Do not locate the output capacitor more than 1cm from the output pin. Make sure the output capacitor returns to

a clean analog ground.

7.1.5.1.1 Tantalum Capacitors (Legacy Chip)

Tantalum capacitors are less desirable than ceramics for use as output capacitors because these components

are more expensive when comparing equivalent capacitance and voltage ratings in the 1µF to 4.7µF range.

Another important consideration is that tantalum capacitors have higher ESR values than equivalent size

ceramics. This condition means that although finding a Tantalum capacitor with an ESR value within the stable

range is possible, the capacitor is larger in capacitance (which means bigger and more costly) than a ceramic

capacitor with the same ESR value.

The ESR of a typical tantalum increases approximately 2:1 as the temperature goes from 25°C down to −40°C,

so allow for some guard band.

7.1.5.2 Recommended Capacitors (New Chip)

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 listed in the Recommended Operating Conditions account for an effective capacitance of

approximately 50% of the nominal value.

7.1.6 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 + 0.3 V.

• 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, use external protection to protect the device. Reverse

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

anticipated.

Figure 7-1 shows one approach for protecting the device.

IN

OUT

GND

CIN

GND

GND

COUT

GND

Internal Body Diode

Schottky Diode

Figure 7-1. Example Circuit for Reverse Current Protection Using a Schottky Diode

LP2992

SNVS171L – NOVEMBER 2001 – REVISED FEBRUARY 2025

www.ti.com

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