LTC690/LTC691 and LTC694/LTC695 are chips used for power supply monitoring and battery control in microprocessor systems. They provide functions such as microprocessor reset, battery backup, CMOS RAM write protection, power failure warning, and watchdog timing. They have a precise internal voltage reference and comparator circuit. When an out-of-tolerance condition occurs in the power supply line, the reset outputs are forced to active states and the chip enable output unconditionally write-protects external memory. In addition, the LTC690 series also has a precise voltage monitoring function for power failure or low battery warning. It is an upgrade for the MAX690 series.
This handbook describes the LTC690 family of microprocessor supervisory circuits, which integrate reset, battery backup, power‑failure warning, and watchdog timing functions in a single chip. It explains the internal architecture, pin functions, and operation modes for the LTC690, LTC691, LTC694, and LTC695 devices.
The document provides electrical characteristics, package options, timing diagrams, and application notes such as battery switchover, memory protection, and external watchdog usage. It also includes recommended external components and design guidelines for reliable operation in microprocessor systems.
| Supply Voltage Range (VCC) | 4.75 V – 5.50 V |
|---|---|
| Battery Backup Voltage (VBATT) | 2.00 V – 4.25 V |
| Reset Assertion Voltage | 1 V |