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Does anyone know if the msp430 supports 5.0 V in the input ports?

ANDRES RADA
Prodigy 235 points

Other Parts Discussed in Thread: MSP430G2231

Hello there,

I would like to know if the msp430g2231 ports are 5.0V tolerant because I want to connect a 8x2 parallel LCD using the R/W pin. 

I'd appreciate any comments or suggestions about it.

Thanks,

Andres Rada.

  • 0
    TI__Expert 3710 points

    Hi,

    The datasheet for this part specifies a maximum of 3.6V. This part is not 5.0V tolerant.

    Regards,

    Nitya

  • 0
    Guru 227245 points

    ANDRES RADA said:
    I would like to know if the msp430g2231 ports are 5.0V tolerant

    [Looking at the absolute maximum ratings table iin any MSP datasheet]: Yes. As long as the diode current into the pin is kept below 2mA. Well, this won't help you much, I guess :)

    All port pins on every MSP have clamp diodes to VCC and GND. If the applied input voltage exceeds teh MSPs VCC (plus the diode forward voltage), current flows from the port pin to VCC (or GND, for negative voltages). The magnitude of the current is such that the effective voltage on the pin breaks down to VCC+diode voltage.

    Well if the diodes do not melt, then technically, only VCC+0.2V is on the port pin, which is definitely not 5V, so I have to change my answer to a 'technically no': the port pins won't bear 5V. If you manage to keep the voltage on the port pin at 5V, thsi either measn that you have fried the clamp diode and the 5V are causing havoc on the port circuitry, or the clamp diode unexpectedly forwards so much current that either the diode voltage raises or VCC raises due to the excess current.

    In any case, the MSP is likely to not survive this.

    However, if you have a series resistor between the por tpin and the 5V signal, the current only needs to rais so much that the excess voltage appears over the series resistor. Technically, you're no longer applying 5V to the port pin then.

    If you want to connect a 5V INPUT to an MSP output, it depends on the strength of the other sides internal pullup. Usually the pullups will only provide a limited current, so if you connect it to an MSP port, the signal voltage will break down to VCC+0.2V when the port pin is set for high output, and ~0V (of course) if it is set to low output. If VCC+0.2V is still accepted as high by the 5V input, then all is well. If not, you'll need a level translator (e.g. a FET or NPN transistor, which inverts the signal and decouples the voltages)

  • 0
    Guru 227245 points

    ANDRES RADA said:
    I would like to know if the msp430g2231 ports are 5.0V tolerant

    [Looking at the absolute maximum ratings table iin any MSP datasheet]: Yes. As long as the diode current into the pin is kept below 2mA. Well, this won't help you much, I guess :)

    All port pins on every MSP have clamp diodes to VCC and GND. If the applied input voltage exceeds teh MSPs VCC (plus the diode forward voltage), current flows from the port pin to VCC (or GND, for negative voltages). The magnitude of the current is such that the effective voltage on the pin breaks down to VCC+diode voltage.

    Well if the diodes do not melt, then technically, only VCC+0.2V is on the port pin, which is definitely not 5V, so I have to change my answer to a 'technically no': the port pins won't bear 5V. If you manage to keep the voltage on the port pin at 5V, thsi either measn that you have fried the clamp diode and the 5V are causing havoc on the port circuitry, or the clamp diode unexpectedly forwards so much current that either the diode voltage raises or VCC raises due to the excess current.

    In any case, the MSP is likely to not survive this.

    However, if you have a series resistor between the por tpin and the 5V signal, the current only needs to rais so much that the excess voltage appears over the series resistor. Technically, you're no longer applying 5V to the port pin then.

    If you want to connect a 5V INPUT to an MSP output, it depends on the strength of the other sides internal pullup. Usually the pullups will only provide a limited current, so if you connect it to an MSP port, the signal voltage will break down to VCC+0.2V when the port pin is set for high output, and ~0V (of course) if it is set to low output. If VCC+0.2V is still accepted as high by the 5V input, then all is well. If not, you'll need a level translator (e.g. a FET or NPN transistor, which inverts the signal and decouples the voltages)

  • 0
    Guru 17650 points

    Hi Andres,

    well, it's your project, but, why do you want to use the R/W pin? What do you want to read back from the LCD (Busy?)?.

    You may want to have a look at 'My Files' for a schematic and driver example (LCD is in write mode only).

    Rgds
    aBUGSworstnightmare 

  • 0 in reply to Joerg Quinten
    Prodigy 235 points

    Dear aBUGSworstnightmare,

    Very good job. I changed your library to 4-bit mode and works perfectly.

    Thanks for your post and everyone in the forum.

    Andres Rada.

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