Tuesday, April 16, 2024

High-Speed Op Amp That Eliminates Oscillation Due To Load Capacitance

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  • ROHM’s newest op-amp is ideal for anomaly detection in systems that work with small signals
  • The company’s EMARMOUR technology helps in providing noise immunity and thus results in fewer parts for noise suppression

ROHM has announced a high-speed sensing CMOS op-amp, BD77501G, that is optimised for industrial and consumer equipment requiring high-speed sensing, such as anomaly detection systems used in measurement and control equipment along with sensors that work with very small signals.

The expansion of IoT in recent years has significantly increased the number of electronic components for advanced control of automotive and industrial applications. For these, op-amps are largely used and are capable of quickly amplifying minute sensor signals in anomaly detection systems for providing safety. However, board design can become problematic as conventional high-speed op-amps are susceptible to oscillation due to capacitive loads (i.e. from wiring). At the same time, disturbance in the form of environmental noise resulting from increased electrification and mounting density makes it extremely difficult to implement noise design for small-signal devices.

EMARMOUR Technology

In response, ROHM developed the EMARMOUR series of op-amps and comparators that have superior noise immunity, allowing users to reduce design resources to address noise issues. The company’s latest offering, the BD77501G helps achieve that. The new high-speed op-amp is ideal for anomaly detection.

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EMARMOUR is a technology that limits output voltage fluctuation to less than ±300mV across the entire noise frequency band during noise evaluation testing. This noise immunity reduces design resources while improving reliability by solving issues related to noise in the development of a variety of systems.

No unwanted oscillation

The BD77501G not only supports high-speed amplification (high slew rate: 10V/us) required in anomaly detection and other systems but also completely eliminates oscillation caused by load capacitance (i.e. wiring). Unlike conventional high-speed op-amps that can become unstable due to load-capacitance-induced oscillation, the new product ensures stable operation with no unwanted oscillation.

Whereas the output voltage for conventional products can fluctuate by ±200mV or more across the entire noise frequency band, the BD77501G provides EMI Immunity (noise immunity) that limits variation to less than ±20mV. This enables high-speed signal amplification without being affected by load capacitance or external noise when installed in sensor applications, improving reliability and reducing design time.

Key Features

Minimises design time related to load capacitance

The BD77501G leverages ROHM’s Nano Cap power supply technology to achieve extremely stable control, allowing complete elimination of oscillation induced by load capacitance (i.e. wiring) while supporting high-speed amplification (high slew rate: 10V/us) required in anomaly detection and other systems.

Unlike conventional op-amps that can be difficult to use due to restrictions imposed on the wiring and peripheral components resulting from instability caused by load capacitance, the BD77501G eliminates oscillation to ensure stable operation and facilitate application design.

Better noise immunity

Whereas the output voltage of conventional products can fluctuate by ±200mV or more across the entire noise frequency band, the EMARMOUR series op-amp achieves unprecedented noise immunity that limits variation to less than ±20mV. This eliminates the need for filter circuits for each noise frequency, reducing the noise design resources for sensors and facilitates application design while improving system reliability.

Fewer parts are required for noise suppression

The BD77501G provides superior noise immunity that eliminates the need for external noise countermeasure components such as RC filters for the power supply, input, and output pins. For example, in the case of a 1ch op-amp, the BD77501G uses 10 fewer external components than conventional solutions.

Other features

  • No. of circuits: 1
  • Supply voltage range: 7.0V to 15.0V
  • Input Offset Voltage: ±4mV (Typ.)
  • Common Mode Input Voltage Range: VSS to VDD -2.0V
  • Operating Temperature Range: -40 degrees Celsius to +85 degrees Celsius
  • Package: SSOP5 2.9 x 2.8 x 1.25 mm

Application Examples

  • Facility management equipment such as abnormal current and gas detectors
  • Motors requiring high-speed control (signal transmission)
  • Inverter control equipment
  • Pre-drive buffers for driving transistors

Other applications are in industrial and consumer fields requiring high-speed signal transmission and amplification without the need to consider load capacitance.

Product samples are available now with OEM quantities to begin from October 2020.


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