TLV61224: Part Not Working Properly - Unexpected Behavior

Robert S

Part Number: TLV61224

Hi,

I have two different designs using the TLV 61224 step-up converter. The input voltage comes from 2 AA alkaline batteries. We need a stable Vout = 3V. The load of the circuit is around 9mA. The first PCB layout works fine. The second layout doesn't work at all. The circuit has some crazy oscillations and the consumed current gets up to 200 mA damaging the TLV61224. Please, help me out with my questions below,

I'm using a BAS21 diode after the batteries input to prevent the user damaging the TLV61224 when placing the 2 AA batteries backwards. Is this diode necessary in this design? Is this diode causing the circuit to behave erratically?
The positive output from the AA batteries is located around 2 inches away from the device. Do I need a 47 uF tantalum capacitor?
Why is this PCB layout not working?

Thank you for your help,

Robert

THIS CIRCUIT LAYOUT WORKS FINE

THIS CIRCUIT LAYOUT DOESN'T WORK. IT OSCILLATES CREATING A CURRENT UP TO 200 mA DAMAGING THE TLV61224 CHIP

over 5 years ago

0 Robert S over 5 years ago

Intellectual 550 points

THIS CIRCUIT LAYOUT WORKS FINE

THIS CIRCUIT LAYOUT DOESN'T WORK. IT OSCILLATES CREATING A CURRENT UP TO 200 mA DAMAGING THE TLV61224 CHIP

0 Jasper Li over 5 years ago in reply to Robert S

TI__Mastermind 46905 points

Hi Roberto,

the issue is caused by the layout, refer to this FAQ

https://e2e.ti.com/support/power-management/f/196/t/841128?tisearch=e2e-sitesearch&keymatch=faq%20TPS61220

0 Robert S over 5 years ago in reply to Jasper Li

Intellectual 550 points

Jasper,

Thank you for your help. But, about my other two questions?

Do I need to place a diode in the circuit to prevent the user from reversing the polarity of the AA batteries? Does the TLV61224 get damaged if the polarity is reversed?
The batteries are located about two inches away from the TLV61224. Do I need to place a 47uF tantalum capacitor at Vin?

Thank you,

Robert