News and Information

2021-10

2021-10-29

HJ5B40 Isolation Amplifier

In modern electronic measurement, engineers often need to acquire a specific physical quantity—such as current, voltage, or their variations—with high reliability and fidelity from an extremely complex electromagnetic environment (for example, the magnetic field generated by cables carrying large currents). However, the measured quantities are typically very small and frequently accompanied by significant interference, such as high common-mode voltages (CMV), strong electromagnetic interference (EMI), and rapid transient disturbances (dV/dt or dI/dt). If these interference issues are not effectively addressed, the accuracy of the acquired measurements can degrade, potentially posing serious risks to system reliability and safety. The following interference analysis diagram can be used to illustrate this: Interference Analysis Diagram To solve these problems, engineers naturally turn to isolated amplification and conditioning circuits. Such circuits must exhibit excellent electromagnetic compatibility (EMC), robust resistance to breakdown under high common-mode voltages (CMV), and superior common-mode transient immunity (CMTI); otherwise, they remain inadequate solutions. - EMC: The ability of a device or system to operate as intended within its electromagnetic environment without generating unacceptable levels of electromagnetic interference to other devices in that environment. It encompasses both electromagnetic interference (EMI)—the disturbance caused by one electronic component on another—and electromagnetic susceptibility (EMS)—the response of electronic components to electromagnetic fields. - CMV: The average value of the phasor voltage between any conductor and a specified reference point. - CMTI: The minimum rate of change of voltage or current (dV/dt or dI/dt) required to cause a transient across an isolation barrier that disrupts the driver’s output state. Design philosophies and configurations of isolated amplification and conditioning circuits vary considerably. Different approaches emphasize distinct aspects of addressing the three key factors mentioned above, which in turn limits the adaptability of individual products. Recognizing the application context of isolation amplifiers and drawing upon mature design concepts from abroad, Hangjing Microelectronics has leveraged its team’s extensive engineering expertise in power conversion, modulation/demodulation, and analog PID control. By further integrating advanced microelectronic isolation technologies, the company has successfully developed the HJ5B40 isolated amplifier module, designed to emulate the imported 5B40 product. This module features pin compatibility with foreign counterparts, a footprint half that of similar foreign products, an isolation withstand voltage of 3800 V—higher than comparable international offerings—and superior CMTI performance. HJ5B40 Isolated Amplifier 1. Overview The HJ5B40 isolated amplifier is a specialized operational amplifier that isolates the power supply circuit, input circuit, and output circuit by breaking ground loops. Designed specifically for isolating and amplifying weak signals in complex electromagnetic environments, it reliably and faithfully converts input signals ranging from -100 mV to +100 mV into an isolated, conditioned output of -5 V to +5 V. The loop gain is internally set to 50×, though it can be customized according to customer requirements. Additional related products can also be developed based on customer needs. Key Features: 1. Electrically isolates and amplifies weak signals under test. 2. Operates on a single 5 V digital supply. 3. Three‑terminal system: power supply ground (PGND), signal ground (SGND), and output ground (OGND). 4. Strong common-mode transient suppression capability (CMTI ≥ 50 kV/μs). 5. High isolation voltage (CMV ≥ 3800 V). 6. Includes surge absorption, protection, and filtering functions. 7. Measurement bandwidth of 10 kHz. 8. Compact size and lightweight construction. 9. Optional open‑drain output. 2. Principle of Operation of the Isolated Amplifier The HJ5B40 isolated amplifier provides a single analog input channel that is amplified, electrically isolated, and converted into a high‑level analog voltage output. The output voltage is controlled by a logic switch, enabling the module to share a common analog bus without requiring an external multiplexer. Its power supply, input, and output circuits are fully isolated at all three terminals; complete isolation means no electrical connections are needed between the input, output, and shared power supply to ensure proper operation. To enable output, simply connect the enable terminal to the power supply ground. A specialized RC network at the input end accurately samples ±100 mV AC/DC input signals regardless of polarity. After being processed through a wideband preamplifier, the input signal is isolated on the side of the shielding magnetic field. Following amplification, the signal is coupled via an isolation transformer using proprietary technology developed by Shaanxi Hangjing Microelectronics to suppress the transmission of common-mode spikes or noise. Finally, a filter removes any remaining high-frequency carrier components, while the introduction of an analog PID controller further enhances system stability. Electrical Schematic Diagram 3. Package Type and Pin Functions Pin functions are summarized in Table 1 below. 4. Relevant Applications The HJ5B40 is ideally suited for placement far from the target being measured. However, when the local electromagnetic environment is particularly harsh, users are advised to employ shielded twisted-pair cabling, connecting the outer shielding layer to PGND. If the HJ5B40 is installed away from the acquisition board, maintaining an optimal signal-to-noise ratio requires the use of a standard 4–20 mA current loop, with I/V conversion performed remotely. Hangjing Microelectronics offers related products, including the HJU126B current-loop transmitter and the HJU0420 three‑wire high‑temperature precision 4–20 mA/0–20 mA current-loop transmitter. Related Products: - HJ278 three‑terminal isolated amplifier - HJU126B current-loop transmitter - HJU0420 three‑wire high‑temperature precision 4–20 mA/0–20 mA current-loop transmitter

2021-10

2021-10-29

Shaanxi Hangjing Microelectronics Co., Ltd. convened a supplementary design certification review meeting for certain products.

2021-10

2021-10-28

Silicon Carbide Module Device Packaging and Application Technology Training Seminar

2021-10

2021-10-28

The HJMAG803A high-temperature, three-axis, high-precision weak magnetic field measurement module carried aboard the satellite.

2021-10

2021-10-08

Hangjing has launched a domestically produced LVDT signal-conditioning circuit.

2021-09

2021-09-30

Domestic LVDT Signal Conditioning Circuit – HJG598

As international uncertainties persist and Sino‑U.S. tensions continue to escalate, the pressure exerted by the United States and other countries on China’s integrated circuit industry is steadily intensifying. Procuring imported ICs has become increasingly difficult, with prices soaring by hundreds or even thousands of times, severely impacting China’s economic development and national security. Consequently, pursuing domestic production in the IC sector has inevitably become an overarching trend. In light of the government’s growing policy support for the IC industry and its gradual efforts to achieve domestic substitution across the entire IC supply chain, our company, building upon more than 200 domestically produced IC products, has, after extensive market research, solution validation, experimental testing, and leveraging our own technological expertise, launched the HJG598 LVDT signal conditioning circuit—designed and manufactured in-house—which can functionally replace the imported AD598. Overview The HJG598 is an LVDT signal conditioning circuit designed using thick-film integration technology. It incorporates a sine‑wave oscillator and power driver to generate the excitation signal that drives the primary winding of the LVDT. Simultaneously, the HJG598 conditions and converts the amplitude-modulated (AM) output from the rotary transformer into a DC voltage, providing both an adjustable sum output (A+B) and a differential output (A−B). Unlike the AD598, which performs ratio division internally within the chip, the HJG598 allows users to directly assess whether the electrical connections between the excitation source and the LVDT are functioning properly based on the sum output (A+B). Users can then implement division operations and perform angular calculations via DSPs or microcontrollers equipped with computational capabilities. The HJG598 LVDT signal conditioning circuit is ideally suited for precision industrial positioning and metrology applications, offering advantages such as low temperature drift, high measurement accuracy, excellent reliability, and high sensitivity. It finds widespread use in angle‑position sensing systems across servo control systems, aerospace, electronics, and other fields. In summary, the HJG598 truly achieves domestic replacement of the AD598. A comparative table of key characteristics between the domestically produced HJG598 and the imported AD598 is provided in Table 1. Electrical Schematic Diagram Package Type and Pin Functions 1. Package Type The device is available in two ceramic package options: HD14-02B, a dual‑in-line ceramic package, and HD14-02C, a surface-mount ceramic leadless package. Their external dimensions are shown in Figure 2 below: 2. Pin Functions Table 2 lists the functions of each pin in the package. Electrical Characteristics Unless otherwise specified, VCC = +15 V, VEE = −15 V, TA = 25°C. Typical Application Circuit Diagram Note: 1. Adjusting RSCL enables variation of the EXC amplitude. 2. Capacitors CT1 and CT2 must be paired and selected from NPO/COG dielectric materials. 3. The REF terminal allows adjustment of the zero point for the VA–B output voltage.

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