X2Bit Bitcell

A new programming method yields 10X power reduction


The X2Bit™  Bitcell Technology

The X2Bit bitcell retains the configuration of the existing bitcell in the current XPM™, Gusto-2™, and SecretCode™ OTP products.  However, using a patented new programming method, the new bitcell achieves a much lower turn-on voltage, the voltage at which the “1” memory bitcell generates current to distinguish itself from the “0” bitcell.  For example, in the 55nm technology, popular for IoT devices, traditional Kilopass OTP bitcells have a typical turn-on voltage of more than 1V. With the X2Bit bitcell, the turn-on voltage that is much lower than 1V. As a result, Kilopass products employing the X2Bit bitcell would operate with core voltage supplies as low as 0.75V that are used in the emerging Ultra-Low-Power (ULP) process technologies from semiconductor manufacturers.

The patent-pending X2Bit bitcell has been silicon proven since Q2 2015, and its use in the macro-level Gusto™ product line will be optimized for extremely low-power Internet of Things (IoT) devices in Q1 2016. The X2Bit bitcell achieves 10 times power reduction without having to change any bitcell architecture, topology, or layout, which means it can go right to the market and deliver the benefits to our licensees without years of field trial and validation.

Implementation Benefits

The X2Bit bitcell is ideally suited for next-generation IoT devices that demand less than 10uA/MHz in read currents. Currently available eNVM technologies typically consume 100uA/MHz under comparable operating conditions. The X2Bit bitcell lowers the turn-on voltage by optimizing the programming condition. This patent-pending implementation results in a more ohmic programming of the N-MOS transistor with controlled locality toward the source, drain region rather than in the middle of the channel.

Benefits are twofold. First, since power consumption is directly proportional to the square of operating voltage, lowering the read voltage by two-thirds would result in tenfold power reduction. Equally important, with lower turn-on voltage, the memory macro would be able to operate at the same operating voltage as the rest of the chip, without resorting to power consuming charge pumps and voltage regulators.


Kilopass has completed the mini-array test vehicle of the X2Bit bitcell in a 65nm manufacturing process technology. The first product, likely the next-generation Gusto, using the X2Bit bitcell will tape-out in Q1, 2016.  Pricing is available upon request.

For more information about taking advantage of the X2Bit bitcell, contact info@kilopass.com.