STMicroelectronics’ New Gate Driver Enhances Motor-control Flexibility for Automotive Systems

STMicroelectronics’ (ST) L9908 3-phase gate driver unit (GDU) operates in 12-V, 24-V, and 48-V automotive systems and features six separate PWM (pulse-width modulation) input pins that allow for independent management of the pre-driver stages. This arrangement enables designers to adopt a wide variety of motor-control strategies. 

 

The L9908. Image [modified] used courtesy of STMicroelectronics

 

The L9908, announced April 4, enables control of the six N-channel FETs in brushless motors. Users can independently configure each of the three half-bridge driver channels, consisting of high-side (HS) and low-side (LS) couples, and can also control the pre-driver stages’ six dedicated parallel inputs. This ability to independently control the pre-driver stages allows for duty cycle operations ranging from 0 to 100%. 

 

A block diagram of the L9908. The device provides 3 gate high-side (GHS) and 3 gate low-side (GLS) outputs. Image used courtesy of STMicroelectronics

 

The highly integrated GDU includes a wide variety of internal regulators, charge pumps and bootstrap circuits, making it adaptable for deployment in electric vehicles (EVs), hybrids or conventional vehicles.

 

Simplifying the Design Process

The L9908 includes three differential current monitors that make ground-referenced measurements, in addition to three channels for real-time phase-voltage monitoring. The device’s robust integration, accuracy and flexibility should smooth the design of automotive pumps, ventilation and heating systems.

 

More on Flexibility 

The gate driver can accommodate motor supply-voltage ranging from 4.5 to 75 V, and it can also handle -14 to +95 V on its motor-connection pins. Internal chip logic is supplied from an internally integrated 3.3 V supply. The unit’s digital I/O pins are compatible with both 3.3 V and 5 V logic.

 

Safety and Diagnostics

The L9908’s internal diagnostics expedite the pathway to ISO 26262 certification for OEM products, while allowing users to utilize the device in safety-related systems such as emergency braking and advanced electronic power steering. 

Safety features also include SPI-programmable dead-time insertion with shoot-through diagnostic, vital in ensuring that the HS and LS FET don’t fire in opposition to one another. Open-load detection is also here, together with diagnostics for both short-to-ground and short-to-battery.

Temperature warnings and measurements are communicated via a 32-bit, 10-MHz SPI bus. There is an SPI-programmable temperature warning and SPI-readable junction-temperature measurement. 

Other diagnostics include ground-loss detection, over-voltage and under-voltage detection for the power supply pins and FET-driver supply, and also a fault-status flag.

 

Applications

• Electronic power steering
• Heating, ventilation, and air conditioning (HVAC) blowers
• Electronic brake boosters
• Engine cooling fans
• Electronic fuel pumps (EFPs)
• Electronic water pumps (EWPs)
• Electric oil pumps (EOPs)

 

Regulatory Notes

• The L9908 is AEC-Q100 certified
• ISO26262-compliant, ASIL-D systems ready

 

Physical Considerations

• The GDU is available in a thermally-enhanced, 48-pin, 7 x 7 x 1-mm TQFP48 package
• The unit operates over a temperature range of -40 to +150 ℃

 

Feature image used courtesy of JP Valery/Unsplash