TPS62122: TVS Diode for Long Distance Power Source

RAVI TEJA

Part Number: TPS62122
Other Parts Discussed in Thread: TLV713P,

This is related to our an earlier question we asked, link below please

We are designing a 12V to 3.3V (Buck + LDO) Power Supply for Bluetooth MESH network. We are using TPS62122 to step down 12V to 3.6V and filtering the output ripple through TLV713P to get 3.3V.
In total, 30 Bluetooth Nodes will be connected to a 12V line over 100 meters. Average and Peak Current Consumptions of each Bluetooth Node are 5.5mA and 25mA (9.9mA RX, 25mA TX and 1.4uA Sleep).

Just to give an idea, the final connections look as below,

We have run few TINA Simulations and decided to use 100uF 200 ohms Aluminium Electrolytic Cap for every Buck Converter. The peak Input Transient Voltage during Start Vin Overshoot is 15V.

Kindly help us with the question below,

1) Considering there are no Inductive loads connected to 12V supply line, is a TVS Diode still required on every Buck-Converter to provide Input Transient Protection?

Thanks,

Ravi

over 4 years ago

0 Excel Regidor over 4 years ago

TI__Mastermind 26736 points

Hello Ravi,

It is still highly recommended to add TVS diode on each buck converter to ensure the Vin will not exceed the absolute max rating considering the very long connection which may result to high stray inductance along the PCB tracks between the 12V output and the Vin pin of TPS62122.

Best regards,

Excel

0 RAVI TEJA over 4 years ago in reply to Excel Regidor

Intellectual 270 points

Thank you Excel Regidor. Can you kindly help us with the below questions also,

1) Could you please suggest the best TVS diode parameters for our case?

(Since the recommended operating voltage of TPS62122 is <15V, we are considering to pick a TVS Diode with Working Voltage 14V and BreakDown Voltage 14.5V)

2) On the Vin side of TPS62122, is a Resistor 'R' in series to both TVS Diode and TPS62122 recommended in our case (as shown in fig below)? Or does the long distance cable provide enough resistance to limit current in-case of Breakdown Operation? If a resistor is required, could you please suggest the resistor value.