Hi All,
I have a question about TPL7407L.
Are there any restrictions on the relationship between COM pin and OUTx pins?
Conditions: COM = 8.5V / OUTx = 40V
Does it work properly with the above input voltage?
Do you need COM=OUTｘ or COM>OUTx conditions?
Best Regards,
Ishiwata
Ishiwata-san,
Thanks for your question,
Shuji Ishiwata said:Are there any restrictions on the relationship between COM pin and OUTx pins?
The restirction is that you do NOT want the internal protectio diode to be forward biased during normal operation. The protection diode is designed to shunt current away during inductive switching , e.g. motor. The inductive spike causes the voltage on OUTx to be HIGHER than your 40V supply and the diode becomes forward biased and shunts the current away.
If you did
Conditions: COM = 8.5V / OUTx = 40V
This would kill the device. It is better to float COM if you can't connect it to the OUTx supply.
Just use the same HIGH supply for COM/OUTx supplies and you will be fine.
If you are not driving an inductive load you do not necessarily need to connect COM to the high supply, but it wont hurt.
Please see the figure from the datasheet below which shows how supplies are utilized with COM/OUTx
I hope this helps, and let me know if you would need any additional information on this topic we will be happy to help.
If this answers your questions please let me know by pressing the green button .
Best
Dimitri
Dimitri-san,
Thank you for your reply.
Conditions: COM = 8.5V / OUTx = 40V
I found that it doesn't work under the above conditions.
Where is it listed prerequisite of COM and OUTx in the datasheet?
Initially, I decided that it would work with the following datasheet content:
Best Regards,
Ishiwata
Ishiwata-san,
Section 6.3 shows the full possible range of each , but
, that doesn't mean that VOUT (max) used with Vcom (min) condition will work.
VF of the internal EMF clamp diode is 1.4V max.
You do not want this diode to become forward biased during normal operation, and you want it to be able to shunt away current during inductive kickback such as for motor driving applications. You also do not want to place supplies across the clamp diode that are greater than VF as it will instantly destroy the device.
For this reason, VCOM should be kept EQUAL to VSUP. if you kept COM pin voltage at 8.5V and applied VSUP of 40V, the device would pop and make burning smells.
If this answers your questions please let me know by pressing the green button .
Best
Dimitri
