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PDF MIC5191BML Data sheet ( Hoja de datos )
| Número de pieza | MIC5191BML | |
| Descripción | Ultra High-Speed/ High-Current Active Filter/LDO Controller | |
| Fabricantes | Micrel Semiconductor | |
| Logotipo |  |
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Hay una vista previa y un enlace de descarga de MIC5191BML (archivo pdf) en la parte inferior de esta página. Total 13 Páginas | ||
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MIC5191
Micrel
MIC5191
Ultra High-Speed, High-Current Active Filter/LDO Controller
General Description
The MIC5191 is an ultra high-speed linear regulator. It uses
an external N-Channel FET as its power device.
The MIC5191's ultra high-speed abilities can handle the fast
load demands of microprocessor cores, ASICs, and other
high-speed devices. Signal bandwidths of greater than 500kHz
can be achieved with a minimum amount of capacitance
while at the same time keeping the output voltage clean,
regardless of load demand. A powerful output driver delivers
large MOSFETs into their linear regions, achieving ultra-low
dropout voltage.
1.25VIN ±10% can be turned into 1V ±1% without the use of
a large amount of capacitance.
MIC5191 (1.0V reference) is optimized for output voltages of
1.0V and higher.
The MIC5191 is offered in 10-lead 3mm × 3mm MLF™ and
10-lead MSOP-10 packages and has an operating junction
temperature range of –40°C to +125°C.
All support documentation can be found on Micrel’s web
site at www.micrel.com.
Features
• Input voltage range:
VIN = 1.0V to 5.5V
• +1.0% initial output tolerance
• Dropout down to 25mV@10A
• Filters out switching frequency noise on input
• Very high large signal bandwidth >500kHz
• PSRR >40dB at 500kHz
• Adjustable output voltage down to 1.0V
• Stable with any output capacitor
• Excellent line and load regulation specifications
• Logic controlled shutdown
• Current limit protection
• 10-lead MLF™ and MSOP-10 packages
• Available –40°C to +125°C junction temperature
Applications
• Distributed power supplies
• ASIC power supplies
• DSP, µP, and µC power supplies
Typical Application
VCC = 12V
C1
0.01µF
VIN = 1.2V
GND
C3
0.01µF
IR3716S
MIC5191
IS OUT
VIN
VCC1
FB
VCC2
EN
COMP
R3
12.5kΩ
PGND
SGND
VOUT =1.0V@7A
C2
10µF
GND
MicroLeadFrame and MLF are trademarks of Amkor Technology, Inc.
PowerPAK is a trademark of Siliconix, Inc.
Micrel, Inc. • 1849 Fortune Drive • San Jose, CA 95131 • USA • tel + 1 (408) 944-0800 • fax + 1 (408) 474-1000 • http://www.micrel.com
April 2004
1 M9999-042804
1 page  
MIC5191
Functional Characteristics
Enable Transient
TIME (10µs/div)
10A Load Transient
TIME (100µs/div)
Disable Transient
Micrel
TIME (100µs/div)
Transient Response
TIME (100µs/div)
April 2004
5 M9999-042804
5 Page 
MIC5191
Feedback Resistors
IR3716S
VOUT
MIC5191
FB
R1
R2 COUT
GND
Figure 10. Adjustable Output
The feedback resistors adjust the output to the desired
voltage and can be calculated as follows:
VOUT
=
VREF 1+
R1
R2
VREF is equal to 1.0V for the MIC5191. The minimum output
voltage (R1=0) is 0.5V. For output voltages less than 1V, use
the MIC5190.
The resistor tolerance adds error to the output voltage. These
errors are accumulative for both R1 and R2. For example, our
resistors selected have a ±1% tolerance. This will contribute
to a ±2% additional error on the output voltage.
The feedback resistors must also be small enough to allow
enough current to the feedback node. Large feedback resis-
tors will contribute to output voltage error.
VERROR = R1× IFB
VERROR = 1kΩ × 12µA
VERROR = 12mV
For our example application, this will cause an increase in
output voltage of 12mV. For the percentage increase,
Micrel
Active Filter
Another application for the MIC5191 is as an active filter on
the output of a switching regulator. This improves the power
supply in several ways.
First, using the MIC5191 as a filter on the output can signifi-
cantly reduce high frequency noise. Switching power sup-
plies tends to create noise at the switching frequency in the
form of a triangular voltage ripple. High frequency noise is
also created by the high-speed switching transitions. A lot of
time, effort, and money are thrown into the design of switch-
ing regulators to minimize these effects as much as possible.
Figure 9 shows the MIC5191 as a post regulator.
VOUT = 1V
ILOAD = 10A
TIME (1µs/div)
Figure 11. Ripple Reduction
Figure 11 shows the amount of ripple reduction for a 500 KHz
switching regulator. The fundamental switching frequency is
reduced from greater than 100mV to less than 10mV.
VERROR %
=
VERROR
VOUT
× 100
VERROR %
=
12mV
1.5V
×
100
VERROR% = 0.8%
By reducing R1 to 100Ω, the error contribution by the feed-
back resistors and feedback current is reduced to less than
0.1%. This is the reason R1 should not be greater than 100Ω.
Applying the MIC5191
Linear Regulator
The primary purpose of the MIC5191 is as a linear regulator,
which enables an input supply voltage to drop down through
the resistance of the pass element to a regulated output
voltage.
TIME (100µs/div)
Figure 12. 10A Load Transient
The transient response also contributes to the overall AC
output voltage deviation. Figure 12 shows a 1A to 10A load
transient. The top trace is the output of the switching regulator
(same circuit as Figure10). The output voltage undershoots
by 100mV. Just by their topology, linear regulators have the
ability to respond at much higher speeds than a switching
regulator. Linear regulators do not have the limitation or
restrictions of switching regulators which must reduce their
bandwidth to less than their switching frequency.
April 2004
11 M9999-042804
11 Page | ||
| Páginas | Total 13 Páginas | |
| PDF Descargar | [ Datasheet MIC5191BML.PDF ] | |
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