نیمه‌هادی‌ گسسته ترانزیستور با کاربرد ویژه

Product Attributes

Introduction

ALD810017/ALD910017 are members of the ALD8100xx (quad-channel) and ALD9100xx (dual-channel) Supercapacitor Auto Balance MOSFET (SAB™ MOSFET) family. SAB MOSFETs are fabricated using production-proven EPAD® technology, designed to address voltage and leakage current balancing in 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 ALD810017 provides each of its four SAB MOSFET devices with a unique, precisely matched set of operating voltage and current characteristics. It can be used to balance up to four series-connected supercapacitors. The ALD910017 provides each of its two SAB MOSFET devices with a unique set of precisely matched electrical operating characteristics, suitable for up to two series-connected supercapacitors.

Each SAB MOSFET features a precise gate threshold voltage in V_t mode, defined as 1.70V when the gate-drain-source terminals are connected together (VGS = VDS) at a drain-source current of IDS(ON) = 1μA. In this mode, the input voltage VIN = VGS = VDS. Varying VIN produces an output current IOUT = IDS(ON) characteristic, forming an effective variable resistance whose value varies exponentially with VIN. When VIN is connected across each series supercapacitor, the voltage and current of each supercapacitor can be balanced within its rated limits.

When VIN = 1.70V is applied to the ALD810017/ALD910017, IOUT is 1μA. When VIN increases by 100mV to 1.80V, IOUT increases approximately tenfold. For the ALD910017, when VIN further increases to 1.92V (1.94V for the ALD810017), IOUT increases one-hundredfold to 100μA. Conversely, when VIN decreases by 100mV to 1.60V, IOUT drops to one-tenth of its previous value, i.e., 0.1μA. A further 100mV reduction in input voltage brings IOUT down to 0.01μA. Therefore, when the ALD810017/ALD910017 SAB MOSFET is connected across a supercapacitor charged to below 1.50V, it draws virtually no power.

The voltage-dependent on-resistance characteristics of the ALD810017/ALD910017 are highly effective in controlling overvoltage rise across connected supercapacitors. 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, opposing current levels, drawing negligible additional leakage current beyond that already 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
• Single IC package balances up to 4 supercapacitors
• Supports balancing of 2, 3, or 4 series-connected supercapacitors
• Scalable to larger supercapacitor banks and arrays
• Near-zero additional leakage current
• Zero leakage current at 0.3V below rated voltage
• Balances supercapacitors in series and/or parallel configurations
• Leakage current is an exponential function of cell voltage
• Active current range from <0.3nA to >1000μA
• Always active with fast response time
• Minimizes 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