LM5164-Q1: Output Voltage Protection

Rohan Patwardhan1

Part Number: LM5164-Q1
Other Parts Discussed in Thread: LM5164

Hi TI Team,

For LM5164, we were analysing a failure mode if Vout (voltage after Cout) shorts to input voltage. We have observed that the FB pin voltage is rated only for 5.5V which can damage the IC.

Our current configuration is as follows:-

Vin Max = 70V, RFB1 = 440K, RFB2 = 49.9K Vout = 12V. As per calculations voltage at FB pin shall be 70*49.9/(49.9+440) = 8V

What protection scheme do you recommend to avoid this?

Thanks,
Rohan

over 3 years ago

0 Samuel Jaffe over 3 years ago

TI__Mastermind 25590 points

Rohan,

You could add a zener diode to the FB node but that may affect stability. You could instead place a 100 ohm or similar resistor in series with the top feedback resistor connecting to VOUT (VOUT --> 100 ohms --> RFBT --> RFBB --> GND) and place the zener at the mid-point of the 100 ohm and RFBT.

-Sam

0 Rohan Patwardhan1 over 3 years ago in reply to Samuel Jaffe

Intellectual 340 points

Hi Sam,

Are you suggesting a configuration in attached file?

Thanks,

Rohan

0 Samuel Jaffe over 3 years ago in reply to Rohan Patwardhan1

TI__Mastermind 25590 points

Rohan,

Sorry I didn't specify. The zener will connect annode to GND and cathode to the midpoint between 100 ohms and RFBT. That way the capacitance from the diode will not affect the FB node and the 100 ohms will limit the current flowing through the zener. You may need to adjust the resistance of the 100 ohm resistor depending on max VIN and zener voltage to avoid overheating the 100 ohm.

-Sam