MIC47300
3A, Low Voltage, Adjustable LDO
Regulator with Dual Input Supply
*See Thermal Design Section
Micrel Inc. • 2180 Fortune Drive • San Jose, CA 95131 • USA • tel +1 (408) 944-0800 • fax + 1 (408) 474-1000 • http://www.micrel.com
October 2009 M9999-102309-A
General Description
The MIC47300 is a high-bandwidth, low-dropout, 3A volt-
age regulator ideal for powering core voltages of low-
power microprocessors. The MIC47300 implements a dual
supply configuration allowing for very low output
impedance and very fast transient response.
The MIC47300 requires a bias input supply between 3V
and 6.5V for proper operation. The main input supply rail
operates from 1.4V to 6.5V that allows for adjustable
output voltages down to 0.9V.
The MIC47300 requires a minimum of 1µF output
capacitance for stability, and optimal operation is achieved
with small ceramic capacitors.
The MIC47300 is available in a 5-pin power D-Pak
package (TO-252) with an operating temperature range of
–40°C to +125°C.
Datasheets and support documentation can be found on
Micrel’s web site at: www.micrel.com.
Features
• Input Voltage Range:
– VIN: 1.4V to 6.5V
– VBIAS: 3.0V to 6.5V
• Stable with 1µF ceramic capacitor
• ±1% initial tolerance
• Maximum dropout voltage (VIN–VOUT) of 400mV
over temperature
• Adjustable output voltage down to 0.9V
• Ultra fast transient response (Up to 10MHz bandwidth)
• Excellent line and load regulation specifications
• Power D-Pak package (TO-252)
• Thermal shutdown and current-limit protection
• Junction temperature range: –40°C to 125°C
Applications
• Graphics processors
• PC add-in cards
• Microprocessor core voltage supply
• Low voltage digital ICs
• High efficiency linear power supplies
• SMPS post regulators
__________________________________________________________________________________________
Typical Application*
Figure 1. Typical Application Circuit
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Ordering Information
Part Number Output Current Voltage Junction Temp. Range Package
MIC47300WD* 3A Adjustable –40° to +125°C 5-Pin TO-252
Note:
* RoHs compliant with ‘high-melting solder’ exemption.
Pin Configur ation
5-Pin TO-252 D-Pak (D)
Pin Description
Pin Number Pin Name Pin Name
1 ADJ
Adjustable Regulator Feedback Input: Connect to the resistor voltage divider that is
placed from OUT to GND in order to set the output voltage.
2 BIAS
Input Bias Voltage: Voltage for powering all internal circuitry of the regulator with the
exception of the output power device.
3 GND, TAB Ground: TAB is also connected internally to the IC’s ground on D-Pak.
4 IN Input Voltage: Supplies the current to the output power device
5 OUT
Regulator Output: The output voltage is set by the resistor divider connected from OUT
to GND (with the divided connection tied to ADJ). A minimum value capacitor must be
used to maintain stability. See Applications Information.
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Absolute Maximum Ratings(1)
Supply Voltage (VIN).........................................................8V
Bias Supply Voltage (VBIAS)..............................................8V
Power Dissipation .....................................Internally Limited
ESD Rating(3).................................................................. 2kV
Operating Ratings(2)
Supply Voltage (VIN)......................................... 1.4V to 6.5V
Bias Supply Voltage (VBIAS)................................. 3V to 6.5V
Junction Temperature (TJ) ..................–40°C ≤ TJ ≤ +125°C
Maximum Power Dissipation..................................... Note 4
Package Thermal Resistance
TO-252 (θJC) ........................................................3°C/W
TO-252 (θJA).......................................................56°C/W
Electrical Characteristics(5)
VIN = VOUT + 1V, VBIAS = VOUT + 2.1V, IOUT = 10mA; TA = 25°C, bold values indicate –40°C≤ TJ ≤ +125°C, unless noted.
Symbol Parameter Condition Min Typ Max Units
VLNREG Line Regulation VIN = VOUT +1V to 6.5V –0.1 0.01 +0.1 %/V
VLDREG Load Regulation IOUT = 10mA to A 0.2 0.5 %
VDO Dropout Voltage (VIN -VOUT) IOUT = 1.5A
IOUT = 3A
105
230
200
400 mV
mV
VDO(BIAS) Dropout Voltage (VBIAS - VOUT)
Note 6 IOUT = 3A
1.24
2.1 V
IGND Ground Pin Current, Note 7 IOUT = 10mA
IOUT = 3A
25
25
50 mA
mA
IBIAS Current thru VBIAS I
OUT = 10mA
IOUT = 3A
20
50
35
150
mA
mA
ILIM Current Limit VOUT = 0V 6.5 10 A
Thermal Shutdown 168 °C TSD
Thermal Shutdown Hysteresis 10 °C
Reference (Adjust Pin)
VADJ Reference Voltage 0.891
0.882
0.9 0.909
0.918
V
V
IADJ Adjust Pin Current VADJ = 1.2V 0.01 1 μA
Notes:
1. Exceeding the absolute maximum rating may damage the device.
2. The device is not guaranteed to function outside its operating rating.
3. Devices are ESD sensitive. Handling precautions recommended. Human body model, 1.5kΩ in series with 100pF.
4. PD(MAX) = (TJ(MAX) – TA) / θJA, where θJA, depends upon the printed circuit layout. See “Applications Information.”
5. Specification for packaged product only.
6. For VOUT ≤1V, VBIAS dropout specification does not apply due to a minimum 3V VBIAS input.
7. IGND = IBIAS + (IIN – IOUT). At high loads, input current on VIN will be less than the output current, due to drive current being supplied by VBIAS.
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Typical Characteristics
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Typical Characteristics (continued)
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Functional Characteristics
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Functional Description
The MIC47300 is an ultra-high performance, low-dropout
linear regulator designed for high current applications
requiring fast transient response. The MIC47300 utilizes
two input supplies, significantly reducing dropout
voltage, perfect for low-voltage, DC-to-DC conversion.
The MIC47300 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 type and
tantalum type capacitors.
The MIC47300 regulator is fully protected from damage
due to fault conditions, offering linear current limiting and
thermal shutdown.
Bias Supply Voltage
VBIAS, requiring relatively light current, provides power to
the control portion of the MIC47300. VBIAS requires
approximately 50mA for a 3A 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 230mV at a 3A load
current. Bypassing on the bias pin is recommended to
improve performance of the regulator during line and
load transients. Small ceramic capacitors from VBIAS to
ground help reduce high frequency noise from being
injected into the control circuitry from the bias rail and
are good design practice. Good bypass techniques
typically include one larger capacitor such as 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 VBIAS input voltage must
be 2.1V above the output voltage with a minimum VBIAS
inpt voltage of 3 volts.
Input Supply Voltage
VIN provides the high current to the collector of the pass
transistor. The minimum input voltage is 1.4V, allowing
conversion from low voltage supplies.
Output Capacitor
The MIC47300 is designed to be stable with a minimal
capacitance value and without ESR constraints.
However, proper capacitor selection is important to
ensure desired transient response. A 1µF ceramic chip
capacitor should satisfy most applications and output
capacitance can be increased without bound. See
“Typical Characteristic” 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.
Input Capacitor
Additional bypass capacitance is recommended when
the device is more than 2 to 3 inches away from the bulk
supply capacitance, or when the supply is a battery.
Small, surface-mount, ceramic chip capacitors can be
used for the bypassing. A 1μF or greater ceramic input
capacitor should be placed next to 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-specific parameters:
• Maximum ambient temperature (TA)
• Output current (IOUT)
• Output voltage (VOUT)
• Input voltage (VIN)
• Ground current (IGND)
First, calculate the power dissipation of the regulator
from these numbers and the device parameters from this
datasheet.
P
D = VIN × IIN + VBIAS × IBIAS – VOUT × IOUT
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:
()
CSJC
D
AJ(MAX)
SA θθ
P
TT
θ+−
⎟
⎟
⎠
⎞
⎜
⎜
⎝
⎛−
=
The heat sink may be significantly reduced in
applications where the maximum input voltage is known
and large compared 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 MIC47300
allow significant reductions in regulator power dissipation
and the associated heat sink without compromising
performance. When this technique is employed, a
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capacitor of at least 1µF is needed directly between the
input and regulator ground. Refer to “Application Note 9”
for further details and examples on thermal design and
heat sink specification.
The maximum power allowed can be calculated using
the thermal resistance (θJA) of the D-Pak adhering to the
following criteria for the PCB design: 2 oz. copper and
100mm2 copper area for the MIC47300. Given a
maximum ambient temperature (TA=75°C), and without
the use of a heat sink, the maximum power allowed that
would not exceed the IC’s maximum junction
temperature (125°C) is
PD(MAX) = (TJ(MAX) – TA)/θJA = (125°C – 75°C)/(56°C/W)
= 0.893W
Minimum Load Current
The MIC47300, unlike most other high current
regulators, does not require a minimum load to maintain
output voltage regulation.
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Application Information
Adjustable Regulator Design
The MIC47300 allows programming the output down to
0.9V. From the typical application in Figure 1, the output
voltage is set by placing a resistor divider network from
OUT to GND and is determined by the following
equation:
⎟
⎠
⎞
⎜
⎝
⎛+×= 1
R2
R1
0.9VOUT
where VOUT is the desired output voltage.
The resistor value between VOUT and the adjust pin
should not exceed 10kΩ. Larger values can cause
instability. The resistor values are calculated from the
above equation, resulting in the following:
⎟
⎟
⎠
⎞
⎜
⎜
⎝
⎛−×= 1
0.9
V
R2R1 OUT
Evaluation Board Layout
The MIC47300 evaluation board layout is shown in
Figures 2 and 3. For customer application boards,
recommended variations include using a static resistor
for R2 in place of the potentiometer as well as the
elimination of all test points and jumper options that are
included on the MIC47300 evaluation board.
Figure 2. MIC47300 EVB Top Layer
Figure 3. MIC47300 EVB Bottom Layer
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Evaluation Board
Bill of Materials
Item Part Number Manufacturer Description Qty.
C1 C1206C106K8RACTU Kemet(1) 10µF, 10V, X7R Ceramic Capacitor 1
C2 C0805C105K8RACTU Kemet 1µF, 10V, X7R Ceramic Capacitor 1
C3 C0805C105K8RACTU Kemet 1µF, 10V, X7R Ceramic Capacitor 1
R1 CRCW08051800F Vishay(2) 180Ω Resistor, Film, 0805 1
R2 PV36W502C01B00 Murata(3) 5kΩ Potentiometer 1
U1 MIC47300WD Micrel, Inc.(4) MIC47300 LDO Regulato r 1
Notes:
1. Kemet: www.kemet.com
2. Vishay: www.vishay.com
3. Murata: www.murata.com
4. Micrel, Inc.: www.micrel.com
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Package Information
5-Pin TO-252 Power D-Pak (D)
MICREL, INC. 2180 FORTUNE DRIVE SAN JOSE, CA 95131 USA
TEL +1 (408) 944-0800 FAX +1 (408) 474-1000 WEB http://www.micrel.com
The information furnished by Micrel in this data sheet is believed to be accurate and reliable. However, no responsibility is assumed by Micrel for its
use. Micrel reserves the right to change circuitry and specifications at any time without notification to the customer.
Micrel Products are not designed or authorized for use as components in life support appliances, devices or systems where malfunction of a product
can reasonably be expected to result in personal injury. Life support devices or systems are devices or systems that (a) are intended for surgical implant
into the body or (b) support or sustain life, and whose failure to perform can be reasonably expected to result in a significant injury to the user. A
Purchaser’s use or sale of Micrel Products for use in life support appliances, devices or systems is a Purchaser’s own risk and Purchaser agrees to fully
indemnify Micrel for any damages resulting from such use or sale.
© 2009 Micrel, Incorporated.
