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PDF MIC22200 Data sheet ( Hoja de datos )
| Número de pieza | MIC22200 | |
| Descripción | 2A Integrated Switch Synchronous Buck Regulator | |
| Fabricantes | Micrel Semiconductor | |
| Logotipo |  |
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MIC22200
2A Integrated Switch Synchronous
Buck Regulator with Frequency
Programmable from 800kHz to 4MHz
General Description
Features
The Micrel MIC22200 is a high-efficiency, 2A integrated
switch synchronous buck (step-down) regulator. The
MIC22200 switching frequency is programmable from
800kHz to 4MHz, allowing the customer to optimize their
designs either for efficiency or for the smallest footprint.
The regulator achieves efficiencies as high as 95% while
still switching at 1MHz over a broad load range.
The ultra high-speed control loops keep the output voltage
within regulation even under the extreme transient load
swings commonly found in FPGAs and low-voltage ASICs.
The output voltage can be adjusted down to 0.7V to
address all low-voltage power needs.
The MIC22200 offers a full range of sequencing and
tracking options. The EN/DLY pin, combined with the
Power-On-Reset (POR) pin, allows multiple outputs to be
sequenced in many ways during turn on and turn off. The
RC (ramp control) pin allows the device to be connected to
another device in the MIC22X00 family of products to keep
the output voltages within a certain delta V on start up.
The MIC22200 is available in a 3mm × 3mm 12-pin MLF®
package with a junction operating range from –40°C to
+125°C.
• Input voltage range: 2.6V to 5.5V
• Adjustable output voltage option down to 0.7V
• Output load current to 2A
• Full sequencing and tracking capability
• Easy RC compensation
• Power-On-Reset (POR) output
• Efficiency >90% across a broad load range
• Operating frequency: Programmable from 800 kHz up to
4MHz
• Ultra-fast transient response
• 100% maximum duty cycle
• Fully integrated MOSFET switches
• Micropower shutdown
• Thermal-shutdown and current-limit protection
• Available in Pb-free 3mm × 3mm MLF-12-pin MLF®
Package
• –40°C to +125°C junction temperature range
Applications
• High power density point-of-load conversion
Data sheets and support documentation can be found on
Micrel’s web site at www.micrel.com.
• Servers/routers
• DVD recorders and multimedia players
• Computing peripherals
• Base stations
• FPGAs, DSP and low voltage ASIC devices
_________________________________________________________________________________________________________________________
Typical Application
Micrel Inc. • 2180 Fortune Drive • San Jose, CA 95131 • USA • tel +1 (408) 944-0800 • fax + 1 (408) 474-1000 • http://www.micrel.com
December 2010
M9999-120310-C
1 page  
Micrel, Inc.
Typical Characteristics
Shutdown Current
vs. Input Voltage
10
8
6
4
2
TA = 25°C
20.5 3 3.5 4 4.5 5 5.5
INPUT VOLTAGE (V)
1300
1250
1200
1150
1100
1050
1000
1.3
Quiscent Current
vs. Temperature
VIN = 3.3V
No Switching
FB = 0.9V
TA = 25°C
02 55 07 5 100 125
TEMPERATURE (°C)
Enable Voltage
vs. Temperature
1.26
1.22
1.18
1.14
1.1
VIN = 3.3V
02 55 07 5 100 125
TEMPERATURE (°C)
Shutdown Current
vs. Temperature
10
8
6
4
2
0 02 55 07 5 100 125
TEMPERATURE (°C)
Reference Voltage
vs. Input Voltage
0.71
0.705
0.7
0.695
TA = 25°C
0.629.5 3 3.5 4 4.5 5 5.5
INPUT VOLTAGE (V)
Enable Hysterisis
vs. Temperature
16
15
14
13
12
11
10
9
8
VIN = 3.3V
02 55 07 5 100 125
TEMPERATURE (°C)
MIC22200
1600
Quiescent Current
vs. Input Voltage
1500
1400
1300
1200
1100
10020.5
No Switching
FB = 0.9V
TA = 25°C
3 3.5 4 4.5 5 5.5
INPUT VOLTAGE (V)
Reference Voltage
vs. Temperature
0.71
0.705
0.7
0.695
0.69
1100
1075
1050
1025
1000
975
950
VIN = 3.3V
02 55 07 5 100 125
TEMPERATURE (°C)
Frequency
vs. Temperature
CF = 220pF
VIN = 3.3V
02 55 07 5 100 125
TEMPERATURE (°C)
December 2010 5 M9999-120310-C
5 Page 
Micrel, Inc.
Efficiency Considerations
Efficiency is defined as the amount of useful output
power, divided by the amount of power consumed:
Efficiency
%
=
⎜⎛
⎝
VOUT
VIN
×
×
IOUT
IIN
⎟⎞
⎠
×
100
Maintaining high efficiency serves two purposes. It
decreases power dissipation in the power supply,
reducing the need for heat sinks and thermal design
considerations and it decreases consumption of current
for battery-powered applications. Reduced current draw
from a battery increases the devices operating time,
critical in hand held devices.
There are mainly two loss terms in switching converters:
static losses and switching losses. Static losses are
simply the power losses due to VI or I2R. For example,
power is dissipated in the high-side switch during the on
cycle. Power loss is equal to the high-side MOSFET
RDS(ON) multiplied by the RMS Switch Current squared
(ISW2). During the off cycle, the low-side N-Channel
MOSFET conducts, also dissipating power. Similarly, the
inductor’s DCR and capacitor’s ESR also contribute to
the I2R losses. Device operating current also reduces
efficiency by the product of the quiescent (operating)
current and the supply voltage. The current required to
drive the gates on and in the frequency range from
800kHz to 4MHz and the switching transitions make up
the switching losses.
Figure 2 shows an efficiency curve. The portion, from 0A
to 0.2A, efficiency losses are dominated by quiescent
current losses, gate drive and transition losses. In this
case, lower supply voltages yield greater efficiency in
that they require less current to drive the MOSFETs and
have reduced input power consumption.
Figure 2. Efficiency Curve
MIC22200
The region, 0.2A to 2A, efficiency loss is dominated by
MOSFET RDSON and inductor DC losses. Higher input
supply voltages will increase the gate-to-source voltage
on the internal MOSFETs, reducing the internal RDSON.
This improves efficiency by reducing DC losses in the
device. All but the inductor losses are inherent to the
device. In which case, inductor selection becomes
increasingly critical in efficiency calculations. As the
inductors are reduced in size, the DC resistance (DCR)
can become quite significant. The DCR losses can be
calculated as follows:
LPD = IOUT2 × DCR
From that, the loss in efficiency due to inductor
resistance can be calculated as follows:
Efficiency
%
=
⎢⎡1−
⎣
⎜⎜⎝⎛
VOUT × IOUT
(VOUT × IOUT) + LPD
⎟⎟⎠⎞⎥⎦⎤
× 100
Efficiency loss due to DCR is minimal at light loads and
gains significance as the load is increased. Inductor
selection becomes a trade-off between efficiency and
size in this case.
Alternatively, under lighter loads, the ripple current due
to the inductance becomes a significant factor. When
light load efficiencies become more critical, a larger
inductor value may be desired. Larger inductances
reduce the peak-to-peak inductor ripple current, which
minimize losses. The following graph in Figure 3
illustrates the effects of inductance value at light load:
Efficiency
vs. Inductance
94
92 4.7µH
90
88 1µH
86
84
82
80
78
760 0.2 0.4 0.6 0.8 1 1.2
OUTPUT CURRENT (A)
Figure 3. Efficiency vs. Inductance
December 2010 11 M9999-120310-C
11 Page | ||
| Páginas | Total 22 Páginas | |
| PDF Descargar | [ Datasheet MIC22200.PDF ] | |
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