Boasting gate currents of up to 2A, Microchip’s recently-introduced MCP14700 MOSFET driver is an effective and inexpensive way to implement high-efficiency DC-DC buck converters for today’s high-powered processor chips, larger FPGAs, and in some BLDC motor drive applications. Although Microchip did not mention it, I suspect that it might also be great for helping supply power to some of today's higher-powered FPGAs.  It is a follow-on to their MCP14700 which has been on the market about a year. Both devices come in compact SOIC and 3 mm x 3 mm DFN Packages, and are designed specifically to drive newer, faster MOSFETs which have 5V gate voltages. They also both have a an auto-disable that turns off the gate drivers when their PWM inputs are tri-stated, allowing standby power to drop to sub-uAmp levels for an exceptionally “green” standby mode.

The big difference between the two drivers is that the ‘14700 has independent controls for the high-side and low-side gate drives and several other features that allow it to be used with either a fixed-function PWM generator (typically their MCP1630 or a microcontroller (most likely one of their dsPICs). Software control of each leg of the switch gives you the freedom to tinker with the dead time and other parameters at the expense of a slightly more complexity design but the extra effort is repaid by the added efficiency and flexibility it buys you. This means that you’ll have to use software to implement the FCCM (forced continuous conduction mode) mode that’s implemented in hard logic on the MCP14628 to support efficient low-power operation. Software control also opens up the option of running a single leg of the converter or even dropping out PWM phases during extremely low-power operation.

There are several similar converters on the market but Microchip says that the ‘14700 is the only one that directly accepts the low-voltage (3V) logic levels used by many PICs and microcontrollers. This makes it a natural fit with their 16-bit sPIC processors which feature basic signal processing capabilities and lots of practical I/O connections at the price you’d expect to pay for a basic PIC. I guess that’s why I was so surprised to learn that Microchip does not have a reference design or reference software available at this time.

Don’t get me wrong - I think that most power designers are capable of rolling their own code and will probably want to tweak any canned packages they get to meet their specific needs but a reference design is always a handy place to start. And, given the fact that a software glitch could easily result in turning on both the high and low legs of the switch, a little bit of proven code would be good insurance against a small, but annoying, lab fire. Fortunately, Microchip says that they have an evaluation board and some reference code in the works for both a DC-DC converter and a 3-phase motor drive – although they declined to say when it would b e available.

Device Packaging, Pricing & Availability

The MCP14628 and MCP14700 MOSFET drivers are available in 8-pin SOIC and 3 mm x  3 mm DFN packages, for $1.17 and $1.33 each respectively, in 10,000-unit quantities. 

Click here to see data sheets for the MCP147000 MOSFET driver.

Click here to see data sheets for the MCP14628 MOSFET driver.

Click here to see an application circuit of a Digital DC-to-DC Converter featuring the MCP14700

Click here to see an application circuit of a 3-Phase BLDC Motor Application Circuit featuring the MCP14700

Click here to order samples of the MCP14700. 

Click here to place volume-production-quantity orders of the MCP 14700. .