Other Parts Discussed in Thread: TPS54622
Hello, TI experts,
I plan to use BQ24703 as the AC adaptor and battery charger controller in my new system design. I would appreciate it very much if you could help me to understand more detailed requirement in design and application. Please see my question as follows;
(1) If my Li-Ion battery pack is 14.8V, is there any limit in selection of the minimum output voltage of the AC adaptor when using with BQ24703?
Is that OK if I use the AC adaptor with the same 14.8VDC-output, or better to use an AC adaptor with 1-2V higher than the voltage of the battery pack in this application?
(2) In BQ24703 datasheet/Page-10/Application Diagram;
- Any special requirement for D4? If the battery is equipped with OVP/OCP, do I still need to use U4 here?
- How to select Zener diodes D5&D6, if they are used with smaller R19&R21 resistors? Should I select 30V Zener diodes for protection of the SRP&SRN input range (-0.3 to 30V)?
- How to select the Zener diodes (no reference numbers here) connected to U4/SI4435DY?
Are these Zener diodes needed only if VS is grounded/disabled?
If used, should I select 15V Zener diodes for clamping the voltage over +/-15V if a 14.8V battery is used here?
- Is it better in design, if the same current flow from the Source to Drain of U4/SI4435DY is kept as that of U2&U3/SI4435DY? Or there is no big difference to have the S-to-D or D-to-S current flow of U4 here.
(3) In BQ24703 datasheet/Page-21/Selecting Output&Input Capacitors:
Are there the formulas available for directly calculating the input/output/filtering capacitance (C12,C11,C8), like those formulas given in other TI power ICs application notes?
When using Formulas (8)&(9) given for calculation of the in/output ripple currents, how to select the D value (duty cycle) here?
Thanks a lot for your time and help!
QH