Dear TI support members,
I have an issue with the charging of bq25601.
When i disconnect the plague and battery only supplies the system (load) it works well, the problem is when i connect the plague to charge the battery (in both cases the system is on or the system is off). With thermistor disabled (resistor divider 10k from REGN to TS to GROUND), it seems the only condition where bq25601 charges the battery (3.7 V) is when on V_BUS (or VAC) are 4.5 V (through a digital controlled DC power supply). Actually this situation is variable because sometimes works with 4.5 V on V_BUS, sometimes works with 4.6 V on V_BUS and if in this last case i try to lower until 4.5 V the charge reduces from 400-500 mA to 50 mA even if VBUS_STAT is 011 (PSEL low) and OVP from the registers appears to be in deafult setting 01 (6.5 V): in all this two situations when i try to go under 4.5 V the I_charge reduces to 0 (and this seems to be in accordance with deafault settings). In the situation over mentioned i have another issue: if i try to read the configuration of bq25601 from the registers it is in fast charge, and if i try to write in this register (REG02) another value from the default value something changes, but the actual current supplied (with the load disconnected) is far from the expected value of 2040 mA, that is the default value. All other register values seems to coincide with the expected values. Now i come to what happens specifically when bq25601 cannot rise above 4.5-4.6 V : if i connect a led to STAT when is in the abnormal status (VBUS > 4.5 V) it switches on and switches off at frequencies very higher than 1 Hz (as shown in the pictures below), not fixed, in an abnormal way. The current supplied does the same according to the led indicator. Picture 1) is about what happens if V_BUS rises above 4.5-4.6 V: in blue V_BUS (6.12 V DC), in yellow V_REGN (load disconnected).
Picture 2 is about V_SYS (yellow) with V_BUS 5.42 V DC (blue).
Picture 3: is V_REGN is V_REGN when V_BUS is 5.42 V.
In all this 3 not desired pictures V_BAT remains unchanged at the current battery voltage. In the stable situation (4.5-4.6 V power supply): as mentioned above the issue in this case is that the current value is not as expected 2040 mA as read from the registers (CHRG_STAT = 10 fast charge) versus actual 400 mA, and Vbat value is not as read in REG04 (VREG= 4.208 V) but the battery is charging with 3.9 V. When V_BUS is in the ok condition (4.5-4.6 V) V_REGN doesn't switch as in the pictures, but holds 4.4 V as expected.
Best reguards,
Alpha.
