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PGA308: part selection and design

user6243139
Prodigy 180 points
Part Number: PGA308

Hello,

I have some questions below. Please confirm these items.

1; Can the PGA308 is used with 6 wire bridge resistor (force sensor)? If yes, do we have any point about this design in this case?

2; Can we use the PGA308's setting value is written(programed) to internal ram from CPU or something when the equipment start up every time? For example, we cannot use the OTP.

* We can use only based on 3.3V power supply now.

3; How many times internal memory's lifecycle?

I apologize for my poor English.

Best regards

KoT

  • 0
    TI__Mastermind 49455 points

    Hi KoT,

    1. The PGA308 is an instrumentation amplifier designed to connect to bridge sensors providing digital calibration for offset, gain and fault detection functions.

    The bridge excitation circuit is external to the PGA308 amplifier.  Therefore, you could design an external excitation circuit for the 6-wire bridge sensor using a couple of operational amplifiers creating the bridge excitation voltage Kelvin connections. The PGA308EVM provides a circuit example for a typical 4-wire bridge sensor (EXC+, EXC-, VIN+, VIN-).   

    2.  It is possible to configure the PGA308 controlled by an MCU overriding the contents of the OTP and writing the PGA308 configuration registers using an MCU.  Please consult the PGA308 User Guide on Chapter 5 for more information on PGA308 operation modes; in particular section 5.7 and 5.8 discussing software mode:

    http://www.ti.com/lit/ug/sbou069b/sbou069b.pdf

    3.  The PGA308 can operate at a supply voltage of 3.3-V (minimum operation is 2.7-V).  However, it is important to emphasize, the PGA308 OTP programming sequence requires a supply larger than VS>4.5V during OTP memory programming to ensure reliable OTP programming.

    The PGA308 offers seven banks of OTP Memory.  The bank select register OTP can only be programmed 4 times; so for practical purposes, the PGA308 OTPs can be programmed a maximum of 4 times.

    Thank you and Regards,

    Luis

  • 0 in reply to Luis Chioye
    Prodigy 180 points

    Hi Luis-san,

    Thank you for your reply.  I will try to continue to design it.

    I have one more question about #3 question. The PGA308 has OTP and RAM. Does the RAM have the specification about the lifecycle?

    Best regards,

    KoT

  • 0 in reply to user6243139
    TI__Mastermind 49455 points

    Hi KoT,

    There is no specification about the lifecycle for RAM; since the RAM is expected to be re-written every time the device is powered up with either the contents programmed on the OTPs or by the MCU/controller in software mode.

    Thank you and Regards,

    Luis

  • 0 in reply to user6243139
    Guru 140200 points

    Hi KoT,

    I don't think that the RAM has a shorter lifetime then the rest electronics of PGA308. This would not make any sense.

    Kai

  • 0 in reply to Luis Chioye
    Prodigy 180 points

    Hi Luis-san,

    I have one more question about the User's guide page 59 Fig. 5-2.  

    Optional RPU is pull up resistor for noise. Can we use pull down resistor here? If yes, is the pull down resistor effect to noise?

    Best regards,

    KoT

  • 0 in reply to user6243139
    Guru 140200 points

    Hi KoT,

    why would you want to use a pulldown resistor?

    Kai

  • 0 in reply to kai klaas69
    Prodigy 180 points

    Hi Kai-san,

    If I can choice pull up or pull down, I want to choice pull down. Because from around circuit and schematics now.

    I can use pull up. So if the resistance need pull up, please tell me that reason.

    Best regards,

    KoT

  • 0 in reply to user6243139
    Guru 140200 points

    Hi KoT,

    I think the pullup is used to assure logic high level.

    Kai

  • 0 in reply to kai klaas69
    TI__Mastermind 49455 points

    HI KoT,

    We recommend the pull-up resistor; and not a pull-down.  The digital 1-wire UART interface is a open drain interface, therefore a pull-up resistor is used where the interface is expected to idle high.  Communication occurs when the master or slave pulls the bus low.

    Thank you and Regards,

    Luis