Binary Weighted DAC

N-bit DAC based on R-2R weighted resistor architecture

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Library:
Mixed-Signal Blockset / DAC / Architectures

Description

The R-2R DAC is one of the most common types of Binary-Weighted DACs. It consists of a parallel binary-weighted resistor bank. Each digital level is converted to an equivalent analog signal by the resistor bank.

The input/output transfer curve of the binary weighted DAC can be nonmonotonic, which means that the transfer curve can reverse its direction.

The R-2R DAC architecture is low resolution and consumes more power due to the large number of resistors required to implement the architecture.

Ports

Input

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`digital`— Digital input signal to DAC
integer

Digital input signal to DAC, specified as an integer.

If theInput polarityparameter is set toBipolar, the allowed range of the signal is [−2^NBits-1, 2^NBits1]。

If theInput polarityparameter is set toUnipolar, the allowed range of the signal is [0, 2^NBits-1].

`start`— External clock to start conversion
scalar

External clock to start conversion, specified as a scalar. The digital-to-analog conversion process starts at the rising edge of the signal at thestartport.

Dependencies

To enable this port, selectUse external start clockin theGeneraltab.

Data Types:double

Output

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`analog`— Converted analog output signal
scalar

Converted analog output signal, returned as a scalar.

Data Types:double

`ready`— Indicates whether digital-to-analog conversion is complete
scalar

Indicates whether the digital-to-analog conversion is complete, returned as a scalar.

Dependencies

To enable this port, selectShow ready portin theGeneraltab.

Data Types:double

Parameters

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General

`Number of bits`— Number of bits in input word
`5`(default) | positive real integer

Number of bits in the input word, specified as a unitless positive real integer.Number of bitsdetermines the resolution of the DAC.

Programmatic Use

Block parameter:NBits

Type:character vector

Values:positive real integer

Default:5

Data Types:double

`Input polarity`— Polarity of input signal to DAC
`Bipolar`(default) |`Unipolar`

Polarity of the input signal to the DAC.

Programmatic Use

Block parameter:Polarity

Type:character vector

Values:Bipolar|Unipolar

Default:Bipolar

`Use external start clock`— Connect to external start conversion clock
on (default) | off

Select to connect to an external start conversion clock. By default, this option is selected. If you deselect this option, aSampling Clock Sourceblock inside the Segmented DAC is used to generate the start conversion clock

`Conversion start frequency (Hz)`— Frequency of internal start conversion clock
`1e6`(default) | positive real scalar

Frequency of the internal start conversion clock, specified as a real scalar in Hz. TheConversion start frequency参数确定圣的转化率art of conversion.

Dependencies

To enable this parameter, deselectUse external start clock.

Programmatic Use

Block parameter:StartFreq

Type:character vector

Values:positive real scalar

Default:1e6

Data Types:double

`Reference (V)`— Reference voltage
`2`(default) | real scalar

Reference voltage of the DAC, specified as a real scalar in volts.Reference (V)helps determine the output from the input digital code,Number of bits, andBias (V)using the equation:

$DAC output = ((\frac{Digital input code}{2^{Number of bits}}) Reference) + Bias$ .

Programmatic Use

Block parameter:Ref

Type:character vector

Values:real scalar

Default:2

Data Types:double

`Bias (V)`— Bias voltage added to output
`0`(default) | real scalar

Bias voltage added to the output of the DAC, specified as a real scalar in volts.Bias (V)helps determine the output from the input digital code,Number of bits, andReference (V)using the equation:

$DAC output = ((\frac{Digital input code}{2^{Number of bits}}) Reference) + Bias$ .

Programmatic Use

Block parameter:Bias

Type:character vector

Values:real scalar

Default:0

Data Types:double

`Show ready port`— Enable ready port on block
off (default) | on

Select to enable thereadyport on the block. This option is deselected by default.

Impairments

`Enable linearity impairments`— Enable offset and gain errors in DAC simulation
on (default) | off

Select to enable impairments such as offset error and gain error in DAC simulation. This parameter is selected. by default.

`Offset error`— Shifts quantization steps by specific value
`0 LSB`(default) | real scalar

Shifts quantization steps by a specific value, specified as a scalar in %FS (percentage full scale), FS (full scale), or LSB (least significant bit).

Offset erroris applied beforeReference (V)andBias (V).

Dependencies

To enable this parameter, selectEnable linearity impairmentsin theImpairmentstab.

Programmatic Use

Block parameter:OffsetError

Type:character vector

Values:real scalar

Default:0 LSB

Data Types:double

`Gain error`— Error in slope of DAC transfer curve
`0 LSB`(default) | real scalar

Error in the slope of the straight line interpolating the DAC transfer curve, specified as a real scalar in %FS (percentage full scale), FS (full scale), or LSB (least significant bit).

Gain erroris applied beforeReference (V)andBias (V).

Dependencies

To enable this parameter, selectEnable linearity impairmentsin theImpairmentstab.

Programmatic Use

Block parameter:GainError

Type:character vector

Values:real scalar

Default:0 LSB

Data Types:double

`Enable timing impairments`— Enable timing impairments in DAC simulation
on (default) | off

Select to enable timing impairments such as settling time or slew rate in DAC simulation. This parameter is selected. by default.

`Specify switch timing using`— Specify how DAC calculates switch timing
`Settling time`(default) |`Slew rate`

Specify whether the Binary Weighted DAC calculates switch timing using the settling time parameters or the slew rate parameters.

Dependencies

To enable this parameter, selectEnable timing impairmentsin theImpairmentstab.

`Settling time (s)`— Time required for output to settle
`2e-7`(default) | nonnegative real scalar

The time required for the output of the DAC to settle to within some fraction of its final value, specified as a nonnegative real scalar in seconds.

Dependencies

To enable this parameter, selectEnable timing impairmentsand setSpecify switch timing usingtoSettling timein theImpairmentstab.

Programmatic Use

Block parameter:SettlingTime

Type:character vector

Values:real scalar

Default:2e-7

Data Types:double

`Settling time tolerance (LSB)`— Tolerance for calculating settling time
`0.5`(default) | positive real scalar

The tolerance allowed for calculating settling time, specified as a positive real scalar in LSB. The output of the DAC must settle within theSettling time tolerance (LSB)bySettling time (s).

Dependencies

To enable this parameter, selectEnable timing impairmentsand setSpecify switch timing usingtoSettling timein theImpairmentstab.

Programmatic Use

Block parameter:SettlingTimeTolerance

Type:character vector

Values:positive real scalar

Default:0.5

Data Types:double

`Rising slew rate`— Switch rising slew rate for DAC
`5015625`(默认)|正真正的标量|正real vector

Switch the rising slew rate for the DAC, specified as a positive real scalar or vector. IfRising slew rateis scalar, it specifies the same slew rate for all the switches. IfRising slew rateis a vector of lengthNbits, it specifies the slew rate for each individual switch.

Dependencies

To enable this parameter, selectEnable timing impairmentsand setSpecify switch timing usingtoSlew ratein theImpairmentstab.

Programmatic Use

Block parameter:RisingSlewRate

Type:character vector

Values:positive real scalar | positive real vector

Default:5015625

`Falling slew rate`— Switch falling slew rate for DAC
`-5015625`(default) | negative real scalar | negative real vector

Switch the falling slew rate for the DAC, specified as a positive real scalar or vector. IfFalling slew rateis scalar, it specifies the same slew rate for all the switches. IfFalling slew rateis a vector of lengthNbits, it specifies the slew rate for each individual switch.

Dependencies

To enable this parameter, selectEnable timing impairmentsand setSpecify switch timing usingtoSlew ratein theImpairmentstab.

Programmatic Use

Block parameter:FallingSlewRate

Type:character vector

Values:negative real scalar | negative real vector

Default:-5015625

Model Examples

Measure Offset and Gain Error of Binary Weighted DAC

Find the offset and gain errors of a binary weighted DAC block.

Open Script

Measure AC Performance Metrics of Binary Weighted DAC

Find the AC performance metrics such as SNR, SINAD, SFDR, ENOB, noise floor and settling time of a binary weighted DAC block.

Open Script

Version History

Introduced in R2020a

Binary Weighted DAC

Description

Ports

Input

digital— Digital input signal to DACinteger

start— External clock to start conversionscalar

Dependencies

Output

analog— Converted analog output signalscalar

ready— Indicates whether digital-to-analog conversion is completescalar

Dependencies

Parameters

General

Number of bits— Number of bits in input word5(default) | positive real integer

Programmatic Use

Input polarity— Polarity of input signal to DACBipolar(default) |Unipolar

Programmatic Use

Use external start clock— Connect to external start conversion clockon (default) | off

Conversion start frequency (Hz)— Frequency of internal start conversion clock1e6(default) | positive real scalar

Dependencies

Programmatic Use

Reference (V)— Reference voltage2(default) | real scalar

Programmatic Use

Bias (V)— Bias voltage added to output0(default) | real scalar

Programmatic Use

Show ready port— Enable ready port on blockoff (default) | on

Impairments

Enable linearity impairments— Enable offset and gain errors in DAC simulationon (default) | off

Offset error— Shifts quantization steps by specific value0 LSB(default) | real scalar

Dependencies

Programmatic Use

Gain error— Error in slope of DAC transfer curve0 LSB(default) | real scalar

Dependencies

Programmatic Use

Enable timing impairments— Enable timing impairments in DAC simulationon (default) | off

Specify switch timing using— Specify how DAC calculates switch timingSettling time(default) |Slew rate

Dependencies

Settling time (s)— Time required for output to settle2e-7(default) | nonnegative real scalar

Dependencies

Programmatic Use

Settling time tolerance (LSB)— Tolerance for calculating settling time0.5(default) | positive real scalar

Dependencies

Programmatic Use

Rising slew rate— Switch rising slew rate for DAC5015625(默认)|正真正的标量|正real vector

Dependencies

Programmatic Use

Falling slew rate— Switch falling slew rate for DAC-5015625(default) | negative real scalar | negative real vector

Dependencies

Programmatic Use

Model Examples

Measure Offset and Gain Error of Binary Weighted DAC

Measure AC Performance Metrics of Binary Weighted DAC

Version History

See Also

`digital`— Digital input signal to DAC
integer

`start`— External clock to start conversion
scalar

`analog`— Converted analog output signal
scalar

`ready`— Indicates whether digital-to-analog conversion is complete
scalar

`Number of bits`— Number of bits in input word
`5`(default) | positive real integer

`Input polarity`— Polarity of input signal to DAC
`Bipolar`(default) |`Unipolar`

`Use external start clock`— Connect to external start conversion clock
on (default) | off

`Conversion start frequency (Hz)`— Frequency of internal start conversion clock
`1e6`(default) | positive real scalar

`Reference (V)`— Reference voltage
`2`(default) | real scalar

`Bias (V)`— Bias voltage added to output
`0`(default) | real scalar

`Show ready port`— Enable ready port on block
off (default) | on

`Enable linearity impairments`— Enable offset and gain errors in DAC simulation
on (default) | off

`Offset error`— Shifts quantization steps by specific value
`0 LSB`(default) | real scalar

`Gain error`— Error in slope of DAC transfer curve
`0 LSB`(default) | real scalar

`Enable timing impairments`— Enable timing impairments in DAC simulation
on (default) | off

`Specify switch timing using`— Specify how DAC calculates switch timing
`Settling time`(default) |`Slew rate`

`Settling time (s)`— Time required for output to settle
`2e-7`(default) | nonnegative real scalar

`Settling time tolerance (LSB)`— Tolerance for calculating settling time
`0.5`(default) | positive real scalar

`Rising slew rate`— Switch rising slew rate for DAC
`5015625`(默认)|正真正的标量|正real vector

`Falling slew rate`— Switch falling slew rate for DAC
`-5015625`(default) | negative real scalar | negative real vector