JAJSFC8A april 2018 – january 2021 BQ25121A
PRODUCTION DATA
The device implements a simple voltage battery monitor which can be used to determine the depth of discharge. Prior to entering High-Z mode, the device will initiate a VBMON reading. The host can read the latched value for the no-load battery voltage, or initiate a reading using VBMON_READ to see the battery voltage under a known load. The register will be updated and can be read 2ms after a read is initiated. The VBMON voltage threshold is readable with 2% increments with ±1.5% accuracy between 60% and 100% of VBATREG using the VBMON_TH registers. Reading the value during charge is possible, but for the most accurate battery voltage indication, it is recommended to disable charge, initiate a read, and then re-enable charge.
A typical discharge profile for a Li-Ion battery is shown in Table 9-2. The specific battery to be used in the application should be fully characterized to determine the thresholds that will indicate the appropriate battery status to the user. Two typical examples are shown below, assuming the VBMON reading is taken with no load on the battery.
This function enables a simple 5-bar status indicator with the following typical performance with different VBATREG settings:
VBATREG | BATTERY FULL | 95% to 65% REMAINING CAPACITY | 65% to 35% REMAINING CAPACITY | 35% to 5% REMAINING CAPACITY | BATTERY EMPTY |
---|---|---|---|---|---|
4.35 V | VBMON > 90% | VBMON = 88% | VBMON = 86% | VBMON = 84% | VBMON < 82% |
4.2 V | VBMON > 98% | VBMON = 94% or 96% | VBMON = 90% or 92% | VBMON = 86% or 88% | VBMON < 84% |