Rising Popularity of Flash EPROMs and the MAX732 IC
Despite their more challenging reprogramming process compared to EEPROMs, Flash EPROM are gaining popularity due to their lower cost, higher density, and faster programming speed. To address the reprogramming difficulty, Maxim, a specialized manufacturer of various small converters, has developed a dedicated integrated circuit (IC) called the MAX732. This IC is designed to generate the necessary programming voltage of 12 V at 50 mA.
MAX732: A Comprehensive Solution for Mini Switch-Mode Power Supply
The MAX732 offers a comprehensive solution for creating a mini switch-mode power supply. It operates on a 5 V input voltage and produces a 12 V output, which is required only during programming. The output can be disabled through the shut-down input (pin 1), allowing for efficient power management.
Overcoming Passive Component Challenges with MAX-1.001
One challenge in switch-mode power supply production is the availability of specific passive components, especially the inductor. The Sumida type CD54-470KC, available from various retailers and Maxim dealers as Type MAX-1.001, is utilized here. In cases where these components are unavailable, a triac choke can be used as an alternative, although this may slightly reduce the converter’s efficiency. Adjustments to inductance can be made by adding or removing turns, bearing in mind that inductance is proportional to the square of the number of turns.
Critical Components and Prototyping Considerations
Diode D1 must be a Type 1N5187 or its equivalent; a 1N4001 diode is not sufficient for the task. The prototype successfully delivered a 12 V output and an output current (Io) of up to 200 mA, suitable for powering a flash EPROM. The current drawn from the 5 V supply was approximately 2.4 times Io. To ensure proper grounding and minimize noise, use a single grounding point and directly decouple the IC at its designated points.
An EPROM (rarely EROM), or erasable programmable read-only memory, is a type of programmable read-only memory (PROM) chip that retains its data when its power supply is switched off. Computer memory that can retrieve stored data after a power supply has been turned off and back on is called non-volatile. It is an array of floating-gate transistors individually programmed by an electronic device that supplies higher voltages than those normally used in digital circuits. Once programmed, an EPROM can be erased by exposing it to a strong ultraviolet light source (such as a mercury-vapor lamp). EPROMs are easily recognizable by the transparent fused quartz (or, on later models, resin) window on the top of the package, through which the silicon chip is visible and which permits exposure to ultraviolet light during erasing.