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Product Attributes

Introduction

ALD810020/ALD910020 are members of the ALD8100xx (quad-channel) and ALD9100xx (dual-channel) Supercapacitor Auto Balancing MOSFET (SAB™ MOSFET) family. SAB MOSFETs are fabricated using production-proven EPAD® technology, designed to address voltage and leakage current balancing of series-connected supercapacitors. Supercapacitors, also known as ultracapacitors or supercaps, are balanced against leakage current by connecting one or more devices across each supercapacitor cell to prevent overvoltage.

The ALD810020 provides each of its four SAB MOSFET devices with a unique, precise set of operating voltage and current characteristics. It can be used to balance up to four series-connected supercapacitors. The ALD910020 provides each of its two SAB MOSFET devices with its own unique, precise operating electrical characteristics, suitable for up to two series-connected supercapacitors.

Each SAB MOSFET operates in Vt mode with a precise gate threshold voltage of 2.00V when the gate-drain-source terminals (VGS = VDS) are connected together at a drain-source current IDS(ON) = 1μA. In this mode, the input voltage VIN = VGS = VDS. Different VIN levels produce output current IOUT = IDS(ON) characteristics, forming an effective variable resistance whose value varies exponentially with VIN. When this VIN is applied across each series-connected supercapacitor, the voltage and current of each supercapacitor can be balanced within its limits.

When VIN = 2.00V is applied to the ALD810020/ALD910020, its IOUT is 1μA. Increasing VIN by 100mV to 2.10V increases IOUT by approximately 10×. For the ALD910020, a further increase of VIN to 2.22V (2.24V for the ALD810020) increases IOUT by 100×, reaching 100μA. Conversely, reducing VIN by 100mV to 1.90V decreases IOUT to one-tenth of the previous value, i.e., 0.1μA. A further reduction of 100mV in input voltage reduces IOUT to 0.01μA. Therefore, when the ALD810020/ALD910020 SAB MOSFET is connected across a supercapacitor charged to below 1.80V, it consumes essentially no power.

The voltage-dependent on-resistance characteristics of the ALD810020/ALD910020 are highly effective in controlling overvoltage rise across connected supercapacitors. In a series supercapacitor stack, when the voltage across one supercapacitor rises, the voltages across the others fall, with the supercapacitor exhibiting the highest leakage current having the lowest voltage. The SAB MOSFETs connected across these supercapacitors present complementary, inverse current levels, contributing virtually no additional leakage current beyond that generated by the supercapacitors themselves.

Features

• Simple and cost-effective to use
• Factory-precision trimmed
• Automatic regulation and balancing of leakage current
• Effective charge balancing for supercapacitors
• Balance up to 4 supercapacitors per IC package
• Supports balancing of 2-cell, 3-cell, and 4-cell series configurations
• Scalable to larger supercapacitor banks and arrays
• Near-zero additional leakage current
• Zero leakage current at 0.3V below rated voltage
• Balance supercapacitors in series and/or parallel connections
• Leakage current is an exponential function of cell voltage
• Active current range from < 0.3nA to > 1000μA
• Always active with fast response time
• Minimized leakage current and power consumption

Applications

• Series supercapacitor cell leakage current balancing
• Energy harvesting
• Long-term backup battery with supercapacitor output
• Zero-power voltage divider at selected voltage
• Matched current mirrors and current sources
• Zero-power mode maximum voltage limiter
• Extended supercapacitor banks and arrays