AMS, the Analog and Mixed-Signal division of Integrated Silicon Solution Inc. (ISSI), announced the IS32LT3124 family of quad-channel linear LED drivers for the automotive lighting market. The family features dynamic headroom voltage control to preserve a low IC voltage even under high input voltage conditions. The drivers consist of four LED channels. Each channel is capable of sourcing up to 150mA with independent PWM making them suitable for photometric corrected taillights, animated turn signaling, and daytime running lights.
High current linear controllers like the IS32LT3124 operate cooler when their input voltage is managed to a low operating voltage (headroom). AMS designed the IS32LT3124 family to support an external circuit to actively reduce the IC voltage and shift thermal energy away from the IC because voltage above the LED forward voltage contributes to an increase in IC thermal energy. The desired headroom voltage and the operating range are fully programmable, and component values can be calculated using the supplied worksheet.
For even more flexibility, the external circuit made up of a power FET and a power resistor can be managed so that most of the thermal energy is transferred to the FET or the power resistor. This unique feature gives effective heat distribution on the PCB and maintains the IS32LT3124 at a low temperature so it can monitor and drive a constant LED brightness.
Differentiating features among the six IS32LT3124 family members are the dimming method, fault detection response, and LED short detection threshold. For example, the IS32LT3124A model is dimmed by applying a PWM signal to the EN pin. It detects a short when the channel voltage is less than 1.22V, and the fault response is that one channel fault shuts down the remaining 3 LED channels.
For another model, the IS32LT3124C, dimming can be individually applied to each LED channel, and a short detection threshold is 4.8V. With this model, a single channel fault will not shut down the remaining 3 channels.
According to AMS, this level of granularity provides unprecedented flexibility in choosing the right LED controller to meet specific fault response requirements.
"The IS32LT3124 family offers the utmost flexibility and performance for designing animated tail and indicator lights a much sought-after feature preferred by major Auto manufacturers who are using lighting to differentiate their brands with the highest performance," said Ven Shan, VP of AMS the Analog and Mixed Signal Division of ISSI. "The thermal design and fault protections option afforded by using IS32LT3124 makes this a best-in-class solution above any other product in this category in the market."
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Pricing and availability
The AEC-Q100 automotive qualified IS32LT3124 family is available in an eTSSOP-16 package with exposed pad for enhanced thermal dissipation.
