The spectacular growth of the IoT in recent years has led to a significant increase in the number of electronic components used for advanced control in a wide variety of automotive and industrial applications. Among these, operational amplifiers are used to rapidly amplify minute sensor signals in anomaly detection systems that provide safety. However, board design can be problematic, as conventional high-speed operational amplifiers are susceptible to oscillation due to capacitive loads (i.e., wiring). At the same time, the degradation of the noise environment resulting from increased electrification and assembly density is making noise design for small-signal devices extremely difficult.
In response, ROHM has developed the EMARMOUR™ series of operational amplifiers and comparators*1, which have been well-received in the automotive and industrial markets due to their superior noise immunity, allowing users to reduce design resources when addressing noise issues. This time, ROHM has expanded the range by adding a new high-speed type ideal for anomaly detection, which prevents oscillation across the entire load capacitance range.
The BD77501G is the industry's first operational amplifier that not only supports the high-speed amplification (high slew rate: 10 V/µs) required in anomaly detection and other systems, but also completely eliminates oscillation caused by load capacitance (i.e., wiring). Unlike conventional high-speed operational amplifiers that can become unstable due to load capacitance-induced oscillation, ROHM's new product ensures stable operation without unwanted oscillations. Furthermore, while the output voltage of conventional products can fluctuate by ±200 mV or more across the entire noise frequency band, the BD77501G provides unprecedented EMI*2 immunity (noise immunity) that limits the variation to less than ±20 mV (1/10 A). This allows for the amplification of high-speed signals without being affected by load capacitance or external noise when installed in the later stages of sensor applications, thereby improving reliability and reducing design time.
ROHM has committed to expanding this product range to the automotive market in the near future.
What is EMARMOUR™?
EMARMOUR™ is ROHM's exclusive brand for products that utilize proprietary technologies covering circuit design, layout, and processing to achieve ultra-high noise immunity. This technology limits output voltage fluctuation to less than ±300 mV across the entire noise frequency band during noise evaluation tests under the international standard ISO 11452-2. This unprecedented noise immunity reduces design resources while improving reliability by addressing noise-related issues in the development of a wide range of systems.
Key features
1. The industry's first high-speed, oscillation-free op-amps that minimize load capacitance-related design time.
The BD77501G utilizes original Nano Cap™ power supply technology to achieve extremely stable control, making it the industry's first op-amp to completely eliminate load capacitance-induced oscillation (i.e., wiring) while supporting the high-speed amplification (high slew rate: 10 V/µs) required in anomaly detection and other systems.
Unlike conventional operational amplifiers that can be difficult to use due to restrictions imposed on wiring and peripheral components as a result of instability caused by load capacitance, ROHM's new operational amplifier eliminates oscillation to ensure stable operation and facilitate application design.
2. Superior noise immunity reduces noise design requirements (exclusive EMARMOUR™).
While the output voltage of conventional products can fluctuate by ±200 mV or more across the entire noise frequency band, ROHM's latest EMARMOUR™ series operational amplifier provides unprecedented noise immunity, limiting the variation to less than ±20 mV. This eliminates the need for countermeasures (filtering circuits) for each noise frequency, reducing noise design resources for sensors (which play a critical role in a wide variety of systems), simplifying application design, and simultaneously improving system reliability.
3. Eliminates 10 components needed for noise suppression (exclusive EMARMOUR™)
The BD77501G provides superior noise immunity, eliminating the need for external noise countermeasure components conventionally required for standard products (i.e., RC filters for the power supply, input, and output pins). For example, in the case of a 1-channel op-amp, the new ROHM products require 10 fewer components than conventional solutions. 
Availability: immediate (samples), October 2020 (OEM quantities)
Application examples
• Facility management equipment, such as abnormal current and gas detectors
• Motors requiring high-speed control (signal transmission)
• Inverter control equipment
• Pre-suppressors for transistor control
...and other applications in the industrial and consumer fields that require high-speed signal transmission and amplification without needing to consider load capacitance.
What is Nano Cap™?
Nano Cap refers to ultra-stable control technology achieved by combining expertise in advanced analog design, encompassing circuit design, processes, and layout, using ROHM's vertically integrated production system. Stable control eliminates the operational stability issues associated with capacitors in analog circuits, helping to reduce design time for a wide range of applications in the automotive, industrial equipment, consumer, and other sectors.
Specifications in the table
Terminology
*1) Operational Amplifiers / Comparators
Operational amplifiers are designed to amplify input signals. They are often used to amplify tiny signals, such as those from sensors, to a voltage level that can be recognized by a microcontroller (MCU).
Comparators are commonly used to determine the threshold value of input signals. They output a High/Low signal after performing a threshold judgment on the sensor's output signal.
(Fig. 6)
2*) EMI Immunity (Electromagnetic Interference)
EMI immunity is a parameter that indicates the degree of tolerance to ambient noise. Noise generated in the environment can cause malfunctions in systems with low EMI immunity, requiring protective measures such as the incorporation of filters (i.e., resistors/capacitors) or shielding (metal plates). In contrast, high EMI immunity ensures stable operation without concern for the effects of noise, providing a significant advantage by virtually eliminating the design burden for noise mitigation measures.
*Nano Cap™ and EMARMOUR™ are trademarks or registered trademarks of ROHM Co., Ltd.
