MIC38C44AYM

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