ON Semiconductor has recently unveiled a couple of devices aimed at vehicle lighting systems. The NCV7691 is a current controller for automotive LED lamps while the NCV78763 is an advanced smart power ballast and dual channel LED driver that provides a highly efficient single-chip automotive lighting solution that can drive two strings of LEDs up to 60V.

The NCV78763 can support a DC current of 1.6A on each output. The built-in current-mode voltage booster controller enables input current filtering. An internal pulse-width modulated (PWM) dimming function, covering frequencies up to 4kHz, is also included in addition to the option of PWM direct-feed for full frequency and resolution control from the external MCU. Optimised for front lighting applications, this device can be employed in high beam, low beam, turn indicator, static cornering, fog and daytime running lights. For each individual LED channel there is an independent buck switch output, through which both the output current and voltage can be configured to meet specific application criteria.

Configuration is done via the device's serial peripheral interface (SPI). Integrated diagnostic features mean that less of the system MCU's resources need to be devoted to safety monitoring, thereby improving overall effectiveness of the lighting design. If more than two LED channels are required on one lighting module, then multiple NCV78763 devices can be combined together. Due to the serial peripheral interface (SPI) programmability, this solution is highly flexible, permitting the scaling up of designs so that more LED strings can be used. This results in multiple system configurations that are able to address an expansive range of automobile models, with significantly faster design cycles and lower engineering overheads. Furthermore, the NCV78763 supports high operating frequencies and thus permits specification of smaller inductors, thus reducing BOM costs.

The other device, the NCV7691, is targeted predominantly at automotive rear combination lamps (RCL), centre high-mounted stop lamps (CHMSL) and day-time running lights (DRL). This highly integrated pre-driver contains PWM and diagnostic capabilities, as well as battery connection and negative temperature coefficient (NTC) input in a single chip. Through use of external bipolar transistor(s) combined with feedback resistors, this device accurately regulates the LED driver current with up to eight LED strings being driven concurrently. Engineers have the flexibility to add channels to create multi-channel systems. A dedicated dimming feature is included via the PWM input pin. LED brightness levels can be programmed in a straightforward manner using an external resistor in series with the bipolar transistor. This approach gives engineers the ability to use this device over a range of currents. Set back power limit reduces the drive current during over-voltage conditions. Open LED string and short-circuit diagnostic functions ensure that operational reliability is maintained. By connecting the FLTS pins together, multiple devices can be turned off in case of a detected error. AEC-Q100 qualified, the NCV7691 can deal with harsh automotive environments. It has a -55°C to 150°C operational temperature range, detailed the company.

The NCV78763 is offered in three package variants: 5mm x 5mm QFN-32, 7mm x 7mm QFN-32 and 36-pin SSOP, with unit prices starting at $1.85 for 5K unit quantities. The NCV7691 is available in an SOIC-8 package with unit pricing at $0.30 in 3K unit quantities.

By: DocMemory
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