Microchip | MIC38C45YN

The MIC38C45YN 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 14.5 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 20V.

When compared to bipolar 384x 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 MIC38C45YN also features a trimmed oscillator discharge current and bandgap reference. MIC38C45YN denotes 8-pin plastic DIP, SOIC, and MM8™ packages. MIC38C4x-1 denotes 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. For fast rise and fall times and higher output drive, refer to the MIC38HC4x.

Key Features:

• Fast 40 ns output rise and 30 ns output fall times.
• –40°C to +85°C temperature range meets UC284x specifications.
• High-performance, low-power BiCMOS Process.
• Ultralow start-up current (50 µA typical).
• Low operating current (4 mA typical).
• CMOS outputs with rail-to-rail swing
• >= 500 kHz current-mode operation.
• 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.