Minimum voltages range across 1.5 to 2V – see table.
Manufactured in the industry standard DPAK surface mount package, these Industry First devices are
“This technology is a distinct innovation in current limiting device technology,” said Central engineering v-p Joseph Beck. Compared to traditional current regulating devices, the CDCLD series of devices provides designers with a discrete solution for current regulation that is virtually independent of ambient temperature variations when operated within the specified voltage range.”
Rather than being JFET-based, the devices are built using mosfet structure (diagram right).
It is a mosfet with gate and source on the same side, and shorted to form the device cathode. Gate terminal and gate passivation are is sandwiched between two source terminals, and the passivation contacts the device body and p-type regions that surround the source terminals. The drain terminal is on the opposite side of the device.
Positive potential applied to the drain terminal forms an n-channel in the p-type between the sources and gate passivation, allowing electrons to flow from the sources, through the P-type to the body of the device. With a few volts on the drain, the depletion region expandea enough to regulate current flow – due
to the height of the channel being decreased, lowering the pinch-off voltage of the device.
By placing the drain terminal directly opposite the gate-source, vertical charge carrier movement is induced for the electrons that have just moved to drift region, and this large drift region is able to withstand the thermal stress generated by electron flow – removing the free-hole-generation that compromises JFET constant current diodes as they heat and reducing temperature coefficient (left).
The highest current version, CDCLD500, has a limiting voltage of 0.9V and reaches its nominal current at 2V applied (right).
Central compares this with a 350mA JFET constant current diode with a limiting voltage of 1.9V that reaches its nominal
current at 5V. “Using this data, it can be determined
that the mosfet-based diode limiting voltage occurs at an
applied voltage that is only 54% of the required JFET limiting
voltage. Similarly, the pinch-off of the MOSFET-based CLD occurs at an applied voltage that is only 40% of the required JFET pinch-off voltage.
Central’s mosfet-based constant current diodes:
- CDCLD025 – (27.5mA, 1.5V)
- CDCLD040 – (44mA, 1.5V)
- CDCLD080 – (88mA, 1.8V)
- CDCLD100 – (115mA, 2.0V)
- CDCLD120 – (138mA, 2.0V)
- CDCLD200 – (230mA, 2.0V)
- CDCLD400 – (460mA, 2.0V)
- CDCLD500 – (575mA, 2.0V)
Bare die versions are planned.
Applications are foreseen in ideal for industrial and consumer LED lighting systems, as well as test and measurement.
The current limiting mosfet diode product page is here, and Central’s clear and interesting document on the technology is well worth a look.