Datasheet

TPS7A33
www.ti.com SBVS169C –DECEMBER 2011–REVISED FEBRUARY 2013
OUTPUT NOISE
The TPS7A33 provides low output noise when a noise-reduction capacitor (C
NR/SS
) is used.
The noise-reduction capacitor serves as a filter for the internal reference. By using a 1-μF noise reduction
capacitor, the output noise is reduced by almost 80% (from 80 μV
RMS
to 17 μV
RMS
); see Figure 21.
The TPS7A33 low output voltage noise makes it an ideal solution for powering noise-sensitive circuitry.
POWER-SUPPLY REJECTION
The 1-μF noise-reduction capacitor greatly improves TPS7A33 power-supply rejection, achieving up to 10 dB of
additional power-supply rejection for frequencies between 140 Hz and 500 KHz.
Additionally, ac performance can be maximized by adding a 0.01-μF feed-forward capacitor (C
FF
) from the FB pin
to the OUT pin. This capacitor greatly improves power-supply rejection at lower frequencies, for the band from
100 Hz to 100 kHz; see Figure 15.
The very-high power-supply rejection of the TPS7A33 makes it a good choice for powering high-performance
analog circuitry, such as operational amplifiers, ADCs, DACS, and audio amplifiers.
TRANSIENT RESPONSE
As with any regulator, increasing the size of the output capacitor reduces over/undershoot magnitude, but
increases duration of the transient response.
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