MIC38C42/3/4/5 Micrel, Inc. MIC38C42/3/4/5
BiCMOS Current-Mode PWM Controllers General Description Features The MIC38C4x are fixed frequency, high performance, current-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 50ВµA typical
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, especially at lower supply voltages. The MIC38C4x also features
a trimmed oscillator discharge current and bandgap reference.
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 14pin devices separate the analog and power connections for
improved perfomance and power dissipation. 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 …
