Datasheet
Table Of Contents

TPS7A4901
OUT
FB
GND
C
10 F
IN
m
C
10nF
NR/SS
R
1
R
2
C
10nF
BYP
C
10 F
OUT
m
IN
EN
NR/SS
V
IN
V
OUT
V
OUT
V
REF
- 1
R =R
1 2
V
OUT
R +R
1 2
³ 5 Am,where
TPS7A49xx
www.ti.com
SBVS121B –AUGUST 2010–REVISED JANUARY 2010
THEORY OF OPERATION
GENERAL DESCRIPTION
CAPACITOR RECOMMENDATIONS
The TPS7A49xx belongs to a family of new
generation linear regulators that use an innovative
Low ESR capacitors should be used for the input,
bipolar process to achieve ultralow-noise and very
output, noise reduction, and bypass capacitors.
high PSRR levels at a wide input voltage range.
Ceramic capacitors with X7R and X5R dielectrics are
These features, combined with a high thermal
preferred. These dielectrics offer more stable
performance MSOP-8 with PowerPAD package make
characteristics. Ceramic X7R capacitors offer
this device ideal for high-performance analog
improved over-temperature performance, while
applications.
ceramic X5R capacitors are the most cost-effective
and are available in higher values.
ADJUSTABLE OPERATION
Note that high ESR capacitors may degrade PSRR.
The TPS7A4901 has an output voltage range of To ensure stability, maximum ESR must be less than
+1.194 to +33V. The nominal output voltage of the 200mΩ.
device is set by two external resistors, as shown in
Figure 28.
INPUT AND OUTPUT CAPACITOR
REQUIREMENTS
The TPS7A49xx family of positive, high-voltage linear
regulators achieve stability with a minimum input and
output capacitance of 2.2mF; however, it is highly
recommended to use a 10mF capacitor to maximize
ac performance.
NOISE REDUCTION AND BYPASS
CAPACITOR REQUIREMENTS
Figure 28. Adjustable Operation for Maximum AC
Although noise reduction and bypass capacitors
Performance
(C
NR/SS
and C
BYP
, respectively) are not needed to
achieve stability, it is highly recommended to use
R
1
and R
2
can be calculated for any output voltage
0.01mF capacitors to minimize noise and maximize ac
range using the formula shown in Equation 1. To
performance.
ensure stability under no load conditions, this
resistive network must provide a current equal to or
MAXIMUM AC PERFORMANCE
greater than 5mA.
In order to maximize noise and PSRR performance, it
is recommended to include 10mF or higher input and
(1)
output capacitors, and 0.01mF noise reduction and
bypass capacitors, as shown in Figure 28. The
If greater voltage accuracy is required, take into
solution shown delivers minimum noise levels of
account the output voltage offset contributions
15.4mV
RMS
and power-supply rejection levels above
because of the feedback pin current and use 0.1%
52dB from 10Hz to 400kHz; see Figure 18 and
tolerance resistors.
Figure 19.
ENABLE PIN OPERATION
The TPS7A49xx provides an enable feature (EN) that
turns on the regulator when V
EN
> 2.1V.
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