DESCRIPTION

The MC14600 Alarm IC is designed to simplify the process of interfacing an alarm level voltage condition to a piezoelectric horn and/or LED. With an extremely low average current requirement and an integrated low battery detect feature, the part is ideally suited to battery operated applications. The MC14600 is easily configured with a minimum number of external components to serve a wide range of applications and circuit configurations. Typical applications include intrusion alarms, moisture or water ingress alarms, and personal safety devices.

APPLICATION

DEVICE OPERATION

Timing

The internal oscillator of the MC14600 operates with aperiod of 1.65 seconds during no-alarm conditions. Each1.65 seconds, internal power is applied to the entire IC and a check is made for an alarm input level except during LED pulse, Low Battery Alarm Chirp, or Horn Modulation (in alarm). Every 24 clock cycles a check is made for low battery by comparing VDD to an internal zener voltage. Since very small currents are used in the oscillator, the oscillator capacitor should be of a low leakage type.

Detect Circuitry

If an alarm condition is detected, the oscillator period becomes 41.67 ms and the piezoelectric horn oscillator circuit is enabled. The horn output is modulated 167 ms on, 83 ms off. During the off time, alarm detect input (Pin 15) is again checked and will inhibit further horn output if no alarm condition is sensed. During alarm conditions the low battery chirp is inhibited, and the LED pulses at a 1.0 Hz rate. An active guard is provided on a pin adjacent to the detect input (Pin 16). The voltage at this pin will be within 100 mV of the input signal. Pin 16 will allow monitoring of the input signal at pin 15 through a buffer. The active guard op amp is not  power strobed and thus gives constant protection from surface leakage currents. Pin 15 (the Detect input) has internal diode protection against static damage.

Low Battery Threshold

The low battery voltage level is set internally by a voltage divider connected between VDD and VSS. This voltage can be altered by external resistors connected from pin 3 to either VDD or VSS. A resistor to VDD will decrease the threshold while a resistor to GND will increase it.

Alarm Threshold (Sensitivity)

The alarm condition voltage level is set externally through

FEATURES

• High Impedance, FET Input Comparator

• Comparator Outputs for Low Battery and Alarm Detect

• Alarm Detect Threshold Easily Established with 2 Resistors

• Integrated Oscillator and Piezoelectric Horn Driver

• Low Battery Trip Point Set Internally (Altered Externally)

• Horn “Chirp'' During Low Battery Condition

• Pulsed LED Drive Output

• Reverse Battery Protection

• Input Protection Diodes on the Detect Input

• Average Supply Current: 9 μA

• Pb-Free Packaging Designated by Suffix Codes ED and EG

SPECIFICATION

RELEVANT POPULAR RESEARCHES

PICTURE

MC14600P image