MIC38C42A/43A/44A/45A Micrel, Inc.
MIC38C42A/43A/44A/45A
BiCMOS Current-Mode PWM Controllers
General Description Features
The MIC38C4xA are fixed frequency, high performance, Fast 40ns output rise and 30ns output fall times
current-mode PWM controllers. Micrels BiCMOS devices 40C to +85C temperature range
are pin compatible with 384x bipolar devices but feature meets UC284x specifications
several improvements. High-performance, low-power BiCMOS Process
Ultralow start-up current (100A 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
15V supply, start-up current has been reduced to 50A
Trimmed oscillator discharge current
typical and operating current has been reduced to 4.0mA
UVLO with hysteresis
typical. Decreased output rise and fall times drive larger
Low cross-conduction currents
MOSFETs, and rail-to-rail output capability increases effi-
Applications
ciency, especially at lower supply voltages. The MIC38C4xA
also features a trimmed oscillator discharge current and
Current-mode, off-line, switched-mode power supplies
bandgap reference.
Current-mode, dc-to-dc converters.
The MIC38C4xA family is available in 8-pin SOIC and MSOP- Step-down buck regulators
8 (MM8) package options Step-up boost regulators
Flyback, isolated regulators
Forward converters
For fast rise and fall times and higher output drive, refer to the
Synchronous FET converters
MIC38HC4x.
Functional Diagram
VDD
7
5V
UVLO
VREF
Reference
8
Oscillator
RT/CT OUT
4 6
TQ
FB
2R
2
S
Q
2.5V
R
R
COMP GND ISNS
1 5 3
MIC38C42A, MIC38C43A (96% max. duty cycle) versions only
MIC38C44A, MIC38C45A (50% max. duty cycle) versions only
MM8 is a trademark of Micrel, Inc.
Micrel, Inc. 2180 Fortune Drive San Jose, CA 95131 USA tel + 1 (408) 944-0800 fax + 1 (408) 474-1000 MIC38C42A/43A/44A/45A Micrel, Inc.
Ordering Information
Part Number Temperature
Standard Pb-Free Range Package
MIC38C42ABM MIC38C42AYM 40C to +85C 8-pin SOIC
MIC38C43ABM MIC38C43AYM 40C to +85C 8-pin SOIC
MIC38C44ABM MIC38C44AYM 40C to +85C 8-pin SOIC
MIC38C45ABM MIC38C45AYM 40C to +85C 8-pin SOIC
MIC38C42ABMM MIC38C42AYMM 40C to +85C 8-pin MM8
MIC38C43ABMM MIC38C43AYMM 40C to +85C 8-pin MM8
MIC38C44ABMM MIC38C44AYMM 40C to +85C 8-pin MM8
MIC38C45ABMM MIC38C45AYMM 40C to +85C 8-pin MM8
Refer to the Part Number Cross Reference for a listings 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% MIC38C43A MIC38C42A
0% to 50% MIC38C45A MIC38C44A
M9999-042205 2 April 2005