The LM2745/8 are high-speed synchronous buck regulator controllers with an accurate
feedback voltage accuracy of ±1.5%. It can provide simple down conversion to output voltages as low
as 0.6V. Though the control sections of the IC are rated for 3 to 6V, the driver sections are
designed to accept input supply rails as high as 14V. The use of adaptive non-overlapping MOSFET
gate drivers helps avoid potential shoot-through problems while maintaining high efficiency. The IC
is designed for the more cost-effective option of driving only N-channel MOSFETs in both the
high-side and low-side positions. It senses the low-side switch voltage drop for providing a
simple, adjustable current limit.
The LM2745/8 features a fixed-frequency voltage-mode PWM control architecture which is
adjustable from 50 kHz to 1 MHz with one external resistor. In addition, the LM2745 also allows the
switching frequency to be synchronized to an external clock signal over the range of 250 kHz to 1
MHz. This wide range of switching frequency gives the power supply designer the flexibility to make
better tradeoffs between component size, cost and efficiency.
Features include the ability to startup with a pre-biased load on the output, soft-start,
input undervoltage lockout (UVLO) and Power Good (based on both undervoltage and overvoltage
detection). In addition, the shutdown pin of the IC can be used for providing startup delay, and
the soft-start pin can be used for implementing precise tracking, for the purpose of sequencing
with respect to an external rail.
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