LM7310: LM73100 internal power supply and OVLO

Hi Hardy,

I am little bit unclear on questions. Let me know if I understand right.

1. VIN=5 and VOUT=12? Yes BFET will turn off. Other logic will work inside device.

2. What do you mean by not auto recover ? 

If OVLO is connected to VOUT side and OVLO =6V suppose. Now when VIN=7V =VOUT=7, device will turn off . VOUT will slowly fall towards zero and when VOUT goes below 7V device will turn on again. So device is auto recovering . 

Regards

Kunal Goel

Hi Kunal,

1. No. Vin = 0V, Vout = 12V. So, LM73100 internal circuit can be powered from VIN or VOUT. Am I correct?

2. Sorry for unclear question. Please see below picture. In this scenario, not only VIN with 5V sourcing but also VOUT with 12V sourcing. We don't  want to see LM73100 keep auto-recover status. So, I think that connect OVLO to VOUT or VIN will have differential OVP result. Please correct me if my understand is wrong.

Best regards,

Hardy 

Hi Hardy,

1. LM73100 has back to back fet. It will always block reverse current. So when VIN=0 and VOUT =12 V device is off. no internal logic is active or powered up. VOUT will not make VIN=12V.

2. I think you understand VOUT can flow into VIN so you propose this solution? BUT LM73100 does not allow VOUT to charge VIN.

What is customer requirement?

Regards

Kunal Goel

Hi Kunal,

Let me explain customer's application. 

POGO pin is a dual role interface(function like TypeC PD). It not only can sink 5V but also can source 12V. So, we would like to add LM73100 to avoid 12V enter 5V rail. The 5V is from another power converter.

Scenario 1: When POGO pin is not plugged external power, 5V flow power into POGO pin by LM73100.

Scenario 2: When POGO pin is plugged external power, LM73100 should turn off back to back FETs to avoid 12V power enter 5V rail. But if POGO pin unplug external power, LM73100 should turn on FETs to let 5V flow into POGO pin.

Scenario 3: No matter VIN = 5V or 0V, LM73100 should always turn off FETs when 12V exist at POGO pin.

Back to my Q1 and Q2.

1. Look like no matter VIN = 5V or 0V, LM73100 will turn off FETs to avoid reverse current. Am I correct?

2. We don't want to see VOUT(12V) flow to VIN(5V). Also, we don't want to see LM73100 auto-recovery when OVP condition. So, I would like to know whether LM73100 can keep OVP latch when we connect VOUT to OVLO.

Best regards

Hardy

Hi Hardy,

1. Yes

2. What do you mean by OVP in this case? Do you mean when voltage at IN pin exceed certain threshold ? When VOUT =12 device is anyway turning off because of reverse current blocking mechanism, so adding resistor divider at output does not make sense. Is my understanding correct.

Regards

Kunal Goel

Hi Kunal,

2: When IN pin = 5V and OUT pin = 12V, do you mean that reverse current protection will always trigger faster than overvoltage protection and both of these two protections are triggered? If yes, look like we just connect OVLO to VIN because the FETs will keep turn off until OUT pin < 5V. Am I correct?

Best regards,

Hardy

Hi Kunal,

Got it. Thanks for your patient to reply my question. 

Best regards,

Hardy