The present invention relates generally to integrated circuit (IC) design, and more particularly to voltage down converter for externally programming memories.
In a deep submicron technology for a typical IC chip, device feature sizes, such as gate oxide thickness and channel length, have greatly reduced. In order to work with such small geography devices, the power supply voltage have to be lowered, otherwise the gate oxide may breakdown and the transistor channel may punch through. For instance, for a 90 nm technology, the power supply voltage is about 1.0V. However, in a system level, i.e., outside the IC chip, a power supply voltage may still be 2.5V or 3.3V. In order to allow such deep submicron IC chip to properly work in the high voltage system, voltage down converters have to be employed to convert an external high voltage power supply to a predetermined internal low voltage power supply.
In case of one-time-programmable (OTP) memory, a programming voltage from an external source also needs to be converted to a lower internal programming voltage. Conventionally, a voltage reference is used in this voltage down converting. However, due to high peak driving current requirement, the conventional voltage down converter may take up a large layout area. Besides, the conventional voltage down converter is more complicated to design. As different customers may have different voltage requirements, OTP memories that use the conventional voltage down converter will require longer design cycles. Even though the conventional voltage down converter using the reference voltage approach provides good accuracy, it is often an over kill for the OTP memory programming application.
As such, what is desired is a simple and effective voltage down converter fits the OTP memory programming application.
The present invention discloses a voltage down converter for programming a one-time-programmable (OTP) memory which comprises a bonding pad for coupling to a programming power supply, and at least one forward biased diode coupled between the bonding pad and the OTP memory, wherein a programming voltage received by the OTP memory is lowered from the programming power supply by the voltage drop across the forward biased diode, which is about 0.75V. According to one aspect of the present invention, the diode is formed by a lateral P-N junction. According to another aspect of the present invention, the diode is formed by a gate-and-drain shorted NMOS or PMOS transistor.
The construction and method of operation of the invention, however, together with additional objectives and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.
The drawings accompanying and forming part of this specification are included to depict certain aspects of the invention. A clearer conception of the invention, and of the components and operation of systems provided with the invention, will become more readily apparent by referring to the exemplary, and therefore non-limiting, embodiments illustrated in the drawings.
The present invention discloses a voltage down converter that employs forward biased diodes to provide a certain amount of voltage drop. This voltage down converter is particularly fit for programming one-time-programmable (OTP) memories, as in that application accuracy is less of a concern but small layout area is much more desirable for low cost, and simplicity shortens design cycle.
During a programming of the OTP memory 120, an external high voltage power source is applied at the programming power supply bonding pad 102. The voltage down converter 110 converts the high voltage to a desired low voltage that is then supplied to the OTP memory 120.
Referring again to
The above illustration provides many different embodiments or embodiments for implementing different features of the invention. Specific embodiments of components and processes are described to help clarify the invention. These are, of course, merely embodiments and are not intended to limit the invention from that described in the claims.
Although the invention is illustrated and described herein as embodied in one or more specific examples, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims. Accordingly, it is appropriate that the appended claims be construed broadly and in a manner consistent with the scope of the invention, as set forth in the following claims.
This application claims the benefits of U.S. Provisional Patent Application Ser. No. 61/057,503, which was filed on May 30, 2008, and entitled “DIODE AS VOLTAGE DOWN CONVERTER FOR OTP HIGH PROGRAMMING VOLTAGE APPLICATIONS.”
Number | Date | Country | |
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61057503 | May 2008 | US |