Super-effective battery power

Designers working on line-powered systems are in luck; whilst wasting power is always bad, a few mA of waste don’t really matter. When working on battery powered systems, every bit of energy helps – an efficient switching regulator can be helpful in various ways.

First of all, the holy grail of battery powered systems is connecting your electronics directly to the battery. Controllers with a wide input range can “float” around the battery voltage, thereby eliminating switching losses completely. Sadly, this is not always possible – LCD modules and various other elements demand fixed voltages or tight voltage ranges.

In this case, a highly efficient voltage regulator can be valuable. Microchip’s MCP1640 boasts with a 96% conversion rate, and furthermore it comes with a power-saving shutdown mode as shown in figure A.

The MCP1640’s external circuitry looks similar to other switching regulators

Due to the high switching frequency – the PWM modules work at 500KhZ – the inductors required are small; their weight is comparable with that of SMD resistors, thereby ensuring “minimal grief” when used in surface-mount form factors.

Focus on the family

Microchip provides designers with a set of power-gating methods which are designated by the letter after the part number. On the B series, the EN pin completely disconnects the output from the power supply – this yields a loss current of less than 1 microampere.

The C and D family, instead, use output bypass. This means that the battery voltage is “passed through” via the FET when the EN pin is used to switch off the regulator – especially useful in cases where the load can also run in a lower-voltage hibernation mode.

Let this table be your guide to the world of the MCP1640

Another, albeit more “esoteric”, difference involves the switching mode used when currents are very low; in principle, Microchip provides a trade-off between higher efficiency and lower ripple.

Part Number PWM/PFM PWM-Only True Disconnect Input to Output Bypass
MCP1640 X   X  
MCP1640B   X X  
MCP1640C X     X
MCP1640D   X   X

This product can, for example, be used to isolate OLED modules and their driver circuitry from low-power parts of the system.

Author: Tam Hanna
Published: March 12, 2021