Wide-input voltage range regulators target infotainment applications

April 19, 2016 // By Christoph Hammerschmidt
Automotive infotainment systems are a particularly demanding application field for power supplies: A wide input voltage range combines with the need for high transient resilience and very low quiescent current. Allegro Microsystems Europe has developed two new DC/DC step-down switching regulator chips that meet exactly these requirements.

The two new products – A8586 and A8587 – both feature an integrated high-side power MOSFET.  The A8586 provides up to 3.5 A output current; while the A8587 has output current of up to 2.0 A.  Both devices are AEC-Q100 qualified and incorporate current mode control for fast transient response. The wide input range of 3.8 V to 36 V makes both devices suitable for a wide range of step-down applications, including those in an automotive input environment.  Battery driven “keepalive” applications benefit from the low 30 µA operational quiescent current.


Both devices are designed to robustly handle a load dump condition with 40 V maximum rating as well as idle-stop and cold crank conditions with 3 V UVLO rating.


These new regulators maintain high-efficiency across a wide range of loads in the PWM mode and incorporate pulse frequency modulation (PFM) as the load reduces. This in turn reduces switching and gate driver losses at light loads. Both the A8586 and A8587 incorporate frequency fold back to help prevent inductor current runaway during startup and provide enhanced dropout performance.  Extensive safety and robust protection features include, pulse-by-pulse current limit, hiccup mode short circuit protection, open/short freewheeling diode protection, BOOT open/short voltage protection, VIN under-voltage lockout, and thermal shutdown. The A8587 also has a Negative Power On Reset (NPOR) function to indicate in-regulation and out-of-regulation status. 


The A8586, A8586-2 and A8587 are designed to aid in EMC performance by including frequency dithering, soft freewheel diode turn off, and well controlled switch node slew rates. A 4MHz oscillator allows the devices to switch outside EMI sensitive frequency bands such as the AM band or ADSL bands. The A8586-1 disables the frequency dithering feature. The A8586-1 and A8586-2 devices are options that disable the PFM function.  


Both A8586 and A8587 are targeted at the automotive and industrial markets, including applications such as infotainment, centre stack and instrument clusters,