
1.60
Removed IgnoreSleep parameter from the
customizer.
The Vref component can’t remain powered in low
power mode. The IgnoreSleep parameter has no
effect.
1.50.c
Minor datasheet edits and updates
1.50.b
Updated description of Vdda(HiZ)
Description was unclear.
Updated AutoEnable section to include
quarter volt Vref
0.256-V Vref has the same AutoEnable properties as
the 1.024-V Vref.
1.50.a
Added characterization data to datasheet
Datasheet edits
1.50
Added AutoEnable and IgnoreSleep
parameters to the customizer.
The AutoEnable and IgnoreSleep parameters provide
additional functionality and a more intuitive user
experience.
Added the special purpose Vccd Vref for use
with SIO pins.
The Vccd reference is used with SIO pins.
Added Vbat, Vddd, and Vdda references.
The Vbat, Vddd, and Vdda references were added to
provide additional functionality.
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Document Number: 002-10643 Rev. **
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