THVD4431: Need comparison table for replace F81435N

Hi Len,

The THVD4431 is the right IC to compete with the F81435N - it is important to note it is not a drop in pin to pin replacement - but the THVD4431 is the superior device.

Its pretty much impossible to do a direct comparison because all of the comps test conditions are different and we test way more parameters than they do. 

The big comparison is this - comp device claims to be compliant with RS-232 and RS-485 - but it isn't. RS-232 isn't tested at a high enough capacitive load to guarantee full compliance and the rs-485 threshold is in violation so badly that this device cannot communicate with absolutely any other RS-485 device - this means if they need RS-485 compliance this part cannot be used. 

I just want to point out four major issues with competition.

1. RS-232 has two speeds for comp device - 250kbps at 1000pF and 3Mbps at 100pF - RS-232 doesn't need to go above 1Mbps in the vast majority of applications and 100pF means essentially no cabling at all - the IC's need to be pretty much right next to each other (RS-232 is spec'd at 1000pF or 2500pF - not 100pF) Our slow speed for the THVD4431 is going to be 250kbps at 2500pF and 1Mbps at 1000pF - so our device will have stronger drive strength than comp. 

2. RS-485 does not have a capacitive loading requirement - because RS-485 is long wired communication and there could be a decent amount of capacitance. Comp says max of 47pF - which means the drive strength of their driver is subpar and poorly designed. And it would be risky to add even a few meters of cable because they will just say you are using the part out of spec - essentially negating the entire datasheet. 

3. It isn't RS-485 compliant - its minimum threshold goes below - 200mV - which means comp device cannot be used for RS-485 and end customer is forced to only use comp device - leaving no flexibility in the system. 

4. Comp device isn't compliant with RS-422 VOD with 100 Ohm load at VCC = 3.3V 

For those three reasons alone the comp device shouldn't even be considered because they set out to make an RS-232/RS-485 Multiprotocol transceiver and have failed on both aspects. If customer cares about the system's performance this part shouldn't even be considered.  

So just from a top level if customer uses this device they will get subpar performance on RS-232 and RS-485. 

Also competition datasheet blatantly lies and hopes customer can't do basic math: "The -100mV to -250mV threshold complies with the +-200mV  EIA/TIA-485 standard" , problem being -200mV is larger than -250mV - which means it is not compliant - so I don't think this datasheet is even accurate because its lying about what the part is throughout the entirety of the datasheet.

With all that being said it comes down to this:

1. Comp device isn't compliant with the protocols it says it is compliant with. Ours is - if customer cares at all about system robustness then the other part shouldn't be considered at all. 

2. If they are already using Comp device - do you know why they'd want to switch - because while our part is better- from a system level it probably wouldn't make much of a difference and guessing by how just how subpar the comp part is I would imagine it's cheap - because its design is not good - so if they are looking to switch for price reasons this isn't the right part because ours is performance designed and this is the only real option we have

3. Due to unrealistic system expectations they have laid out (47pF max loading for RS-485, 100pF max RS-232 for its "higher speed setting") means that real world applications are going to be severely limited in bus length - RS-485 should be able to reach about 1.2km and RS-232 is about 15m - with current ratings you'd be lucky to a get a fraction of that - so if the system has issues comp will be able to point to the fact you are not following "design conditions" which are extremely unrealistic to begin with.   

Please let me know if you have any questions - but basically the parts are completely different in performance -the comp barely works and ours actually works and is compliant with what it is stated to be compliant with.

Best,

Parker Dodson