Synchronous 34V input buck switching regulator controller

These applications encompass devices such as set-top boxes, media players, Internet gateways, and car infotainment/navigation systems.

The NC2780AK features a broad input voltage range of 4.0 to 34V and an adjustable output voltage from 0.7 to 5.3V. To construct a complete buck switching regulator controller, an additional external high-side and low-side N-Channel MOSFET, along with some passive components, are required. This product offers considerable adaptability to meet diverse application requirements.

Users can adjust the oscillator frequency between 250kHz and 1MHz with an external resistor or synchronise it with an external clock to reduce noise issues common in power supplies with multiple switching regulators. Additionally, phase compensation can be fine-tuned using an external resistor and capacitor, enhancing stability and transient response by mitigating oscillations.

The NC2780AK is designed to maintain high efficiency under both heavy and light loads. It achieves this by automatically transitioning from Pulse Width Modulation (PWM) to Pulse Frequency Modulation (PFM) mode, though a fixed PWM mode is also an option.

Safety is a key feature of the NC2780AK, with built-in protections including thermal shutdown to prevent overheating, and over- and under-voltage detection circuits to safeguard against voltage irregularities. The Under Voltage Lock Out (UVLO) feature ensures operation within a specified voltage range, turning off the output if the input voltage drops too low.

This series also offers a soft-start function, controlling the ramp-up of the output voltage. This timing can be adjusted by adding an external capacitor. In terms of output current limitation, users have the choice between Hiccup and Latched current limit circuits, which protect against excessive output currents. The Hiccup mode allows for automatic restart after an overcurrent condition, whereas the Latched mode requires manual resetting.

Additionally, the NC2780AK includes a Power Good output, signalling when the regulator is functioning within its specified parameters and the output voltage is stable. This is active only when the chip is enabled and after a soft-start.

For automotive applications, a Duty-Over function is incorporated to ensure stable output voltage during events like engine cranking, which can cause significant transient drops in input voltage. In such scenarios, the operating frequency is gradually reduced.

An optional Spread Spectrum Clock Generator (SSCG) function is available to modulate the clock frequency signal, spreading the energy of the clock signal across a range of frequencies. This helps in meeting EMC and EMI regulatory standards, essential in applications where reducing EMI is critical.

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

Specifications NC2780AK

Voltage (Maximum Rating): 4.0 to 34V (36V)

Start-Up Voltage: 4.5V

Output Voltage: 0.7 to 5.3V

Feedback Voltage Tolerance: 0.64V ± 1 %

Quiescent Current: Typ. 15μA (PFM at no load)

Oscillation Frequency: 250kHz to 1MHz

Soft-Start: 500μs (When C_SS is open, adjustable by an external capacitor)

Minimum On-Time: Typ. 100ns

Minimum OFF-Time: Typ. 120ns

Duty-Over: Oscillation Frequency × 1 to 1/4^th

Operating mode: Auto switch mode, Force PWM mode, PLL sync mode

Operating Temperature Range: -40 to 105°C

Optional: SSCG (Spread Spectrum Clock Generator)

Power-Good Output, Anti-Phase Clock Output

Under Voltage Lockout (UVLO) Function: V_CC = Typ. 3.3V

Overvoltage Detection (OVD), Undervoltage Detection (UVD)

Thermal Shutdown: Typ. 160°C

Output Overcurrent Protection: Hiccup mode / Latch mode

Short-Circuit Protection Function: SW to V_IN or GND

Package: HSOP-18-AK (L5.2 x W6.2 x H1.5mm)

Datasheet: Consumer, Industrial, Automotive