B4150CK5-2.5 Bay Linear, Inc., B4150CK5-2.5 Datasheet - Page 3

• Manufacturer Part Number: B4150CK5-2.5
• Description: 2.5V 150mA CMOS low dropout LDO
• Manufacturer: Bay Linear, Inc.

PRODUCT DESCRIPTION
The B4150 is precision fixed output voltage regulator.
Unlike bipolar regulators, the B4150 supply current
does not increase with load current. In addition, V
remains stable and within regulator at very low load
currents (an important consideration in RTC and
CMOS RAM battery back-up application).
Figure 1 shows a typical application circuit. The
regulator is enabled any time the shutdown input is at
or above V
at or below V
logic gate, or I/O port of a micro controller. If the
SHDN input is not. Required, it should be connected
directly to the supply. While in shutdown, supply
current decreases to 0.05µA (typical) and V
zero volts.
Bypass Input
A 470pF capacitor connected from the bypass input to
ground reduces noise present on the internal reference,
which in turn significantly reduces output noise. If
output noise is not a concern, this input maybe left
unconnected. Larger capacitor values maybe used, but
it results in a longer time period to rated output
voltage power is initially applied.
Output Capacitor
A 1µF (min) capacitor from V
Then output capacitor should have an effective series
resistance of 5Ω or less. A 1µA capacitor should be
connected from V
inches of wire between the regulator and the AC filter
capacitor, or if a battery is used as the power source.
Aluminum electrolytic or tantalum capacitor types can
be used. (since many aluminum electrolytic capacitors
freeze at approximately- 30°C, solid tantalums are
recommended for applications operating below –25
°C.) When operating from sources other than
batteries, supply-noise rejection and transient response
can be improved by increasing the value of the input
and output capacitors and employing passive filtering
techniques.
Thermal Considerations
Thermal Shutdown
Integrated thermal protection circuitry shuts the
regulator off when die temperature exceeds 160°C.
The regulator remaining off until the die temperature
drops to approximately 150 °C.
Bay Linear, Inc
IH.
And shutdown (disabled) when SHDN is
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. SHDN maybe controlled by a CMOS
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to GND if there is more than 10
out
to ground is required.
out
falls to
out
Power Dissipation
The amount of power the regulator dissipates is
primarily a function of input and output voltage, and
output current. The following equation is used to
calculate worst case power dissipation:
Where:
P
V
V
I
The maximum allowable power dissipation is function
of the maximum ambient temperature (T
maximum allowable die temperature (125°C) and the
thermal resistance from junction-to-air (θ
pin SOT-23A package has a θ
220°C/Watt when mounted on a single layer FR4
dielectric copper clad PC board.
This can be caused in conjunction with other equation
to ensure regulator thermal operation is within limit.
For example:
Given:
V
V
I
T
T
Find:
1. Actual power dissipation
2. Maximum allowable dissipation
Actual power dissipation:
P
=[(3.0 x 1.1)-(2.7 x 0.975)]40 x 10
=26.7mW
Maximum allowable power dissipation:
These equations can be used to calculate maximum
current and/or input voltage limits.
LOADMAX
LOADMAX
D
D
JMAX
AMAX
INMAX
OUTMIN
INMAX
OUTMIN
= worst case actual power dissipation
=(V
=125°C
=55°C
INMAX
= Maximum voltage on V
=3.0V+10%
Where all terms are previously defined
=Minimum regulator output voltage
=2.7V-2.5%
= maximum output (LOAD) Current
=40 mA
P
-V
D
P
=(V
OUTMIN
DMAX
P
DMAX
INMAX
=(125-55)/220
=(T
)I
=(T
=318Mw
LOADMAX
-V
JMAX
JMAX
OUTMIN
-T
-T
AMAX
AMAX
)I
IN
JA
LOADMAX
-3
)/ θ
of approximately
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B4150
AMAX
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