TPS92391: Over Current fault always on issue

Hi,

Could you please send me your registers value?

BR

Patrick

Hi Patrick,

Thanks for your help. Please see below the register values.

OFFSET                 Acronym                                               Name                                              Value

0x00                      BRT_CONTROL                                    Display Brightness                         0x3333

0x02                      LED_CURR_CONFIG                           LED Current                                  0x02b2

0x04                      USER_CONFIG1                                  User Config 1                                0x02a0

0x06                      USER_CONFIG2                                  User Config 2                                0x0100

0x08                      SUPPLY_INT_EN                                 Supply Interrupt Enable                0x2aaa

0x0A                      BOOST_INT_EN                                  Boost Interrupt Enable                  0xa028

0x0C                      LED_INT_EN                                       LED Interrupt Enable                    0x00aa

0x0E                      SUPPLY_STATUS                               Supply Fault Status                       0x0080

0x10                      BOOST_STATUS                                Boost Fault Status                         0x0000

0x12                      LED_STATUS                                      LED Fault Status                           0x0000

0x14                      FSM_DIAGNOSTICS                          Device State Diagnostics              0x0012

0x16                      PWM_INPUT_DIAGNOSTICS            PWM Input Diagnostics                 0x0000

0x18                      PWM_OUTPUT_DIAGNOSTICS        PWM Output Diagnostics              0x0000

0x1A                      LED_CURR_DIAGNOSTICS              LED Current Diagnostics              0x0000

0x1C                      ADAPT_BOOST_DIAGNOSTICS      Adaptive Boost Diagnostics           0x06f5

0x1E                      AUTO_DETECT_DIAGNOSTICS      Auto Detect Diagnostics                 0x0031

Hi,

Thanks, I will give you feedback later.

BR

Patrick

Hi,

What are your VIN and VOUT? And may I know how you connect SGND and PGND?

Could you please also capture the inductor current waveform when powering on the IC?

BR

Patrick

Hi,

We have VIN = 24 VDC and VOUT = 0VDC as the driver chip cuts out due to the fault.

SGND and PGND are joined together on the PCB so both are the same grounds.

And there is nothing happening on the inductor side. SD pin does not do any switching at all so everything is quiet and off.

Thanks

Ali

Hi Ali,

I understand that when OCP occurs, the powerline FET will be turned off. But what I want to know is the inductor current behavior during powering on the device. I think the process is like the inductor current will rise at first, and finally trigger the OCP. So the waveform is to know the real inductor current behavior during this process.

BR

Patrick

Hi Patrick,

We get nothing on the inductor on power up. 

We have our scope connected and when we power up there is nothing happening.

There must be something that we are doing wrong here. We have read the datasheet twice now but we can not figure out what the problem is.

Thanks

Ali

Hi Ali,

Could you please try connecting the PWM pin to VDD and retry again?

BR

Patrick

I did that.

I connected PWM to VDD (3.3V) and still nothing is happening.

Thanks

Ali

Hi Ali,

This IC uses RISENSE resistor (R42+R43 in your schematic) to detect the VIN OCP fault. So could you please measure the voltage on resistor both side to see if the voltage has risen up to 220mV when powering on?

BR

Patrick

Hi Patrick,

There is not voltage across the R42 + R43. The MOSFET is not turning on at all. 

It seems like the SD pin on the driver chip stay off the entire time.

Thanks

Ali

Hi Ali,

Were the "3V3 supplied to VDD" and "LED_EN" stable?

BR

Patrick