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Product Attributes

Introduction

ALD810022/ALD910022 are members of the ALD8100xx (quad-channel) and ALD9100xx (dual-channel) supercapacitor Auto-Balance MOSFET (SAB™ MOSFET) series. SAB MOSFETs are fabricated using production-proven EPAD® technology, designed to address voltage and leakage current balancing issues in series-connected supercapacitors. Supercapacitors, also known as ultracapacitors or supercaps, balance leakage current by connecting one or more devices across each supercapacitor bank to prevent overvoltage.

The ALD810022 provides each of its four SAB MOSFET devices with a unique, precisely defined set of operating voltage and current characteristics. It can be used to balance up to four series-connected supercapacitors. The ALD910022 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 has a precise gate threshold voltage in Vt mode. When the gate-drain-source terminals are connected together (VGS = VDS), this voltage is 2.20V at a drain-source current of IDS(ON) = 1μA. In this mode, input voltage VIN = VGS = VDS. Different VIN values produce output current IOUT = IDS(ON) characteristics, forming an effective variable resistance whose value varies exponentially with VIN. When this VIN is connected across each series supercapacitor, each supercapacitor can be balanced within its voltage and current limits.

When VIN = 2.20V is applied to the ALD810022/ALD910022, IOUT is 1μA. When VIN increases by 100mV to 2.30V, IOUT increases approximately 10-fold. For the ALD910022, when VIN further increases to 2.42V (2.44V for the ALD810022), IOUT increases 100-fold to 100μA. Conversely, when VIN decreases by 100mV to 2.10V, IOUT drops to one-tenth of its previous value, i.e., 0.1μA. A further 100mV decrease in input voltage reduces IOUT to 0.01μA. Therefore, when the ALD810022/ALD910022 SAB MOSFET is connected across a supercapacitor charged to below 2.00V, it consumes essentially no power.

The voltage-dependent characteristics of the ALD810022/ALD910022 on-resistance are highly effective in controlling overvoltage rise when connected across supercapacitors. In a series supercapacitor stack, when the voltage across one supercapacitor rises, the voltages across the other supercapacitors decrease, with the supercapacitor having the highest leakage current exhibiting the lowest voltage. The SAB MOSFETs connected across these supercapacitors will present complementary inverse current levels, generating virtually no additional leakage current beyond that caused by the supercapacitors themselves.

Features

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

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