ISO7340C: is there a fixed working frequency inside the digital Isolator?

Hi Jeff,

Q. 1. I know TI uses capacitor isolation architecture. is the frequency crossing the isolation capacitor fixed or variable? my application is sensitive to some frequencies. I would like to know if the noise could be problem.

A.

The PWM modulated communication is packetized. The packets repeat every 8us. The packet structure has a custom header and tail, and the body of the packet has the sampled low frequency information of all the channels. The smallest pulse width inside the PWM packet is ~20ns.

It is difficult to define a value for the carrier frequency for the PWM path.

This is a digital channel, and the filter performance or carrier leakage cannot be defined. We can however say the following:

1. Any transitions on the input pins (which are high frequency by definition) are conveyed to the outputs with a fixed propagation delay.

2. If the inputs are in a DC state (low frequency by definition), and the outputs happen to be in error, for example due to to excess noise or common mode transients beyond spec  (not expected normally) the outputs will be corrected roughly wihtin 16us (this is the response time of the low frequency path).

Q. 2. some isolators, like RS485 transceiver, with power. Does the power supply use inductor inside? does it work in strong magnetic field?

A. The  ISO7340C does not have a built in power supply. You must supply power externally. The ISOW7840 does have an internal isolated power supply if that is something you would like. 

Respectfully,

Lucas Schulte

Applications Engineer

Jeff,

Is there anything else I can help with? If not, can you mark the thread as answered? 

Lucas Schulte

Applications Engineer