MIC38C42/3/4/5 Micrel, Inc.
MIC38C42/3/4/5
BiCMOS Current-Mode PWM Controllers
General Description Features
The MIC38C4x are xed frequency, high performance, cur- Fast 40ns output rise and 30ns output fall times
rent-mode PWM controllers. Micrels BiCMOS devices are 40C to +85C temperature range
pin compatible with 384x bipolar devices but feature several meets UC284x specications
improvements. High-performance, low-power BiCMOS Process
Ultralow start-up current (50A typical)
Undervoltage lockout circuitry allows the 42 and 44 versions
Low operating current (4mA typical)
to start up at 14.5V and operate down to 9V, and the 43 and
CMOS outputs with rail-to-rail swing
45 versions start at 8.4V with operation down to 7.6V. All
500kHz current-mode operation
versions operate up to 20V.
Trimmed 5V bandgap reference
When compared to bipolar 384x devices operating from a
Pin-for-pin compatible with UC3842/3843/3844/3845(A)
15V supply, start-up current has been reduced to 50A typical
Trimmed oscillator discharge current
and operating current has been reduced to 4.0 mA typical.
UVLO with hysteresis
Decreased output rise and fall times drive larger MOSFETs,
Low cross-conduction currents
and rail-to-rail output capability increases efciency, espe-
cially at lower supply voltages. The MIC38C4x also features Applications
a trimmed oscillator discharge current and bandgap refer-
Current-mode, off-line, switched-mode power supplies
ence.
Current-mode, dc-to-dc converters.
The MIC38C4x denotes 8-pin plastic DIP, SOIC, and MSOP Step-down buck regulators
packages. MIC384Cx-1 denotes 14-pin plastic DIP and Step-up boost regulators
SOIC packages. 8-pin devices feature small size, while 14- Flyback, isolated regulators
pin devices separate the analog and power connections for Forward converters
improved perfomance and power dissipation. Synchronous FET converters
For fast rise and fall times and higher output drive, refer to
the MIC38HC4x.
Functional Diagram
*
VDD
7 (12)
35V
5V
(VD)
UVLO
VREF
(11)
Reference
8 (14)
RT/CT Oscillator OUT
4 (7) 6 (10)
T Q
FB
2R
2 (3)
(PGND)
(8)
S
Q
2.5V
R
R
*
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 MIC38C42/3/4/5 Micrel, Inc.
Ordering Information
Part Number* Temperature Range Package
Standard Pb-Free
MIC38C42BN MIC38C42YN -40C to +85C 8-pin Plastic DIP
MIC38C43BN MIC38C43YN -40C to +85C 8-pin Plastic DIP
MIC38C44BN MIC38C44YN -40C to +85C 8-pin Plastic DIP
MIC38C45BN MIC38C45YN -40C to +85C 8-pin Plastic DIP
MIC38C42-1BN Contact Factory -40C to +85C 14-pin Plastic DIP
MIC38C43-1BN Contact Factory -40C to +85C 14-pin Plastic DIP
MIC38C44-1BN MIC38C44-1YN -40C to +85C 14-pin Plastic DIP
MIC38C45-1BN Contact Factory -40C to +85C 14-pin Plastic DIP
MIC38C42BM MIC38C42YM -40C to +85C 8-pin SOIC
MIC38C43BM MIC38C43YM -40C to +85C 8-pin SOIC
MIC38C44BM MIC38C44YM -40C to +85C 8-pin SOIC
MIC38C45BM MIC38C45YM -40C to +85C 8-pin SOIC
MIC38C42BMM MIC38C42YMM -40C to +85C 8-pin MSOP
MIC38C43BMM MIC38C43YMM -40C to +85C 8-pin MSOP
MIC38C44BMM MIC38C44YMM -40C to +85C 8-pin MSOP
MIC38C45BMM MIC38C45YMM -40C to +85C 8-pin MSOP
MIC38C42-1BM MIC38C42-1YM -40C to +85C 14-pin SOIC
MIC38C43-1BM MIC38C43-1YM -40C to +85C 14-pin SOIC
MIC38C44-1BM MIC38C44-1YM -40C to +85C 14-pin SOIC
MIC38C45-1BM MIC38C45-1YM -40C to +85C 14-pin SOIC
* Refer to the Part Number Cross Reference for a listing of Micrel devices equivalent to UC284x and UC384x devices.
Selection Guide
UVLO Thresholds
Startup 8.4V Startup 14.5V
Duty Cycle Minimum Operating 7.6V Minimum Operating 9V
0% to 96% MIC38C43 MIC38C42
0% to 50% MIC38C45 MIC38C44
M9999-091107 2 September 2007