Ground

IN

OUT

SD

ERROR

Input

Capacitor

Output

Capacitor

Pullup

Resistor

Pullup

Resistor

LP3961, LP3964

www.ti.com

SNVS056J – MAY 2000 – REVISED JUNE 2015

9 Power Supply Recommendations

The LP396x devices are designed to operate from an input voltage supply range between 2.5 V and 7 V. The

input voltage range provides adequate headroom in order for the device to have a regulated output. This input

supply must be well regulated. An input capacitor of at least 68

μF is required.

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 IN, OUT, and GND pins of the LP396x using

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

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 LP396x 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 its capacitors fixed the problem.

Because high current flows through the traces going into the IN pin and coming from the OUT pin, Kelvin connect

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

10.2 Layout Example

Figure 26. LP3961 TO-263 Package Typical Layout

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Product Folder Links: LP3961 LP3964