SN74LVC1G373: Clocked latch

Ofer Braitbart

Part Number: SN74LVC1G373
Other Parts Discussed in Thread: SN74LVC1G175, SN74HCS74

Hello,

How can I perform the 74LVC1G373 or other suitable device as a clocked latch as LE behave more like a pass throuh must support low current consumption.

required functionality:

On power up Q output =Low.
On latch pulse Q will go High
On non active latch input, Q output holds the High output (i.e. LE shall perform as a rising clock.)

I'm not sure that 74LVC1G373 on power up Q output is Low

over 2 years ago

0 Owen Westfall over 2 years ago

TI__Expert 7511 points

Hi Ofer,

Please see [FAQ] What is the default output of a latched device? (Flip-Flop, latch, register). Unless you can provide the signals D - H LE - H OE - L before power on the device then there is no way to know what the state would be in.

For your latch pulse If your pulse is tied to LE then while it is high You would need to force D to be high during the duration until the latch goes low again (If D goes low first it will hold low)

Then whenever your latch pulse is not high the output would hold that value from before it changed.

All values obtained from this truth table in the Datasheet

Regards,

Owen

0 Ofer Braitbart over 2 years ago

Prodigy 20 points

Hi Owen,
Thanks for your answer but I was aiming of using the device as clocked latch (transaction and not level) like a DFF
Data sheet schematic seems like LE is the clock input but actually it behaves as a level control.
Best regards,
Ofer

0 Clemens Ladisch over 2 years ago

Guru 276230 points

Use a flip-flop like the SN74LVC1G175 (with D = high).

Use the /CLR input to initialize/reset it. (If you do not have a reset signal, you can use an R-C circuit to generate a low pulse on power up, but then you should use a device with Schmitt-trigger inputs like the SN74HCS74.)

0 Ofer Braitbart over 2 years ago in reply to Clemens Ladisch

Prodigy 20 points

Thanks !

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SN74LVC1G373: Clocked latch