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Synchronous PWM DC/DC Converter with advanced solutions

Published: 13 February 2017 - Sarah Mead

The R1275 is a new advanced Step-Down Synchronous PWM DC/DC Converter belonging to the current R1270 / R1272 / R1273 flagship series, these products are designed for use in a wide range of consumer, industrial and automotive applications. It has a controller and high- and low-side N-channel MOSFETs assembled in a single package.

There are a number of remarkable features to mention, such as an optional Spread-Spectrum Clock Generator, which causes the oscillator frequency to modulate mildly. As a result, it will decrease EMI noise interference amplitudes considerably, avoiding issues in nearby noise sensitive circuits.

Another advantage of the R1275 is the option to synchronise the oscillator frequency. Especially in case the power supply consists of multiple DC/DC Converters, the independent switching frequencies can result in a significant noise in common ground wiring. By synchronising the oscillator to an external clock signal, one is able to achieve a significant noise reduction in ground wiring.

As for automotive applications, the R1275 has a special feature to respond to a cranking condition. This phenomenon is the drop in the battery voltage when the car engine is started, it may result in an unstable output voltage of power management ICs in general. The R1275 responds by decreasing the oscillator frequency resulting in a constant output voltage level.

The device also features multiple protection circuits contributing to a safe operation of the application. As for excessive output currents, a Hiccup overcurrent protection is available. The circuit will be triggered when the output voltage drops during current limiting and shuts down the IC, protecting it from overheating. The IC will resume automatically to normal operation as soon the fault condition has been released.

A Power-Good output pin provides a fault signal to the system when the device is not ready for regular operation or when any of the protection circuits or states are active.

R1275 Features:

Operating Voltage - 3.6V to 30V
Output Voltage Range - 3.3V to 5.0V
Output Current - Max. 2A
Feedback Voltage Tolerance - 0.64V ±1.0%
Adjustable Oscillation Frequency - 2.0MHz
External Synchronizable Clock Frequency - 1.8 to 2.2MHz
Spread Spectrum Clock Generator Diffusion Rate - Typ. ±8%
Adjustable Soft-start Time - External Capacitor
Power Good Output - NMOS Open-Drain
Safety Circuits - UVLO, OVLO, Thermal, UVD, OVD, Hiccup Over Current Protection
R1275 automotive version - AEC-Q100 compliant
Package - (5.2 x 6.2 x 1.5mm) HSOP-18


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