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