Linear's 42V latest triple synchronous step-down converter delivers 93% efficiency



LT8601 42V input capable high-efficiency triple-output synchronous monolithic step-down switching regulator

Linear Technology announced the LT8601, a 42V-input capable, high-efficiency triple-output synchronous monolithic step-down switching regulator. Its triple-channel design combines two high voltage 2.5A and 1.5A channels with a lower voltage 1.8A channel to deliver three independent voltage outputs as low as 0.8V. Its synchronous rectification topology delivers up to 93% efficiency while Burst Mode® operation keeps quiescent current under 30µA (all channels) in no-load standby conditions, ideal for always-on systems. For noise sensitive applications, the LT8601 can utilize its pulse-skipping mode to minimize switching noise and it meets the CISPR25, Class 5 EMI requirements. Switching frequency can be programmed from 250kHz to 2.2MHz and is synchronizable throughout this range.

The LT8601’s 60ns minimum on-time enables 16VIN to 0.8VOUT step-down conversions while switching at 2MHz, enabling designers to avoid critical noise-sensitive frequency bands, such as AM radio, while using a very compact solution footprint. Its 3V to 42V input voltage range is ideal for automotive applications which must regulate through cold-crank and stop-start scenarios with minimum input voltages as low as 3V and load dump transients in excess of 40V. Each channel of the LT8601 maintains a minimum dropout voltage of only 250mV at 1A under all conditions, enabling it to excel in scenarios such as automotive cold-crank. Programmable power-on reset and power good indicators for each channel ensure overall system reliability. The LT8601’s 40-lead thermally enhanced 6mm x 6mm QFN package and high switching frequency keeps external inductors and capacitors small, providing a compact, thermally efficient footprint.

The LT8601 utilizes triple internal top and bottom high efficiency power switches with the necessary boost diodes, oscillator, control and logic circuitry integrated into a single die. Channel 1 switches 180° out-of-phase with channels 2 and 3 to reduce output ripple. Each channel has a separate input for added design flexibility, but most applications will run the low voltage channel directly from one of the two high voltage channels to offer a very simple, high frequency triple output design. Low ripple Burst Mode operation maintains high efficiency at low output currents while keeping output ripple below 15mVP-P. Unique design techniques and a new high speed process enable high efficiency over a wide input voltage range, and the LT8601’s current mode topology enables fast transient response and excellent loop stability. Other features include internal compensation, power good flags, output soft-start/tracking, short-circuit and thermal protection.

The LT8601 is available in a thermally enhanced 40-lead 6mm x 6mm QFN package. Two temperature grades are available, with operation from -40°C to 125°C junction for the extended E and industrial I grades. The industrial grade’s electrical parameters are guaranteed throughout the -40°C to 125°C junction temperature range. The 1,000-piece price starts at $5.15 each. All versions are available from stock. 

Summary of Features: 
Flexible Power Supply System Providing Three Outputs Over a Wide Input Voltage Range
Two High Voltage Synchronous Buck Regulators
3V to 42V Input Voltage Range
Output Currents up to 2.5A & 1.5A
High Efficiency up to 93%
One Low Voltage Synchronous Buck Regulator
2.6V to 5.5V Input Voltage Range
Output Current up to 1.8A & 95% Efficiency
Resistor Programmable & Synchronizable from 250kHz to 2.2MHz Switching Frequency
Low Ripple Burst Mode® Operation:
30µA IQ at 12VIN to 3.3VOUT2
Output Ripple < 15mV
Programmable Power-On Reset
Power Good Indicators
2-Phase Clock Reduces Input Current Ripple
Available in Thermally Enhanced 40-Lead QFN 6mm x 6mm Package


Linear Technology