LP38500-ADJ, LP38502-ADJ

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SNVS539H – NOVEMBER 2007 – REVISED SEPTEMBER 2015

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 LP38500-ADJ and LP38502-ADJ devices can provide 1.5-A output current with 2.7-V to 5.5-V input voltage.

These ultra-low-dropout linear regulators respond very quickly to step changes in load, making them suitable for

low-voltage microprocessor applications. Input and output capacitors of at least 10 µF are required.

8.2 Typical Applications

Figure 17. Typical Circuit (LP38500)

Figure 18. Typical Circuit (LP38502)

8.2.1 Design Requirements

For LP3850x-ADJ typical applications, use the parameters listed in Table 1 as the input parameters.

Table 1. Design Parameters

DESIGN PARAMETERS

VALUE

Input voltage

2.7 V to 5.5 V

Output voltage

0.6 V to 5 V (adjustable)

Output current

1.5 A (maximum)

Input capacitor

10 µF (minimum)

Output capacitor

10 uF (minimum)

8.2.2 Detailed Design Procedure

8.2.2.1 External Capacitors

The LP38500-ADJ and LP38502-ADJ require that at least 10-µF (±20%) capacitors be used at the input and

output pins located within one cm of the device. Larger capacitors may be used without limit on size for both CIN

and COUT. Capacitor tolerances such as temperature variation and voltage loading effects must be considered

when selecting capacitors to ensure that they will provide the minimum required amount of capacitance under all

operating conditions for the application.

In general, ceramic capacitors are best for noise bypassing and transient response because of their ultra low

ESR. It must be noted that if ceramics are used, only the types with X5R or X7R dielectric ratings should be used

(never Z5U or Y5F). Capacitors which have the Z5U or Y5F characteristics will see a drop in capacitance of as

much as 50% if their temperature increases from 25°C to 85°C. In addition, the capacitance drops significantly

with applied voltage: a typical Z5U or Y5F capacitor can lose as much as 60% of its rated capacitance if only half

of the rated voltage is applied to it. For these reasons, only X5R and X7R ceramics should be used.

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