MAX3232: MAX3232IPWR - Current Consumption

An active output that is connected to a 5 kΩ receiver would consume about 2.2 mA. RS-232 speeds are so slow that the frequency-dependent power consumption is negligible.

Hi Asha,

First you cannot leave DIN pins floating - that will increase supply current and could possibly cause application issues. If unused you need to tie to GND or VCC. Also we have 1T1R RS-232 devices so you really you should probably since you are underutilizing this device and are paying for channels that you aren't using. 

That being said if you fix the floating DIN issue -  ultimately you will have to qualify this value for your specific system and we can't directly do that because there are multiple system level parameters that could impact this value. 

However I can give some guidance of how to look at the power consumption of the device - the total active ICC is basically going to approximate to: ICC(idle) + I_load + I_AC_loss - this is a slight oversimplification due to the charge pump but for a rough estimate its okay. 

ICC(idle) is 1mA max for this device (300uA typical), the I_load  is the VOUT of the bus pins divided by the RIN of of the receiver. RIN for RS-232 devices is minimum 3k and nominally 5k. This device has an output swing of +/-5.4V typical on a 3k input - which would lead to about 1.8mA  (Clemens approximation of 2.2mA is also a decent value to use). Clemens is also right that the I_AC_loss is basically going to be very low because 250kbps is not fast enough to have major losses in the IC more most devices - so it's most likely negligible. 

However system setup is very important - the cabling, the ports, layout, etc.... can also impact the current values as what is seen. As well as temperature shifts within operating environment that is why it is very import to qualify the device in your specific setup as there are variables outside of the IC that will dictate how the IC reacts w.r.t. total power consumption.

Best,

Parker Dodson