Smart Power Modules provide efficient drive to sub-100W motors

May 23, 2014 // By Graham Prophet
Fairchild’s FSB70xxx series of advanced Motion SPM 7 modules is intended for driving small power motors under 100 W, with light-load efficiency up to 44% better than the alternative products, plus robust on-module protection, and superior thermal efficiency up to 12% better from junction to case.

The FSB70xxx series integrates an optimised gate driver for the built-in MOSFETs (using FRFET technology) to minimise EMI and losses, while also providing multiple on-module protection features including under-voltage lockouts, thermal monitoring, fault reporting and interlock function. Controlled dI/dt and dV/dt values in the switching waveforms minimise EMI. The PQFN package can save up to 50% of board space, and offers a low thermal resistance of 0.8degree/W. It measures 13 x 13 mm, and is the highlighted area on an example small-motor, axis-mounted PCB pictured above.

A company spokesman noted that although losses are substantially reduced over prior generation modules, they are not reduced by the same 50% as the package size, which therefore has better heat paths to the circuit board/substrate, with greater pad area, “and a design that is relatively immune to [soldering] voids.”

SPM 7 modules use Fairchild’s UniFET MOSFETs for 250 and 500V ratings; later, the same package will house a 600V version built with the company’s SuperFET devices.

Features include;

- A high-performance inverter output stage for AC induction, brushless DC (BLDC) and permanent magnet synchronous motors (PMSM)

- Optimised for low EMI

- HVIC temperature-sensing built-in

- Separate open-source pins from low-side MOSFETs for three-phase current-sensing

- Active-HIGH interface, works with 3.3 / 5V logic, Schmitt-trigger input

- HVIC for gate driving with under-voltage protection and interlock function

- Isolation rating: 1500 Vrms / min.

Pricing ranges from $3.98 to $4.55 (1000).

Fairchild; /