NCV4264 ON Semiconductor, NCV4264 Datasheet - Page 6

• Manufacturer Part Number: NCV4264
• Description: 5.0v, 3.3v / 150ma Low Dropout Voltage Regulator
• Manufacturer: ON Semiconductor

Circuit Description
regulator. The device has current capability of 150 mA,
with 500 mV of dropout voltage at 100 mA of current. The
regulation is provided by a PNP pass transistor controlled
by an error amplifier with a bandgap reference. The
regulator is protected by both current limit and short circuit
protection. Thermal shutdown occurs above 150°C to
protect the IC during overloads and extreme ambient
temperatures.
Regulator
sample of the output voltage (V
a PNP series pass transistor by a buffer. The reference is a
bandgap design to give it a temperature−stable output.
Saturation control of the PNP is a function of the load
current and input voltage. Over saturation of the output
power device is prevented, and quiescent current in the
ground pin is minimized.
Regulator Stability Considerations
compensating input line reactance. Possible oscillations
caused by input inductance and input capacitance can be
damped by using a resistor of approximately 1 W in series
with C
helps determine three main characteristics of a linear
regulator: startup delay, load transient response and loop
stability. The capacitor value and type should be based on
cost, availability, size and temperature constraints. A
tantalum or aluminum electrolytic capacitor is best, since
a film or ceramic capacitor with almost zero ESR can cause
instability. The aluminum electrolytic capacitor is the least
expensive solution, but, if the circuit operates at low
temperatures (−25°C to −40°C), both the value and ESR of
the capacitor will vary considerably. The capacitor
manufacturer ’s
information. The value for the output capacitor C
shown in Figure 2 should work for most applications;
however, it is not necessarily the optimized solution.
Stability is guaranteed at values CQ = 10 mF and an ESR
= 9 W within the operating temperature range. Actual limits
are shown in a graph in the Typical Performance
Characteristics section.
The NCV4264 is a precision trimmed 5.0 V fixed output
The error amplifier compares the reference voltage to a
The input capacitor C
IN2
. The output or compensation capacitor, C
data
IN1
sheet
in Figure 2 is necessary for
out
usually
) and drives the base of
provides
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OUT
OUT
this
6
Calculating Power Dissipation in a Single Output
Linear Regulator
regulator (Figure 3) is:
Where:
application, and I
consumes at I
permissible value of R
package section of the data sheet. Those packages with
R
the die temperature below 150°C. In some cases, none of
the packages will be sufficient to dissipate the heat
generated by the IC, and an external heat sink will be
required. The current flow and voltages are shown in the
Measurement Circuit Diagram.
Heat Sinks
package to improve the flow of heat away from the IC and
into the surrounding air. Each material in the heat flow path
between the IC and the outside environment will have a
thermal resistance. Like series electrical resistances, these
resistances are summed to determine the value of R
Where:
R
interface between them. These values appear in data sheets
of heat sink manufacturers. Thermal, mounting, and heat
sinking are discussed in the ON Semiconductor application
note AN1040/D, available on the ON Semiconductor
Website.
qJA
qSA
The maximum power dissipation for a single output
V
V
I
Once the value of P
The value of R
A heat sink effectively increases the surface area of the
R
R
R
R
Like R
Q(max)
qJC
qCS
qSA
qJA
IN(max)
OUT(min)
’s less than the calculated value in Equation 2 will keep
are functions of the package type, heat sink and the
= the junction−to−case thermal resistance,
appears in the package section of the data sheet.
= the case−to−heat sink thermal resistance, and
= the heat sink−to−ambient thermal resistance.
qJA
P D(max) + [V IN(max) * V OUT(min) ] @
is the maximum output current for the
is the maximum input voltage,
, it too is a function of package type. R
R qJA + R qJC ) R qCS ) R qSA
is the minimum output voltage,
Q(max)
qJA
q
P qJA +
is the quiescent current the regulator
.
can then be compared with those in the
I Q(max) ) V I(max) @ I q
qJA
D(Max)
can be calculated:
150
o
C * T A
P D
is known, the maximum
qCS
(eq. 1)
(eq. 2)
(eq. 3)
qJA
and
: