Skip to content

AD7998BRU-0’s Small-Footprint TSSOP FPGA Design

Field Programmable Gate Arrays (FPGAs) are used to make modifiable changes in the circuits of electronic devices. However, most of these circuits are now interoperable with other circuit boards and can further be programmed across different facets.

AD7998BRU-0 is an interoperable and small-footprint FPGA, in the sense that it utilizes a smaller architecture. The architecture is the TSSOP and it is one of the broader FPGA packages under the Small Outline Package (SOP) for FPGAs.

Read this article to find out most of the properties and outstanding features of the AD7998BRU-0 FPGA:

AD7998BRU-0 as an ADC

The first point to note is that AD7998BRU-0 is an Analog-to-Digital Converter or ADC. As such, it helps to convert the analog signals into the digital signal variant.

Although it is now obsolete, the manufacturer, Analog Devices Incorporated has made a couple of FPGAs to serve as the replacement. We would talk more about those later in this article.

The ADC design is just one of the major backgrounds to what the AD7998BRU-0 has to offer. Through the ADC architecture, AD7998BRU-0 is now compatible with the I2C. The compatibility paves the way for the I2C serial interface to support several modes, including the standard, high-speed and the fast modes.

Features of AD7998BRU-0


In this part of the article, we are going to talk about some of the features making AD7998BRU-0 one of the best ADCs in the market.

Here are some of those features:

1. It Handles Higher Input Frequencies

Unlike some FPGAs with low or lesser input frequencies, it is impressive to see that of AD7998BRU-0 soaring higher.

According to the information in the datasheet, AD7998BRU-0’s parts contain both the track-and-hold amplifier and the 8-channel multiplexer. The combination of these two (2) help in increasing the FPGA’s input frequency up to 11 MHz.

2. Higher Input Range

The input frequency and the input range may seem like one and the same but they are slightly different. While the input frequency clocks up to 11 MHz, the input range is dynamic and potentially has the widest dynamic range to the Analog-to-Digital Converter (ADC).

AD7998BRU-0’s widest dynamic range is obtainable because of the external reference applied to the REFIN pin. The application of the pin helps in pushing up the operating range up to 1.2 volts to the VDD.

3. Automated Conversion Rates

The values of the conversion must be balanced and that is one of the features that make AD7998BRU-0 awesome. It supports a one-shot and automatic conversion rate balancer, thus taking out the guesswork in striking the balance.

The process of making this balance can be a bit technical, but here is how it works. First, AD7998BRU-0 is designed as a successive approximation Analog-to-Digital Converter (ADC), meaning that it based around a capacitive Digital-to-Analog Converter (DAC).

For the conversion rates to be balanced, the AD7998BRU-0’s ADC uses the schematics to follow the acquisition and conversion phases. The focus is to find out an imbalance at the beginning or in the course of the balancing.

Once the comparator becomes imbalanced, the input has to be disconnected for the next stage of the conversion to take place. This time, the capacitive DAC and the control logic would be used to add and subtract some fixed amounts of charge from the sampling capacitor.

The removal leads to triggering a return of the comparator back to the balanced condition it ought to be in.

The control logic would generate the output code for AD7998BRU-0’s ADC to finalize the comparator’s balancing.

4. AD7998BRU-0 Uses Internal Registers for Device Configuration

AD7998BRU-0’s internal registers play different roles, ranging from configuring, controlling and storing the conversion results of the target devices.

Up to 17 internal registers are supported, with the conversion results stored as a read-only. For easy configuration, each of the internal registers must have a unique address to be referenced by the address pointer register during the communication phase.

5. Alert Function

Do not work “blindly” but rather, work with a “sense of purpose.” AD7998BRU-0 has an alert function, which is also called the out-of-range indicator. The indicator lets you know when critical information is to paid attention to.

For easy management, the out-of-range indicator can be enabled and disabled with software.

Another point about the indicator is that it activates mostly when the predefined values or programmed values of the low and high limits have been exceeded, especially during the conversion process.

In that case, the out-of-range indicator is there to help you stick to the programmed high and low limits, as preset with the on-chip limit registers.

6. Low Power Usage

For an FPGA functioning at this magnitude, it is expected that the power consumption should skyrocket.

On the contrary, the opposite of this assumption is the case. AD7998BRU-0’s power usage is lowered, majorly because of the low power converters used.

This FPGA also saves power by delegating the automatic shutdown function to shut down or turn of the parts that are not in use. It is expected that the power consumption is reduceable to 1 µA while on a 3-volt shutdown mode.

7. Multiple Device Support

Several devices can be connected at once to the AD7998BRU-0 because two of the AD7997 and the AD7998 versions allow up to 5 AD7977 and AD7988 devices to be connected at the same time.

AD7998BRU-0’s Technical Properties

Below are some of this ADC’s technical attributes:

  • Operating temperature between 40˚C and 85˚C.
  • AD7998BRU-0 has up to 12 RAM bits.
  • Both the analog and digital voltage supplies are pegged at 2.7 volts (minimum) to 5.5 volts (maximum).
  • The sampling rate is 188k
  • AD7998BRU-0 uses a Surface Mount style and uses a 20-TSSOP case.
  • The input type is single-ended, while the supported data interface is I2C.

The TSSOP Package

AD7998BRU-0’s Thin-Shrink Small-Outline Package (TSSOP) is one of the packages grouped under the Small-Outline Package (SOP).

The TSSOP package/case is ideal for consumer electronics, gate drivers, telephone handsets and optoelectronics. This rectangular, thin-body package component is also ideal for video & audio appliances, wireless devices, disk drives, controllers, speed dialers and recordable optical disks.

Final Words

AD7998BRU-0 is your go-to FPGA for real-time Analog-to-Digital conversions (ADCs), as well as getting the maximum conversion results possible from the internal registers.