SN74AHC1G14: What are the differences in electrical characteristics among different screen prints?

user6481287

Part Number: SN74AHC1G14
Other Parts Discussed in Thread: TLV9030

Tool/software:

When using SN74AHC1G14 as the trigger output PWM control output current; The deviation of the products with silk-screen printing of 38SH is much greater than that of the products with silk-screen printing of A14S, A14J and A14F. Moreover, the output frequency and output duty cycle of 38SH vary greatly. The attachment is the schematic diagram and the test record of the cross-test. How should kissing be resolved? A total of 1,000 units were produced, among which about 200 units were abnormal

3377.不同丝印的74AHC1G14在F2-AO3-V1.1A产品上的对比测试-20250603.xlsx

4 months ago

0 Clemens Ladisch 4 months ago

Guru 317480 points

The switching thresholds of logic Schmitt-trigger inputs are not very well specified; they are designed to handle logic signals with slow edges, not for precise analog signals. The change was likely introduced by PCN#20230927000.1, but both old and new devices are inside the datasheet limits.

If you care about the frequency and duty cycle, then you have to use a comparator (e.g., TLV9030) and configure the amount of hysteresis yourself.

0 user6481287 4 months ago

Intellectual 970 points

The switching threshold is somewhat different, but it should not cause a significant change in the frequency of PWM. What causes such a large change in frequency?

0 user6481287 4 months ago in reply to Clemens Ladisch

Intellectual 970 points

The switching threshold is somewhat different, but it should not cause a significant change in the frequency of PWM

0 Clemens Ladisch 4 months ago in reply to user6481287

Guru 317480 points

The frequency is affected by the amount of hysteresis, and the ΔV_T range is specified as 0.35 V…1.4 V.

0 Malcolm Lyn 4 months ago in reply to user6481287

TI__Mastermind 26670 points

Here's the formula for a Schmitt trigger oscillator. Frequency varies with the hysteresis value.

Best,

Malcolm

0 user6481287 3 months ago in reply to Malcolm Lyn

Intellectual 970 points

At present, the screen printing of A14S and A14J can meet the requirements, but 38SH cannot meet the precision. May I ask what the similarities are between A14S and A14H? For example, is it the same as a wafer fabrication plant?
Can we all use products with the A14 silk-screen printing prefix to replace each other in the future?

0 Clemens Ladisch 3 months ago in reply to user6481287

Guru 317480 points

In the future, all devices will use the new die. You have to change the circuit.

0 user6481287 3 months ago in reply to Clemens Ladisch

Intellectual 970 points

Which silk-screen printing uses a new die?

0 Malcolm Lyn 3 months ago in reply to user6481287

TI__Mastermind 26670 points

Parts from RFAB will be have like this. You need to look at the shipping label to determine which lots are from RFAB.

0 user6481287 3 months ago in reply to Malcolm Lyn

Intellectual 970 points

May I ask how to confirm the FAB version number through the shipping label? Will the main shipments in the future be 38SH? Will the A14 be gradually discontinued?

0 Malcolm Lyn 3 months ago in reply to user6481287

TI__Mastermind 26670 points

The top marking tells you what AT site the device came from, but not the FAB version. So, you can still get a device with either top marking unpredictably.

The shipping label will say something like "CSO: RFB" on it. This tells you the device is from RFAB and not SFAB. Devices from RFAB are on the new die. Here is an example picture:

Logic

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SN74AHC1G14: What are the differences in electrical characteristics among different screen prints?