New Industry Products

Maxim’s Two Way Regulator Targets Supercapacitor-Based Backup

June 10, 2021 by Gary Elinoff

The bidirectional, 2.5V-to-5.5V buck/boost regulator features 94% peak efficiency in a compact form factor.

While outside power is flowing, the MAX38889 “bucks” the system voltage down to a level appropriate to charge a backup supercapacitor. When the power is gone, the regulator “boosts” the supercapacitor’s stored charge back up to the system’s optimal voltage level to power the system, until outside power is again available.

Image courtesy of Maxim
Image courtesy of Maxim


The MAX38889 supercapacitor backup regulator functions to transfer power between a system supply rail and the supercapacitor tasked for backup. When the main power source is available, the MAX38889 charges the supercapacitor with an average current of 1.5A.

When the main power is temporarily not present, the MAX38889 draws from the energy now stored in the supercapacitor. The energy is used to supply the system with its predetermined voltage level, with a maximum peak inductor current of 3A. 


Maxim’s Commitment 

“Maxim’s Continua family of backup voltage regulators uses advanced switching regulator design to deliver bi-directional buck/boost featuring tight output regulation that minimizes space while increasing power efficiency,” said Anil Telikepalli, managing director of the Core Products Group at Maxim Integrated. “This is the third product from our Continua line as Maxim strives to enable always-on applications by solving the design engineer’s toughest backup power challenges.” 


Electrical Specifications

The MAX38889 is the newest member of the company’s Continua backup regulator family. The device is user programmable for maximum supercapacitor charging voltage, system backup voltage, peak charging, and peak backup inductor currents. System voltages over a range of from 2.5 to 5.5 volts are possible, as are supercapacitor voltage ranges of from 0.5 to 5.5 volt.

While the external system voltage is present and the supercapacitor is fully charged the MAX38889 draws 4µA, which is enough to maintain the supercapacitor in its charged state. 

Simplified application diagram for the MAX38889. Image courtesy of Maxim’s Datasheet
Simplified application diagram for the MAX38889. Image courtesy of Maxim’s Datasheet


The MAX38889 switches at 1.2 MHz and offers 94% peak efficiency, fully 9% higher than the closest competitive solution. Additionally the unit is also only one-third the size of the competition, a great advantage for today’s space-constrained designs.

Backup status is monitored by the RDY and BKB pin, with the former indicating that the supercapacitor is charged while the latter signaling that backup is in progress. If desired, backup can be disabled by driving the ENB pin low, and charging can similarly be prevented through a low input on the ENC pin.



The MAX38889 can serve to regulate backup power for both portable and non-portable applications. These include:

  • Handheld Industrial Equipment 
  • Industrial Sensor and Actuators 
  • Portable devices
  • Retail price scanners
  • Surveillance cameras
  • Remote IoT nodes 


Physical Considerations

  • The MAX38889 is available in a 3 x 3 mm, 16-Pin TQFN Package.
  • The device operates over a -40 to +125°C temperature range, with current capacity derating of 23.1mW/°C at temperatures above +70°C.


Getting to Market Faster

The MAX38889EVKIT evaluation kit is available to enable designers to study the function of the MAX38889.

The MAX38889AEVKIT. Image courtesy of Maxim
The MAX38889AEVKIT. Image courtesy of Maxim

This developmental aid provides a flexible platform from which to evaluate the full range of the MAX38889’s capabilities.