How Tiny Data Converters Give You More Value in Smaller Size

As systems get smaller, every square millimeter of printed circuit board (PCB) area counts. At the same time, as the demand for data increases, more sensors need to be monitored.

This article will discuss how to significantly reduce PCB footprint, increase channel density and maximize the advantages of high integration of other components and functions with TI micro data converters to create more value in a smaller size.

The first advantage: PCB takes up less space

Advances in packaging technology have made electronic components smaller and smaller.

As shown in Figure 1, TI’s latest single-channel ADC (ADS7042) takes up 2.25mm2, almost half the footprint of a similar ADC from ten years ago. Similarly, TI’s latest single-channel DAC (DAC53401) is one-quarter the footprint of a similar DAC from ten years ago. Similarly, for multi-channel applications, TI’s latest 8-channel ADC (ADS7138) and DAC (DAC53608) both take up 9mm2 (about 1mm2 per channel).

Figure 1: TI's smallest data converter

These tiny data converters can reduce PCB size in space-constrained designs, or fit more channels into the same PCB footprint, or both.

Advantage 2: Integrated simulation function

Many systems use discrete and passive components to implement various analog functions, such as signal conditioning, biasing and comparators. Because TI's small data converters integrate these functions, they can eliminate many discrete and passive components, thereby reducing PCB size, simplifying design, and improving performance and reliability.

Some examples of such integrations include:

Fewer external components

As shown in Figure 2, the DAC53401 integrates an output buffer and an internal reference, saving PCB area and cost.

Figure 2: Integrated reference and buffer in the DAC53401

Another example is the ADS7138 shown in Figure 3. For most applications, the ADS7138 does not require a driver amplifier at the input, again saving PCB area and cost.

Figure 3: The ADS7138 does not require an external amplifier

Bias voltage generation (fixed and variable)

The electrically erasable programmable read-only memory (EEPROM) and slew rate control features of the DAC53401 provide excellent conditions for generating fixed or variable bias voltages. Figure 4 shows an example of a lighting application.

Figure 4: DACx3401 biasing an LED

Analog and digital comparators

Comparators are often used in such systems because they immediately alert the host controller when any critical signal such as current, voltage, and temperature deviates from its expected range. This comparator should have a fast response time and be able to avoid false alarms.

As shown in Figure 5, a separate feedback pin (FB) allows you to use the DAC53401 as an analog comparator with a programmable threshold voltage.

Figure 5: The DACx3401 can access its internal amplifier feedback path

As shown in Figure 6, the ADS7138 integrates digital comparator functionality with programmable thresholds, hysteresis, and event counters to greatly reduce the possibility of false alarms.

Figure 6: ADS7138 as a digital comparator

Advantage 3: Integrated digital features

Smaller data converters allow not only remote sensor conditioning but also remote data processing. Local processing improves the performance of remote sensors, reduces response time in the event of an alarm, and frees up some processing bandwidth in the central processor.

Examples include:

Improved noise performance output averaging

To reduce the effects of noise in a system, it is common practice to average the sensor readings over a short period of time. As shown in Figure 7, the ADS7138 can average up to 128 samples, which can reduce the effects of noise by more than 10 times.

Figure 7: Average characteristics within the ADS7138

General Purpose Input/Output (GPIO)

In many systems, detecting an alarm event requires an immediate control action (such as turning off a heating element or turning on a hazard indicator). In the ADS7138, some analog input channels can monitor sensors, while unused analog input channels can be used as GPIO pins. As shown in Figure 8, the monitored sensor can control the state of the GPIO pin locally, or a central processor using an I2C interface can control the state remotely.

Figure 8: ADS7138: ADC and GPIO

Waveform Generation

In some systems, you need to generate specific waveforms to produce a chime (such as in medical applications) or to create an LED breathing effect (such as in lighting applications). DACs like the DAC53401 have a feature called continuous waveform generation that enables you to generate triangle, square, trapezoidal, or sawtooth waveforms, as shown in Figure 9.

Figure 9: DACx3401 generating multiple waveforms

Cyclic Redundancy Check (CRC)

When using ADCs such as the ADS7138 for critical monitoring functions or redundant measurements, data integrity must be maintained. The ADS7138 achieves this by performing a CRC on the data communication between the ADC and the central processor, as shown in Figure 10.

Figure 10: ADS7138 with CRC on input and output data

As shown in Figure 11, DACs such as the DAC53401 and DAC43401 use a CRC to ensure that the content written to or loaded from nonvolatile memory or EEPROM is not corrupted.

Figure 11: DACx3401 with CRC on NVM

Integrating these analog functions and digital features may result in a more complex integrated circuit, but it can greatly reduce the complexity of the overall system by adding processing and diagnostic capabilities.