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MIC3172YM 参数 Datasheet PDF下载

MIC3172YM图片预览
型号: MIC3172YM
PDF下载: 下载PDF文件 查看货源
内容描述: 100kHz的1.25A开关稳压器 [100kHz 1.25A Switching Regulators]
分类和应用: 稳压器开关
文件页数/大小: 17 页 / 158 K
品牌: MICREL [ MICREL SEMICONDUCTOR ]
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MIC2172/3172
Micrel, Inc.
MIC2172/3172
100kHz 1.25A Switching Regulators
General Description
The MIC2172 and MIC3172 are complete 100kHz SMPS
current-mode controllers with internal 65V 1.25A power
switches. The MIC2172 features external frequency syn-
chronization or frequency adjustment, while the MIC3172
features an enable/shutdown control input.
Although primarily intended for voltage step-up applications,
the floating switch architecture of the MIC2172/3172 makes
it practical for step-down, inverting, and Cuk configurations
as well as isolated topologies.
Operating from 3V to 40V, the MIC2172/3172 draws only
7mA of quiescent current making it attractive for battery
operated supplies.
The MIC3172 is for applications that require on/off control of
the regulator. The MIC3172 is externally shutdown by
applying a TTL low signal to EN (enable). When disabled, the
MIC3172 draws only leakage current (typically less than
1µA). EN must be high for normal operation. For applications
not requiring control, EN must be tied to V
IN
or TTL high.
The MIC2172 is for applications requiring two or more SMPS
regulators that operate from the same input supply. The
MIC2172 features a SYNC input which allows locking of its
internal oscillator to an external reference. This makes it
possible to avoid the audible beat frequencies that result from
the unequal oscillator frequencies of independent SMPS
regulators.
A reference signal can be supplied by one MIC2172 desig-
nated as a master. To insure locking of the slave’s oscillators,
the reference oscillator frequency must be higher than the
slave’s. The master MIC2172’s oscillator frequency is in-
creased up to 135kHz by connecting a resistor from SYNC to
ground (see applications information).
The MIC2172/3172 is available in an 8-pin plastic DIP or
SOIC for –40°C to +85°C operation.
Features
1.25A, 65V internal switch rating
3V to 40V input voltage range
Current-mode operation
Internal cycle-by-cycle current limit
Thermal shutdown
Low external parts count
Operates in most switching topologies
7mA quiescent current (operating)
<1µA quiescent current, shutdown mode (MIC3172)
TTL shutdown compatibility (MIC3172)
External frequency synchronization (MIC2172)
External frequency trim (MIC2172)
Fits most LT1172 sockets (see applications info)
Applications
Laptop/palmtop computers
Toys
Hand-held instruments
Off-line converter up to 50W
(requires external power switch)
• Predriver for higher power capability
• Master/slave configurations (MIC2172)
Typical Applications
+5V
(4.75V min.)
L1
27µH
V
IN
N/C
SYNC
MIC2172
R3
1k
COMP GND
FB
P1 P2 S
C3
1µF
V
SW
1N5822
D1
V
IN
4V to 6V
C1*
22µF
V
OUT
+12V, 0.14A
R1
10.7k
1%
R2
C2
1.24k
470µF 1%
Enable
Shutdown
T1
R4*
C3*
D2
1N5818
C4
470µF
V
OUT
5V, 0.25A
R1
3.74k
1%
C1
22µF
V
IN
EN
MIC3172
D1*
V
SW
1:1.25
L
PRI
= 100µH
R3
1k
COMP GND
FB
P1 P2 S
C2
1µF
R2
1.24k
1%
* Locate near MIC2172 when supply leads > 2"
* Optional voltage clipper (may be req’d if T1 leakage inductance too high)
Figure 1.
MIC2172 5V to 12V Boost Converter
Figure 2.
MIC3172 5V Flyback Converter
Micrel, Inc. • 2180 Fortune Drive • San Jose, CA 95131 • USA • tel + 1 (408) 944-0800 • fax + 1 (408) 474-1000 • http://www.micrel.com
April 2005
1
M9999-042205