LM5060: LM5060 24VPower monitoring

Saravanakumar Balasubramanian

Part Number: LM5060

Hi,

We are using LM5060MM/NOPB in our design for 24V power supply monitoring. We calculated voltage divider resistor values for OVP, UVLO conditions by considering Vin(min) as 19.2V and Vin(max) as 28.8V. We used FDS5351 MOSFET for switching. But we are getting 5V at the timer pin when we give Vin as 24V. Can you please clarify how the 5V coming at the timer pin. Here I have attached the snapshot of the design for reference. In this design, we have changed R453 to 510Kohms and R454 to 620Kohms recently.

over 4 years ago

0 Rakesh over 4 years ago

TI__Guru** 105531 points

Hi Sravan,

Thanks for reaching out!

Can you confirm whether GATE voltage came up during startup or not ? For fault cases, timer gets charged till ~5V.

Please share Vout, GATE, Timer and input current waveforms during startup

BR, Rakesh

0 Arun M1 over 4 years ago in reply to Rakesh

Intellectual 665 points

Hello Rakesh,

I am replying on behalf of Saravan, No. Gate voltage is not coming. I guess it is going to VDS faukt, Timer is charging. I wil share the waveform later today.

Regards,

Arun

0 Rakesh over 4 years ago in reply to Arun M1

TI__Guru** 105531 points

Ok Arun

0 Saravanakumar Balasubramanian over 4 years ago in reply to Rakesh

Prodigy 190 points

Hi Rakesh,

We are getting 5V across the Timer capacitor and low voltage at the Vout and Gate. Please find below snapshots for reference.

Timer pin voltage

Timer-pin

Vout

Gate voltage

Gate

0 Rakesh over 4 years ago in reply to Saravanakumar Balasubramanian

TI__Guru** 105531 points

Hi Sravan,

It looks like a Vgs fault (Figure 22 in the datasheet) but if you can get test waveform similar to Figure 35 it will easy to debug.

Can you check whether FET is good or not ? Is the behavior same across multiple boards? what is the load ?

Can you check with out any capacitance at GATE ?

BR, Rakesh

0 Saravanakumar Balasubramanian over 4 years ago in reply to Rakesh

Prodigy 190 points

Hi Rakesh,

We have taken the test waveform similar to fig.35 in the datasheet. Output is still at 0 voltage. Can you give comments on the observed voltages. PFB snapshot for reference.

channel 1(Vin), channel 2(timer), channel 3 (gate).

0 Rakesh over 4 years ago in reply to Saravanakumar Balasubramanian

TI__Guru** 105531 points

Hi Sravan,

Are you sure that channel 2 is timer and channel 3 is gate.? I think its otherwise.

It is a Vgs fault.

Can you check whether FET is good or not ? Is the behavior same across multiple boards? what is the load ?

Can you check with out any capacitance at GATE ?

BR, Rakesh

0 Saravanakumar Balasubramanian over 4 years ago in reply to Rakesh

Prodigy 190 points

Hi Rakesh,

I think we we have probed channel 2 and channel 3 alternately as you said. If it is Vgs fault, what can be the solution to make the mosfet ON condition. Do we need to change any capacitor value?

Again we will share the test waveform for you reference.

MOSFET(FDS5351) is working fine. We have observed this same issue in 3 boards. System load current is 0.33A.

0 Rakesh over 4 years ago in reply to Saravanakumar Balasubramanian

TI__Guru** 105531 points

Hi Sravan,

Reducing C702 or increasing C699 helps.

Please test for the below cases and let me know if it helps to powerup.

1. C699 = 1uF

2. in other case, keep C699 same and remove C702, EC3

BR, Rakesh

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LM5060: LM5060 24VPower monitoring