Automotive Voltage Regulator with Keep Alive Control

The LM9070 is a 5V, 3% accurate voltage regulator which have 250mA low-dropout. The regulator has an active low delayed reset output flag feature. This feature can be used to reset microprocessor system on turn-ON and in the event that the regulator output falls out of regulation for any season. Before the reset output can return high, an external capacitor programs a delay time interval.

The LM9070 contains a variety of protection features such as reverse battery, overvoltage shutdown, thermal shutdown, input transient protection and a wide operating temperature range because it’s designed for automotive application.

To enable or disable the regulator output, we can use a unique two-input logic control scheme. An ignition switch derived signal while a second, Keep-Alive input, is generated by a system controller can provide ON/OFF input. After ignition has been switched OFF, this will allow for a system to remain ON. After which command the regulator OFF to a low quiescent current state (60 uA max), the system controller can then execute a power-down routine.

When subjected to high levels of RF energy (300V/m from 2 MHz to 400 MHz), Design techniques have been employed to allow the regulator to remain operational and not generate false reset signals. [Circuit’s schematic diagram source: National Semiconductor Application Note]