Microchip | MIC38HC44YN

The MIC38HC44YN family are fixed frequency current-mode PWM controllers with 1 A drive current capability. Micrel’s BiCMOS devices are pin-compatible with 384x bipolar devices. Their high output drive, with fast rise and fall times, combined with low startup current make it an ideal PWM controller where high efficiency is required.

Undervoltage lockout circuitry allows the ’42 and ’44 versions to start up at 14.5 V and operate down to 9 V, and the ’43 and ’45 versions start at 8.4 V with operation down to 7.6 V. All versions operate up to 20 V. When compared to bipolar UC384x devices operating from a 15 V supply, start-up current has been reduced to 50 μA 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 MIC38HC44YN also features a trimmed oscillator discharge current and bandgap reference. MIC38HC4x-1 is available in 14-pin plastic DIP and SOIC packages. 8-pin devices feature small size, while 14-pin devices separate the analog and power connections for improved performance and power dissipation.

Key Features:

• Fast 20 ns output rise and 15 ns output fall times.
• –40°C to +85°C temperature range exceeds UC284x specifications.
• High-performance, low-power BiCMOS Process.
• Ultralow start-up current (50 μA typical).
• Low operating current (4 mA typical).
• High output drive (1 A peak current, HC version).
• CMOS outputs with rail-to-rail swing.
• Current-mode operation up to 500 kHz.
• Trimmed 5 V 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.
• Forward converters.
• Synchronous FET converters.