CS5231-3GDF8 ONSEMI [ON Semiconductor], CS5231-3GDF8 Datasheet - Page 7

• Manufacturer Part Number: CS5231-3GDF8
• Description: 500 mA, 3.3 V Linear Regulator with Auxiliary Control
• Manufacturer: ONSEMI [ON Semiconductor]

V
V
Figure 18. Power−Up, V
V
AUXDRV
AUXDRV
AUXDRV
Because the Difference Between V
V
“Oscillatory Performance” Mode Lasts Longer
V
V
V
Difference in Voltage is Now I
OUT
OUT
V
IN
V
OUT
the Difference in Supply Voltages (3.3 − V
Figure 16. Power−Up, V
Figure 17. Power−Down, V
IN
IN
is Compensated By Higher Value of V
I
OUT
I
I
OUT
OUT
= 375 mA V
= 375 mA V
= 375 mA V
Greater
AUX
= 3.465 V. I
AUX
AUX
AUX
AUX
= 3.135 V
AUX
= 3.135 V. The
OUT
= 3.465
= 3.135
= 3.135 V. The
AUX
y R
OUT
DS(ON)
and 3.3 is
y R
AUX
DS(ON)
AUX
Plus
http://onsemi.com
)
7
characteristics of a linear regulator: startup, transient
response and stability.
charged. At initial startup, the V
present, and the output capacitor will be charged through the
PFET. The PFET will initially provide current to the load
through its body diode. The diode will act as a voltage
follower until sufficient voltage is present to turn the FET
on. Since most commercial power supplies have a fairly low
ramp rate, charging through the body diode should
effectively limit in−rush current to the capacitor.
requirements will be satisfied from the charge stored in the
output capacitor until either the linear regulator or the
auxiliary supply can respond. Larger values of capacitance
will improve transient response, but will also cost more. A
linear regulator will respond within microseconds, where an
external power supply may take milliseconds to react. The
output capacitance will provide the difference in current
until this occurs. The result will be an instantaneous voltage
change at the output. This change is the product of the
current change and the capacitor ESR:
ESR must be minimized if output voltage must be
maintained within tight tolerances. In such a case, it is often
advisable to use a parallel network of different types of
capacitors. For example, electrolytic capacitors provide
high charge storage capacity in a small size, while tantalum
capacitors have low ESR. The parallel combination will
result in a high capacity, low ESR network. It is also
important to physically locate the capacitance network close
to the load, and to connect the network to the load with wide
PC board traces to minimize the metal resistance.
V
AUXDRV
The output capacitor helps determine three main
Startup is affected because the output capacitor must be
During normal operation, transient load current
This limitation directly affects load regulation. Capacitor
V
V
OUT
IN
Figure 19. Power−Down, V
STABILITY CONSIDERATIONS
DV OUT + DI LOAD
I
OUT
= 375 mA V
AUX
AUX
IN
= 3.465
= 3.465 V
supply may not be
ESR