LMG708B0

The LMG708B0 is a GaN synchronous buck DC/DC converter offered from a family of devices that provide ultra-high current density and excellent power conversion efficiency. The integrated low RDS(on) GaN FETs with near-zero dead-time switching performance enable up to 20A of output current across a wide input voltage range from 5V to 65V (with transients to 80V).

Phase stackable with synchronized interleaving, the peak current-mode architecture of the LMG708B0 supports accurate current sharing with paralleled phases for even higher output current. Along with constant-voltage (CV) operation, a dual-loop architecture with shared compensation provides constant-current (CC) regulation for battery charging and other current-source type loads. This cohesive approach enables a seamless transition between CV and CC modes, and high accuracy for voltage (±1%) and current (±4.5%) regulation, effectively reducing the bill-of-materials (BOM) cost for applications that require average output current control. VSET and ISET inputs facilitate dynamic adjustment of the respective CV and CC loop setpoints, and an IMON output provides average output current monitoring.

The LMG708B0 has a thermally enhanced package (TEP) with optional top-side cooling (TSC) through exposed package connections and low package parasitic inductance for quiet switching performance.

A high-side switch minimum on-time of 25ns facilitates large step-down ratios, enabling the direct conversion from 24V or 48V inputs to low-voltage rails for reduced system design cost and complexity. The LMG708B0 continues to operate during input voltage dips as low as 5V, at close to 100% duty cycle if needed. The 20µA sleep quiescent current with the output voltage in regulation extends operating run-time in battery-powered systems.

The LMG708B0 includes several features to simplify compliance with CISPR 11 and CISPR 32 conducted emissions requirements. Predictably timed GaN FET gate drivers along with integrated bootstrap switch and capacitor minimize deadtime during switching transitions, reducing switching losses and improving EMI performance at high input voltage and high switching frequency. To reduce input capacitor ripple current and EMI filter size, interleaved operation using a SYNCOUT signal with programmable phase shift works well for cascaded, multichannel or multiphase designs. Resistor-adjustable switching frequency as high as 2.2MHz can be synchronized to an external clock source up to 2.64MHz to eliminate beat frequencies in noise-sensitive applications. Finally, the LMG708B0 has dual-random spread spectrum (DRSS), a unique EMI-reduction feature that combines low-frequency triangular and high-frequency random modulations to mitigate EMI disturbances across lower and higher frequency bands, respectively.

Additional features of the LMG708B0 include 135°C maximum case temperature operation, user-selectable PFM mode for lower current consumption during light-load conditions, integrated bootstrap capacitor with synchronous charging for robust level shifting, open-drain power-good (PG) indicator for fault reporting and output monitoring, precision enable input for input UVLO, monotonic start-up into prebiased loads, dual-input VCC bias subregulator, 30mV full-scale current sensing, hiccup-mode overload protection, and thermal shutdown protection with automatic recovery for the controller.

The LMG708B0 comes in a 4.5mm × 6mm, thermally enhanced, 22-pin eQFN package using a flip-chip routable leadframe (FCRLF) packaging technique. Leveraging high-performance GaN power FETs (based on TI’s proprietary GaN IC technology), thermal management and EMI mitigation features, CC/CV operation, and small design size, the LMG708B0 represents an excellent point-of-load regulator choice for applications requiring the most efficient GaN design with useable current, lifetime reliability, and cost advantages.