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Document Brief

Custom Silicon Solutions, Inc....

Application Circuits...

CSS555/CSS555C PART DESCRIPTION...

The CSS555 is a micro-power version of the popular 555 Timer IC. It is pin-for-pin compatible with the standard 555 timer and features an operating current under 5 A. Its minimum supply voltage is 1.2V, making it ideal for battery-operated applications. A six-decade programmable counter is included to allow generation of long timing delays. The analog circuits are temperature compensated to provide excellent stability over a wide temperature range. Configuration data for the counter is held in EEPROM. A straightforward four-wire interface provides Read/Write access to the memory. The CSS555C device includes an internal 100pF timing capacitor. Block diagrams of the standard 555 IC and the CSS555C are shown below....

Standard 555 Timer Block Diagram...

CSS555C Block Diagram...

Custom Silicon Solutions, Inc. 2009...

Version 1.0, May 2009...

CSS555(C)...

The following 555 timer circuits have been assembled to help show the advantages of the CSS555C timer. Its advanced features offer unique capabilities that can reduce power, decrease PCB area and eliminate the external timing capacitor. These circuits demonstrate many of the basic 555 timer functions. They can also be used as a starting point to improve existing timer circuits or to develop new ones....

Miscellaneous Notes...

Power Supply Bypassing The original 555 Timer IC's were made using a bipolar technology and required significant power supply bypassing (like early digital TTL ICs). Current spikes during output transitions could exceed 250mA. The CSS555C employs a "break-before-make" CMOS output driver that eliminates these spikes. Minimal supply bypassing is therefore required. A 0.001 uF capacitor is usually adequate for most applications. If a large capacitive load needs to be driven by the Timer Output, a larger bypass capacitor may be required. Control Voltage The Control Voltage input (pin 5) provides access to the upper level trip point. It is derived from a high impedance resistive divider. As with any high impedance node, it should be isolated from sources of DC leakage and high-level clock/data signals that might be capacitively coupled into it. Keep this trace as short as possible. When possible, surround (shield) the Control Voltage signal with an AC ground. In most applications it does not require a bypass capacitor. Stray Capacitance When using the CSS555C,...

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