The MC34129/MC33129 are high performance current mode switching regulators specifically designed for use in low power digital telephone applications. These integrated circuits feature a unique internal fault timer that provides automatic restart for overload recovery. For enhanced system efficiency, a start/run comparator is included to implement bootstrapped operation of VCC. Other functions contained are a temperature compensated reference, reference amplifier, fully accessible error amplifier, sawtooth oscillator with sync input, pulse width modulator comparator, and a high current totem pole driver ideally suited for driving a power MOSFET.

Also included are protective features consisting of soft–start, undervoltage lockout, cycle–by–cycle current limiting, adjustable deadtime, and a latch for single pulse metering.

Although these devices are primarily intended for use in digital telephone systems, they can be used cost effectively in many other applications.

• Current Mode Operation to 300 kHz

• Automatic Feed Forward Compensation

• Latching PWM for Cycle–by–Cycle Current Limiting

• Continuous Retry after Fault Timeout

• Soft–Start with Maximum Peak Switch Current Clamp

• Internally Trimmed 2 Bandgap Reference

• High Current Totem Pole Driver

• Input Undervoltage Lockout

• Low Startup and Operating Current

• Direct Interface with Motorola SENSEFET Products