Bay Linear
Inspire the Linear Power
500 mA Low Dropout Voltage Regulators
B4500
Preliminary Information
Description
The B4500 series are a group of positive output voltage,
three-pin regulators, that provide a high current even
when the input/output voltage differential is small. Very
low power consumption, only 2µA typ., and high
accuracy is achieved though CMOS construction and
programmable fuse technologies. Output voltage: 2.0V
to 6.0V in 0.1V increments.
The B4500 consists of a high-precision voltage
reference, an error correction circuit, and a current
limited output driver.
Available in SOT223 (500mW) and SOT-89 (300mW)
packages minimizing the usage of board real state.
Features
•
•
•
•
Maximum Output Current: 500 mA.
Highly accurate: Output voltage +/- 2%.
Only 2µA power Consumption.
µ
Very Low Dropout:
0.11V @ 100mA
0.3V @ 300mA
0.5V @ 450mA
Offered in SOT-89 & SOT-223 Packages
•
Applications
•
•
•
•
Battery Powered Equipment
Notebook PC, Palmtops, PDA
Portable Cameras and Video Recorders
Reference Voltage Sources
Pin Connection
Ordering Information
Package
SOT-223
SOT-89
Part No.
B4500CN-X.X
B4500CR-X.X
SOT-89 (R)
X.X = Fixed Output Voltages from 2.0V to 6.0V
SOT-223 (N)
Vin
Vin
2
2
1
Vss
2
3
1
Vss
2
3
Vin Vout
Vin Vout
Top View
Top View
Bay Linear, Inc
2478 Armstrong Street, Livermore, CA 94550 Tel: (925) 606-5950, Fax: (925) 940-9556
www.baylinear.com
B4500
PRODUCT DESCRIPTION
The B4500 is precision fixed output voltage regulator.
Unlike bipolar regulators, the B4500 supply current
does not increase with load current. In addition, V
out
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
IH.
And shutdown (disabled) when SHDN is
at or below V
IL
. SHDN maybe controlled by a CMOS
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
out
falls to
zero volts.
P
D
=(V
INMAX
-V
OUTMIN
)I
LOADMAX
Where:
P
D
= worst case actual power dissipation
V
INMAX
= Maximum voltage on V
IN
V
OUTMIN
=Minimum regulator output voltage
I
LOADMAX
= maximum output (LOAD) Current
The maximum allowable power dissipation is function
of the maximum ambient temperature (T
AMAX
). The
maximum allowable die temperature (125°C) and the
thermal resistance from junction-to-air (θ
JA
).
P
DMAX
=(T
JMAX
-T
AMAX
)/
θ
JA
Where all terms are previously defined
This can be caused in conjunction with other equation
to ensure regulator thermal operation is within limit.
For example:
Given:
V
INMAX
=3.3V+10%
V
OUTMIN
=2.7V-2.5%
I
LOADMAX
=275 mA
T
JMAX
=125°C
T
AMAX
=95°C
θ
JA
= 59°C/W
Find:
1. Actual power dissipation
2. Maximum allowable dissipation
Output Capacitor
A 1µF (min) capacitor from V
out
to ground is required.
Then output capacitor should have an effective series
resistance of 5Ω or less. A 1µA capacitor should be
connected from V
in
to GND if there is more than 10
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 140
°C.
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:
V
IN
C
1
1
µ
F
BATTREY
GND
V
OUT
C
2
1
µ
F
B4500
Bay Linear, Inc
2478 Armstrong Street, Livermore, CA 94550 Tel: (925) 606-5950, Fax: (925) 940-9556
www.baylinear.com
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