Article ID: 000085908 Content Type: Troubleshooting Last Reviewed: 04/18/2015

Do Altera device input buffers have built-in Schmitt triggers?

Environment

BUILT IN - ARTICLE INTRO SECOND COMPONENT
Description

In cases where a digital device input comes from a noisy source (e.g., a switch) or a slow edge rate, a Schmitt trigger is used to introduce hysteresis to the input signal. However, such hysteresis causes slower performance, higher power consumption, and higher silicon cost.

The device families that offer optional Schmitt triggers on the input buffers for user I/O pins are the MAX® II and MAX V device families. For other device families, if a Schmitt trigger is necessary, Altera® recommends using an external Schmitt trigger device.

Joint Test Action Group (JTAG) pins are not speed-critical, so Schmitt triggers that are added for noise resistance do not impact system performance. Refer to the respective device handbook or datasheet to see if the devices have Schmitt triggers on the JTAG inputs.

For example, the following ISP capable device families offer Schmitt triggers on the JTAG programming pins: MAX II, MAX 7000AE, MAX 7000B, MAX 3000A.

The following ISP capable device families do not have Schmitt triggers on the JTAG programming pins: MAX 7000S and 7000A (non-AE).

 

Related Products

This article applies to 1 products

Intel® Programmable Devices