B4500 Datasheet, PDF (3/6 Pages) List of Unclassifed Manufacturers – 500 mA Low Dropout Voltage Regulators

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.
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:
Where:
P_D=(V_INMAX-V_OUTMIN)I_LOADMAX
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
V_IN
C₁
1µF
V_OUT
C₂
1µF
BATTREY
B4500
GND
Bay Linear, Inc 2478 Armstrong Street, Livermore, CA 94550 Tel: [phone], Fax: [phone]
www.baylinear.com