Other Parts Discussed in Thread: TPS62933, TPS54302
Hi TI Technical Support Team,
I have designed battery charger based on TPS54331 to charge 12V 2.2Ah Lead Acid Battery. I have used design steps given in TI app note "Simple CC/CV Charger using TPS54331". The power supply of this circuit can provide 320mA at most so I have set charger current to about 260mA using R7 + R8 + R9 = 3 ohm. I am charging battery up to ~13.7V. My sense resistors are 1 ohm 0.25W resistors. The battery is used to power some circuit and sensors that draws around max 20mA during normal operation. However, when sensor output exceeds some threshold (rarely) value my aim is to activate the switch (12VDC relay) and power solenoid valve which may draw around 2.5 Ampere.
My question is related to driving solenoid valve. R7, R8 and R9 resistor are ok during normal operation but, when battery is used to power solenoid valve (switch is closed), I guess R7, R8 and R9 resistors will be burned as 2.5Ampere will pass through them. I have following questions.
1. How can I modify my circuit so that it will be able to supply 2.5 ampere (switch closed)? Increasing power rating of R7, R8 and R9 is not suitable for me as it will increase their footprint size and I dont have that much space on my PCB. Is it possible to convert this circuit to the battery charger with high side current sense (in this case my problem will be solved)?
2. Is there any cheap buck converter solution with high side current sense feature that I can use to charge battery and can solve my problem (operation will not be ruined during powering solenoid valve). The price of IC is important for me as this circuit will be used >5000 pcs/year.
Thank you for your help in advance
Regards
Ahmet
