CS5253B-1 ONSEMI [ON Semiconductor], CS5253B-1 Datasheet - Page 8

• Manufacturer Part Number: CS5253B-1
• Description: 3.0 A LDO 5-Pin Adjustable Linear Regulator with Remote Sense Applications
• Manufacturer: ONSEMI [ON Semiconductor]

V
brings the pass transistor out of dropout. In this manner, any
output voltage less than 13 V may be regulated, provided the
V
where V
theoretical limit to the regulated voltage as long as the
V
− V
circuit conditions will result in the immediate operation of
the pass transistor outside of its safe operating area.
Overvoltage stresses will then cause destruction of the pass
transistor before overcurrent or thermal shutdown circuitry
can become active. Additional circuitry may be required to
clamp the V
if fail safe operation is required. One possible clamp circuit
is illustrated in Figure 21; however, the design of clamp
circuitry must be done on an application by application
basis. Care must be taken to ensure the clamp actually
protects the design. Components used in the clamp design
must be able to withstand the short circuit condition
indefinitely while protecting the IC.
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 overtemperature. Tantalum and aluminum
electrolytic capacitors work best, with electrolytic
External
OUT
POWER
POWER
Supply
There is a possibility of damaging the IC when V
The output compensation capacitor helps determine three
CS5253B−1 Can Be Short−Circuit Protected When
Figure 21. This Circuit Is an Example of How the
OUT
is in regulation. Further increase in the supply voltage
External Supply
is greater than 6.0 V if a short circuit occurs. Short
CONTROL
to V
to V
POWER
OUT
OUT
Operating With V
V
V
CONTROL
POWER
differential is less than 6.0 V. In the case
differential of 6.0 V is not exceeded.
and V
CS5253B−1
to V
V
ADJ
OUT
POWER
V
SENSE
differential to less than 6.0 V
V
OUT
OUT
are shorted, there is no
> 6.0 V
POWER
http://onsemi.com
CS5253B−1
8
capacitors being less expensive in general, but varying more
in capacitor value and ESR overtemperature.
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
IC pins; the compensation capacitor located right at the pins
with a minimum lead length; the adjust feedback resistor
divider ground, (bottom of R2 in Figure 20), 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
overtemperature, 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:
where T is the time for the regulation loop to begin to
respond. The very fast transient response time of the
CS5253B−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
the CS5253B−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
The CS5253B−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
When large external capacitors are used with a linear
OUT
DV + DI
DV + DI
connected to V
ESR
T C
SENSE
CONTROL
directly at the
drops. In