Analog ICs are vital electronic components that process continuously varying signals (analog signals) found in the real world. Real-world changes, such as sound, temperature, and pressure, follow smooth, uninterrupted curves, and analog ICs enable these signals to be accurately processed within electronic devices. With the rapid shift of machines toward electronic operation, analog ICs have become indispensable in supporting and driving this transformation.

Definition of Analog ICs

Analog ICs are integrated circuits that combine electronic components such as transistors, resistors, capacitors, and diodes on a single chip to perform specific functions. They process analog signals that represent physical quantities like voltage and current, enabling operations such as signal amplification, filtering, modulation, and demodulation. These ICs are used extensively across applications including communications, automotive systems, and medical devices. They are also essential in products like smartphones and electric vehicles, where demand continues to grow rapidly.

What are Analog Signals?

Analog ICs are found in nearly all electronic devices that process analog signals such as sound, temperature, and pressure.
By combining them with digital signal processing, even more advanced functionalities can be achieved. They play a critical role across diverse fields, from smartphones and medical devices to automotive sensor systems. Below, we introduce examples of analog ICs used in various applications.

Audio Equipment

Industrial Equipment

Communication Equipment

Consumer Electronics

Computers

Power Supplies

Automotive

Smartphones

Lighting Equipment

• Details of each application

Reducing carbon dioxide (CO2) emissions has become a global priority, driving rapid growth in hybrid vehicles and fully electric vehicles (EVs). Alongside full hybrids, lower-cost mild hybrid vehicles are also attracting attention. Mild hybrids operate at comparatively low motor voltage, using the motor solely to assist the engine - unable to run on motor power alone - but still contribute to improved fuel efficiency.
These vehicles employ a 48V power system that offers higher efficiency than older 12V systems. However, their electronic control units (ECUs) typically operate at much lower voltages, around 2.5V to 3.3V.
Conventional DC-DC converter ICs, which step one DC voltage down to another, have generally been limited to operating frequencies of several hundred kHz. This often required using two converters in sequence to reach the desired voltage. By enabling operation at higher frequencies, the same voltage conversion can be achieved with a single converter. Higher frequency operation also allows for smaller external inductors (coils), since shorter switching intervals reduce the required inductance. As coils are among the largest external components, downsizing them directly contributes to overall system miniaturization.

ROHM’s Nano Pulse Control™

For example, ROHM’s BD9V100MUF buck DC-DC converter IC with built-in MOSFET achieves high-speed switching at 2.1MHz , enabling step-down conversion from 60V to 3.3V using a single chip. ROHM has branded this ultra-high-speed pulse control technology Nano Pulse Control™, and has introduced a series of products incorporating it.

• More about Nano Pulse Control™

Wearable and IoT devices are typically battery powered, creating a strong need to reduce power consumption to extend operating time.
One approach is to increase the resistance value in the circuit, which can lower power usage but also introduces several drawbacks.

• Increased current leakage
  Higher resistance can lead to greater leakage current from components, resulting in wasted power.
• Reduced noise immunity
  Circuits become more susceptible to noise, potentially causing unstable operation.
• Lower response speed
  Increasing resistance slows the circuit’s response time, degrading overall performance.

The following countermeasures are effective in mitigating these issues.

• Adopting a high-performance reference voltage circuit
  A reference voltage circuit maintains a constant voltage regardless of supply voltage or temperature variations. Using a high-performance reference circuit prevents excess power consumption in other parts of the system.
• Utilizing high-density, high-resistance components
  High-density, high-resistance components increases resistance per unit area while minimizing the influence of parasitic elements. This enables faster circuit operation, reduces chip size, and improves layout efficiency.
• Coordinating circuit design with components and manufacturing processes
  Aligning circuit design, chip layout, and manufacturing methods helps minimize leakage current and enhance noise immunity.
  Specific measures include:
  - Optimizing device placement and wiring: Strategic placement of transistors and wiring suppresses leakage currents.
  - Using high-k (high dielectric constant) materials: Applying high-k materials in the gate insulation layer reduces gate leakage current.
  - Noise-resistant design: Designing circuits with high noise tolerance and implementing layout techniques such as shielding can prevent malfunctions.

ROHM's Nano Energy™

ROHM's Nano Energy™ technology integrates advanced innovations to deliver ultra-low current consumption with high efficiency. For example, ROHM’s BD70522GUL DC-DC converter achieves an exceptionally low standby current of just 180nA, providing up to twice the battery life compared to conventional products. This dramatically improves the performance of battery-powered devices, enabling extended operation over long periods.
Nano Energy™ technology is particularly effective in reducing power consumption for wearables and IoT devices, helping to minimize battery replacement frequency and support long-term, maintenance-free operation.

• More about Nano Energy™

With the growing awareness of sustainable energy use, electrification is accelerating across many industries. In the automotive sector in particular, the rise of electric vehicles (EVs) and autonomous driving technologies has driven a sharp increase in the number of electronic components used. These components often operate at different power supply voltages, requiring numerous capacitors to stabilize these voltages.
However, a large number of capacitors increases both the PCB (printed circuit board) size and component costs. To address this issue, it is crucial to enhance linear regulators (LDOs) so they can maintain stable operation even when paired with smaller capacitors. Reducing capacitor capacitance, however, raises the risk of output voltage instability or oscillation when input voltage or load fluctuations fluctuate.
For example, when powering an MCU through a linear regulator, an output capacitor is typically used along with a bypass capacitor connected to the MCU’s power supply pin (located at the closest point). If the output capacitor is removed or its capacitance is too low, these stability and oscillation issues can occur.

ROHM’s Nano Cap™

Nano Cap™ is ROHM's proprietary technology designed to enhance the transient response of LDO (Low Drop Out) linear regulators by minimizing internal wiring and parasitic elements (unwanted effects caused by circuit characteristics such as wiring length or layout. Excessive parasitic elements can introduce noise, slow signal transmission, and destabilize operation, making precise signal processing more difficult. Reducing these factors delivers several key benefits.

• Reduced noise
  Less noise within the circuit enables operation closer to the intended design.
• Faster signal transmission
  Optimized wiring and component placement improve signal speed, enabling high-speed feedback control.
• Stable operation
  Lower parasitic influence improves overall circuit stability, reducing the risk of malfunctions or unexpected behavior.
  Nano Cap™ technology increases the responsiveness of internal LDO circuits, resulting in more stable output voltage.

For example, in the case of powering an MCU, Nano Cap™ technology allows stable operation with only a single nano-level capacitor on the MCU side.
This reduces component count and PCB size, saving both design effort and board space, ultimately enabling a stable voltage supply at lower cost.

• More about Nano Cap™

So far, we have explored the challenges and advancements in power ICs - one of the most versatile categories of analog ICs. Another essential and widely used type is the op amp (operational amplifier).
All real-world physical phenomena exist as analog signals that change continuously, and op amps play a crucial role in allowing electronic devices to capture, amplify, and process these signals.

Role of Op Amps

Op amps are analog ICs designed to amplify and process analog signals, making them indispensable in modern electronics.

1. Signal Amplification

The primary function of an op amp is to amplify weak analog signals, such as those output from sensors or microphones, so they can be processed by subsequent electronic circuits.

2. Filter Circuits

Op amps are used to build band-pass and low-pass filters that limit the signal frequency range and remove unwanted harmonics or noise. Typical applications include audio bandwidth limitation and modulation/demodulation for signal transmission.

3. Signal Conversion and Processing

Op amps also perform signal conversion and advanced processing. Examples include current-to-voltage and voltage-to-current conversion, enabling compatibility between different signal formats. They can also execute arithmetic operations such as addition, subtraction, differentiation, and integration, enabling complex analog signal processing.

Challenges of Op Amps - Addressing Electromagnetic Interference

EMS (Electromagnetic Susceptibility) refers to the degree to which electronic devices are affected by external electromagnetic noise. The sources of EMS can be classified into three main categories Natural Causes: Electromagnetic waves generated by natural phenomena, such as lightning and solar activity.
Man-Made Causes: Electromagnetic waves emitted by devices such as wireless communication equipment, radar, motors, and switching power supplies.
Electrostatic Discharge (ESD): Static electricity discharged from a person or object into electronic equipment.

Effective EMS countermeasures involve optimizing internal circuit design to reduce noise intrusion paths. This can include physically separating noise sources from sensitive circuits, shielding specific sections to block external interference, and adding filters to inputs and outputs to suppress noise. While such measures can be applied to various components, such as sensors and LDOs, they are especially important for op amps.
When op amps are exposed to internal or external electromagnetic noise, their ability to process signals or output voltages accurately may be compromised, potentially leading to system malfunctions. This is particularly critical in applications like ADAS (Advanced Driver Assistance Systems), where electronic devices must operate reliably despite constant exposure to external noise. For example, if noise interferes with an automatic braking system, it could result in a dangerous malfunction.
In addition, in electric vehicles (EVs), high-voltage batteries, drive equipment, and high-power motors, such as those in AC and power steering systems, generate substantial internal noise, further increasing EMS risks.

Common EMS Countermeasures for Op Amps

• Adding input filters: Filters at the op amp's input terminals block high-frequency noise.
• Placing decoupling capacitors: Capacitors on the power supply lines absorb supply noise.
• Using shielding: Enclosing noise-generating components in shielding to block electromagnetic interference.
• Optimizing circuit layout: Physically separating noise sources from sensitive circuits to reduce noise coupling.。

ROHM’s EMARMOUR™ Series

EMARMOUR™ is ROHM's brand for products engineered with advanced electromagnetic susceptibility (EMS) countermeasures, delivering exceptional noise immunity in evaluations conducted under the ISO 11452-2 international standard. The series is primarily focused on op amps.
ROHM's EMARMOUR™ op amps can suppress output voltage fluctuations to within ±1% across the entire noise frequency spectrum. In comparison, typical products from other manufacturers often exhibit fluctuations between ±3.5% to 10%. This outstanding EMI immunity eliminates the need for external CR filters or shielding, reducing both space requirements and costs. Despite their enhanced noise resistance, EMARMOUR™ op amps maintain the same general-purpose performance as standard op amps, enabling seamless integration into existing designs. They also meet the AEC-Q100 automotive electronic component standard, ensuring high reliability. The superior noise immunity of the EMARMOUR™ series is made possible through ROHM's proprietary circuit design, optimized layout, and advanced process technologies.

• EMARMOUR™ Lineup
• More about EMARMOUR™

Comparing Digital and Analog Power Supply Control

Digital Control

Precise control: Utilizes MCUs or DSPs (Digital Signal Processors) to execute software-based control, enabling extremely accurate regulation.
Flexibility: Control parameters can be modified via software, allowing easy adaptation to different applications and conditions.
High efficiency: Selects optimal operating modes and frequencies according to load conditions, maximizing power conversion efficiency.
Communication capability: Supports communication with other devices for centralized system management.

Analog Control

Simple architecture: Uses dedicated analog circuits for fixed, predefined control. The straightforward design makes development easier, depending on performance requirements.
Low cost: Eliminates the need for expensive MCUs or DSPs, reducing system costs.
Low power consumption: Without high-speed DSPs or control MCUs, the power supply itself consumer less energy.

Summary

Digital control: Offers precision, flexibility, high efficiency, and communication capabilities.
Analog control: Delivers simplicity, low cost, and low power consumption.

In power management applications, analog control remains dominant in low-power domains, such as those in industrial equipment power systems, mainly due to its ability to minimize power consumption at the source. Conversely, digital control is mainstream in high-power domains because of its high efficiency and operational flexibility. While analog control still prevails in the mid-power range (approx. 50W to 1kW), ongoing development focuses on fusing analog and digital technologies to further enhance performance.

ROHM’s LogiCoA™ Solutions

LogiCoA™ is ROHM’s brand of power electronics solutions built on a design philosophy that integrates digital elements to maximize the performance of analog circuits. Each LogiCoA™ solution is composed of three core elements: power topology, LogiCoA™ MCU, and power control OS, offering the following features and benefits.

Balancing low cost, low power consumption, compact size, and superior functionality

Achieving advanced functionality with purely analog control alone is challenging, while full digital control often increases cost and power consumption. ROHM addresses this by introducing LogiCoA™ MCUs - cost effective, low-power microcontrollers designed to work seamlessly with analog circuitry.
Key features include log data acquisition and interface capabilities, enabling the monitoring and analysis of operating conditions. This allows for the detection of abnormal operation, assessment of maintenance needs, and estimation of service life.
Working together with RMOS (ROHM's power control OS), the LogiCoA™ MCU can control two topologies simultaneously, reducing both size and cost. For example, it can manage both the PFC (Power Factor Correction) and DC-DC stages, making it possible to regulate LED lighting and dimming directly from an AC power source.

High accuracy

A built-in calibration function compensates for component variations, enabling the use of smaller components while enhancing circuit performance. For example, it can reduces the size of inductors and power devices while improving operational efficiency.

Ease of implementation

The availability of reference boards and RMOS streamlines software development, allowing designers to create optimized (customized) power supplies tailored to specific application requirements. Using the provided reference boards and RMOS for each power topology, engineers can accelerate design while ensuring performance.
LogiCoA™ solutions are adaptable to a wide range of applications, particularly power supply systems, and are especially effective in the small- to medium-power market for industrial equipment.

• LogiCoA™ Lineup
• More about LogiCoA™