ALD810030/ALD910030 are new members of the ALD8100xx (quad-channel) and ALD9100xx (dual-channel) Supercapacitor Auto Balance MOSFET (i.e., SAB™ MOSFET) series. SAB MOSFETs are fabricated 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, when connected in series, can achieve leakage current balancing by connecting one or more devices across each supercapacitor bank to prevent overvoltage.
The ALD810030 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 ALD910030 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 has a precise gate threshold voltage in Vt mode, which is 3.00V when the gate-drain-source terminals (VGS = VDS) are connected together at drain-source current IDS(ON) = 1μA. In this mode, input voltage VIN = VGS = VDS. Different VIN values produce output current IOUT = IDS(ON) characteristics, forming an effectively variable resistance whose value varies exponentially with VIN. When VIN is connected across each series-connected supercapacitor, it can balance the voltage and current of each supercapacitor within its limits.
When VIN = 3.00V is applied to the ALD810030/ALD910030, IOUT is 1μA. When VIN increases by 100mV to 3.10V, IOUT increases approximately tenfold. For the ALD910030, when VIN further increases to 3.22V (3.24V for the ALD810030), IOUT increases one hundredfold to 100μA. Conversely, when VIN decreases by 100mV to 2.90V, IOUT drops to one-tenth of its previous value, i.e., 0.1μA. A further 100mV decrease in input voltage will reduce IOUT to 0.01μA. Therefore, when the ALD810030/ALD910030 SAB MOSFET is connected across a supercapacitor charged to below 2.80V, it consumes virtually no power.
The voltage-dependent characteristics of the ALD810030/ALD910030 on-resistance are highly effective in controlling overvoltage rise when connected across supercapacitors. In a series-connected supercapacitor bank, when the voltage of one supercapacitor rises, the voltages of the other supercapacitors decrease, and the supercapacitor with the highest leakage current has the lowest voltage. The SAB MOSFETs connected across these supercapacitors exhibit complementary inverse current levels, generating virtually no additional leakage current beyond that produced by the supercapacitors themselves.
Advanced Linear Devices ALD910030SALI