It provides a versatile evaluation platform capable of processing input signals from DC to 2 GHz, supporting frequency-domain and time-domain applications.
The Oscilloscope Front-End Reference Design is a versatile and high-performance solution that simplifies the development of precision measurement systems. Designed to cater to engineers, researchers, and developers, this reference design offers a robust signal acquisition and analysis platform. The design ensures optimal application performance by featuring key elements such as high-speed analogue-to-digital converters (ADCs), low-noise pre-amplifiers, and configurable signal conditioning circuits. Ideal for use in electronic test equipment, signal processing labs, and embedded systems development, this design serves as a reliable foundation for creating custom oscilloscope solutions or integrating oscilloscope functionalities into broader systems.
This reference design outlines a high-performance analog front-end tailored for a 50Ω-input oscilloscope application. The signal chain is designed to ensure optimal signal integrity, precision, and adaptability, making it suitable for advanced measurement and data acquisition systems. The reference design TIDA-00826 by Texas Instruments, begins with a three-step differential π-attenuator relay circuit for input voltage amplitude adjustment, offering three selectable attenuation settings: 1:1, 2:1, and 5:1. This is followed by the LMH5401, a low-noise, wideband, fully-differential amplifier (FDA) used for single-ended to differential signal conversion. It features a 6 GHz bandwidth, excellent linearity from DC to 2 GHz, and low input-voltage noise of 1.25 nV/√Hz, making it ideal for precision signal conditioning.
The LMH6401 digitally-controlled variable-gain amplifier (DVGA) is employed for precise gain adjustment, programmable via an SPI interface in 1-dB steps across a 32-dB range (-6 dB to 26 dB). This device drives a fifth-order 2.2 GHz low-pass filter, ensuring signal integrity before digitization. An ADC12J4000 12-bit analog-to-digital converter (ADC), operating at 4 GSPS, digitizes the filtered signal. The ADC boasts excellent noise and linearity performance up to and beyond 3 GHz, achieving an effective number of bits (ENOB) of 6 to 8 for oscilloscope applications.
The design supports AC/DC input coupling with DC offset nulling via a potentiometer. The LMH6559 buffer provides DC-level shift, while an OPA376 servo-loop maintains the ADC’s optimal common-mode voltage. A 4 GHz ADC clock is generated using the TRF3765 PLL and 100 MHz oscillator, ensuring low phase noise (-128 dBc/Hz at 1 MHz). The LMK04828 synchronizes the ADC and FPGA for seamless JESD204 communication. With a 2 GHz input bandwidth, ±3V signal support, and +5V or +12V power options, it suits digital oscilloscopes, TDRs, and high-speed data acquisition systems.
TI has tested this reference design. It comes with a bill of materials (BOM), schematics, assembly drawing, printed circuit board (PCB) layout, and more. The company’s website has additional data about the reference design. To read more about this reference design, click here.
