Radiation Tolerant 2.5kVRMS Digital Isolators for SmallSats

Renesas Electronics Corporation introduced two plastic packaged, radiation-tolerant digital isolators that boast the highest isolation protection (2,500VRMS) from high voltage spikes in power supply stages and serial communications interfaces used in low Earth orbit (LEO) Small Satellites (SmallSats).

Private "New Space" companies intend to launch thousands of SmallSats forming large constellations that operate in multiple low earth orbit planes. SmallSat mega-constellations enable the ubiquitous broadband Internet of Things (IoT) communications anywhere across the globe, and Earth observation high-resolution imaging for air, sea, and land asset tracking. The above product image features the Renesas' Intersil brand name.

The passive input ISL71610M and active input ISL71710M are said to provide superior performance across essential electrical specifications, such as isolation voltage, dynamic current, data rate, common mode transient immunity, propagation delay, and quiescent current.

The company says that the Giant Magneto Resistive (GMR) digital isolators are ideal replacements for optocouplers that are susceptible to cloudy optics from total ionizing dose (TID) radiation.

Renesas also asserts that both GMR isolators also out-perform transformer-based digital isolators that encounter electromagnetic interference (EMI) resulting from radiated emissions of edge and dipole radiation. Renesas GMR digital isolators are characterization tested at a total ionizing doze (TID) of up to 30krads(Si), and for single event effects (SEE) at a linear energy transfer (LET) of 43MeV•cm2/mg.

In isolation partitioned power supply designs, the ISL71610M and ISL71710M provide an instantaneous 2.5kVRMS of isolation and 600VRMS continuous working voltage at 85°C.

In serial communications subsystems that need the transmitter and receiver electrically isolated from each other, the ISL71610M reportedly operates up to 100 Mbps, and the ISL71710M up to 150Mbps.

The company claims that both provide the New Space industry's highest data rates which are 6x higher than competitive solutions, making them ideal for serial communications links including RS-422, RS-485, and Controller Area Network (CAN).

According to Renesas, the ISL71610M and ISL71710M both have significantly lower quiescent current than the competition, and the ISL71710M features nearly 4x lower dynamic current than Class V isolators.

"The ISL71610M and ISL71710M use a GMR inductive structure that is inherently immune to radiation effects, and build on Renesas' six decades of spaceflight experience," said Philip Chesley, Vice President, Industrial Analog and Power Business Division, Renesas Electronics Corporation. "GMR makes our space-grade digital isolators more desirable than optical-based designs, and Renesas' radiation-tolerant plastic flow provides the optimal cost versus radiation performance in comparison to Class V isolators."

Key Features of ISL71610M and ISL71710M

• Supply range of 3V to 5.5V
• Isolation voltage of 2.5kVRMS for 1 minute, and 600VRMS continuous
• Data rates up to 100Mbps (ISL71610M), and 150Mbps (ISL71710M)
• Common mode transient immunity of 20kV/µs (ISL71610M), and 50kV/µs (ISL71710M)
• Propagation delay of 8ns (ISL71610M), and 10ns (ISL71710M)
• Quiescent current of 1.3mA (ISL71610M), and 1.8mA (ISL71710M
• Full military temperature range operation
  • TA = -55°C to +125°C
  • TJ = -55°C to +150°C
• Radiation characterization at Low Dose Rate (LDR) (0.01rad(Si)/s): 30krad(Si)
• SEE characterization: No SEB/SEL, VDD = 7V; LET = 43MeV•cm2/mg
• Isolated 100V Half-Bridge Power Supply Reference Design

The Renesas' radiation-hardened half-bridge power stage reference design uses the ISL71610M passive input digital isolator. The reference design's ISL73040SEH4Z evaluation board demonstrates a half-bridge power stage design capable of taking 100V input from a satellite's solar panels and generating step-down power rail voltages--28V, 12V, 5V, and 3.3V--with a power efficiency of up to 94 percent.

Isolated CAN Bus Application

The ISL71710M can be used with a single-ended CAN Bus input signal to provide fault tolerant serial communications isolation between the CAN Bus controller and ISL71026M rad-tolerant CAN Bus transceiver, or the ISL72026SEH rad-hard CAN Bus transceiver. This application can be extended to RS-422 by using the ISL71710 with the HS-26C31 rad-hard RS-422 transmitter and HS-26C32 rad-hard RS-422 receiver.

Pricing and Availability

The ISL71610M and ISL71710M radiation-tolerant digital isolators are available now in 8-lead 5mm x 4mm SOIC packages. The passive input ISL71610M is priced at $61.53 USD, and the active input ISL71710M is priced at $64.18 USD, both in 1,000-unit quantities.