ALD’s Specialty Module Aimed at Protecting Ultra-Low-Voltage Designs from Overvoltage DamageOctober 26, 2020 by Gary Elinoff
Advanced Linear Devices’ SABMBOVP family of voltage clamps are designed for systems of 5 volts or less.
Advanced Linear Devices’ (ALD) SABMBOVP circuit board series are designed to protect low-voltage circuits from overvoltage failure. These are all too common hazards caused by transient voltage spikes inherent to electronic circuitry
ALD’s SABMBOVP devices protect vulnerable circuitry from overvoltage through the employment of very low-voltage precision enhancement-mode MOSFETs for improved clamping function. ALD’s EPAD technology was developed specifically for low-power, low-voltage, low-power, highly precise linear applications.
What is EPAD Technology?
ALD’s electrically programmable analog technology (EPAD) is a CMOS based analog methodology that allows for software-based circuit trimming. Up to 100,000 discrete voltage steps, with resolutions as low as 0.1 mV is possible.
EPAD is based on MOSFETs with programmable threshold voltages. The voltage levels are stored permanently, and once programmed, the set voltage and current levels are stored indefinitely inside the device, even with power removed.
Image courtesy of Advanced Linear Devices
Because it is a solid-state technology, the difficulties inherent to potentiometers and other mechanical modalities are avoided.
ALD’s SABMBOVP devices are populated by the ALD9100xx family of EPAD MOSFETs
SABMBOVP vs. Zener Diode Options
The SABMBOVP has a quiescent current of less than 100nA max, significantly less than a low-voltage Zener. It also features more precise voltages than even precision Zeners, and it sports better voltage-versus-current characteristics, too. At less than 100ns, response times also best those of Zeners. Additionally, the ALD units can clamp at voltages far lower than any Zener can.
Surge handling capacity for the SABMBOVP is over 100mA
Most importantly, SABMBOVP is an entirely self-contained unit. In order for a Zener-protected circuit to keep going during a spike, other components, including amplifier buffering and voltage regulator circuits, as well as a resistor divider will be required. As such, use of the SABMBOVP will reduce part count, and as a side benefit also reduce power consumption.
Each ALD Board Contains Two Clamp Voltage Channels
While the channels on each individual board are identical, the two SABMBOVP channels can be connected in series, allowing for different combinations of clamp voltages. In addition, different boards with different voltages can be appended to the stack.
The highly versatile SABMBOVP can be used for a wide variety of purposes
Super Capacitor Balancing
Supercapacitors exposed to more than their rated voltage are likely to fail. In addition, if they are wired in series, exact balancing is essential. As detailed in the SABMBOVP Data Sheet, choosing the right EPAD MOSFET to employ targets the correct voltage for two supercapacitors. More SABMBOVP’s can be connected in series as needed.
The effect is to generate just the right amount of current to keep the voltage at precisely the correct level.
SABMBOVP PCB employed to balance supercapacitors. Image courtesy of SABMBOVP Data Sheet
Supercapacitors are also used in energy harvesting applications. The MOSFETs protect the supercapacitor from high transient energy spurts that can cause damage or degradation. Additionally, energy harvesting often involves sources measured in the microamp range. None of this minuscule amount can be wasted overcoming capacitor leakage or the power dissipation inherent to classical charge balancing circuitry.
The ALD MOSFETs, with their extremely low charge loss and auto-balancing abilities, is a wise choice for this type of application.
Physical and Environmental Facts
Members of the SABMBOVP family measure 0.6 by 1.6 inches
They are RoHS compatible
It operates over the industrial temperature range of -40 to +85℃