ST ISOSD61 and ISOSD61L sigma-delta modulators
Commonly provided 16-bit resolution ADC and 86dB SNR
Replacing discrete current sensors with small shunt resistors


On the 1st, STMicroelectronics released the galvanically isolated ISOSD61 and ISOSD61L secondary-side 16-bit sigma-delta modulators. The two new devices are suitable for industrial applications such as motor control, electric vehicle (EV) charging stations, solar inverters, uninterruptible power supplies (UPS), and power supply units (PSUs) for servers and communications.

The ISOSD61 features TTL/CMOS compatible clock input and data output signal levels, while the ISOSD61L is compatible with LVDS (Low-Voltage Differential Signaling). Both devices provide a signal-to-noise ratio (SNR) of typically 86 dB with a 16-bit resolution ADC (Analog-to-Digital Converter).

Power consumption is reduced through galvanic isolation, and it prevents performance degradation of other optical coupling converters while transmitting data quickly. Converts an analog input signal with a maximum amplitude of ±320mV into a high-speed 1-bit digital data stream at a maximum speed of 25Msamples/s.

Through insulation between the two sides, it guarantees a maximum transient and surge insulation voltage of up to 6kV under normal operating conditions, and the maximum operating voltage is up to 1.2kV. It also features a common-mode transient immunity of 30kV/μs to eliminate fast transient noise that frequently occurs in harsh industrial environments.

It supports an external sampling frequency of 25 MHz, making it suitable for wide input signal bandwidths. Accordingly, it supports high-frequency signal processing capabilities and measurement accuracy suitable for the latest inverter technology and high-speed switching in high-resolution motor control applications utilizing next-generation power technologies such as silicon carbide (SiC).

Integrating ADC and isolated UART peripheral functions into a single chip reduces the Bill of Materials (BOM), enhances noise immunity and reliability, and lowers the overall cost of the final application. Discrete current sensors are not required and can be replaced by small shunt resistors.

Housingd in an SO16W surface-mount plastic package, it meets creepage and clearance requirements of 8 mm. Both devices are certified for an extended industrial temperature range of –40 to 125°C. The 'EVALST-ISOSD61T' for ISOSD61 and 'EVALST-ISOSD61L' for ISOSD61L evaluation boards provide coaxial cables and header pins for connecting to inputs and outputs, along with additional pads for shunt current sensors.

Both devices are currently in production, and the price is $2.50 per 1,000 units.