2.4MHz DC-DC buck regulator has low quiescent power
Allegro MicroSystems has launched a DC-DC buck regulator with a low quiescent current for ‘always on’ applications.
The ARG81800 has a quiescent current of 8μA and includes all the control and protection circuitry to produce a PWM regulator with ±1.5 percent output voltage accuracy. There are two versions available, handling 500 mA and 1 A, so the physical size of the power components can be optimized for lower current systems, reducing PCB area and saving cost. PWM switching frequency can be programmed over a wide range to balance efficiency, component sizing, and EMC performance. If VIN decays and the duty cycle reaches its maximum, the ARG81800 will automatically fold back its PWM frequency to extend the duty cycle and maintain VOUT.
The ARG81800 employs a Low-Power (LP) mode to maintain the output voltage at no load or very light load conditions while drawing only micro-amps from VIN, as well as a a PWM/AUTO control pin so the system can dynamically force either PWM or AUTO mode by setting this pin high or low, respectively.
The 150°C operating temperature supports automotive or industrial operating conditions, and the chip includes the ability to handle pin open/short and component faults.
EMI is reduced by using spread spectrum frequency modulation (dithering) to a non-dithered external SYNC clock as well as providing a dithered clock output to be used for other converters in the system. It uses a wide switching frequency up to 2.4 MHz to avoid frequency bands such as the AM band, as well as frequency dithering and slew rate control to minimise switching noise. It also offers unique “dithering-on-sync” CLKOUT, which can be used for other switching converters in the system.
“The ARG81800 is at the forefront of technology,” said Mark Gaboriault, Marketing Director at Allegro. “The features that we have added solve real-world challenges for our customers.”
The DC-DC buck regulator draws 8 μA, from VIN while regulating 3.3V or 5.0 Vout at no load. In comparison to the 100 μA typically budgeted for battery-powered subsystems, the low quiescent power frees up significant overhead to be allocated to other current draws that may occur in the system, allowing more design margin.
“The onus of passing EMC has historically been solely on our customer,” he said. “We embraced the opportunity to offer solutions that make it easier for our customers to meet their EMC requirements, including reference designs and design notes.”
Pin opens and pin shorts happen, but the design of the ARG81800 protects against IC and PCB damage during manufacturing and eliminates associated scrap costs. The 150°C Tj operating capability makes the ARG81800 suitable for harsh underhood and industrial automation applications. A power-good output signal with rising-edge makes system power sequencing easier and provides diagnostic coverage.
Other protection features of the DC-DC buck regulator include pulse-by-pulse current limit, hiccup mode short circuit protection, BOOT open/short voltage protection, VIN undervoltage lockout, VOUT overvoltage protection, and thermal shutdown.
The ARG81800 is supplied in a low profile 20-pin wettable flank QFN package with exposed power pad. Samples and evaluation boards are available.
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