LP3872 datasheet(16/28 Pages) TI1

16 / 28 page

LP3872, LP3875

SNVS227H – FEBRUARY 2003 – REVISED JANUARY 2015

www.ti.com

9 Power Supply Recommendations

The LP397x devices are designed to operate from an input supply voltage range of 2.5 V to 7 V. The input

supply should be well regulated and free of spurious noise. To ensure that the LP387x output voltage is well

regulated, the input supply should be at least VOUT + 0.5 V, or 2.5 V, whichever is higher. A minimum capacitor

value of 10

μF is required to be within 1 cm of the IN pin.

10 Layout

10.1 Layout Guidelines

Good PC layout practices must be used or instability can be induced because of ground loops and voltage drops.

The input and output capacitors must be directly connected to the input, output, and ground pins of the regulator

using traces which do not have other currents flowing in them (Kelvin connect).

The best way to do this is to lay out CIN and COUT near the device with short traces to the IN, OUT, and GND

pins. The regulator ground pin should be connected to the external circuit ground so that the regulator and its

capacitors have a single-point ground.

It should be noted that stability problems have been seen in applications where vias to an internal ground plane

were used at the ground points of the IC and the input and output capacitors. This was caused by varying ground

potentials at these nodes resulting from current flowing through the ground plane. Using a single-point ground

technique for the regulator and it's capacitors fixed the problem.

Because high current flows through the traces going into VIN and coming from VOUT, Kelvin connect the capacitor

leads to these pins so there is no voltage drop in series with the input and output capacitors.

Submit Documentation Feedback

Product Folder Links: LP3872 LP3875

LP3872 Datasheet(PDF) 16 Page - Texas Instruments