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Technical Article

What Is a Smart DAC?

Gavin Bakshi27
Engineers are always striving to make things more effective, more efficient and less expensive. Systemdesigners typically use a precision digital-to-analog converter (DAC) when they need very precise control ofan analog output. A design that requires precise control of auxiliary functions typically also needs a combinationof discrete analog components and microcontrollers (MCUs) to control the DAC’s output.
The process of choosing the right components, writing software and ensuring that the system works cohesivelycan be unnecessarily complicated, even when implementing basic functions. In this article, I will explore how you
can improve system performance while reducing cost and development time with a new type of device: a smart
DAC.
Smart DACs are factory programmable precision DACs that have integrated non-volatile memory (NVM),
programmable state-machine logic, pulse-width modulation (PWM) generators and custom waveform generators
built in. Because smart DACs eliminate the need for software, they fill the gap between DAC-based circuits,
MCU-based circuits and entirely discrete circuits built with components like precision resistors, capacitors andinductors. Figure 1 shows how smart DACs provide a unique approach to conventional implementations.

Figure 1. A Smart DAC Bridges the Gap between Discrete-, DAC- and MCU-based Circuits
Here are several use cases where you can use smart DACs to perform simple functions with fewer system
resources, saving time and system cost.
Achieve Reliable Power-up and Basic Programmability without Software
Software-based MCU designs, while extremely useful for the primary monitoring and control applications insome automotive and industrial applications, require an excessive amount of resources when you are designingsecondary applications or subsystems that only require auxiliary voltage margining, biasing or trimming.
Applications such as lighting control need only a simple sense-measure-control feedback loop. Another example
is in appliances, where a light in your microwave turns on when the door is open. Because this is a simple
function requiring minimal resources, a smart DAC can help.
Figure 2 shows a smart DAC with integrated NVM. The ability to store register settings in memory during systemproduction enables you to program the smart DAC’s power-up state in memory. Automotive Electronics CouncilQ100-qualified smart DACs can support memory retention for 20 years at 125°C operating temperatures,making them a good choice for automotive and industrial applications like multi-slope thermal foldback forautomotive daytime running lights, or land and mobile radios in aerospace and defense.
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Figure 2. DAC53701 Block Diagram with NVM
Generate Custom Outputs
Smart DACs will also work in applications that require PWM generation – such as long-distance fault
management with built-in, configurable analog-to-PWM duty-cycle translation or general-purpose input (GPI)to-PWM conversion. Unlike MCUs or timer-based solutions like 555 timers, smart DACs don’t require R&Dtime or additional discrete components prone to temperature drift. Figure 3 shows an example of temperatureto-PWM conversion using DAC53701 in which the pulse width of the PWM output adjusts with changes intemperature. You can learn about other PWM applications in the technical article, “Generating pulse-widthmodulation signals with smart DACs.”

Figure 3. The DAC53701 Adjusts PWM Output with Changes in Temperature
You can also implement these waveforms when generating tones in patient monitoring systems, where smart
DACs can be used to generate medical alarms by providing preconfigured patterns and general-purpose input/
output (GPIO)-based trigger functionality. Our “Demystifying medical alarms” series explores this topic in moredetail.
Produce LED Fade-in, Fade-out and Thermal Foldback
In lighting applications for appliances and vehicles, smart DACs produce fade-in and fade-out signals thatprovide digital input triggering and programmable timing. Designers can build modular systems and tune
something like LED brightness on each individual board by reprogramming the NVM, thus reducing development
time and cost.
LED reliability is inversely proportional to the operating temperature, and to improve the life of the LEDs, anactive thermal foldback is necessary to improve thermal management. The daytime running light (DRL) inautomotive lighting remains on at all times and is exposed to sunlight during daytime hours. Thermal foldback
here is a necessity to maximize LED life, and smart DACs help simplify the system design with built-in features.

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Figure 4 shows a circuit and the relationship between the GPI input and DAC output, and how the rise and fallof the DAC output can be controlled directly by the GPI to produce a slewed LED fade-in or fade-out. Appliances
typically use a sensor to determine whether the door is open or closed, which the GPI will represent as high orlow.

Figure 4. GPI Pulse Time vs. DAC Output Ramp Time for Appliance Fade-in and Fade-out
Act as a Programmable Comparator
In appliances, medical devices, retail automation and other industrial applications, smart DACs can also act as aprogrammable comparator, providing programmable hysteresis or output latching functions and helping simplify
fault-management software while reducing board size.
Figure 5 shows the programmable hysteresis and latching comparator function, and how the DAC output istracked within a threshold set by margin-high and margin-low values stored in NVM.
For programmable hysteresis, if the input exceeds the margin-high value, then the GPI will toggle low. If thetracked value continues to drop below margin-high, then no change occurs on the GPI until the value drops
below the margin-low value, which will cause the GPI to trigger high. This is useful to raise alarms when a givenvalue exceeds a finite range. For the latching comparator implementation, the feedback voltage only needs to beless than VDD (because the operational amplifier is supplied by VDD), so it is possible that the output will toggle
low again if it was latched high.

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Figure 5. A Smart DAC as a Programmable Comparator, with Hysteresis and a Latching Comparator
Conclusion
As these use cases show, smart DACs can help you design self-reliant circuits by replacing discrete analog
circuits and MCUs with a simple one-chip solution at a lower system cost. Explore TI’s portfolio of smart DACs
using this prefiltered product search.
Additional Resources• View the DAC53701 data sheet.
• The DAC53701-Q1 data sheet shows the implementation of a thermal foldback loop.
• Browse the smart DAC FAQ on our TI E2ETM forums.
• Explore three other devices in the smart DAC family, the DAC53204, DAC63204 and DAC63004.

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