Component - 8-Bit Voltage DAC (VDAC8) V1.60 Datasheet.pdf

8-Bit Voltage Digital to Analog Converter (VDAC8)
1.60
Features
•
Voltage output ranges: 1.020 V and 4.080 V full scale
•
Software or clock driven output strobe
•
Data source may be CPU, DMA, or UDB
General Description
The VDAC8 component is an 8-bit voltage output Digital to Analog Converter (DAC). The output
range may be from 0 to 1.020 Volts (4 mV/bit) or from 0 to 4.08 Volts (16 mV/bit). The VDAC8
may be controlled by hardware, software, or a combination of both hardware and software.
Input/Output Connections
This section describes the various input and output connections for the VDAC8. An asterisk (*) in
the list of I/Os indicates that the I/O may be hidden on the symbol under the conditions listed in
the description of that I/O.
Vout – Analog
The Vout terminal is the connection to the DAC’s voltage output. It may be routed to any analog
compatible pin on the PSoC.
data[7:0] – Input *
This 8-bit wide data signal connects the VDAC8 directly to the DAC Bus. The DAC Bus may be
driven by UDB-based components or control registers, or it may be routed directly from GPIO
pins. This input is enabled by setting the Data_Source parameter to "DAC Bus". If the "CPU or
DMA" option is selected instead, the bus connection will disappear from the component symbol.
Use the data[7:0] input when hardware is capable of setting the proper value without CPU
intervention. When using this option, the strobe option should be set as "External" as well.
For many applications this input is not required, but instead the CPU or DMA will write a value
directly to the data register. In firmware, use the VDAC8_SetRange() function or directly write a
value to the VDAC8 data register.
Cypress Semiconductor Corporation • 198 Champion Court • San Jose, CA 95134-1709 • 408-943-2600
Document Number: 001-65743 Rev. **
Revised December 14, 2010
8-Bit Voltage Digital to Analog Converter (VDAC8)
strobe – Input *
The strobe input is an optional signal input and is selected with the Strobe_Mode parameter.
•
If Strobe_Mode is set to "External," the strobe pin will be visible and must be connected
to a valid digital source. In this mode the data is transferred from the VDAC8 register to
the DAC on the next positive edge of the strobe signal.
•
If Strobe_Mode is set to "Register Write," the pin will disappear from the symbol and any
write to the data registers will be immediately transferred to the DAC.
For audio or periodic sampling applications, the same clock used to clock the data into the DAC
could also be used to generate an interrupt. Each rising edge of the clock would transfer data to
the DAC and cause an interrupt to get the next value loaded into the DAC register.
Parameters and Setup
Drag a VDAC8 component onto your design and double-click it to open the Configure dialog.
The VDAC8 component provides the following parameters.
Data_Source
This parameter selects the source of the data to be written into the DAC register. If the CPU
(firmware) or the DMA will write data to the VDAC8, select "CPU or DMA." If data is written
directly from the UDBs or a UDB-based component, select "DAC Bus."
When DAC Bus is selected, the input is indicated on the VDAC symbol. There is only one DAC
Bus, so multiple VDACs cannot have independent hardware (UDB) data sources.
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Document Number: 001-65743 Rev. **
8-Bit Voltage Digital to Analog Converter (VDAC8)
Initial_Value
This is the initial value the VDAC8 will present after the VDAC8_Start() command is executed.
The VDAC8_SetValue() function or a direct write to the DAC register will override the default
value at anytime. Legal values are between 0 and 255, inclusive.
Strobe_Mode
This parameter selects whether the data is immediately written to the DAC as soon as the data is
written into the VDAC8 data register. This mode is selected when the "Register Write" option is
selected. When the "External" option is selected, a clock or signal from the UDBs controls when
the data is written from the DAC register to the actual DAC.
VDAC_Range
This parameter allows you to set one of two voltage ranges as the default value. The range may
be changed at any time during runtime with the VDAC8_SetRange() function.
Range
Lowest Value
Highest Value
Step Size
Range_1_Volt
0.0 mV
1.020 V
4 mV
Range_4_Volt
0.0 mV
4.080 V
16 mV
Output equations:
•
1 Volt range – Vout = (value/256) * 1.024 Volts
•
4 Volt range – Vout = (value/256) * 4.096 Volts
Note The term "value" is a number between 0 and 255.
VDAC_Speed
This parameter provides two settings: "Low Speed" and "High Speed." In "Low Speed" mode, the
settling time is slower but consumes less operating current. In "High Speed" mode, the voltage
settles much faster, but at a cost of more operating current.
Resources
The VDAC8 component uses one viDAC8 analog block.
API Memory
(Bytes)
Digital Blocks
Analog Blocks
1 viDAC8 HW
Datapaths
Macro
cells
Status
Registers
Control
Registers
Counter7
Flash
RAM
Pins (per
External I/O)
N/A
N/A
N/A
N/A
N/A
354
3
1
Document Number: 001-65743 Rev. **
Page 3 of 15
8-Bit Voltage Digital to Analog Converter (VDAC8)
Application Programming Interface
Application Programming Interface (API) routines allow you to configure the component using
software. The following table lists and describes the interface to each function. The subsequent
sections cover each function in more detail.
By default, PSoC Creator assigns the instance name "VDAC8_1" to the first instance of a
component in a given design. You can rename the instance to any unique value that follows the
syntactic rules for identifiers. The instance name becomes the prefix of every global function
name, variable, and constant symbol. For readability, the instance name used in the following
table is "VDAC8".
Function
Description
void VDAC8_Start(void)
Initialize the VDAC8 with default customizer values.
void VDAC8_Stop(void)
Disables the VDAC8 and sets it to the lowest power state.
void VDAC8_SetSpeed(uint8 speed)
Sets DAC speed.
void VDAC8_SetValue(uint8 value)
Sets value between 0 and 255 with the given range.
void VDAC8_SetRange(uint8 value)
Sets range to 1 or 4 volts.
void VDAC8_Sleep(void)
Stops and saves the user configuration.
void VDAC8_WakeUp(void)
Restores and enables the user configuration.
void VDAC8_Init(void)
Initializes or restores default VDAC8 configuration
void VDAC8_Enable(void)
Enables the VDAC8.
void VDAC8_SaveConfig(void)
Empty function. Provided for future usage.
void VDAC8_RestoreConfig(void)
Empty function. Provided for future usage.
Global Variables
Variable
VDAC8_initVar
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Description
Indicates whether the VDAC8 has been initialized. The variable is initialized to 0 and set to 1 the
first time VDAC8_Start() is called. This allows the component to restart without reinitialization
after the first call to the VDAC8_Start() routine.
If reinitialization of the component is required, then the VDAC8_Init() function can be called
before the VDAC8_Start() or VDAC8_Enable() function.
Document Number: 001-65743 Rev. **
8-Bit Voltage Digital to Analog Converter (VDAC8)
void VDAC8_Start(void)
Description:
This is the preferred method to begin component operation. VDAC9_Start() sets the initVar
variable, calls the VDAC8_Init() function, calls the VDAC8_Enable() function, and powers up
the VDAC8 to the given power level. A power level of 0 is the same as executing the stop
function.
Parameters:
None
Return Value:
None
Side Effects:
If the initVar variable is already set, this function only calls the VDAC8_Enable() function.
void VDAC8_Stop(void)
Description:
Powers down VDAC8 to lowest power state and disables output.
Note This API is not recommended for use on PSoC 3 ES2 and PSoC 5 ES1 silicon.
These devices have a defect that causes connections to several analog resources to be
unreliable when not powered. The unreliability manifests itself in silent failures (e.g.
unpredictably bad results from analog components) when the component utilizing that
resource is stopped. It is recommended that all analog components in a design should be
powered up (by calling the VDAC8_Start() APIs) at all times. Do not call the
VDAC8_Stop() APIs.
Parameters:
None
Return Value:
None
Side Effects:
None
void VDAC8_SetSpeed(uint8 speed)
Description:
Set DAC speed.
Parameters:
(uint8) speed: Sets DAC speed, see table below for valid parameters.
Option
Description
VDAC8_LOWSPEED
Low speed (low power)
VDAC8_HIGHSPEED
High speed (high power)
Return Value:
None
Side Effects:
None
Document Number: 001-65743 Rev. **
Page 5 of 15
8-Bit Voltage Digital to Analog Converter (VDAC8)
void VDAC8_SetRange(uint8 range)
Description:
Sets range to 1 or 4 volts.
Parameters:
(uint8) range: Sets full scale range for VDAC8. See table below for ranges.
Option
Description
VDAC8_RANGE_1V
Set full scale range of 1.020 V
VDAC8_RANGE_4V
Set full scale range of 4.080 V
Return Value:
None
Side Effects:
None
void VDAC8_SetValue(uint8 value)
Description:
Sets value to output on VDAC8. Valid values are between 0 and 255.
Parameters:
(uint8) value: Value between 0 and 255. A value of 0 is the lowest (zero) and a value of 255
is the full scale value. The full scale value is dependent on the range which is selectable with
the SetRange API.
Return Value:
None
Side Effects:
On PSoC 3 ES2 and PSoC 5 ES1 silicon, the VDAC8_SetValue() function should be called
after enabling power to the VDAC.
void VDAC8_Sleep(void)
Description:
This is the preferred API to prepare the component for sleep. The VDAC8_Sleep() API saves
the current component state. Then it calls the VDAC8_Stop() function and calls
VDAC8_SaveConfig() to save the hardware configuration.
Call the VDAC8_Sleep() function before calling the CyPmSleep() or the CyPmHibernate()
function. Refer to the PSoC Creator System Reference Guide for more information about
power management functions.
Parameters:
None
Return Value:
None
Side Effects:
None
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Document Number: 001-65743 Rev. **
8-Bit Voltage Digital to Analog Converter (VDAC8)
void VDAC8_Wakeup(void)
Description:
This is the preferred API to restore the component to the state when VDAC8_Sleep() was
called. The VDAC8_Wakeup() function calls the VDAC8_RestoreConfig() function to restore
the configuration. If the component was enabled before the VDAC8_Sleep() function was
called, the VDAC8_Wakeup() function will also re-enable the component.
Parameters:
None
Return Value:
None
Side Effects:
Calling the VDAC8_Wakeup() function without first calling the VDAC8_Sleep() or
VDAC8_SaveConfig() function may produce unexpected behavior.
void VDAC8_Init(void)
Description:
Initializes or restores the component according to the customizer Configure dialog settings. It
is not necessary to call VDAC8_Init() because the VDAC8_Start() API calls this function and
is the preferred method to begin component operation.
Parameters:
None
Return Value:
None
Side Effects:
All registers will be set to their initial values. This will reinitialize the component. Calling the
VDAC8_Init() function requires a call to VDAC8_SetValue() if you intend to set a new value
other than what is currently in the register.
void VDAC8_Enable(void)
Description:
Activates the hardware and begins component operation. It is not necessary to call
VDAC8_Enable() because the VDAC8_Start() API calls this function, which is the preferred
method to begin component operation.
Parameters:
None
Return Value:
None
Side Effects:
None
void VDAC8_SaveConfig(void)
Description:
This function saves the component configuration. This will save non-retention registers. This
function will also save the current component parameter values, as defined in the Configure
dialog or as modified by appropriate APIs. This function is called by the VDAC8_Sleep()
function.
Parameters:
None
Return Value:
None
Side Effects:
Empty function. Implemented for future usage. No effect on component by calling this
function.
Document Number: 001-65743 Rev. **
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8-Bit Voltage Digital to Analog Converter (VDAC8)
void VDAC8_RestoreConfig(void)
Description:
This function restores the component configuration. This will restore non-retention registers.
This function will also restore the component parameter values to what they were prior to
calling the VDAC8_Sleep() function.
Parameters:
None
Return Value:
None
Side Effects:
Empty function. Implemented for future usage. No effect on component by calling this
function.
DMA Wizard
VDAC8 components do not require implementation of a DMA Request signal. The typical usage
is signal generation and the data rate to VDAC8 components should be controlled externally.
The DMA Wizard can be used to configure DMA operation as follows:
Name of DMA source /
destination in DMA Wizard
VDAC8_Data_PTR
Direction
DMA Req
Signal
Destination N/A
DMA Req
Type
N/A
Description
Stores the DAC value between 0 to 255
Sample Firmware Source Code
PSoC Creator provides numerous example projects that include schematics and example code
in the Find Example Project dialog. For component-specific examples, open the dialog from the
Component Catalog or an instance of the component in a schematic. For general examples,
open the dialog from the Start Page or File menu. As needed, use the Filter Options in the
dialog to narrow the list of projects available to select.
Refer to the "Find Example Project" topic in the PSoC Creator Help for more information.
Functional Description
When used as a VDAC8, the viDAC8 analog block is configured as voltage DAC and can be
used as voltage source.
When used as a VDAC, the output is an 8-bit digital-to-analog conversion voltage to support
applications where reference voltages are needed. Here the reference source is a voltage
reference from the Analog reference block called VREF(DAC). The DAC can be configured to
work in voltage mode by setting the DACx_CR0 [4] register. In this mode, there are two output
ranges selected by the DACx_CR0[3:2] register:
•
0 V to 1.024 V
•
0 V to 4.096 V
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Document Number: 001-65743 Rev. **
8-Bit Voltage Digital to Analog Converter (VDAC8)
Both output ranges have 255 equal steps. The VDAC is implemented by driving the output of the
current DAC through resistors and obtaining a voltage output. Because no buffer is used, any
DC current drawn from the DAC affects the output level. Therefore, in this mode any load
connected to the output should be capacitive.
The VDAC is capable of converting up to 1 Msps. In addition, the DAC is slower in 4 V mode
than 1 V mode, because the resistive load to Vssa is 4 times larger. In 4 V mode, the VDAC is
capable of converting up to 250 ksps.
Block Diagram and Configuration
The following shows the block diagram for the VDAC8 component.
VDDA
VCC(Regulated)
DAC Value Mirror
1x, 2x ... 255x (8 bit)
Calibration Mirror
VOUT
R
Reference
Current Source
1.024V
Output
ISOURCE
Scaler
R
3R
Registers
The functions provided support most of the common runtime functions required for most
applications. The following register references provide brief descriptions for the advanced user.
The VDAC8_Data register may be used to write data directly to the DAC without using the API.
This may be useful for either the CPU or DMA.
Table 1 VDAC8_CR0
Bits
Value
7
6
5
RSVD
4
mode
•
mode: Sets DAC to either voltage or current mode.
•
range[1:0]: DAC range settings.
•
hs: Use to set data speed.
Document Number: 001-65743 Rev. **
3
2
Range[1:0]
1
0
hs
RSVD
Page 9 of 15
8-Bit Voltage Digital to Analog Converter (VDAC8)
Table 2 VDAC8_CR1
Bits
7
Value
6
RSVD
5
4
3
2
1
0
mx_data
reset_udb_en
mx_idir
idirbit
Mx_ioff
ioffbit
•
mx_data: Select data source.
•
reset_udb_en: DAC reset enable.
•
mx_idir: Mux selection for DAC current direction control.
•
idirbit: Register source for DAC current direction.
•
mx_off: Mux selection for DAC current off control.
•
ioffbit: Register source for DAC current off
Table 3 VDAC8_DATA
Bits
7
6
5
4
Value
•
3
2
1
0
Data[7:0]
Data[7:0]: DAC data register.
DC and AC Electrical Characteristics
The following values are based on characterization data. Specifications are valid for -40°C £ TA £
85°C and TJ £ 100°C except where noted. Unless otherwise specified in the tables below, all
Typical values are for TA = 25°C, Vdda = 5.0V, output referenced to analog ground (Vssa), fast
mode.
VDAC8 DC Electrical Characteristics
Parameter
Description
Conditions
Resolution
Min
Typ
Max
Units
–
8
–
bits
INL1
Integral nonlinearity
1 V scale
–
±2.1
±2.5
LSB
DNL1
Differential nonlinearity
1 V scale
–
±0.3
±1
LSB
Rout
Output resistance
1 V scale
–
4
–
k
4 V scale
–
16
–
k
1 V scale
–
1
–
V
4 V scale, Vdda = 5 V
–
4
–
V
Monotonicity
–
–
Yes
–
VOS
Zero scale error
–
0
±0.9
LSB
FSGainErr
Full scale gain error
1 V scale
–
±1.6
±2.5
%
4 V scale
–
±1.5
±2.5
%
VOUT
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Output voltage range,
code = 255
Document Number: 001-65743 Rev. **
8-Bit Voltage Digital to Analog Converter (VDAC8)
Parameter
TCGainErr
IDD
Description
Conditions
Min
Typ
Max
Units
Temperature coefficient,
gain error
1 V scale
–
–
0.02
%FSR / °C
4 V scale
–
–
0.02
%FSR / °C
Operating current
Slow mode
–
–
100
µA
Fast mode
–
–
500
µA
Figures
INL versus DAC Code, 1.0V Range
INL versus DAC Code, 4.0V Range
0.6
0.6
0.4
0.4
0.2
0.2
Bits
1
0.8
Bits
1
0.8
0
0
-0.2
-0.2
-0.4
-0.4
-0.6
-0.6
-0.8
1V INL
-1
0
32
64
96
128
160
Code
192
224
-0.8
0
256
0.2
0.2
0.15
0.15
0.1
0.1
0.05
0.05
Bits
0
-0.05
-0.1
-0.1
1V DNL
-0.2
64
96
128
160
Code
192
-0.15
32
64
96
128
160
Code
Document Number: 001-65743 Rev. **
192
256
4V DNL
-0.2
0
224
0
-0.05
-0.15
32
DNL versus DAC Code, 4.0V Range
Bits
Typical DNL versus DAC Code, 1.0V Range
4V INL
-1
224
256
0
32
64
96
128
160
Code
192
224
256
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8-Bit Voltage Digital to Analog Converter (VDAC8)
VDAC INL vs Temperature, 1 V Mode
VDAC DNL vs Temperature, 1 V Mode
VDAC Full Scale Error vs Temperature, 1 V Mode
VDAC Full Scale Error vs Temperature, 4 V Mode
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Document Number: 001-65743 Rev. **
8-Bit Voltage Digital to Analog Converter (VDAC8)
VDAC Operating Current vs Temperature, 1V Mode,
Slow Mode
VDAC Operating Current vs Temperature, 1 V Mode,
Fast Mode
VDAC8 AC Electrical Characteristics
Parameter
FDAC
TsettleP
TsettleN
SRP
SRN
Description
Update rate
Settling time to 0.1%,
step 25% to 75%
Settling time to 0.1%,
step 75% to 25%
Slew rate, step 10% to 90%
Slew rate, step 90% to 10%
Conditions
Min
Typ
Max
Units
1 V scale
–
–
1000
ksps
4 V scale
–
–
250
ksps
1 V scale, Cload = 15 pF
–
0.45
1
µs
4 V scale, Cload = 15 pF
–
0.8
3.2
µs
1 V scale, Cload = 15 pF
–
0.45
1
µs
4 V scale, Cload = 15 pF
–
0.7
3
µs
1 V scale, Cload = 15 pF
–
0.3
0.5
µs
4 V scale, Cload = 15 pF
–
0.5
1.3
µs
1 V scale, Cload = 15 pF
–
0.3
0.5
µs
4 V scale, Cload = 15 pF
–
0.3
1.3
µs
Terminology
Integral Nonlinearity (INL)
INL, integral nonlinearity, is a measure of the maximum deviation, in LSBs, from a best fit
straight line over the operating range of the DAC.
Differential Nonlinearity (DNL)
DNL, differential nonlinearity, is the difference between the measured change and the ideal 1
LSB change between any two adjacent codes. This VDAC is guaranteed monotonic by design.
Document Number: 001-65743 Rev. **
Page 13 of 15
8-Bit Voltage Digital to Analog Converter (VDAC8)
The output is "thermometer-encoded," each successive step is made by turning on a separate
output source which is summed with previously enabled output sources.
Montonicity
A DAC is defined as monotonic if the output increases or stays the same with each increasing
digital code input value. The VDAC8 component is monotonic over the full operating range of
voltage and temperature.
Zero-scale Error
Zero-scale error is the difference between the measured value at code 0x00 and the value of the
best-fit straight line at code 0x00.
Full Scale Gain Error
Full scale gain error is the measure of the difference between the measured value and the
nominal value at maximum code. The maximum value is either 1.020 V or 4.080 V at code = 255
(0x00).
Full Scale Gain Temperature Coefficient (TC)
Full scale gain temperature coefficient is a measure of the change in full scale value (maximum
code 0xFF) with change in temperature. Gain changes at lower values are proportional to code
value.
Power Supply Rejection Ratio (PSRR)
Power supply rejection ratio measures the isolation of the VDAC's output from the power supply.
Settling Time
Settling time is the amount of time required for the output to settle to a specific level for a specific
digital input change.
Slew Rate
The slew rate is the maximum rate of change of the output of the VDAC. Slew rate is measured
from 10% to 90% of full scale value
Glitch Amplitude
Glitch amplitude is the peak amplitude of the pulse injected into the output when the input code
changes a single count at mid-scale (0x7f to 0x80). The pulse is in excess of the difference
between the static values before and after data change.
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Document Number: 001-65743 Rev. **
8-Bit Voltage Digital to Analog Converter (VDAC8)
Voltage Noise
Voltage noise is the sum of the noise of the VDAC's output resistance and the current output
noise times the output resistance of the VDAC. This noise will vary as a function of code value.
Component Changes
This section lists the major changes in the component from the previous version.
Version
1.60
Description of Changes
Added a GUI Configuration Editor
Reason for Changes / Impact
Previous configuration window did not provide enough
information for ease of use.
Added characterization data to
datasheet
Minor datasheet edits and updates
1.50
Added Sleep/Wakeup and
Init/Enable APIs.
To support low power modes, as well as to provide common
interfaces to separate control of initialization and enabling of
most components.
Added DMA capabilities file to the
component.
This file allows the VDAC8 to be supported by the DMA Wizard
tool in PSoC Creator.
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WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. Cypress reserves the right to make changes without further notice to the materials described herein.
Cypress does not assume any liability arising out of the application or use of any product or circuit described herein. Cypress does not authorize its products for use as critical components in lifesupport systems where a malfunction or failure may reasonably be expected to result in significant injury to the user. The inclusion of Cypress’ product in a life-support systems application
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Use may be limited by and subject to the applicable Cypress software license agreement.
Document Number: 001-65743 Rev. **
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