Datasheet

TPS7A47
+LDO
IN
+18 V
OUT
EN GND
-18 V
TPS7A33
-LDO
IN OUT
EN GND
EVM
+15 V
-15 V
TPS7A33
SBVS169C –DECEMBER 2011–REVISED FEBRUARY 2013 www.ti.com
APPLICATION INFORMATION
POWER FOR PRECISION ANALOG
One of the primary TPS7A33 applications is to provide ultralow-noise voltage rails to high-performance analog
circuitry in order to maximize system accuracy and precision.
The TPS7A33 family of negative, high-voltage linear regulators provides ultralow noise, positive and negative
voltage rails to high-performance analog circuitry such as operational amplifiers, ADCs, DACs, and audio
amplifiers.
Because of the ultralow noise levels at high voltages, analog circuitry with high-voltage input supplies can be
used. This characteristic allows for high-performance analog solutions to optimize the voltage range, thus
maximizing system accuracy.
POST DC-DC CONVERTER FILTERING
Most of the time, the voltage rails available in a system do not match the voltage specifications demanded by
one or more of its circuits; these rails must be stepped up or down, depending on specific voltage requirements.
DC-DC converters are the preferred solution to stepping up or down a voltage rail when current consumption is
not negligible. They offer high efficiency with minimum heat generation, but they have one primary disadvantage:
they introduce a high-frequency component, and the associated harmonics, on top of the dc output signal.
If not filtered properly, this high-frequency component degrades analog circuitry performance, reducing overall
system accuracy and precision.
The TPS7A33 offers a wide-bandwidth, very-high power-supply rejection ratio. This specification makes it ideal
for post dc-dc converter filtering, as shown in Figure 30. It is highly recommended to use the maximum
performance schematic shown in Figure 28. Also, verify that the fundamental frequency (and its first harmonic, if
possible) is within the bandwidth of the regulator PSRR, shown in Figure 16.
Figure 30. Post DC-DC Converter Regulation to High-Performance Analog Circuitry
AUDIO APPLICATIONS
Audio applications are extremely sensitive to any distortion and noise in the audio band from 20 Hz to 20 kHz.
This stringent requirement demands clean voltage rails to power critical high-performance audio systems.
The very-high power-supply rejection ratio (> 60 dB) and low noise at the audio band of the TPS7A33 maximize
performance for audio applications; see Figure 16.
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