Hi, I am currently working on developing a BMS system based on MC33771B IC for my graduation project. I have some questions to finish my hardware design of the board:
- Firstly, I cannot find some values for the zener diodes used in hotplug protection, so I was wondering if I could use two or more zener diodes and connect them in series to get 75 volts, such as 3 zener diodes, each with a value of 25 volts, or two zener diodes, each with a value of 36 volts, or something else. This is to replace the zener diode with a value of 75 volts between VPWR and GND.
[gw]In the reference design schematic we have the part number for hotplug,you can download the MC33771B EVB schematic:
FRDM33771BSPIEVB | MC33771 SPI EVB | NXP Semiconductors
- And is it also possible to replace the diode between VPWR and CB_12 with a diode with a value of 22 volts instead of 20 volts?
[gw]Yes.
- Also, for ISENSE+/-, is it possible to use a diode in the range of 2.5 to 2.9 volts instead of 2 volts?
[gw] Meanless for select 2.5V to 2.9V.
- CGND, AGND, DGND, GNDREF and GNDFLAG are all these pins connected to the same GND which is the negative terminal of cell 1.
[gw]Yes.
- Is the TVS between the VPWR and CT14 in case of VPWR exceeds 55V is optional or necessary?
[gw]No understanding this question
- Also, regarding measuring current, I plan to use a group of current measuring resistors and connect them in parallel, or use a PCB copper trace as current sense shunt resistor to measure the charging and discharging current of the cells; so I wanted to make sure whether the voltage difference between the ISENSE+/- terminals should not exceed +/-150mV in both charging and discharging states, so the maximum current that can be measured should not exceed 0.150 divided by the value of the shunt resistor (I_max = 0.150 / R_shunt).
[gw]Yes.
Hi, I am currently working on developing a BMS system based on MC33771B IC for my graduation project. I have some questions to finish my hardware design of the board:
- Firstly, I cannot find some values for the zener diodes used in hotplug protection, so I was wondering if I could use two or more zener diodes and connect them in series to get 75 volts, such as 3 zener diodes, each with a value of 25 volts, or two zener diodes, each with a value of 36 volts, or something else. This is to replace the zener diode with a value of 75 volts between VPWR and GND.
[gw]In the reference design schematic we have the part number for hotplug,you can download the MC33771B EVB schematic:
FRDM33771BSPIEVB | MC33771 SPI EVB | NXP Semiconductors
- And is it also possible to replace the diode between VPWR and CB_12 with a diode with a value of 22 volts instead of 20 volts?
[gw]Yes.
- Also, for ISENSE+/-, is it possible to use a diode in the range of 2.5 to 2.9 volts instead of 2 volts?
[gw] Meanless for select 2.5V to 2.9V.
- CGND, AGND, DGND, GNDREF and GNDFLAG are all these pins connected to the same GND which is the negative terminal of cell 1.
[gw]Yes.
- Is the TVS between the VPWR and CT14 in case of VPWR exceeds 55V is optional or necessary?
[gw]No understanding this question
- Also, regarding measuring current, I plan to use a group of current measuring resistors and connect them in parallel, or use a PCB copper trace as current sense shunt resistor to measure the charging and discharging current of the cells; so I wanted to make sure whether the voltage difference between the ISENSE+/- terminals should not exceed +/-150mV in both charging and discharging states, so the maximum current that can be measured should not exceed 0.150 divided by the value of the shunt resistor (I_max = 0.150 / R_shunt).
[gw]Yes.
