Electronic Design

Small Mixed-Signal Memory Chip Packs A Large Punch

Dallas Semiconductor/Maxim brings the memory shopping mall to you. With a 2-kbit (256 by 8) EEPROM, 12 user-programmable I/O channels, a real-time clock/calendar/alarm, CPU reset monitor, 64-bit factory-programmed ROM ID, battery monitor, and watchdog timer, the DS28DG02 (see figure) offers one-stop shopping.

The I/O channels may be configured as inputs, outputs, open drains, or push-pulls. The EEPROM registers allow the I/Os to power up in a defined state. If your system includes a battery backup, the DS28DG02 "actively" monitors the "health" of the battery by applying a 10-µA (typical) test load with a 1-second duration to the battery each hour. It then follows with a programmable battery terminal voltage comparison to a programmable test point. An interrupt output is generated if the terminal voltage is below the programmed threshold.

The voltage monitor is factory-programmed to generate a 328-ms (typical) reset at 3.3 V, with a 2.5% accuracy threshold over the operating range. The monitor's reset output can also be used as a pushbutton I/O with debounce. The watchdog is user-programmable with timeout options ranging from 0.2 to 1.64 s (typical).

Since the device replaces four or more discrete ICs, Dallas Semiconductor estimates it will typically save around 20% printed-circuit-board (PCB) space and reduce bill of materials costs by about 30%. If you consider the overall hardware design aspects of a discrete implementation, typical complications include multidevice bus interfacing, power-supply bypass filtering, and increased PCB layout effort. Communications with the device are performed via the serial peripheral interface (SPI).

All this can be yours for only $1.81 in quantities of 1000. The device is available in a small thin-shrink small-outline package (TSSOP) or quad flat no-lead (QFN) package.

Dallas Semiconductor

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