DAC7750IPWPR.B datasheet(26/56 Pages) TI2

26 / 56 page

The time required for the output to slew over a given range is expressed as Equation 5.

Slew Time =

Output Change

Step Size Update Clock Frequency LSB Size

(5)

where

• Slew Time is expressed in seconds

• Output Change is expressed in amps (A) for IOUT or volts (V) for VOUT

When the slew rate control feature is enabled, all output changes happen at the programmed slew rate. This

configuration results in a staircase formation at the output. If the CLR pin is asserted, the output slews to the

zero-scale value at the programmed slew rate. Read bit 1 (SR-ON) of the Status Register to verify that the slew

operation has completed. The update clock frequency for any given value is the same for all output ranges. The

step size, however, varies across output ranges for a given value of step size because the LSB size is different

for each output range. Figure 8-4 shows an example of IOUT slewing at a rate set by the previously described

parameters. In this example for the DAC8750 (LSB size of 305 nA for the 0-mA to 20-mA range), the settings

correspond to an update clock frequency of 6.9 kHz and a step size of 128 LSB. As shown in the case with no

capacitors on CAP1 or CAP2, the steps occur at the update clock frequency (6.9 kHz corresponds to a period

close to 150 µs), and the size of each step is approximately 38 µA (128 × 305 nA). Calculate the slew time for a

specific code change by using Equation 5.

Time (150 µs/ div)

no cap

3 nF CAP1

3 nF CAP2

10 nF CAP1

10 nF CAP2

0 mA to 20 mA range

C001

SRCLK=1100h

SRSTEP = 111h

Figure 8-4. IOUT vs Time With Digital Slew Rate Control

Apply the desired programmable slew rate control setting before updating the DAC data register because

updates to the DAC data register in tandem with updates to the slew rate control registers can create race

conditions that may result in unexpected DAC data.

DAC7750, DAC8750

SBAS538D – DECEMBER 2013 – REVISED DECEMBER 2021

www.ti.com

Submit Document Feedback

Product Folder Links: DAC7750 DAC8750

DAC7750IPWPR.B Datasheet(PDF) 26 Page - Texas Instruments