MAX232E: Baudrate support

Ryuuichi machida

Guru 12085 points

Part Number: MAX232E

Tool/software:

Hi,

I would like you to confirm about below.

Q1, I understand that this device support up to 250kbps as data rate.
So, I understand that this device support baudrate "115200 bps".
Is my understanding correct ?

Best Regards,

3 months ago

0 Clemens Ladisch 3 months ago

Guru 297270 points

Correct.

0 Ethan Sempsrott 3 months ago

TI__Expert 8357 points

Ryuuichi,

That is correct: 115200bps or 115.2kbps is supported.

Best,

Ethan

0 Ryuuichi machida 3 months ago in reply to Ethan Sempsrott

Guru 12085 points

Hi,

Thank you for your reply.

I have additional question.

Q. According to Figure7-1 of datasheet of MAX232E, "1mF" is described for external cap of charge pump.
However, on the other hand, "1uF" is described in "6.3.1 power" section of datasheet.
Which one is correct ?

BR,

0 Ryuuichi machida 3 months ago in reply to Ryuuichi machida

Guru 12085 points

Hi,

I would like you to ask one more.

Q. According to datasheet, output voltage is defined as shown below.

* typ 7V (-7V)
* min 5V (max -5V)
(@3kohm load)

However, how I should consider rate of "typ".
Does it follow "6σ" idea ?

And what parameter will affect this value ? (Output drive current ?)
(However, In general, output drive current depends on output voltage and receiver input impedance.
So, it seems output voltage should be constant from above...)

BR,

0 Clemens Ladisch 3 months ago in reply to Ryuuichi machida

Guru 297270 points

"mF" is a typo; this should have been "µF".

The RS-232 specification requires voltages between ±3 V and ±15 V for a load of 5 kΩ ±2 kΩ. The driver uses a minimum of ±5 V to allow a voltage drop over the cable. The charge pump's output is regulated, so it will drop only if the load is too high.

0 Ethan Sempsrott 3 months ago in reply to Ryuuichi machida

TI__Expert 8357 points

Hi Ryuuichi,

For your first question, 1uF is the correct value for the charge pumps.

For the second question, "typ" represents the typical setup, not a statistical measure. The load impedance will affect this value.

Best,

Ethan

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MAX232E: Baudrate support