­Synchronous 34V Input Buck Switching Regulator Controller


Nisshinbo Micro Devices has launched the NC2780AK series switching regulators intended for consumer, industrial and automotive applications.

Nisshinbo Micro Devices

Nisshinbo Micro Devices has launched the NC2780AK series switching regulators intended for consumer, industrial and automotive applications.


The NC2780AK has a wide input voltage range from 4.0 to 34 V and an externally adjustable output voltage from 0.7 to 5.3 V. An additional external high-side and low-side N-Channel MOSFET and some passive components are required to complete the buck switching regulator controller. The product is highly versatile and can be tweaked in many ways to satisfy the requirements of the application.


The oscillator frequency is adjustable in a range from 250 kHz to 1 MHz using an external resistor, or it can be synchronised with an external clock to minimise common noise issues when using multiple switching regulators in the power supply. The phase compensation can also be adapted through an external resistor and capacitor to ensure stable and reliable operation of the switching regulator by preventing oscillations and improving the transient response.


To maintain the efficiency performance at a high level under heavy and light load conditions, the NC2780AK is able to switch automatically from PWM into PFM mode but can be set in a manually fixed PWM mode as well.


Various built-in safety features are present to protect the system and ensure reliable operation. A thermal shutdown mechanism triggers when the die temperature exceeds a specified threshold to prevent overheating and protect the components from damage. Over- and under-voltage detection circuits detect when the output voltage goes above or below specific thresholds. The regulator will respond accordingly to protect the system from potential damage or unstable operation.


A UVLO feature ensures that the regulator operates within a specified voltage range. If the input voltage falls below the UVLO threshold, the regulator turns off the output to prevent improper operation and protect peripheral devices.


The NC270xMA series offers a soft-start function that controls the timing for the output voltage to reach the set output level after the chip is enabled. By connecting an additional external capacitor, the soft-start time can be adjusted.


As for the output current limitation, a selection can be made between a Hiccup or Latched current limit circuit. These circuits protect against excessive output currents. In the case of a Hiccup current limit, the regulator will try an automatic restart after an overcurrent condition is detected, while a Latched current limit will require manual intervention to reset the circuit.


Furthermore, a Power Good output is included and provides a logic signal when the switching regulator is operating within the specified parameters and the output voltage is stable. The power-good output signal is only valid when the chip is enabled and powered up after a soft-start and all safety circuits and events are in the normal state.


A Duty-Over function is implemented and is common in automotive power electronics, where the power supply must cope with harsh operating conditions. It ensures that the switching regulator can still provide a stable output voltage even during events like engine cranking when the input voltage experiences a significant transient drop. In such a case, the operating frequency is lowered linearly over time until it reaches one-fourth of its set frequency.


An optional function is the Spread Spectrum Clock Generator (SSCG), which intentionally modulates the clock frequency signal. By spreading the energy of the clock signal across a range of frequencies, SSCG can reduce the peak energy at any specific frequency. This helps comply with regulatory standards for electromagnetic compatibility (EMC) and electromagnetic interference (EMI). SSCG techniques are commonly deployed in applications where EMI reduction is crucial.

The NC2780AK is available in consumer, industrial, and automotive versions, and the AEC-Q100 grade 1 qualification is in progress.