SN74LS624: Crystal connection method and internal circuit

user6165533

Part Number: SN74LS624

What is the circuit for connecting a crystal oscillator to the CX1 and CX2 pins of SN74LS624?

(1) Is there any problem in connecting a capacitor (30pF) between the CX1 and CX2 pins and GND to stabilize oscillation? Use Vcc = OSCVcc = RNG = FREQ CONT = DC5V (fixed). The crystal is 8MHz and the internal resistance is 16pF.

(2) This is a question when the capacitor connection in (1) cannot be recommended. There is a concern that oscillation margin and negative resistance will be lower than the manufacturer's recommended values, and oscillation cannot be started. I would like any advice on this point.
(3) Please disclose the internal circuit of SN74LS624.

over 4 years ago

0 Karan Kotadia over 4 years ago

TI__Genius 16725 points

Hi,

Hello and welcome to the E2E forums. This part belongs to the LS family which is one of our oldest parts that we support. I am not sure on the internal circuitry to help answer this question. I believe there should not be a problem connecting the 30pF capacitors that you have shown but I cannot guarantee that. The fastest way to find out would be to order some samples and test the device.

Thanks!

-Karan

0 user6165533 over 4 years ago in reply to Karan Kotadia

Prodigy 20 points

Karan, thank you for your answer. As a result of the test, it works without problems.

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SN74LS624: Crystal connection method and internal circuit