ELM412

Elm Electronics – Circuits for the Hobbyist

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Pin Descriptions

Ordering Information

These integrated circuits are available in either the 300 mil plastic DIP format, or in the 200 mil SOIC surface

mount type of package. To order, add the appropriate suffix to the part number:

300 mil Plastic DIP............................... ELM412P

200 mil SOIC..................................... ELM412SM

2 of 4

Absolute Maximum Ratings

Storage Temperature....................... -65°C to +150°C

Ambient Temperature with

Power Applied....................................-40°C to +85°C

Voltage on any other pin with

Note:

Stresses beyond those listed here will likely damage

the device. These values are given as a design

guideline only. The ability to operate to these levels

is neither inferred nor recommended.

All rights reserved. Copyright ©1999 Elm Electronics.

Every effort is made to verify the accuracy of information provided in this document, but no representation or warranty can be

given and no liability assumed by Elm Electronics with respect to the accuracy and/or use of any products or information

described in this document. Elm Electronics will not be responsible for any patent infringements arising from the use of these

products or information, and does not authorize or warrant the use of any Elm Electronics product in life support devices and/or

systems. Elm Electronics reserves the right to make changes to the device(s) described in this document in order to improve

reliability, function, or design.

This pin is the positive supply pin, and should

always be the most positive point in the circuit.

Internal circuitry connected to this pin is used to

provide power on reset of the microprocessor, so

an external reset signal is not required. Refer to

the Electrical Characteristics section for further

information.

F2 (pin 2), F1 (pin 3) and F0 (pin 4)

These are the frequency select inputs. One of

eight frequencies are selected according to the

logic levels on these pins, as shown in Table 1.

Enable (pin 5)

This schmitt trigger input pin is used to control

the output. A high level at this input will allow the

outputs to appear at pins 6 and 7, while a low

level inhibits the output. The schmitt trigger input

is convenient for interfacing to slowly changing

signals, as from an RC coupled circuit.

Out2 (pin 6) and Out1 (pin 7)

These complementary outputs are used to drive

the piezo-electric element through a current

limiting resistor. The outputs switch between Vdd

and

Vss

with

a

combined

duty

cycle

of

approximately 67% (see Figure 2). This results

in reduced harmonics in the output signal and

more energy to the fundamental. The output

always consists of complete cycles, as the cycle

that is in progress when the enable input goes

low will always be allowed to complete.

Circuit common is connected to this pin. This is

the most negative point in the circuit.

ELM412DSB