EN

IN

OUT

GND

VIN

VEN

GND

VOUT

LP3990

COUT

1 µF

CIN

1 µF

OFF

ON

GND

LP3990

www.ti.com

SNVS251J – MAY 2004 – REVISED SEPTEMBER 2014

8 Application and Implementation

NOTE

Information in the following applications sections is not part of the TI component

specification, and TI does not warrant its accuracy or completeness. TI’s customers are

responsible for determining suitability of components for their purposes. Customers should

validate and test their design implementation to confirm system functionality.

8.1 Application Information

The LP3990 is a linear voltage regulator for digital applications designed to be stable with space-saving ceramic

capacitors as small as 1 µF.

8.2 Typical Application

Figure 13 shows the typical application circuit for the LP3990. The input and output capacitances may need to be

increased above the 1

μF shown for some applications.

Figure 13. LP3990 Typical Application

8.2.1 Design Requirements

DESIGN PARAMETER

EXAMPLE VALUE

Input voltage range

2 V to 6 V

Output voltage

1.8 V

Output current

100 mA

Output capacitor range

1 µF

Input/output capacitor ESR range

5 m

Ω to 500 mΩ

8.2.2 Detailed Design Procedure

To begin the design process, determine the following:

•

Available input voltage range

•

Output voltage needed

•

Output current needed

•

Input and output capacitors

8.2.2.1 Power Dissipation and Device Operation

The permissible power dissipation for any package is a measure of the capability of the device to pass heat from

the power source, the junctions of the IC, to the ultimate heat sink, the ambient environment. Thus, the power

dissipation is dependent on the ambient temperature and the thermal resistance across the various interfaces

between the die junction and ambient air.

The maximum allowable power dissipation for the device in a given package can be calculated using Equation 1:

PD-MAX = ((TJ-MAX - TA) / RθJA)

(1)

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