UVLO

VIN

VCC

SW Pin

Inductor

Current

SS Pin

t2

7.0V

2.5V

t1

LM5010A

LM5010A-Q1

SNVS376D – OCTOBER 2005 – REVISED DECEMBER 2008

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FUNCTIONAL DESCRIPTION

Figure 1. Startup Sequence

The LM5010A Step Down Switching Regulator features all the functions needed to implement a low cost,

efficient buck DC-DC converter capable of supplying in excess of 1A to the load. This high voltage regulator

integrates an 80V N-Channel buck switch, with an easy to implement constant on-time controller. It is available in

the thermally enhanced LLP-10 and TSSOP-14EP packages. The regulator compares the feedback voltage to a

2.5V reference to control the buck switch, and provides a switch on-time which varies inversely with VIN. This

feature results in the operating frequency remaining relatively constant with load and input voltage variations.

The switching frequency can range from less than 100 kHz to 1.0 MHz. The regulator requires no loop

compensation resulting in very fast load transient response. The valley current limit circuit holds the buck switch

off until the free-wheeling inductor current falls below the current limit threshold, nominally set at 1.25A.

The LM5010A can be applied in numerous applications to efficiently step down higher DC voltages. This

regulator is well suited for 48V telecom applications, as well as the 42V automotive power bus. Features include:

Thermal shutdown, VCC under-voltage lock-out, gate drive under-voltage lock-out, and maximum duty cycle limit.

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