I have a customer who is trying to use the SN74LVTH16244A. He has the VCC pins tied to 3.3V. He has 5V TTL inputs and he's seeing outputs going to 4.7V, well above the 3.3V supply. Is this to be expected? He expects and wants to see outputs limited to VCC max (about 3.3V max).
The SN74LVTH16244A datasheet indicates that it has these features:
Supports Mixed-Mode Signal Operation (5-V Input and Output Voltages With 3.3-V VCC). The 'LVTH16244A devices are 16-bit buffers and line drivers designed for low-voltage (3.3-V) VCC operation, but with the capability to provide a TTL interface to a 5-V system environment.
Does this "Mixed Mode" result in high output voltages (like 4.7V) with 5V inputs, even with VCC being tied to 3.3V? (These features aren’t described in detail in the datasheet).
If this is normal behavior for the SN74LVTH16244A, would you suggest using the SN74LVC244A instead? Our TI Voltage Level Translation Guide shows how our AHC, AUC, AVC, LV-A and LVC devices can be used for down translation from 5V to 3.3V logic levels, using the SN74LVC244A as an example.
Thanks, David
---------------------------------
David Hildebrand
Analog Field Applications
South Region
Texas Instruments, Inc.
Office: 214-479-0917
Cell: 972-841-6499
david.hildebrand@ti.com
---------------------------------
