2& =

6,(/#:) . 6#)

4à,#

IN

BYPASS

LP3981

2.2 µF

EN

OUT-SENSE

OUT

2(2)

7(6)

1(1)

4(3)

6(5)

5(4)

2.2 µF

LP3981

SNVS159H – OCTOBER 2001 – REVISED JULY 2015

www.ti.com

9 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 must

validate and test their design implementation to confirm system functionality.

9.1 Application Information

The LP3981 can provide 300-mA output current with 2.5-V to 6-V input. It is stable with a 2.2-

μF ceramic output

capacitor. An optional external bypass capacitor reduces the output noise without slowing down the load

transient response. Typical output noise is 35 µVRMS at frequencies from 10 Hz to 100 kHz. Typical power supply

rejection is 60 dB at 1 kHz.

9.2 Typical Application

Figure 17. LP3981 Typical Application

9.2.1 Design Requirements

Example requirements for typical voltage inverter applications:

Table 1. Design Parameters

DESIGN PARAMETER

EXAMPLE VALUE

Input voltage

3.5 V, ±10%

Output voltage

2.5 V, ±5%

Output current

300 mA (maximum)

RMS noise, 10 Hz to100 kHz

35

μVRMS

PSRR at 1 kHz

60 dB

9.2.2 Detailed Design Procedure

9.2.2.1 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 device, to the ultimate heat sink, the ambient environment. Thus, the

power dissipation is dependant on the ambient temperature and the thermal resistance across the various

interfaces between the die and ambient air.

As stated in the notes for Absolute Maximum Ratings and Recommended Operating Conditions, the allowable

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

(1)

12

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