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The SAA1305T is an on/off logic IC, intended for use in car radios to interface between a
microcontroller and various input signals such as ignition, low supply detection, on/off
key and external control signals.
The SAA1305T can replace an existing on/off logic built-up with discrete components.
The SAA1305T contains 8 inputs with accurate Schmitt triggers and clamp circuits. The
main function of this IC is an intelligent I/O expander with 2 modes of operation:
- 1. Normal I/O expander: the microcontroller (leader) is running and the SAA1305T acts
like a follower.
- 2. Sleep mode of the total application: the microcontroller is
stopped and the SAA1305T acts like a leader. During an event, the microcontroller is
The communication with the IC is performed via the I²C-bus (400 kHz). Extra functions of
the SAA1305T are:
- LED blinker circuit
- One-day watch
- Watchdog timer.