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Nicholas Gray

Nicholas has worked in the Semiconductor industry for over 30 years and has authored a number of published articles about data converters (ADCs and DACs) and signal integrity issues.

 

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  • in reply to Former Member
    I am sorry, but I am not sure just what kind of "help" you need because the part types are indicated on the schematic. U1 is a "7805" type linear regulator, U2 is a "MAX232", J2 is what is known as a "DB9" connector which is used for RS-232RS-232 interfaces and J1 appears to be a header to connect to whatever is sending and receiving data over the RS-232RS-232 port.

    The 7805 comes in TO-3, TO-220, TO-263 and SOT-223 packages. I believe that any of these packages would be satisfactory, but the SOT-223 and TO-263 packages MIGHT not handle the power requirements of this circuit (max 105mW) without care in how it is mounted. See the data sheet for proper mounting considerations. The TO-220 package should have no problems with power dissipation. Furthermore, I would prefer the LM340 because its specification shows a a little tighter tolerance on the output voltage. Data sheet is at http://www.national.com/ds/LM/LM340.pdf.

    The MAX232 was first introduced by Maxim Integrated Products, but is now available from other semiconductor manufacturers and is available in 16-pin plastic DOP and SOIC. C2 and C3 are used for the on-chip voltage multiplier to boost the +5V from the 7805 or LM340 to +12V and -12V. Data sheet is at http://datasheets.maxim-ic.com/en/ds/MAX220-MAX249.pdf.

    If none of this answers your questions, please clarify just what you need and I will try to provide your answers.
Reply
  • in reply to Former Member
    I am sorry, but I am not sure just what kind of "help" you need because the part types are indicated on the schematic. U1 is a "7805" type linear regulator, U2 is a "MAX232", J2 is what is known as a "DB9" connector which is used for RS-232RS-232 interfaces and J1 appears to be a header to connect to whatever is sending and receiving data over the RS-232RS-232 port.

    The 7805 comes in TO-3, TO-220, TO-263 and SOT-223 packages. I believe that any of these packages would be satisfactory, but the SOT-223 and TO-263 packages MIGHT not handle the power requirements of this circuit (max 105mW) without care in how it is mounted. See the data sheet for proper mounting considerations. The TO-220 package should have no problems with power dissipation. Furthermore, I would prefer the LM340 because its specification shows a a little tighter tolerance on the output voltage. Data sheet is at http://www.national.com/ds/LM/LM340.pdf.

    The MAX232 was first introduced by Maxim Integrated Products, but is now available from other semiconductor manufacturers and is available in 16-pin plastic DOP and SOIC. C2 and C3 are used for the on-chip voltage multiplier to boost the +5V from the 7805 or LM340 to +12V and -12V. Data sheet is at http://datasheets.maxim-ic.com/en/ds/MAX220-MAX249.pdf.

    If none of this answers your questions, please clarify just what you need and I will try to provide your answers.
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