Datasheet

TPS7A3001-EP
SBVS174 –OCTOBER 2011 www.ti.com
CAPACITOR RECOMMENDATIONS
Low ESR capacitors should be used for the input, output, noise reduction, and bypass capacitors. Ceramic
capacitors with X7R and X5R dielectrics are preferred. These dielectrics offer more stable characteristics.
Ceramic X7R capacitors offer improved over-temperature performance, while ceramic X5R capacitors are the
most cost-effective and are available in higher values.
Note that high ESR capacitors may degrade PSRR.
INPUT AND OUTPUT CAPACITOR REQUIREMENTS
This negative, high-voltage linear regulator achieves stability with a minimum input and output capacitance of
2.2μF; however, it is highly recommended to use a 10μF capacitor to maximize ac performance.
NOISE REDUCTION AND BYPASS CAPACITOR REQUIREMENTS
Although noise reduction and bypass capacitors (C
NR/SS
and C
BYP
, respectively) are not needed to achieve
stability, it is highly recommended to use 0.01μF capacitors to minimize noise and maximize ac performance.
MAXIMUM AC PERFORMANCE
In order to maximize noise and PSRR performance, it is recommended to include 10μF or higher input and
output capacitors, and 0.01μF noise reduction and bypass capacitors, as shown in Figure 30. The solution shown
delivers minimum noise levels of 15.1μV
RMS
and power-supply rejection levels above 55dB from 10Hz to 700kHz;
see Figure 19 and Figure 20.
OUTPUT NOISE
The TPS7A3001 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 0.01μF noise reduction
capacitor, the output noise is reduced by almost 80% (from 80μV
RMS
to 17μV
RMS
); see Figure 21.
TPS7A3001 low output voltage noise makes it an ideal solution for powering noise-sensitive circuitry.
POWER-SUPPLY REJECTION
The 0.01μF noise reduction capacitor greatly improves TPS7A3001 power-supply rejection, achieving up to 20dB
of additional power-supply rejection for frequencies between 110Hz and 400KHz.
Additionally, ac performance can be maximized by adding a 0.01μF bypass capacitor (C
BYP
) from the FB pin to
the OUT pin. This capacitor greatly improves power-supply rejection at lower frequencies, for the band from
10Hz to 200kHz; see Figure 19.
The very high power-supply rejection of the TPS7A3001 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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