MP2760 Vsys minimal voltage setting

Battery Management
1

Hi,

We are students currently working with the MP2760 evaluation board.

We are trying to regulate the Vsys_min voltage via I2C, but we have encountered some counterintuitive information in the datasheet:

  1. In the Electrical Characteristics section, Vsys_min is described as configurable (REG07h) depending on the number of battery cells, ranging from 3.53V (1S) to a maximum of 12.36V (4S).
  2. However, in the REG07h description, it states: “Range: Up to 25.4V.” Based on this, we attempted to set it to a higher voltage (e.g., 10V with a 2-cell battery) but were unsuccessful.
  3. In the REG10h (Config Reg 2) description, the Vtrack setting states that Vsys is strictly regulated to Vsys_min + (Vtrack × BAT_NUM). However, this is obviously not true, as we set Vsys_min to higher values, but Vsys remained unchanged.

Our main questions:

  • Which information should we rely on? The Electrical Characteristics section, which states a maximum of 7.4V for a 2-cell battery, or the REG07h description, which indicates a range of up to 25.4V?
  • Is there a way to set Vsys to a higher voltage than 7.4V with a 2-cell battery (e.g., 16V)?

Any clarification would be greatly appreciated!

2

Hello jankpbcz,

I believe Vsys will always need to be close to Vbatt. There is a fet that connects Vsys to the battery. You should follow the electrical characteristics portion. The battery voltage depends on the number of cells and the cell voltages.

3

Thank you for the explanation,

that makes sense regarding Vsys being close to Vbatt. However, this still doesn’t resolve the inconsistency in the datasheet—if Vsys_min is limited to a value close to Vbatt based on the number of cells, why does REG07h list a range up to 25.4V? This seems misleading if such a value cannot actually be set.
Could you clarify how this value is intended to be used?