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voltage soft-start. Larger value capacitors also improve noise slightly. The TPS79901 is stable in unity-gain

configuration (OUT tied to FB) without CFB.

8.2.3 Application Curve

100

10k

100k

10M

Frequency (Hz)

IOUT = 1 mA

IOUT = 100 mA

IOUT = 250 mA

COUT = 2.2 µF

CNR = 0.01 µF

G001

Figure 8-3. Power-Supply Rejection Ratio vs Frequency

8.3 What To Do and What Not To Do

Do place at least one 2.2-µF ceramic capacitor as close as possible to the OUT pin of the regulator.

Do not place the output capacitor more than 10 mm away from the regulator.

Do connect a 0.1-μF to 1-μF low equivalent series resistance (ESR) capacitor across the IN pin and GND input

of the regulator.

Do not exceed the absolute maximum ratings.

9 Power Supply Recommendations

These devices are designed to operate from an input voltage supply range between 2.7 V and 6.5 V. The

input voltage range provides adequate headroom in order for the device to have a regulated output. This input

supply is well-regulated and stable. If the input supply is noisy, additional input capacitors with low ESR can help

improve the output noise performance.

10 Layout

10.1 Layout Guidelines

10.1.1 Board Layout Recommendations to Improve PSRR and Noise Performance

To improve ac performance (such as PSRR, output noise, and transient response), design the board with

separate ground planes for VIN and VOUT, with each ground plane connected only at the GND pin of the device.

In addition, connect the bypass capacitor directly to the GND pin of the device.

10.1.2 Thermal Information

10.1.2.1 Thermal Protection

Thermal protection disables the output when the junction temperature rises to approximately 165°C, allowing

the device to cool. When the junction temperature cools to approximately 145°C the output circuitry is again

enabled. Depending on power dissipation, thermal resistance, and ambient temperature, the thermal protection

circuit may cycle on and off. This cycling limits the dissipation of the regulator, protecting it from damage

resulting from overheating.

Any tendency to activate the thermal protection circuit indicates excessive power dissipation or an inadequate

heat sink. For reliable operation, limit junction temperature to 125°C maximum. To estimate the margin of safety

in a complete design (including heat sink), increase the ambient temperature until the thermal protection is

triggered; use worst-case loads and signal conditions. For good reliability, thermal protection triggers at least

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TPS799

SBVS056L – JANUARY 2005 – REVISED FEBRUARY 2022

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