Regarding the issue of isolated communication:

QWE4562009

Regarding the issue of isolated communication: [Copy link]

Questions about isolated communication:
1. Is this isolated communication the same as level conversion?

2. As shown in the figure, this is an IIC isolated communication circuit , which uses two high-voltage NMOS, the purpose is to lower cost and power consumption, but will this isolation be unreliable?


------------ If the BQ78350 communication output uses an isolated chip , there will be 3-5mA of self-consumption. I use the discharge FET control pin to control the power supply of the isolated IC, and when the over-discharge protection is turned off, the power supply of the isolated IC will be cut off. In this way, the battery will not be damaged. But the customer does not agree to have a 3-5mA current under normal circumstances. So I want to change the isolation IC to two high-voltage N mos tubes . Add a 5V TVS tube to the communication port. In this way, the self-consumption is reduced. But I don’t know if there are any risks.
Questions about isolated communication:
1. Is this isolated communication the same as level conversion?

2. As shown in the figure, this is an IIC isolated communication circuit , which uses two high-voltage NMOS, the purpose is to lower cost and power consumption, but will this isolation be unreliable?


------------If the BQ78350 communication output uses an isolation chip , there will be 3-5mA of self-consumption. I use the discharge FET control pin to control the power supply of the isolation IC. When the over-discharge protection is turned on, the power supply of the isolation IC will be cut off. This will not damage the battery cell. But the customer does not agree to 3-5mA current under normal circumstances. So I want to change the isolation IC to two high-voltage N mos tubes . Add a 5V TVS tube to the communication port. In this way, the self-consumption will be reduced. But I don’t know if there are any risks.

ZXopen

Regarding the issue of isolated communication

90houyidai

I see others use MOS for level conversion, but I don't know how much isolation it can provide.

freebsder

Isolation? Shouldn't isolation mean different levels? Can MOS do this?

QWE4562009

freebsder posted on 2021-1-7 23:24 Isolation? Shouldn't isolation be non-shared levels? Can mos do this?

This is used in the BMS to prevent high voltage from burning out external devices. IIC communication. The voltage of the BMS itself is several dozen V, while the external chip may be 3.3V.

13719034974

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damiaa

Level conversion and isolated communication are two concepts.

Level conversion is to connect two circuits with different levels so that they can communicate normally.

Isolated communication uses optocouplers and couplers to isolate them so that they are electrically separated but signals can be transmitted to each other.

MOS tubes cannot isolate electrical signals, but they can amplify driving capabilities.

It should be possible to use MOS tubes for level conversion.