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Binary Weighted DAC

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

Since R2020a

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  • Binary Weighted DAC block

Libraries:
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.

Examples

Measure Offset and Gain Error of Binary Weighted DAC

Measure Offset and Gain Error of Binary Weighted DAC

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

Measure AC Performance Metrics of Binary Weighted DAC

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.

Ports

Input

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Digital input signal to DAC, specified as an integer.

If the Input polarity parameter is set to Bipolar, the allowed range of the signal is [−2(NBits-1), 2(NBits-1)-1].

If the Input polarity parameter is set to Unipolar, the allowed range of the signal is [0, 2NBits-1].

Data Types: single | double | int8 | int16 | int32 | uint8 | uint16 | uint32 | fixed point

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

Dependencies

To enable this port, select Use external start clock in the General tab.

Data Types: double

Output

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Converted analog output signal, returned as a scalar.

Data Types: double

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

Dependencies

To enable this port, select Show ready port in the General tab.

Data Types: double

Parameters

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General

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

Programmatic Use

Block parameter: NBits
Type: character vector
Values: positive real integer
Default: 5

Data Types: double

Polarity of the input signal to the DAC.

Programmatic Use

Block parameter: Polarity
Type: character vector
Values: Bipolar|Unipolar
Default: Bipolar

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

Frequency of the internal start conversion clock, specified as a real scalar in Hz. The Conversion start frequency parameter determines the conversion rate at the start of conversion.

Dependencies

To enable this parameter, deselect Use external start clock.

Programmatic Use

Block parameter: StartFreq
Type: character vector
Values: positive real scalar
Default: 1e6

Data Types: double

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, and Bias (V) using the equation:

DAC output = ((Digital input code2Number of bits)Reference)+Bias.

Programmatic Use

Block parameter: Ref
Type: character vector
Values: real scalar
Default: 2

Data Types: double

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, and Reference (V) using the equation:

DAC output = ((Digital input code2Number of bits)Reference)+Bias.

Programmatic Use

Block parameter: Bias
Type: character vector
Values: real scalar
Default: 0

Data Types: double

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

Impairments

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

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 error is applied before Reference (V) and Bias (V).

Note

The full scale range of the converter is defined as the difference between the last and first code on the +0.5 LSB compensated transfer curve. In a +0.5 LSB compensated transfer curve, first code is 0.5 LSB wide while the last code is 1.5 LSB wide. The input values must be considered within the full scale range of the converter.

Note

LSB is calculated by the equation LSB = Full scale range of converter2NBits.

Dependencies

To enable this parameter, select Enable linearity impairments in the Impairments tab.

Programmatic Use

Block parameter: OffsetError
Type: character vector
Values: real scalar
Default: 0 LSB

Data Types: double

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 error is applied before Reference (V) and Bias (V).

Note

The full scale range of the converter is defined as the difference between the last and first code on the +0.5 LSB compensated transfer curve. In a +0.5 LSB compensated transfer curve, first code is 0.5 LSB wide while the last code is 1.5 LSB wide. The input values must be considered within the full scale range of the converter.

Note

LSB is calculated by the equation LSB = Full scale range of converter2NBits.

Dependencies

To enable this parameter, select Enable linearity impairments in the Impairments tab.

Programmatic Use

Block parameter: GainError
Type: character vector
Values: real scalar
Default: 0 LSB

Data Types: double

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

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

Dependencies

To enable this parameter, select Enable timing impairments in the Impairments tab.

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, select Enable timing impairments and set Specify switch timing using to Settling time in the Impairments tab.

Programmatic Use

Block parameter: SettlingTime
Type: character vector
Values: real scalar
Default: 2e-7

Data Types: double

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

Dependencies

To enable this parameter, select Enable timing impairments and set Specify switch timing using to Settling time in the Impairments tab.

Programmatic Use

Block parameter: SettlingTimeTolerance
Type: character vector
Values: positive real scalar
Default: 0.5

Data Types: double

Switch the rising slew rate for the DAC, specified as a positive real scalar or vector. If Rising slew rate is scalar, it specifies the same slew rate for all the switches. If Rising slew rate is a vector of length Nbits, it specifies the slew rate for each individual switch.

Dependencies

To enable this parameter, select Enable timing impairments and set Specify switch timing using to Slew rate in the Impairments tab.

Programmatic Use

Block parameter: RisingSlewRate
Type: character vector
Values: positive real scalar | positive real vector
Default: 5015625

Switch the falling slew rate for the DAC, specified as a positive real scalar or vector. If Falling slew rate is scalar, it specifies the same slew rate for all the switches. If Falling slew rate is a vector of length Nbits, it specifies the slew rate for each individual switch.

Dependencies

To enable this parameter, select Enable timing impairments and set Specify switch timing using to Slew rate in the Impairments tab.

Programmatic Use

Block parameter: FallingSlewRate
Type: character vector
Values: negative real scalar | negative real vector
Default: -5015625

Version History

Introduced in R2020a

See Also

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