On/off logic IC
• 8 accurate Schmitt trigger inputs with clamp circuits
• Very low quiescent current
• Reset generator circuit
• Changed information output
• On/off output to control a regulator IC which supplies the
• 32.768 kHz RC oscillator and/or a 32.768 kHz crystal
• No delayed reset needed (start-up behaviour oscillator
fixed by internal logic)
• Watchdog timer function
• Blinking LED oscillator with drive circuit for LED
• Watch function.
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 (master) is
running and the SAA1305T acts like a slave.
2. Sleep mode of the total application: the microcontroller
is stopped and the SAA1305T acts like a master.
During an event, the microcontroller is awakened.
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.
QUICK REFERENCE DATA
quiescent supply current
maximum SCL clock frequency
virtual junction temperature
VDD = 5 V; standby mode −
plastic small outline package; 24 leads; body width 7.5 mm
2004 Jan 15