Maxim's Microprocessor Supervisor Circuits Provide Battery Backup and CE Gating

Their high integration simplifies designs and minimizes the number of components required for power-supply monitoring. The MAX16016/20/21/23/24 are ideal for a wide variety of applications such as point-of sale (POS) terminals, industrial equipment, fax machines, computers, and set-top boxes.

To protect critical data, these devices automatically switch the real-time clock (RTC) or RAM power source to the backup battery when Vcc falls below the reset threshold and Vbatt. A reset output asserts when Vcc is below the reset-threshold voltage and for at least 145ms after Vcc returns above its threshold. This reset output prevents code-execution errors during power-up, power-down, and brownout conditions. Each device offers an active-low, push-pull reset or an active-low, open-drain reset. A power-fail comparator signals an interrupt when Vpfi falls below 590mV or when Vcc falls below the reset threshold.

The MAX16016/20/21/24 include a battery-on output during battery-backup mode; the MAX16016/20/21 also include a watchdog function that triggers a reset pulse whenever WDI remains high or low for longer than the watchdog-timeout period. The MAX16020/21/24 provide internal gating of the CE signals to prevent erroneous data from corrupting the CMOS RAM. The MAX16023/24 integrate a low-dropout regulator capable of delivering up to 100mA; a manual-reset input; and a user-adjustable reset input for monitoring a second voltage.