Its synchronous rectification design includes internal top and
bottom MOSFETs to deliver efficiencies as high as 96%. Figure 3
shows that it can deliver over 95% efficiency when powering a 5V
load from a nominal 12V input, even with a relatively high 800kHz
switching frequency. This high efficiency operation minimizes wasted
power and eliminates the need for heat sinks even in the most space
constrained applications. In electric vehicles and hybrids, this can
directly translate into increased driving range between battery
Figure 3. LT8610 Efficiency Graph of Typical Automotive Schematic
Additionally, the LT8610’s Burst Mode operation reduces no load
quiescent current to a mere 2.5uA, making it ideal for always-on
applications that must maintain constant voltage regulation even at
no loads while maximizing battery life. Additionally, a very low
ripple Burst Mode operation topology minimizes output noise to below
10mVPK-PK, making it suitable for noise-sensitive applications. If
the application requires external synchronization, the Burst Mode
function can be replaced with a pulse-skipping frequency scheme.
The LT8610s very low dropout performance is also very
beneficial, particularly in applications which must regulate outputs
through use stop-start or cold-crank conditions. Figure 4
even when the input voltage drops below the programmed output
voltage, 5V in this case, the output is always 200mV (@1A) below the
input voltage once the input exceeds 2.9V. This is important because
such ECUs drive require one or multiple
Although these are designed to operate from a nominal 5V, they
continue to operate with supply voltages as low as 3V. So in a
cold-crank scenario, the input can drop as low as 3.2V and the
microprocessor can continue to operate, enabling the ECU to operate
seamlessly through cold crank.
Figure 4. LT8610 Dropout Performance
Furthermore, the LT8610’s fast minimum on-time of only 50ns enables
2MHz constant frequency operation from a 16V input to a 1.8V output,
optimizing efficiency while avoiding critical noise-sensitive
frequency bands such as AM radio.
The rapid growth of very complex electronic systems in automobiles
has created even higher performance demands on power management
ICs. Depending on where the power supply operates on the
automotive power bus, they may be subjected to stop/start,
cold-crank and load-dump conditions and must be capable of
accurately regulating an output voltage throughout these conditions.
Additionally, some of these systems will operate in an always on
standby mode, requiring minimal supply current. As more electronic
systems are added in ever shrinking spaces, minimizing the solution
footprint while maximizing efficiency is also critical. Fortunately
ICs that meet these demands are already available paving the way for
even higher electronic content in future cars.
(Jeff Gruetter is Sr. Product Marketing Engineer, Power Products, at Linear Technology Corp. (Milpitas, Calif.