Buck-boost converter offers 1.3x longer battery life

1st February 2018
Alice Matthews


A buck-boost DC/DC converter with built-in MOSFET has been developed by ROHM, featuring what it claims to be the lowest current consumption in the industry. As a result, it is suitable for electronic devices powered by batteries such as electronic dictionaries, remote controls for home appliances, and items such as toys, and other portable electronic devices.

In recent years, the number of portable devices such as smartphones and wearables that incorporate rechargeable batteries (i.e. lithium ion) has risen dramatically. Meanwhile, the adoption of conventional single use batteries in a wide variety of applications is progressing at a rapid pace, increasing the demand for power supply ICs that can provide greater energy savings.

In response, ROHM applied power processes and analogue circuit technologies cultivated over many years to develop power supply ICs that meet market needs. This includes this latest converter optimised for devices powered by single use batteries. The BU33UV7NUX outputs the 3.3V necessary for driving MCUs in applications requiring 1-3V input from 1-2 batteries. Pursuing lower current consumption in order to prolong operating time in battery-equipped devices allowed ROHM to achieve an industry-low current consumption of 7µA (vs functionally equivalent products).

This can extend the operating time by as much as 175 days compared to conventional products, from 540 days to 715 days (ROHM study, 50µA load current and assuming standby operation in conventional remote controls driven by two alkaline batteries). In addition, a load current mode switching function is built in that allows existing remote controls to support the latest high-performance systems equipped with LCD panels, providing greater energy savings in a wide range of applications.

Key features:

1. Low current consumption and low-voltage drive contribute to longer battery life
In order to prolong operating life with single use batteries, ROHM developed original analogue design techniques and power system processes to achieve a current consumption of 7µA, which is supposedly the smallest in the industry among functionally equivalent products. This makes it possible to increase battery life in conventional remote controls typically powered by two alkaline batteries by approx. 1.3x over existing solutions, providing an extra 175 days of operation (ROHM study, assuming standby mode and a load current of 50µA).

In addition, the BU33UV7NUX can be driven by input voltages as low as 0.9V and supports a variety of battery types including lithium, such as the coin cells commonly used. In addition, the built-in battery leak detection function makes it particularly suited for single use battery applications.

2. Load current mode switching improves efficiency in a wide range of applications
A load current mode switching function is included that allows existing remote controls to support the latest high-performance LCD-equipped sets while delivering superior energy savings.

Adopting a low-power mode, Pulse Frequency Modulation (PFM) control, is adopted for 50mA or lower load currents, featuring 7µA current consumption. The BU33UV7NUX automatically switches to its high-power Pulse Width Modulation (PWM) mode for high-performance (500mA max. load current, 13µA current consumption, PFM/PWM switching control), make it possible to achieve high efficiency power conversion as high as 94% under a wide range of conditions.

Target applications:

  • Electronic dictionaries
  • Remote controls
  • Electronic gadgets (i.e. toys, accessories)
  • Wearables 
  • Electric toothbrushes

…and other devices powered by 1-2 single use batteries (1-3V) or single cell Lithium batteries.

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