MIC49300-1.2WR Micrel Inc, MIC49300-1.2WR Datasheet - Page 6

• Manufacturer Part Number: MIC49300-1.2WR
• Description: IC REG LDO 3A 1.2V SPAK-5
• Manufacturer: Micrel Inc

Specifications of MIC49300-1.2WR

• Regulator Topology: Positive Fixed
• Voltage - Output: 1.2V
• Voltage - Input: Up to 6.5V
• Voltage - Dropout (typical): 0.28V @ 3A
• Number Of Regulators: 1
• Current - Output: 3A
• Operating Temperature: -40°C ~ 125°C
• Mounting Type: Surface Mount
• Package / Case: SPAK-5
• Voltage Regulator Type: Linear
• Topology: LDO
• Regulator Output Type: Fixed
• Polarity Type: Positive
• Number Of Outputs: Single
• Input Voltage (min): 1.4V
• Input Voltage (max): 6.5V
• Output Voltage: 1.2V
• Package Type: SPAK
• Output Current: 3A
• Load Regulation: 0.2%
• Line Regulation: 0.01%/V
• Output Voltage Accuracy: ±1%
• Operating Temp Range: -40C to 125C
• Operating Temperature Classification: Automotive
• Dropout Voltage@current (max): 0.2@1500mA/0.4@3A
• Dropout Voltage@current (typ): 0.125@1500mA/0.28@3A
• Pin Count: 5 +Tab
• Mounting: Surface Mount
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Current - Limit (min): -
• Lead Free Status / Rohs Status: Compliant
• Other names: 576-1811-5; MIC49300-1.2WR

MIC49300
Applications Information
The MIC49300 is an ultra-high performance, low dropout linear
regulator designed for high current applications requiring fast
transient response. The MIC49300 utilizes two input supplies,
signifi cantly reducing dropout voltage, perfect for low-voltage,
DC-to-DC conversion. The MIC49300 requires a minimum
of external components and obtains a bandwidth of up to
10MHz. As a µCap regulator, the output is tolerant of virtually
any type of capacitor including ceramic and tantalum.
The MIC49300 regulator is fully protected from damage due
to fault conditions, offering linear current limiting and thermal
shutdown.
Bias Supply Voltage
V
control portion of the MIC49300. V
33mA for a 1.5A load current. Dropout conditions require
higher currents. Most of the biasing current is used to supply
the base current to the pass transistor. This allows the pass
element to be driven into saturation, reducing the dropout to
300mV at a 1.5A load current. Bypassing on the bias pin is
recommended to improve performance of the regulator dur-
ing line and load transients. Small ceramic capacitors from
V
injected into the control circuitry from the bias rail and are
good design practice. Good bypass techniques typically in-
clude one larger capacitor such as a 1µF ceramic and smaller
valued capacitors such as 0.01µF or 0.001µF in parallel with
that larger capacitor to decouple the bias supply. The V
input voltage must be 1.6V above the output voltage with a
minimum V
Input Supply Voltage
V
transistor. The minimum input voltage is 1.4V, allowing con-
version from low voltage supplies.
Output Capacitor
The MIC49300 requires a minimum of output capacitance
to maintain stability. However, proper capacitor selection
is important to ensure desired transient response. The
MIC49300 is specifi cally designed to be stable with virtually
any capacitance value and ESR. A 1µF ceramic chip capaci-
tor should satisfy most applications. Output capacitance can
be increased without bound. See typical characteristics for
examples of load transient response.
X7R dielectric ceramic capacitors are recommended because
of their temperature performance. X7R-type capacitors change
capacitance by 15% over their operating temperature range
and are the most stable type of ceramic capacitors. Z5U
and Y5V dielectric capacitors change value by as much as
50% and 60%, respectively, over their operating temperature
ranges. To use a ceramic chip capacitor with Y5V dielectric,
the value must be much higher than an X7R ceramic or a
tantalum capacitor to ensure the same capacitance value over
the operating temperature range. Tantalum capacitors have a
very stable dielectric (10% over their operating temperature
range) and can also be used with this device.
M9999-082605-B
BIAS
BIAS
IN
provides the high current to the collector of the pass
, requiring relatively light current, provides power to the
to ground help reduce high frequency noise from being
BIAS
input voltage of 3V.
BIAS
requires approximately
BIAS
6
Input Capacitor
An input capacitor of 1µF or greater is recommended when
the device is more than 4 inches away from the bulk supply
capacitance, or when the supply is a battery. Small, surfac-
emount, ceramic chip capacitors can be used for the bypass-
ing. The capacitor should be placed within 1" of the device
for optimal performance. Larger values will help to improve
ripple rejection by bypassing the input to the regulator, further
improving the integrity of the output voltage.
Thermal Design
Linear regulators are simple to use. The most complicated
design parameters to consider are thermal characteristics.
Thermal design requires the following application-specifi c
parameters:
First, calculate the power dissipation of the regulator from these
numbers and the device parameters from this datasheet.
The input current will be less than the output current at high
output currents as the load increases. The bias current is
a sum of base drive and ground current. Ground current
is constant over load current. Then the heat sink thermal
resistance is determined with this formula:
The heat sink may be signifi cantly reduced in applications
where the maximum input voltage is known and large com-
pared with the dropout voltage. Use a series input resistor to
drop excessive voltage and distribute the heat between this
resistor and the regulator. The low dropout properties of the
MIC49300 allow signifi cant reductions in regulator power dis-
sipation and the associated heat sink without compromising
performance. When this technique is employed, a capacitor of
at least 1µF is needed directly between the input and regula-
tor ground. Refer to Application Note 9 for further details and
examples on thermal design and heat sink specifi cation.
Minimum Load Current
The MIC49300, unlike most other high current regulators,
does not require a minimum load to maintain output voltage
regulation.
Power Sequencing
There is no power sequencing requirement for V
giving more fl exibility to the user.
• Maximum ambient temperature (T
• Maximum ambient temperature (T
• Maximum ambient temperature (T )
• Output Current (I
• Output Voltage (V
• Input Voltage (V
• Ground Current (I
P
θ
SA
D
= V
=









IN
P
P
D
D
D
× I
T
T
T
T
T
J(MAX)
J(MAX)
J(MAX)
–
IN
(
(
(
(
(
(
θ
θ
θ
θ
θ
θ
θ
θ
θ
θ
+ V
JC
JC
JC
JC
IN
OUT
+
+
GND
±
OUT
)
BIAS
θ
θ
θ
θ
θ
θ
θ
θ
θ
θ
T
T
T
T
T
CS
CS
)
A
A
A
)
)
× I
)
)
)
)
)
)









BIAS
– V
OUT
A
A
× I
OUT
August 2005
IN
Micrel, Inc.
and V
BIAS
,