The automobiles that consumers will be driving 10 years from now will differ vastly from those on the road today. The key difference will be the use of electronics to make vehicles safer, more energy-efficient and more fun to drive.
In-vehicle processing power will continue to increase in tandem with advances in electronics, fueling demand for components. According to Texas Instruments Inc., semiconductor content accounts for $250 per vehicle; thus automotive is a key sector in the company's analog chip sales strategy.
But the automotive environment is a harsh one for electronics. Wide operating-voltage requirements, high transient voltages and wide temperature excursions are tough on electronics systems, said Tony Armstrong, product-marketing manager for the Power Product Group at Linear Technology Corp. (Milpitas, Calif.).
So as the number of components increases, space requirements are shrinking. Efficiency thus becomes more critical.
As a result, analog-device makers are tailoring parts--from LED drivers to switching regulators--to meet automotive OEMs' requirements. Those include a wide input voltage operating range; good efficiency over a wide load range; low quiescent current during normal operation, standby and shutdown; low thermal resistance; minimal noise and EMI emissions; and a wide operating temperature range.
Linear Technology, TI, National Semiconductor Corp., Catalyst Semiconductor Inc. and others are flooding the market with analog chips that meet those specs while adhering to the auto environment's space limits.
Switching vs. linear
At low output voltages and moderate current levels, Armstrong said, it is impractical to use a linear regulator to drive system voltages. Thermal constraints have switching regulators replacing linear regulators, he said.
"Although switching regulators generate more noise than linear regulators, their efficiency is far superior," Armstrong said. "Noise and EMI levels have proved manageable in many sensitive applications as long as the switcher behaves predictably. If a switching regulator switches at a constant frequency in normal mode, and the switching edges are clean and predictable with no overshoot, frequency can provide a small, tight layout, which minimizes EMI radiation."
An automotive switching regulator needs to be specified to work over a wide input voltage range, of 3 V to 60 V. The 60-V rating gives a good margin for 14-V systems, which are usually clamped in the range of 36 to 40 V, Armstrong said.
Linear recently unveiled the H-Grade version of the LT3437 step-down switching regulator. The device operates from continuous inputs of 3.3 V to 60 V and withstands transients up to 80 V. Its 500-mA internal switch delivers up to 400 mA of continuous output current at voltages as low as 1.25 V. Burst-mode operation reduces no-load quiescent current to less than 100 µA, maximizing battery run-time for always-on applications.
The H Grade version performs at a junction temperature of 140°C, vs. the E and I Grade versions' 125°C maximum junction temperature. Other features include shutdown current of < 1 µA, a 200-kHz switching frequency, soft-start capability and saturating-switch design of 0.8-ohm on-resistance.
On the switch-mode regulator side, TI is offering the TPIC74100-Q1, with a buck/ boost feature that lets the user extend the input-voltage range even below the output voltage of the device. That feature ensures full operation during a cold-crank operation, such as starting the engine. Other features include low standby current, high efficiency and an input-voltage capability of up to 45 V.
Linear voltage regulators are also part of TI's lineup of automotive parts. Its TLE4275-Q1 offers low quiescent current, helping customers conserve battery energy in applications that are powered even when the car is not in operation.