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Product Attributes

Introduction

ALD810027/ALD910027 are members of the ALD8100xx (quad-channel) and ALD9100xx (dual-channel) Supercapacitor Auto Balancing MOSFET (SAB™ MOSFET) family. SAB MOSFETs are manufactured using production-proven EPAD® technology and are designed to address voltage and leakage current balancing issues in series-connected supercapacitors. Supercapacitors, also known as ultracapacitors or supercaps, are balanced against leakage current by connecting one or more devices in combination across each supercapacitor bank to prevent overvoltage.

As shown in the "Operating Electrical Characteristics" table, the ALD810027 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 ALD910027 provides each of its two SAB MOSFET devices with a unique set of precise operating electrical characteristics, suitable for up to two series-connected supercapacitors.

Each SAB MOSFET features a precise gate threshold voltage in Vt mode, measured at 2.70V 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. Varying VIN produces 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, it balances the voltage and current of each supercapacitor within its limits.

When VIN = 2.70V is applied to the ALD810027/ALD910027, the IOUT is 1μA. When VIN increases by 100mV to 2.80V, IOUT increases approximately 10-fold. For the ALD910027, when VIN further increases to 2.92V (2.94V for the ALD810027), IOUT increases 100-fold to 100μA. Conversely, when VIN decreases by 100mV to 2.60V, IOUT drops to one-tenth of its previous value, i.e., 0.1μA. A further reduction of 100mV in input voltage will bring IOUT down to 0.01μA. Therefore, when the ALD810027/ALD910027 SAB MOSFET is connected across a supercapacitor charged to below 2.50V, it draws essentially no power.

The on-resistance of the ALD810027/ALD910027 exhibits a voltage-dependent characteristic that effectively controls overvoltage rise across supercapacitors when connected in parallel with them. In a series-connected 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 will present complementary, inverse current levels, generating virtually no additional leakage current beyond that produced 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 four supercaps in a single IC package
• Supports 2-cell, 3-cell, and 4-cell series-connected supercap balancing
• Scalable to larger supercapacitor banks and arrays
• Negligible additional leakage current
• Zero leakage current at 0.3V below rated voltage
• Balances series and/or parallel connected supercaps
• Leakage current is an exponential function of individual cell voltage
• Operating current range from <0.3 nA to >1000 μA
• 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
• Maximum voltage limiter in zero-power mode
• Scaled supercapacitor banks and arrays