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Product Attributes

Introduction

ALD810018/ALD910018 are members of the ALD8100xx (quad-channel) and ALD9100xx (dual-channel) series of Supercapacitor Auto Balancing MOSFETs (SAB™ MOSFETs). 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, when connected in series, can achieve leakage current balancing by connecting one or more devices across each supercapacitor bank to prevent overvoltage.

The ALD810018 provides each of its four SAB MOSFET devices with a unique, precisely matched set of operating voltage and current characteristics, suitable for balancing up to four series-connected supercapacitors. The ALD910018 provides each of its two SAB MOSFET devices with a unique set of precision operating electrical characteristics, suitable for up to two series-connected supercapacitors.

Each SAB MOSFET features a precise gate threshold voltage in Vt mode, defined as 1.80V when the gate-drain-source terminals are connected together (VGS = VDS) and the 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 rated limits.

When VIN = 1.80V is applied to the ALD810018/ALD910018, IOUT is 1μA. If VIN increases by 100mV to 1.90V, IOUT increases approximately 10×. For the ALD910018, if VIN further increases to 2.02V (2.04V for the ALD810018), IOUT increases 100× to 100μA. Conversely, if VIN decreases by 100mV to 1.70V, IOUT drops to one-tenth of its previous value, i.e., 0.1μA. A further 100mV reduction in input voltage will bring IOUT down to 0.01μA. Therefore, when the ALD810018/ALD910018 SAB MOSFET is connected across a supercapacitor charged to below 1.60V, it consumes essentially no power.

The voltage-dependent on-resistance characteristics of the ALD810018/ALD910018, when connected across a supercapacitor, effectively control excessive voltage rise across the supercapacitor. In a series-connected supercapacitor bank, when one supercapacitor's voltage rises, the voltages of the other supercapacitors decrease, with the supercapacitor exhibiting the highest leakage current showing the lowest voltage. The SAB MOSFETs connected across these supercapacitors exhibit complementary, opposing current levels, introducing 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 supercapacitor charge balancing
• Balance up to 4 supercapacitors per IC package
• Balances 2-cell, 3-cell, and 4-cell series-connected supercapacitors
• Scalable to larger supercapacitor banks and arrays
• Near-zero additional leakage current
• Zero leakage at 0.3V below rated voltage
• Balances series and/or parallel connected supercapacitors
• Leakage current is an exponential function of cell voltage
• Active current range from <0.3nA to >1000μA
• Always active with consistently 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
• Maximum voltage limiter in zero-power mode
• Scalable supercapacitor banks and arrays