If anyone goes to use the TL7705 part they should make sure to read the data sheet fully. This part is not just a drop in "three terminal" reset component. Use of this component will require the use of additional other components in conjunction with the TL7705.

Of particular note:

1) As with any part this one should be bypassed with a capacitor on the Vcc to GND pins.

2) This part has open collector outputs such that the RESET pin will require a pull down resistor and the NOT_RESET pin will require a pull up resistor.

3) The part has an internal VREF connection that it is advisable to bypass with an external capacitor.

4) The reset time period of the part is established by an external capacitor that needs to be provided as a connection on the CT pin.

5) If the auxillary NOT_RESIN pin is to be used for a reset switch connection a pullup resistor will be required on this pin.

The diagram below is a quick reference to show what is inside the TL7705 part.



I bring these items up in discussion because the TL7705 is a very flexible part that can be adapted and adjusted to fit many design situations. It can even be used to sense a supply voltage that is different from the normal VCC line. (Or you could even use two chips and monitor the VCC bus and another voltage too and then wire-or the two chips outputs together).

All that said however, readers here should be aware that the additional components that one one puts around the TL7705 chip may make it attractive to look at other alternative parts that may cost a little more. In some designs the lower component count solution may be more suitable. If one looks through the web pages of Maxim/Dallas, TI, Microchip and others it is possible to find three terminal VCC voltage supervisor/reset generator chips, that can be used with your particular microcontroller, without the use of additional components beyond the normal VCC bypassing.

Michael Karas