SN74HC08: SN74HC08NSR

The NS package is out of stock, but not obsolete.

The NS and D footprints are not compatible; the NS package is wider (but this is the only difference). It would be possible to have solder pads that can acommondate both packages, but I doubt that your board was designed this way.

If the supply voltage is 5 V, you can use the SN74HCT08. If you do not rely on the positive clamp diodes at the inputs (i.e., if the input signals are not higher than the supply), you can use the SN74AHC08, and at 5 V, SN74AHCT08.

Hello, 

To confirm and summarize: 

1. SN74HC08NSR is not obsolete, just out of stock on TI.com right now (November 26, 2021). You may create a notification for this device on TI.com by following these instructions. 

https://e2e.ti.com/support/logic-group/logic/f/logic-forum/1018654/faq-how-do-i-set-up-a-ti-com-device-re-stock-notification

2. SN74HCT08NSR is available with TI.com inventory right now for purchase. https://www.ti.com/store/ti/en/p/product/?p=SN74HCT08NSR

This is a footprint compatible version where the only difference is TTL-compatible CMOS inputs vs standard CMOS inputs. 

Its very likely that the HCT device will work perfectly fine in the same system as the HC device, but you can see the detailed differences here: https://e2e.ti.com/support/logic-group/logic/f/logic-forum/862744/faq-what-s-the-difference-between-ttl-and-5v-cmos-logic 

3. There are also other alternates available if you do not need the positive clamp diodes which are available in the NS package.

SN74AHC08 and SN74AHCT08

Best,
Michael