Automotive LDOs offer diagnostic functions for functional safety

June 22, 2021 // By Christoph Hammerschmidt
Automotive LDOs offer diagnostic functions for functional safety
With eight selectable fixed output voltages, diagnostic capabilities for functional safety and good thermal characteristics, the L99VR01 series of linear low dropout voltage regulators from STMicroelectronics result in simpler system design and less complicated inventory for numerous automotive applications.

The regulators provide output currents up to 200 mA to loads such as body modules, instrument clusters, sunroof controllers, keyless entry controllers or sensors. The output voltage, which can be set more precisely to values of 0.8 V, 1.2 V, 1.5 V, 1.8 V, 2.5 V, 2.8 V, 3.3 V or 5 V with an external voltage divider and three select pins brought out, varies by no more than ±2 % around the nominal value.

There are two versions of the device to choose from. The L99VR01S has a standard SO-8 package with enable and reset pins, as well as special safety features that include fast output discharge, undervoltage lockout (UVLO), overheat protection and short-circuit protection. The quiescent current consumption drops to 1 µA when deactivated. The operating temperature range of the controller is -40 °C to +150 °C.

The L99VR01J in the PowerSSO-12 package also allows programming of the short-circuit current limit, reports overtemperatures and output overvoltage status, and includes a programmable watchdog that verifies correct operation of the host microcontroller. Another feature of the L99VR01J is its extended operating temperature range of -40 °C to +175 °C.

With integrated output overvoltage monitoring, the new controllers can ensure constant protection of the load. The diagnostic features facilitate the design of functional safety applications and help users achieve the required ASIL value according to ISO 26262. Additional documentation is available on request.

Both versions are certified according to AEC-Q100. They have a wide input voltage range of 2.15 V to 28 V, so that they can be used in applications that are directly connected to the on-board power supply (VBAT) as well as for readjusting an already regulated voltage. The inputs are 40 V tolerant and resistant to load shedding.

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