With many switching buck regulators on the market today that are capable of improving an automotive system design it is hard to choose the optimum one for your design. I patricularly like a new Linear Technology solution, the LT8609, a 2A, 42V input synchronous step-down switching regulator because it is unique in that it does not require an external flyback diode (sometimes called a snubber diode, freewheeling diode, suppressor diode, suppression diode, clamp diode or catch diode) which is a diode used to eliminate flyback, which is the sudden voltage spike seen across an inductive load when its supply voltage is suddenly reduced or removed. This makes for less external components.
The regulator utilizes internal top and bottom high efficiency power switches with the necessary boost diode, oscillator, control and logic circuitry integrated into a single die.
Another feature I think is important is a unique synchronous rectification topology that delivers 93% efficiency while switching at 2MHz (Many such regulators struggle to meet a mere 80% efficiency at 2 MHz) Such high efficiency minimizes the thermal concerns of a design.
Switching at this high 2 MHz frequency enables designers to avoid critical noise-sensitive frequency bands, such as AM radio. Spread spectrum frequency modulation and special design techniques enable this low-EMI operation to minimize noise concerns in automotive and industrial environments. Even with all these features, the regulator provides a highly compact solution footprint.
Burst Mode® operation keeps quiescent current under 2.5µA in no-load standby conditions, making it ideal for always-on systems. The device’s 3.0V to 42V input voltage range makes it ideal for automotive applications which must regulate through cold-crank and stop-start scenarios with minimum input voltages as low as 3.0V and load dump transients in excess of 40V. This comes in handy when battery voltage rises. The internal 3.5A switches can deliver up to 2A of continuous output current with peak load currents of 3A—that’s nice because the switches are integrated and again lessens the need for complex external circuitry making the board larger than it needs to be.
The LT8609 keeps a minimum dropout voltage of only 200mV (at 1A) under all conditions, making it perfect for automotive cold-crank because battery voltages can go below 6V during these conditions and the automotive industry requires regulators to power up digital circuits under these conditions.
A fast minimum on-time of only 45ns enables 2MHz constant frequency switching from a 16V input to a 1.5V output. The IC’s 10-lead thermally enhanced MSOP package and high switching frequency keeps external inductors and capacitors small, providing a compact, thermally efficient footprint.
Low ripple Burst Mode operation maintains high efficiency at low output currents while keeping output ripple below 10mVPK-PK. Linear Technology’s unique design techniques and a new high speed process enable high efficiency over a wide input voltage range, and the regulator’s current-mode topology enables fast transient response and excellent loop stability. Other features include internal compensation, a power good flag, output soft start/tracking and thermal protection.
For more detail: Linear Technology 2A buck converter is 93% efficient at 2MHz
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