Component - 8-Bit Current DAC (IDAC8) V1.50 Datasheet.pdf

PSoC® Creator™ Component Data Sheet
8-Bit Current Digital to Analog Converter (IDAC8)
1.50
Features
•
Three ranges 2040 uA, 255 uA, and 32.875 uA
•
Software or clock driven output strobe
•
Data source may be CPU, DMA, or UDB
•
Current sink or source selectable
General Description
The IDAC8 component is an 8-bit current output DAC (Digital to Analog Converter). You may
configure the IDAC8 component a number of ways depending on your needs. The IDAC8 may
be controlled by hardware, software, or with a combination of both hardware and software. The
IDAC8 is also easily configured as a current sink or source.
When to use a IDAC8
Use the IDAC8 when a fixed or programmable current source is required in an application.
Input/Output Connections
This section describes the various input and output connections for the IDAC8. 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.
output – Analog
The output terminal is the connection to the current source/sink. It may be routed to any analog
compatible pin on the device. When the highest current range is selected (2048 uA), the output
should only be routed to a specific set of pins that provide a direct low resistive path. These port
pins are P0[6], P0[7], P3[0], or P3[1].
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Document Number: 001-63249 Rev. **
Revised August 11, 2010
8-Bit Current Digital to Analog Converter (IDAC8)
PSoC® Creator™ Component Data Sheet
data[7:0] – Input *
This 8-bit wide data signal connects the IDAC8 directly to the DAC bus. The DAC bus may be
driven by UDB based components or control registers, or routed directly from GPIO pins. This
input is enabled by setting the Data_Source parameter to "DAC Bus". If the "DMA or CPU"
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, Strobe_Mode should be enabled 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, you may use the SetRange() function or directly write a
value to the IDAC8_1_Data register (assuming an instance name of "IDAC8_1").
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 pin will be visible and must be connected to a valid digital
source. In this mode the data is transferred from the IDAC8 register to the DAC on the next
positive edge of the strobe signal.
If this parameter 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.
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PSoC® Creator™ Component Data Sheet
8-Bit Current Digital to Analog Converter (IDAC8)
Parameters and Setup
Drag an IDAC8 component onto your design and double-click it to open the Configure dialog.
The IDAC8 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 IDAC8, then select "DMA or CPU". If data is written
directly from the UDBs or UDB-based component, then the "DAC bus" should be selected. Note
that there is only one DAC bus that is shared by all of the viDAC8 analog blocks.
IDAC_Range
This parameter enables the designer to set one of three current ranges as the default value. The
range may be changed at anytime during runtime with the SetRange() function. If the highest
current range, "0 - 2040uA" is selected, the output should be routed to one of the special pins
that provide a low resistive path. These pins are P0[6], P0[7], P3[0], and P3[1].
Range
Lowest Value
Highest Value
Step Size
0 – 32 uA
0.0 uA
31.875 uA
0.125 uA
0 – 255 uA
0.0 uA
255 uA
1 uA
0 – 2040 uA
0.0 uA
2040 uA
8 uA
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8-Bit Current Digital to Analog Converter (IDAC8)
PSoC® Creator™ Component Data Sheet
IDAC_Speed
This parameter provides two settings for the designer, Low Speed and High Speed. In the Low
Speed mode, the settling time is slower but it consumes less operating current. In the High
Speed mode, the current settle much faster, but at a cost of more operating current.
Initial_Value
This is the initial value the IDAC8 will present after the Start() command is executed. The
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.
Polarity
The Polarity parameter allows the designer to select whether the IDAC8 sinks or sources current
to its load. When the "Current Source" option is selected, the output of the DAC will source
current to a load that is connected to Vss. In the "Current Sink" mode, it will supply current to a
load that is connected to Vdd.
Strobe_Mode
This parameter selects whether the data is immediately written to the DAC as soon as the data is
written into the IDAC8 data register. This mode is selected when the "Register Write" option is
selected. When the "External" option is selected, a clock or signal from UDBs controls when the
data is written from the DAC register to the actual DAC.
Resources
The IDAC8 uses one vIDAC8 analog block.
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 "IDAC8_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 "IDAC8."
Function
void IDAC8_Init(void)
Description
Initializes or restores default IDAC8 configuration
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PSoC® Creator™ Component Data Sheet
8-Bit Current Digital to Analog Converter (IDAC8)
Function
Description
void IDAC8_Enable(void)
Enables the IDAC8.
void IDAC8_Start(void)
Initialize the IDAC8 with default customizer values. Enable and power up
the IDAC8.
void IDAC8_Stop(void)
Disables the IDAC8 and sets it to the lowest power state.
Void IDAC8_SetSpeed(uint8 speed)
Set DAC speed.
void IDAC8_SetPolarity(uint8 polarity)
Sets the output mode to current sink or source.
void IDAC8_SetRange(uint8 range)
Sets full scale range for IDAC8.
void IDAC8_SetValue(uint8 value)
Sets value between 0 and 255 with the given range.
void IDAC8_SaveConfig(void)
Empty function. Provided for future usage.
void IDAC8_RestoreConfig(void)
Empty function. Provided for future usage.
void IDAC8_Sleep(void)
Stops and saves the user configuration.
void IDAC8_WakeUp(void)
Restores and enables the user configuration.
Global Variables
Variable
IDAC8_initVar
Description
Indicates whether the IDAC8 has been initialized. The variable is initialized to 0 and set to 1 the
first time IDAC8_Start() is called. This allows the component to restart without reinitialization after
the first call to the IDAC8_Start() routine.
If reinitialization of the component is required, then the IDAC8_Init() function can be called before
the IDAC8_Start() or IDAC8_Enable() function.
void IDAC8_Init(void)
Description:
Initializes/Restores default IDAC8 configuration.
Parameters:
None
Return Value:
None
Side Effects:
All registers will be set to their initial values. This will re-initialize the component. Calling the
Init() function requires a call to SetValue() if you intend to set a new value other than what is
currently in the register.
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8-Bit Current Digital to Analog Converter (IDAC8)
PSoC® Creator™ Component Data Sheet
void IDAC8_Enable(void)
Description:
Enables the IDAC8.
Parameters:
None
Return Value:
None
Side Effects:
None
void IDAC8_Start(void)
Description:
Initialize the IDAC8 with default customizer values. Enable and power up the IDAC8 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:
None
void IDAC8_Stop(void)
Description:
Powers down IDAC8 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
<INSTANCE_NAME>_Start() APIs) at all times. Do not call the <INSTANCE_NAME>_Stop()
APIs.
Parameters:
None
Return Value:
None
Side Effects:
None
void IDAC8_SetSpeed(uint8 speed)
Description:
Set DAC speed.
Parameters:
(uint8) speed: Sets DAC speed, see table below for valid parameters.
Option
Description
IDAC8_LOWSPEED
Low speed (low power)
IDAC8_HIGHSPEED
High speed (high power)
Return Value:
None
Side Effects:
None
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PSoC® Creator™ Component Data Sheet
8-Bit Current Digital to Analog Converter (IDAC8)
void IDAC8_SetPolarity(uint8 polarity)
Description:
Sets output polarity to sink or source.
Parameters:
(uint8) polarity: Sets current sink or source functionality, see table below.
Option
Description
IDAC8_SOURCE
Set mode as current source.
IDAC8_SINK
Set mode to current sink.
Return Value:
None
Side Effects:
None
void IDAC8_SetRange(uint8 range)
Description:
Sets full scale range for IDAC8
Parameters:
(uint8) range: Sets full scale range for IDAC8. See table below for ranges.
Option
Description
IDAC8_RANGE_32uA
Set full scale range to 31.875 uA
IDAC8_RANGE_255uA
Set full scale range to 255 uA
IDAC8_RANGE_2mA
Set full scale range to 2.040 mA
Return Value:
None
Side Effects:
None
void IDAC8_SetValue(uint8 value)
Description:
Sets value to output on IDAC8. 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, the SetValue() function should be called after enabling
the power to the IDAC.
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8-Bit Current Digital to Analog Converter (IDAC8)
PSoC® Creator™ Component Data Sheet
void IDAC8_Sleep(void)
Description:
Stops the operation. Saves the user configuration and the component enable state. Should
be called just prior to entering sleep.
Parameters:
None
Return Value:
None
Side Effects:
None
void IDAC8_Wakeup(void)
Description:
Restores the configuration registers and component enable state. Should be called just after
awaking from sleep.
Parameters:
None
Return Value:
None
Side Effects:
Calling this function without previously calling IDAC8_Sleep() may lead to unpredictable
behavior.
void IDAC8_SaveConfig(void)
Description:
Saves the user configuration.
Parameters:
None
Return Value:
None
Side Effects:
Empty function. Implemented for future usage.
void IDAC8_RestoreConfig(void)
Description:
Restores the user configuration.
Parameters:
None
Return Value:
None
Side Effects:
Empty function. Implemented for future usage.
DMA
IDAC8 components do not require implementation of a DMA Request signal. The typical usage
is signal generation and the data rate to IDAC8 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
IDAC8_Data_PTR
Direction
DMA Req
Signal
Destination N/A
DMA Req
Type
N/A
Description
Stores the DAC value between 0 to 255
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PSoC® Creator™ Component Data Sheet
8-Bit Current Digital to Analog Converter (IDAC8)
Sample Firmware Source Code
The following is a C language example demonstrating the basic functionality of the IDAC8
component. This example assumes the component has been placed in a design with the default
name "IDAC8_1."
Note If you rename your component you must also edit the example code as appropriate to
match the component name you specify.
#include <device.h>
void main()
{
IDAC8_1_Start();
IDAC8_1_SetRange(IDAC8_1_RANGE_255uA);
IDAC8_1_SetValue(100);
}
// Enable IDAC8
// Set full scale range to 255uA
// Set value to 100uA
Functional Description
The DAC generates either a voltage or a current output. It is built using current mirror
architecture; current is mirrored from a reference source to a mirror DAC. Calibration and value
current mirrors are responsible for the 8-bit calibration [DACx_TR] and the 8-bit DAC value. The
current is then diverted into the scaler to generate the current corresponding to the DAC value.
The DAC value can either be given from the register DACx_D or from 8 lines from the UDB. This
selection is made using the DACx_CR1[5] bit.
The DAC is strobed to get its output to change for the input code. The strobe control is enabled
by the DACx_STROBE[3] bit. The strobe sources for the DAC can be selected from the bus write
strobe, analog clock strobe to any UDB signal strobe. This selection is done on the basis of
setting in DACx_STROBE[2:0].
Current (IDAC) Mode
The two mirrors for the current source and sink provide output as a current source or current
sink, respectively. These mirrors also provide range options in the current mode.
When used as an IDAC, the output is an 8-bit digital-to-analog conversion current. This is done
by setting the DACx_CR0 [4] register. The reference source is a current reference from the
analog reference called IREF(DAC). In this mode, there are three output ranges selected by
register DACx_CR0 [3:2]:
•
0 to 2.048 mA, 8 μA/bit
•
0 to 256 μA, 1 μA/bit
•
0 to 32 μA, 0.125 μA/bit
For each level, there are 255 equal steps of M/256 where M = 2.048 mA, 256 μA, or 32 μA. In
the 2.048 mA configuration, the block is intended to output a current into an external 600Ω load.
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8-Bit Current Digital to Analog Converter (IDAC8)
PSoC® Creator™ Component Data Sheet
The IDAC is capable of converting up to 8 Msps. You also have the option of selecting whether
the output is a current source or a sink. This is done by the DACx_CR1[2] register. The selection
between source and sink for the IDAC can also be done using a UDB input. UDB control for the
source sink selection is enabled using the DACx_CR1[3] bit.
Block Diagram and Configuration
The following shows the block diagram for the IDAC8 component.
Registers
The functions provided support most of the common runtime functions that are required for most
applications. The register reference below provides a brief description for the advanced user.
The IDAC8_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 IDAC8_CR0
Bits
Value
7
6
5
reserved
4
mode
•
mode: Sets DAC to either voltage or current mode.
•
range[1:0]: DAC range settings.
•
hs: Use to set data speed.
3
2
Range[1:0]
1
0
hs
reserved
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PSoC® Creator™ Component Data Sheet
8-Bit Current Digital to Analog Converter (IDAC8)
Table 2 IDAC8_CR1
Bits
7
6
reserved
Value
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 IDAC8_DATA
Bits
7
6
5
4
2
1
0
Data[7:0]
Value
•
3
Data[7:0]: DAC data register.
DC and AC Electrical Characteristics
DC Characteristics
Parameter
Description
Conditions
Min
Typ
Max
Units
Resolution
Output current
Iout
2.048
mA
-
256
μA
-
-
32
μA
RL 600 Ω, CL=15 pF
-
-
±1
LSB
RL 600 Ω, CL=15 pF
-
-
±0.5
LSB
-
0
±1
LSB
Uncompensated
-
-
2.5
%
Temperature compensated
-
-
TBD
%
High
Code = 255, Vdda ≤ 2.7 V,
RL 300 Ω
-
-
Medium
Code = 255, RL 600 Ω
-
Low
Code = 255, RL 600 Ω
INL
Integral non linearity
DNL
Differential non linearity
Ezs
Zero scale error
Eg
Gain error
IDAC_ICC
DAC current low speed mode
Code = 0
-
-
100
μA
IDAC_ICC
DAC current high speed mode
Code = 0
-
-
500
μA
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8-Bit Current Digital to Analog Converter (IDAC8)
PSoC® Creator™ Component Data Sheet
AC Characteristics
Parameter
Fdac
Tsettle
Description
Conditions
Update rate
Min
Typ
Max
Units
-
-
8
Msps
Settling time to 0.5LSB
Full scale transition, 600 Ω
load, CL = 15 pF
Fast mode
Independent of IDAC range
setting (Iout)
-
-
100
ns
Slow mode
Independent of IDAC range
setting (Iout)
-
-
1000
ns
Component Changes
This section lists the major changes in the component from the previous version.
Version
1.50
Description of Changes
Reason for Changes / Impact
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 IDAC8 to be supported by the DMA Wizard
tool in PSoC Creator.
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