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PDF MIC4723 Data sheet ( Hoja de datos )
| Número de pieza | MIC4723 | |
| Descripción | Integrated Switch Buck Regulator | |
| Fabricantes | Micrel Semiconductor | |
| Logotipo |  |
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MIC4723
3A 2MHz Integrated Switch
Buck Regulator
General Description
Features
The Micrel MIC4723 is a high efficiency PWM buck (step-
down) regulator that provides up to 3A of output current.
The MIC4723 operates at 2.0MHz and has proprietary
internal compensation that allows a closed loop bandwidth
of over 200KHz.
The low on-resistance internal p-channel MOSFET of the
MIC4723 allows efficiencies over 92%, reduces external
components count and eliminates the need for an
expensive current sense resistor.
The MIC4723 operates from 2.7V to 5.5V input and the
output can be adjusted down to 1V. The devices can
operate with a maximum duty cycle of 100% for use in low-
dropout conditions.
The MIC4723 is available in the exposed pad 12-pin
3mm x 3mm MLF® package with a junction operating
range from –40°C to +125°C.
• 2.7 to 5.5V supply voltage
• 2.0MHz PWM mode
• Output current to 3A
• Up to 94% efficiency
• 100% maximum duty cycle
• Adjustable output voltage option down to 1V
• Ultra-fast transient response
• Ultra-small external components
Stable with a 1µH inductor and a 4.7µF output
capacitor
• Fully integrated 3A MOSFET switch
• Micropower shutdown
• Thermal shutdown and current limit protection
• Pb-free 12-pin 3mm x 3mm MLF® package
• –40°C to +125°C junction temperature range
Data sheets and support documentation can be found on
Micrel’s web site at www.micrel.com.
Applications
• FPGA/DSP/ASIC applications
• General point of load
• Broadband communications
• DVD/TV recorders
• Point of sale
• Printers/Scanners
• Set top boxes
• Computing peripherals
• Video cards
___________________________________________________________________________________________________________
Typical Application
3A 2MHz Buck Regulator
MIC4723
3.3VOUT Efficiency
96
94 4.5VIN
5VIN
92
90 5.5VIN
88
86
84
82
80
78
76
0 0.5 1 1.5 2 2.5
OUTPUT CURRENT (A)
3
MLF and MicroLeadFrame are registered trademarks of Amkor Technology, Inc.
Micrel Inc. • 2180 Fortune Drive • San Jose, CA 95131 • USA • tel +1 (408) 944-0800 • fax + 1 (408) 474-1000 • http://www.micrel.com
May 2007
1 M9999-052307-A
1 page  
Micrel, Inc.
Typical Characteristics (continue)
1.0010
1.0008
1.0006
1.0004
1.0002
1.0000
0.9998
0.9996
0.9994
0.9992
0.99920.7
Line Regulation
3.2 3.7 4.2 4.7 5.2
SUPPLY VOLTAGE (V)
Feedback Voltage
vs. Supply Voltage
1.2
1.0
0.8
0.6
0.4
0.2
VEN = VIN
00 1 2 3 4 5
SUPPLY VOLTAGE (V)
RDSON
vs. Temperature
160
140
120
100
80
60
40
20
VIN = 3.3V
0 20 40 60 80
TEMPERATURE (°C)
1.010
Feedback Voltage
vs. Temperature
1.008
1.006
1.004
1.002
1.000
0.998
0.996
0.994
0.992 VIN = 3.3V
0.990
20 40 60 80
TEMPERATURE (°C)
Quiescent Current
vs. Supply Voltage
800
700
600
500
400
300
200
100
00
VEN = VIN
123456
SUPPLY VOLTAGE (V)
Enable Threshold
vs. Supply Voltage
1.2
1.0
0.8
0.6
0.4
0.2
20.7 3.2 3.7 4.2 4.7
SUPPLY VOLTAGE (V)
MIC4723
Frequency
vs. Temperature
2.5
2.4
2.3
2.2
2.1
2.0
1.9
1.8
1.7
1.6 VIN = 3.3V
1.5 20 40 60 80
TEMPERATURE (°C)
120
115
110
105
100
95
90
85
80
75
720.7
RDSON
vs. Supply Voltage
3.2 3.7 4.2 4.7 5.2
SUPPLY VOLTAGE (V)
Enable Threshold
vs. Temperature
1.2
1.0
0.8
0.6
0.4
0.2
VIN = 3.3V
0 20 40 60 80
TEMPERATURE (°C)
May 2007
5 M9999-052307-A
5 Page 
Micrel, Inc.
high side switch, and lower duty cycles place the power
losses on the Schottky diode.
Inductor conduction losses (PL) can be calculated by
multiplying the DC resistance (DCR) times the square of
the output current;
PL = DCR × IOUT 2
Also, be aware that there are additional core losses
associated with switching current in an inductor. Since
most inductor manufacturers do not give data on the
type of material used, approximating core losses
becomes very difficult, so verify inductor temperature
rise.
Switching losses occur twice each cycle, when the
switch turns on and when the switch turns off. This is
caused by a non-ideal world where switching transitions
are not instantaneous, and neither are currents. Figure 6
demonstrates how switching losses due to the
transitions dissipate power in the switch.
MIC4723
Figure 6. Switching Transition Losses
Normally, when the switch is on, the voltage across the
switch is low (virtually zero) and the current through the
switch is high. This equates to low power dissipation.
When the switch is off, voltage across the switch is high
and the current is zero, again with power dissipation
being low. During the transitions, the voltage across the
switch (VS-D) and the current through the switch (IS-D) are
at middle, causing the transition to be the highest
instantaneous power point. During continuous mode,
these losses are the highest. Also, with higher load
currents, these losses are higher. For discontinuous
operation, the transition losses only occur during the “off”
transition since the “on” transitions there is no current
flow through the inductor.
May 2007
11 M9999-052307-A
11 Page | ||
| Páginas | Total 19 Páginas | |
| PDF Descargar | [ Datasheet MIC4723.PDF ] | |
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