Simple-to-use auto-balancing for supercaps

Advanced Linear Devices (ALD) offers a universal PCB designed to automatically balance leakage currents and manage overvoltage, enabling ultra-low-power usage in supercapacitors used in a series stack. The board uses ALD’s SAB MOSFETs (SABMB16, SABMB8100XX, SABMB9100xx) to balance the leakage current in each individual supercapacitor cell from 0.1 F to 3,000 F. It is designed to allow system engineers to test, evaluate, prototype, or use for in-production products.

Supercapacitor balancing is required by cell manufacturers when used in stacks of two or more. Balancing manages overvoltage limits, a main cause of product failures.

The balancing technology reduces leakage current, enabling ultra-low-power operation. Each device in the ALD8100XX/ALD9100XX SAB MOSFETs provides a circuit design alternative for passive or active balancing methods by offering automatic active leakage current regulation and space and cost-saving alternatives to op-amp-based balancing schemes.

Engineering testing shows that the ALD method of cell balancing extends the product life of stacked caps. Applications for supercaps and this cell-balancing technique include energy harvesting, transportation, backup power, and automation.

SABMB16/SABMB810025/SABMB910025 are universal application boards. The first two versions in the series are SABMB810025 and SABMB910025. These are 2.5-V universal boards allowing designers to select either the ALD810025 SAB MOSFETs or the ALD910025 SAB MOSFETs for installation. A third version is unpopulated to allow engineers to select the appropriate SAB MOSFETs based on their design specifications. All three options are delivered ready to use, designed for balancing any size of supercapacitors with little power dissipation. No user circuit design or hardware engineering is necessary.

Importantly, the charging or discharging of supercapacitor currents pass through the supercapacitors but do not pass through the SABMB16 boards or SAB MOSFETs mounted on the PCB board. In many cases, the total additional leakage current contributed by the PCB is approximately zero, or no more than a small percentage of the highest supercapacitor cell leakage current in the stack. This contrasts with other methods of balancing in which the additional power dissipation used by the balancing circuitry far exceeds the supercapacitor power burn caused by its own leakage current.

The SABMB16 is designed for ease of use as a plug-and-play PCB for supercapacitors of 0.1 F to 3,000 F. The average additional power dissipation due to dc leakage of the supercapacitor is zero, which makes this method of supercapacitor balancing energy-efficient and suited for low-loss energy-harvesting and long-life battery-operated applications.