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Micrel Semiconductor |
MIC38C42/3/4/5
Micrel, Inc.
MIC38C42/3/4/5
BiCMOS Current-Mode PWM Controllers
General Description
The MIC38C4x are fixed frequency, high performance, cur-
rent-mode PWM controllers. Micrel’s BiCMOS devices are
pin compatible with 384x bipolar devices but feature several
improvements.
Undervoltage lockout circuitry allows the ’42 and ’44 versions
to start up at 14.5V and operate down to 9V, and the ’43 and
’45 versions start at 8.4V with operation down to 7.6V. All
versions operate up to 20V.
When compared to bipolar 384x devices operating from a
15V supply, start-up current has been reduced to 50µAtypical
and operating current has been reduced to 4.0 mA typical.
Decreased output rise and fall times drive larger MOSFETs,
and rail-to-rail output capability increases efficiency, espe-
cially at lower supply voltages. The MIC38C4x also features
a trimmed oscillator discharge current and bandgap refer-
ence.
The MIC38C4x denotes 8-pin plastic DIP, SOIC, and MSOP
packages. MIC384Cx-1 denotes 14-pin plastic DIP and
SOIC packages. 8-pin devices feature small size, while 14-
pin devices separate the analog and power connections for
improved perfomance and power dissipation.
Features
• Fast 40ns output rise and 30ns output fall times
• –40°C to +85°C temperature range
meets UC284x specifications
• High-performance, low-power BiCMOS Process
• Ultralow start-up current (50µA typical)
• Low operating current (4mA typical)
• CMOS outputs with rail-to-rail swing
• ≥ 500kHz current-mode operation
• Trimmed 5V bandgap reference
• Pin-for-pin compatible with UC3842/3843/3844/3845(A)
• Trimmed oscillator discharge current
• UVLO with hysteresis
• Low cross-conduction currents
Applications
• Current-mode, off-line, switched-mode power supplies
• Current-mode, dc-to-dc converters.
• Step-down “buck” regulators
• Step-up “boost” regulators
• Flyback, isolated regulators
• Forward converters
• Synchronous FET converters
For fast rise and fall times and higher output drive, refer to
the MIC38HC4x.
Functional Diagram
VDD
7 (12)
VREF
8 (14)
RT/CT
4 (7)
FB
2 (3)
2.5V
35V
5V
Reference
Oscillator
2R
R
UVLO
*
†
T Q‡
S
R
Q
(VD)
(11)
OUT
6 (10)
(PGND)
(8)
*
COMP GND* (AGND) ISNS
1 (1)
5 (9) 3 (5)
( ) pins are on MIC38C4x-1 (14-lead) versions only
* MIC38C4x, (8-lead) versions only
† MIC38C42, MIC38C43 (96% max. duty cycle) versions only
‡ MIC38C44, MIC38C45 (50% max. duty cycle) versions only
Micrel, Inc. • 2180 Fortune Drive • San Jose, CA 95131 • USA • tel + 1 (408) 944-0800 • fax + 1 (408) 474-1000 • http://www.micrel.com
September 2007
1
M9999-091107
http://www.Datasheet4U.com
MIC38C42/3/4/5
Ordering Information
Part Number*
Standard
Pb-Free
Temperature Range
Package
MIC38C42BN
MIC38C42YN
-40°C to +85°C
8-pin Plastic DIP
MIC38C43BN
MIC38C43YN
-40°C to +85°C
8-pin Plastic DIP
MIC38C44BN
MIC38C44YN
-40°C to +85°C
8-pin Plastic DIP
MIC38C45BN
MIC38C45YN
-40°C to +85°C
8-pin Plastic DIP
MIC38C42-1BN
Contact Factory
-40°C to +85°C
14-pin Plastic DIP
MIC38C43-1BN
Contact Factory
-40°C to +85°C
14-pin Plastic DIP
MIC38C44-1BN
MIC38C44-1YN
-40°C to +85°C
14-pin Plastic DIP
MIC38C45-1BN
Contact Factory
-40°C to +85°C
14-pin Plastic DIP
MIC38C42BM
MIC38C42YM
-40°C to +85°C
8-pin SOIC
MIC38C43BM
MIC38C43YM
-40°C to +85°C
8-pin SOIC
MIC38C44BM
MIC38C44YM
-40°C to +85°C
8-pin SOIC
MIC38C45BM
MIC38C45YM
-40°C to +85°C
8-pin SOIC
MIC38C42BMM
MIC38C42YMM
-40°C to +85°C
8-pin MSOP
MIC38C43BMM
MIC38C43YMM
-40°C to +85°C
8-pin MSOP
MIC38C44BMM
MIC38C44YMM
-40°C to +85°C
8-pin MSOP
MIC38C45BMM
MIC38C45YMM
-40°C to +85°C
8-pin MSOP
MIC38C42-1BM
MIC38C42-1YM
-40°C to +85°C
14-pin SOIC
MIC38C43-1BM
MIC38C43-1YM
-40°C to +85°C
14-pin SOIC
MIC38C44-1BM
MIC38C44-1YM
-40°C to +85°C
14-pin SOIC
MIC38C45-1BM
MIC38C45-1YM
-40°C to +85°C
14-pin SOIC
* Refer to the Part Number Cross Reference for a listing of Micrel devices equivalent to UC284x and UC384x devices.
Micrel, Inc.
Selection Guide
Duty Cycle
0% to 96%
0% to 50%
UVLO Thresholds
Startup 8.4V
Startup 14.5V
Minimum Operating 7.6V Minimum Operating 9V
MIC38C43
MIC38C42
MIC38C45
MIC38C44
M9999-091107
2 September 2007
http://www.Datasheet4U.com
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