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SN74LVC244A: SN74LVC244A

Part Number: SN74LVC244A
Other Parts Discussed in Thread: SN74LVC16244A, SN74LVC245A, SN74AHCT244, TXU0204, TXU0102, TXU0101, TXU0304, TXU0104, TXU0202,

Hi,

Please see below queries and request you to suggest

Query1: Regarding 8 Bit Buffer IC SN74LVC244ARGYR , do you have similar one with 16 bit ?  

TSSOP package is also fine in 16 bit i.e. Similar to 8 bit SN74LVC244APW

Query 2:  Can you please suggest 8 bit bidirectional Buffer ICs whose inputs are tolerant to 5V or above ?

Please reply soon as possible.

Regards,

Puspam Nayak

  • 1. SN74LVC16244A

    2. Bidirectional buffers are called transceivers and have the number 74xxx245, e.g., SN74LVC245A.

  • Thank you Clemens for the information. SN74LVC16244A looks good.  

    Need to check SN74LVC245A, I was planning to replace below TXB0108PWR with SN74LVC245A however not sure if SN74LVC245A will solve the purpose because B side is 5V and A side is 3.3V 

    Regards,

    Puspam

  • To convert from 3.3 V to 5 V, you do not need a buffer but a level shifter.

    What are the directions of the eight signals? Why don't you want to use the TXB?

  • Hi Clemens, 

    Was looking to simplify the design by using Buffer whose inputs are 5V tolerant. In the case of Unidirectional signals usage of SN74LVC16244A is fine (inputs are Vi =5.5V tolerant, Vo= Vcc = 3.3V) however for Bidirectional signals I believe usage of TXB is appropriate. 

    Regards,

    Puspam

  • To convert unidirectional signals from 3.3 V to 5 V, you could also use a buffer with TTL-compatible inputs, e.g., SN74AHCT244. (This optimizes for price, not for BOM simplicity.)

    If you have unidirectional signals in different directions, the best choice would be a combination of TXU translators (TXU0104/TXU0204/TXU0304/TXU0102/TXU0202/TXU0101).

    For bidirectional signals (without a direction control signal), you have to use the TXB.

  • In my design most of the signals are from 5V to 3.3V so planned to go with SN74LVC16244A, SN74LVC244A.

    Can you please confirm if selections of these Buffers between ADC LTC1605AISW#PBF and FPGA Spartan 7 is okay? FPGA IOs is configured as LVTTL Inputs 

  • These buffers are OK for the signals output by the ADC (Dxx and /BUSY).

    For /CS, R/C, BYTE, you need to translate up. If you want a single chip for all four ADC control signals, the TXU0304 would match; if you have more signals, separate SN74LVC244A and SN74AHCT244 (or similar) would be fine.

  • Control signals are being driven by FPGA's IO pins, so these control signals are of 3.3V i believe.  Referred datasheet of ADC also, below screenshots of ADC datasheet (Part no. LTC1605AISW#PBF)

    Wish you very Happy New Year in advance :)

    Best Regards,

    Puspam Nayak

  • The /BUSY signal goes in the other direction, so you have 3 and 1 in each direction (when looking only at the four control signals.)

  • Yes, 'Busy' signal (Unidirectional) going to FPGA input Pin so in my previous block diagram have shown that i will be using. SN74LVC244A i.e. 8-bit buffer between ADC and FPGA. Attaching the screenshot again, check left side of block diagram BUSY. Other 3 i.e. CS, R/C, BYTE will be controlled by FPGA.

  • Yes, this will work.