One of the worst things after long travel is coming home to a car that won’t start normally. The reason is simple: the automotive battery is out of power. Who stole the energy from my battery? Some people might be surprised to learn it’s actually the car itself. Even when the car is off, many systems still operate in standby mode, still using the battery’s energy. For example, the immobilizer and remote keyless entry monitor the external signal at all times. Infotainment and cluster need to be on standby because to speed start-up of the system after ignition.
With the rapid development of the automobile in recent decades, people’s expectation of vehicle intelligence is increasing. Higher intelligence vehicles require more electronic control units (ECU). Yet, automotive battery technology hasn’t had a break-through improvement. In order to increase the life of the battery, car manufacturers are beginning to place stricter requirements on the quiescent current of every standby ECU. A request for less than 100uA quiescent current for the entire ECU is spreading quickly over the traditional milliampere level requirement.
For ECUs in standby mode, there are usually at least three kinds of components dissipating power: the microcontroller (MCU) used for system control, the controller area network (CAN)/LIN transceiver used for communication and the power supply components to them. For small ECUs, most customers prefer to select low drop-out regulators (LDOs) as the system power supply because they are easy-to-use and you don’t need to consider EMC issues. In general, a 32-bit MCU will dissipate about 30uA in standby mode, and a CAN transceiver consumes around 20uA. Factor in some quiescent current margin left for the system, and the space left for the LDO is very limited: only 20-30uA. The traditional battery, with a directly connected LDO designed in bipolar technology, usually dissipates more than 100uA quiescent current, which does not meet the latest requirement from OEMs.
To help with increasing the battery life time, TI developed a complete family of automotive battery, direct-connected LDOs with very low quiescent current. The output current capability ranges from 50mA to 450mA, which can cover both “simple” and “complex” ECUs. The TPS7A16xx-Q1 is a 100mA high-voltage LDO with only 5uA ultra-low quiescent current. Its input voltage can survive up to 60V, allowing its use in a 24-V system, like a truck. For 150mA current needs, the TPS7A66xx-Q1 and TPS7A69xx-Q1 with only 12uA quiescent current are available in SOIC and MSOP packages, respectively. In a high-current region, the TPS7B67xx-Q1 can output 450mA of current with only 15uA quiescent current, which is the lowest available in the market. TI has a broad portfolio of automotive LDOs to meet your current needs: find your perfect fit here (hyperlink to LDO selection page).
Using these automotive LDOs with ultra-low quiescent current, you can significantly improve the automotive battery lifetime. What are other ways that you are saving crucial current in your system?