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Subject: LTC2909IDDB-2.5#TRMPBF Reset_N is getting asserted even though Threshold Voltages @ J1 and J2 is Proper.

Category: Hardware
Product Number: Subject: LTC2909IDDB-2.5#TRMPBF Reset_N is getting assereted even though Threshold Voltages @ J1 and J2 is Proper.

Hi,

We are facing an issue with +15V Monitoring Circuit.


According to the resistor divider calculation voltage at J1 and J2 will be 534mV and 469mV.

1. We powered on the board, and the Voltage at J1 and J2 is  1.3 and 1.1 V.

  

2. Removing the IC, the voltage at J1 and J2 is measured to be 534mV and 469mV, as expected.

   The Net 15V_P_MON_OUT has not been connected anywhere. It is "Open" i.e High Impedance.

3. We Replaced the IC, still the voltage at J1 and J2 is measured to be 1.3V and 1.1V and the Voltage at RST_N (pin 5)  is 0.4v (i.e Reset_N is getting asserted).

4. We changed R3 resistor to 15K ohm such that the voltage at J1 is around 0.6V and J2 is 0.4V.

Still, the voltage at RST_N (pin 5)  is 0.4V.

5. We replaced R1, R2, and R3 with 1M ohm, 40K ohm, and 0 Ohm. (We intend to monitor only UNDER Voltage. It is mentioned in the datasheet to ground ADJ2 pin  if unused)

  We found voltage at J1 is around 1v. Still, the RST_N is asserted with a voltage of 0.4v.

We are monitoring -15V and 28v as well. The same kind of issue is present (Voltage at ADJ pin is meeting threshold but reset is asserted)

Please help us Debug this issue.

Regards,

UR Nikhil Bhat



We are monitoring -15V and 28v as well. The same kind of issue is present (Voltage at ADJ pin is meeting threshold but reset is asserted)
[edited by: Nikhil26 at 12:16 PM (GMT -4) on 14 Apr 2023]