One time programmable
One Time Programmable (OTP) is a term used in electronics. An OTP component is a programmable electronic component that contains a non-volatile memory ( PROM ). However, this memory can only be written to once. Depending on the design of the component, a programming device mayalso be required. There are now a large number of components that are also manufactured using OTP technology.
The OTP technology can basically be implemented as fuse technology or as antifuse technology . When the OTP components are manufactured by the semiconductor manufacturer , for example with the antifuse technology, all connection points are open; the relevant connection points are only connected through programming.
However, there are also “fake” OTP memories, which are implemented as so-called “OTP areas” in certain flash memories. These memory areas usually consist of normal flash cells, which are protected against changes by additional logic.
Areas of application
The OTP technology can be used for the following components, for example.
- PLAs ( Programmable Logic Array ) - a rewritable version of this are GALs
- FPGAs ( Field Programmable Gate Array ) - also available reprogrammable
Individual OTP areas also exist in certain components, such as, for example, flash memories, smart cards and microcontrollers, whereby these serve to permanently store serial numbers or other identification data. An example of this is the IMEI of most modern cell phones.
The advantage of the OTP technology is that the circuit function of the programmed components cannot be changed (i.e. not even unintentionally). Compared to components with mask programming , the use of OTP components in the production of assemblies makes it possible to react to changes in the data content at short notice.
In terms of practical circuit design, however, the OTPs have decisive disadvantages which must be taken into account when developing the circuit. Once programmed and once installed on a module, the logic function of this component can only be changed by replacing the component (= unsoldering the old component from the circuit board and soldering the new component onto the circuit board or removing it from the socket). A function expansion, as is customary today, for example, through a software update or when a circuit change is made to the logic function in other programmable logic components, is generally not possible with the OTP components.
Furthermore, the scope of an error in the function or in the programming of the OTP components must not be underestimated. The more extensive the circuit function, the greater the risk that the function contains an error that cannot be found even with the development tests. In extreme cases, a malfunction can result in the end customer removing the device and changing it by the manufacturer.