Active ORing chip cuts power drain

The IR5001S is a universal high-speed controller/N-channel power MOSFET driver for high-performance active ORing circuits.

Available now from International Rectifier, the IR5001S is a universal high-speed controller/N-channel power MOSFET driver for high-performance active ORing circuits.

The active ORing IC, housed in an SO-8 package, is used with an external MOSFET, replacing traditional diode ORing to increase efficiency and reduce power dissipation.

Active ORing is a key requirement for many high-end systems requiring maximum up-time, such as carrier-class communication equipment and telecomms and datacomms system servers.

"Compared with typical Schottky diode ORing circuits, a system using the IR5001S active ORing IC and an optimised external MOSFET for the given power level, will reduce onboard power dissipation by up to 85%, and can be made at least 50% smaller than diode solutions".

"ORing circuits made with Schottky diodes run hotter for the same power level, and in many cases, this means that through-hole devices with heatsinks are needed, increasing bulk and manufacturing complexity", said Carl Smith, Marketing Manager for Networking and Telecommunication Products at International Rectifier.

As a bonus, the IR5001S provides additional diagnostic features that increase system up-time, maximising quality of service.

Active ORing combines two or more power sources to create a redundant power source, preserving the input power supply in case one of the input sources fails.

In the event of an input power failure, the active ORing circuit disconnects the nonfunctioning power source as quickly as possible to prevent the system bus voltage from falling, and to prevent large peak reverse currents.

The IR5001S active ORing controller IC is suitable for a wide range of active ORing circuits, including: -48/-24V input active ORing for carrier-class communication equipment; 24/48V output active ORing for redundant AC/DC rectifiers; 12V output active ORing for multiple-output DC/DC and AC/DC power; and for low voltage output redundant VRM DC/DC processor power.

In 12V output systems, ORing circuits capable of handling currents of 100A can be made using four IRF6609 DirectFET MOSFETs in parallel.

The IR5001S can also be used in reverse polarity applications for 48/24V systems, replacing large D2Pak style diodes and an expensive relay.

When using the IR5001S with the 100V IRF6655 DirectFET MOSFET, 30 to 60W board power levels can be addressed.

The IRF6655 in the small can package offers a space reduction of about 50% compared with solutions in an SO-8 package, and is more appropriate for lower power applications.

The 100V IRF6644 DirectFET MOSFET in the medium can package can also be used for higher power applications, up to about 250 to 300W board power levels, eliminating the need to use multiple SO-8 devices in parallel or larger single package devices.

With the addition of a simple charge pump circuit, the IR5001S can also be implemented in ground ORing in -48V systems, as required by the ATCA specification (Advanced Telecom Computing Architecture).

The input terminals (INN and INP) are used to determine the output voltage by measuring the differential voltage and polarity across the drain and source terminals of the external MOSFET.

The output voltage (Vout) of the IC drives the gate of the external MOSFET.

If the current reverses polarity, the IC will quickly switch the active ORing MOSFET off by pulling the Vout pin low.

The turn-off delay for IR5001S is typically 130ns, with a typical 20ns FET turn-off time, which is the fastest in the industry by a factor of two, in order to minimise voltage sags on the redundant bus voltage.

Usually the reverse polarity protection circuitry is mounted on the rack or panel in the system, and not onboard.

As this solution is so small, the circuit can be mounted onboard, which can significantly simplify system design.

The IR5001S IC includes diagnostic pins (FET check "FETch" and FET status "FETst") to determine the status of the active ORing circuit.

This is important for systems that require the highest level of up-time.

When a logic signal is sent to the FET check pin, the output of the IR5001S (Vout), or the gate drive to the MOSFET, will pull low, turning the MOSFET off.

This momentary off period should cause the voltage across the drain-to-source terminals of the MOSFET to increase, as the current is diverted from the MOSFET channel to the body drain diode.

If the voltage rises from approximately sub-100 to 700mV (as expected for a body drain diode), the MOSFET is functioning normally.

If the voltage does not rise above a 300mV threshold, the MOSFET is shorted.

The FET status pin provides an output signal to the system, depending on the status of the external MOSFET.

This feature enables system-level monitoring of the active ORing circuitry, allowing scheduled maintenance rather than the inconvenience of random system downtime.

Asymmetrical offset voltage prevents output oscillations under light load, increasing reliability.

The IR5001S can be powered from either a 36 to 75V universal telecom bus voltage (100V maximum) or from an external bias supply and a bias resistor for design flexibility.

The IR5001S can also withstand continuous gate short conditions, and up to 100V continuous on the input pins, enabling reliable operation.

The IR5001S is available now.

Pricing is US $0.67 each in 10,000-unit quantities.

Prices are subject to change.

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