7 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, as well as validating and testing their design

implementation to confirm system functionality.

7.1 Application Information

7.1.1 Recommended Capacitor Types

The device is designed to be stable using low equivalent series resistance (ESR) ceramic capacitors at the input

and output. Multilayer ceramic capacitors have become the industry standard for these types of applications and

are recommended, but must be used with good judgment. Ceramic capacitors that employ X7R-, X5R-, and

C0G-rated dielectric materials provide relatively good capacitive stability across temperature, whereas the use of

Y5V-rated capacitors is discouraged because of large variations in capacitance.

Regardless of the ceramic capacitor type selected, the effective capacitance varies with operating voltage and

temperature. Generally, expect the effective capacitance to decrease by as much as 50%. The input and output

capacitors recommended in the Recommended Operating Conditions table account for an effective capacitance

of approximately 50% of the nominal value.

7.1.2 Input and Output Capacitor Requirements

Although an input capacitor is not required for stability, good analog design practice is to connect a capacitor

from IN to GND. This capacitor counteracts reactive input sources and improves transient response, input ripple,

and PSRR. An input capacitor is recommended if the source impedance is more than 0.5Ω. A higher value

capacitor may be necessary if large, fast rise-time load or line transients are anticipated or if the device is

located several inches from the input power source.

Dynamic performance of the device is improved with the use of an output capacitor. Use an output capacitor

within the range specified in the Recommended Operating Conditions table for stability.

7.1.3 Reverse Current

Excessive reverse current can damage this device. Reverse current flows through the intrinsic body diode of the

pass transistor instead of the normal conducting channel. At high magnitudes, this current flow degrades the

long-term reliability of the device.

Conditions where reverse current can occur are outlined in this section, all of which can exceed the absolute

maximum rating of VOUT ≤ VIN + 0.3V.

• If the device has a large COUT and the input supply collapses with little or no load current

• The output is biased when the input supply is not established

• The output is biased above the input supply

If reverse current flow is expected in the application, external protection is recommended to protect the device.

Reverse current is not limited in the device, so external limiting is required if extended reverse voltage operation

is anticipated.

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LM1117-Q1

SBVS468 – DECEMBER 2024

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