Hi,
1. Attached fine the current2.pdf. It contains the actual board which I am using currently.
a)Q1 & Q2 are required in ckt as they protect the battery from charge & discharge error.
b)R1 is sense resitor for measuring current flowing in/out of circuit.
c)Bq34z100-g1 is powered by 3.3V. SO I2C signals are 3.3V.
d) Usage of Q3/Q5 & Q4/Q6 is explained in page 2 of current2.pdf
e) Communication breaks in following cases:
i) Q1 discharge fet off: Q3/Q5 fets off also
ii) Q2 charge fet off: Q4/Q6 fets off also
iii)Q1/Q2 both gets off: Q3/Q5/Q4/Q6 all gets off
f) Reasons for turning off of Q1 or Q2:
i) Q1 off: Battery gets over discharged
ii) Q2 off: Battery gets over charged
iii) Q1 & Q2 both off: Some short circuit in circuit.
2. Now I want that:
a) This problem off communication break do not occur
b) Convert I2C to differential communication RS485/CAN
c) Preferable as hardware asic based
d) As low power as possible, since circuit is battery powered.
3. I have attached a circuit CAN_BUS.pdf.
a) Fets in Communication line are removed.
b) I have used P82B96 & SN65HVD231 for convert I2C to CAN
C) On receiver side, CAN to I2C conversion is done
d) SN65HVD231 has CMR of -2V to 7V, I will select a device with CMR -7V to +7V.
e) On host/receiver side, communication ckt can be either powered from pack+/pack- or external supply.
f) But all return path for communication will be referenced to pack- only.
4. Can this circuit work?
5. Biggest problem will be:
a) When Q1 or Q2 or both gets, there will be no voltage between pack+ & pack-. & suppose receiver side is powered from external supply whose return path is reference to pack-.
In that case, can communication happen?
I think it can, as there is differential communication, moreover CAN IC has CMR of -7Vto+7V, while CAN IC are powered by only +3.3V, so I can be in limits
b) By connecting this circuit, there should be no path between BAT- & Pack-, which can let the current flow through them in case of Q1/Q2 gets off. Otherwise there will be error in batteries or it may get damaged.
6. If this circuit cannot work, then I have to use CAN isolator like ISO1050.
Only problem is creating a low power isolated supply of +5V for ISO1050, I will look into it, if above circuit cannot work.
Any low power isolated power supply IC?