LP3991

OUT

IN

1 PF

EN

GND

VIN

Load

VEN

B2

A2

A1

B1

COUT*

CIN

* For VOUT = 1.3 V or less,

COUT may be reduced to 2.2 PF.

4.7 PF

11

LP3991

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SNVS296J – DECEMBER 2006 – REVISED JUNE 2016

Product Folder Links: LP3991

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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 LP3991 can provide 300-mA output current with 1.65-V to 4-V input. It is stable with a 2.2-

μF or 4.7-µF

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

the load transient response. Typical output noise is 280

μVRMS at frequencies from 10 Hz to 100 kHz. Typical

power supply rejection is 65 dB at 1 kHz.

8.2 Typical Application

Figure 12. LP3991 Typical Application

8.2.1 Design Requirements

For typical linear voltage regulator applications, use the parameters listed in Table 2.

Table 2. Design Parameters

DESIGN PARAMETER

EXAMPLE VALUE

Input voltage

1.65 V to 4 V

Output voltage

1.2 V to 2.8 V

Output current

300 mA (maximum)

RMS noise, 10 Hz to100 kHz

280

μVRMS

PSRR at 1 kHz

65 dB

8.2.2 Detailed Design Procedure

8.2.2.1 External Capacitors

In common with most regulators, the LP3991 requires external capacitors for regulator stability. The LP3991 is

specifically designed for portable applications requiring minimum board space and smallest components. These

capacitors must be correctly selected for good performance.