CS5253-1GDPR5G ONSEMI [ON Semiconductor], CS5253-1GDPR5G Datasheet - Page 8

• Manufacturer Part Number: CS5253-1GDPR5G
• Description: 3.0 A LDO 5−Pin Adjustable Linear Regulator
• Manufacturer: ONSEMI [ON Semiconductor]

Stability Considerations
main characteristics of a linear regulator: loop stability, startup
delay, and load transient response. Different capacitor types
vary widely in tolerance, Equivalent Series Resistance (ESR),
Equivalent Series Inductance (ESI), and variation over
temperature. Tantalum and aluminum electrolytic capacitors
work best, with electrolytic capacitors being less expensive in
general, but varying more in capacitor value and ESR over
temperature.
loop stability. The Stability vs ESR graph in the typical
performance section shows the minimum ESR needed to
guarantee stability, but under ideal conditions. These include:
having V
compensation capacitor located right at the pins with a
minimum lead length; the adjust feedback resistor divider
ground, (bottom of R2 in Figure 19), connected right at the
capacitor ground; and with power supply decoupling
capacitors located close to the IC pins. The actual
performance will vary greatly with board layout for each
application. In particular, the use of the remote sensing feature
will require a larger capacitor with less ESR. For most
applications, a minimum of 33 mF tantalum or 150 mF
aluminum electrolytic, with an ESR less than 1.0 W over
temperature, is recommended. Larger capacitors and lower
ESR will improve stability.
regulator to respond, is also determined by the output
capacitor. For large changes in load current, the ESR of the
output capacitor causes an immediate drop in output voltage
given by:
by:
External
Supply
The output compensation capacitor helps determine three
The CS5253−1 requires an output capacitor to guarantee
The load transient response, during the time it takes the
There is then an additional drop in output voltage given
CS5253−1 Can Be Short−Circuit Protected When
Figure 20. This Circuit Is an Example of How the
External Supply
OUT
connected to V
Operating With V
V
V
CONTROL
POWER
CS5253−1
DV + DI
DV + DI
V
ADJ
V
SENSE
SENSE
V
OUT
OUT
ESR
T C
directly at the IC pins; the
> 6.0 V
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where T is the time for the regulation loop to begin to respond.
The very fast transient response time of the CS5253−1 allows
the ESR effect to dominate. For microprocessor applications,
it is customary to use an output capacitor network consisting
of several tantalum and ceramic capacitors in parallel. This
reduces the overall ESR and reduces the instantaneous output
voltage drop under transient load conditions. The output
capacitor network should be as close to the load as possible
for the best transient response.
Protection Diodes
regulator, it is sometimes necessary to add protection diodes.
If the input voltage of the regulator gets shorted, the output
capacitor will discharge into the output of the regulator. The
discharge current depends on the value of the capacitor, the
output voltage, and the rate at which V
CS5253−1 regulator, the discharge path is through a large
junction and protection diodes are not usually needed. If the
regulator is used with large values of output capacitance and
the input voltage is instantaneously shorted to ground,
damage can occur. In this case, a diode connected as shown
in Figure 21 is recommended.
is required is to solve for current:
where:
typical short circuit current value provided in the
specifications, serious thought should be given to the use of
a protection diode.
When large external capacitors are used with a linear
A rule of thumb useful in determining if a protection diode
I is the current flow out of the load capacitance when
C is the value of load capacitance
V is the output voltage, and
T is the time duration required for V
If the calculated current is greater than or equal to the
V
from high to being shorted.
CONTROL
Figure 21. Diode Protection Circuit
is shorted,
V
V
CONTROL
POWER
CS5253−1
I + C
Adjust
T
V
V
SENSE
V
OUT
CONTROL
CONTROL
drops. In the
to transition