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Original question:

TPS92633Q1EVM: ONE FAULT-ALL FAULT FUNTION PROBLEM

TPS92633Q1EVM: understanding of Input power supply to TPS92633-Q1

Tex
Intellectual 320 points
Part Number: TPS92633Q1EVM
Other Parts Discussed in Thread: TPS92633-Q1

Tool/software:

Hi Forum,

I got TPS92633Q1-EVM , While trying to understand that EVM, i'm not able to understand few things..

As you can see in page number 5 test setup they mentioned input voltage is 9V to 20V..

1. As per my understanding, EVM Min Voltage is 9V and Max is 20V... but, the LED is glowing even if i give 4V and when i gave 9V the IC is consuming Maxing current i.e. 440mA

The LED which is used in EV kit says the Vf of that LED is 2.1V means 6.3V is the min Voltage for that IC.. 

2. For EN pin, can i connect this pin directly to controller pin 5V to ON/OFF with 100Hz frequency ??

Regards,

Tex

  • +1
    TI__Genius 11765 points

    Hi Tex,

    See my answers below.

    Tex said:
    As per my understanding, EVM Min Voltage is 9V and Max is 20V... but, the LED is glowing even if i give 4V

    The TPS92633EVM User's Guide states the typical input voltage is 9-20V. This is based on the default circuit configuration and typical parameters shown in Table 3-1, including a 140mA output across 3 series LEDs.

    The TPS92633-Q1 minimum recommended supply voltage is 4.5V (see table 6.3 Recommended Operating Conditions in datasheet). This is the minimum supply that is recommended for reliable operation of the device itself. It is possible for the device to maintain some or all functionality if operating below this minimum supply, but we do not test or characterize supplies below 4.5V and the results could vary significantly between different devices. For example, on my EVM I can see the LEDs begin to light up at a supply of ~4.4V.

    Tex said:
    when i gave 9V the IC is consuming Maxing current i.e. 440mA

    The EVM is configured to drive 3 channels at 140mA which is 420mA. The typical IQ of the device is 1.5mA. Check your connections and the calibration of your power supply to account for the additional ~18mA.

    Tex said:
    The LED which is used in EV kit says the Vf of that LED is 2.1V means 6.3V is the min Voltage for that IC.. 

    The forward voltage depends on the current and will vary somewhat between different LEDs. In my EVM, the forward voltage is between 1.91V and 1.93V at 140mA. To determine the minimum necessary power supply you must also consider the dropout voltage of the device and the desired external heat dissipation through R(resx) shunt resistors.

    Tex said:
    2. when i give PWM input with 10% duty cycle, the current consumption is reduced by 50% but not 90%..

    Are you measuring this on your DC supply? A DC power supply is designed to measure the DC current supplied to the load. Depending on the supply and duty cycle, this may not be an accurate measurement as the supply is not typically designed to measure and average a fast AC current load.

    For better accuracy, you can use a differential probe to measure the differential voltage across the R(snsx) resistors and determine the PWM current.

    Tex said:
    For EN pin, can i connect this pin directly to controller pin 5V to ON/OFF with 100Hz frequency ??

    Yes, you can use the EN pin or PWM pins to apply PWM dimming. 100Hz can be used for some applications but higher PWM frequencies will help to remove visible flicker. TI typically recommends a 200-Hz PWM signal with 1% to 100% duty cycle input for brightness control.

    Regards,

    Zach

  • 0 in reply to Zach Olson
    Intellectual 320 points

    Hi Zach,

    thanks for your reply,

    Zach Olson said:
    Are you measuring this on your DC supply?

    yes! you are correct i'm using a DC power supply.. 

    1. could you please suggest me a better method to control brightness with this IC. 

    2. Regarding EN pin..

    As you said i have connected to EN pin to the controller.. i'm not understanding that the EN pin is enabled even if the amplitude is zero.. (measured in Oscilloscope)

    3. while testing single LED shorting, All LEDs in 2 strings are turned off, but 1 string where i did the LED shorting except that LED remaining 2 LEDs are glowing with high intensity..I need to achieve as per datasheet, if 1 fail only that particular channel should turn off

    Please help me to understand this..

    Regards,

    Tex

  • +1 in reply to Tex
    TI__Genius 11765 points

    Hi Tex,

    1. could you please suggest me a better method to control brightness with this IC. 

    I you want to control the brightness of each channel individually, you can apply your PWM signal to each PWM pin. If you want to control the brightness of all three channels with one PWM signal, you can use the EN pin.

    2. Regarding EN pin..

    In order to apply PWM dimming to the EN pin you must remove the shunt at J6 and apply your PWM signal to pin 1 of the J6 header. You should see the LEDs turn off as you remove the J6 shunt.

    3. while testing single LED shorting, All LEDs in 2 strings are turned off, but 1 string where i did the LED shorting except that LED remaining 2 LEDs are glowing with high intensity..

    This is the expected operation according to the datasheet. You may refer to the FAULT tables in section 7.3.11.

    When the LED short is detected, all 3 output channels are disabled and the auto recovery sequence is initiated.

    The auto recovery applies a short duration current pulse every 10ms to the channel that has the fault detected. This allows the device to measure the pin voltage every 10ms to determine if the short has been resolved, and normal operation can be restored.

    Visually, this auto recovery looks like a very low duty cycle PWM which is why you can see the LEDs dimly lit on the failed channel. You can verify with an oscilloscope that this is a 300μs pulse every 10ms.

    4.) I need to achieve as per datasheet, if 1 fail only that particular channel should turn off

    The "One-Fails-Others-On" application is only valid for multiple devices sharing the same FAULT bus as shown in figure 7-13.

    To achieve this function, you may use 3 TPS92633-Q1 devices connected as shown. If you do not require the additional channels, you can instead use 3 single-channel devices such as TPS92610-Q1.

    https://www.ti.com/product/TPS92610-Q1 

    Regards,

    Zach

  • 0 in reply to Zach Olson
    Intellectual 320 points

    Thanks for your valuable information Zach,

    Zach Olson said:
    I you want to control the brightness of each channel individually, you can apply your PWM signal to each PWM pin. If you want to control the brightness of all three channels with one PWM signal, you can use the EN pin

    1. Is that okay to give PWM to EN pin ? Does it mentioned in data sheet? If i can give PWM to En, what happens to PWM pins? should we let them float ? How much maximum PWM frequency that can be given to EN pin? does same as PWM pins like 200Hz ?

    2. Is it okay to pass 60Hz Frequency to the EN pin to achieve the LED blinking at 60 Hz frequency ? 

    3. Why i can't be able to make the EN pin low when i connect it to controller pin and make the controller pin low.. (The LEDs are still glowing when i connected the EN pin to controller GPIO pin and made the GPIO pin low (0V from GPIO pin)).

    Zach Olson said:
    To achieve this function, you may use 3 TPS92633-Q1 devices connected as shown. If you do not require the additional channels, you can instead use 3 single-channel devices such as TPS92610-Q1.

    Thanks alot for your valuable information i should be able to achieve SLS circuit part now..

    Apologies for too many queries..

    Kind regards,

    Tex

  • +1 in reply to Tex
    TI__Genius 11765 points

    Hi Tex,

    1. Is that okay to give PWM to EN pin ? Does it mentioned in data sheet? If i can give PWM to En, what happens to PWM pins? should we let them float ? How much maximum PWM frequency that can be given to EN pin? does same as PWM pins like 200Hz ?

    Yes, you may apply 200Hz PWM frequency to the EN pin to control the LED dimming. The PWM pins should be pulled to the battery voltage with a 10k pull-up resistor as shown in the EVM.

    2. Is it okay to pass 60Hz Frequency to the EN pin to achieve the LED blinking at 60 Hz frequency ? 

    You can apply lower PWM frequency if you want to achieve a visual blinking effect. However, this may interfere with your dimming function resulting in an inconsistent brightness. If you need separate control signals for LED brightness control and a lower frequency blink function you can use the PWM pins for your dimming and use the EN pin for the blink function. 

    3. Why i can't be able to make the EN pin low when i connect it to controller pin and make the controller pin low.. (The LEDs are still glowing when i connected the EN pin to controller GPIO pin and made the GPIO pin low (0V from GPIO pin)).

    Did you remove the shunt at J6? If you are measuring 0V at your MCU pin and 9V at your EN pin there must be a connection issue. Please provide clear images of your test configuration including all connections to the EVM and MCU. If you are measuring these pin voltages with an oscilloscope, ensure you have selected "DC coupling".

    Regards,

    Zach

  • 0 in reply to Zach Olson
    Intellectual 320 points

    Thanks for your valuable information zach, 

    now i'm getting a clear image about this IC..

    One last doubt regarding current and voltage adjustment,

    As per my understanding,

    I'm changing sense resistor for setting the maximum current = 2.3Ω for 70mA (70mA is my requirement)

    I'm changing R(resx) to set the maximum voltage = 134Ω for 25V to 30V (I doubt about this resistor setting)

    After changing these values in the EV kit, the the LEDs in the string is turning off when i try to give more than 20V.. Am i missing something ???

    Am i in the right  path or should i need to change something else to get desired current and voltage ?? 

    Regards,

    Tex

  • +1 in reply to Tex
    TI__Genius 11765 points

    Hi Tex,

    If you are planning to operate at 30V supply, Equation 11 gives you a 694Ω R(resx) resistor. Remember that the forward voltage was ~1.9V per LED with 3 in series resulting in an output voltage of 5.7V. Try a resistor between 400Ω-694Ω.

    Your calculation for the sense resistor is correct.

    Regards,

    Zach

  • 0 in reply to Zach Olson
    Intellectual 320 points

    Hi zach,

    I'am using different LED board with different LEDs,

    The LED which i'm using right now has ~3.1V per LED with 8 in series & required voltage is 24.8V..  with 70mA current consumption..

    Best regards,

    Tex

  • 0 in reply to Tex
    TI__Genius 11765 points

    Hi Tex,

    I understand you are now using a custom board to drive up to 8 LEDs in series.

    Please provide a detailed schematic of your custom board so I can help debug your issue.

    Thanks,

    Zach

  • 0 in reply to Zach Olson
    Intellectual 320 points

    Hi Zach,

    The design is same as LED board used in the evm except 1nf capacitors and Icntrl only jumpered but 8 LEDs with 3.1V forward voltage and 70mA current consumption..

    I just removed the Out1 and GND jumpers and then connected them to this circuit..

    Tex with thanks..

  • 0 in reply to Tex
    TI__Genius 11765 points

    Hi Tex,

    Yes, I will need a detailed schematic of your new board showing all resistor values and connections. Otherwise I will not be able to help debug your specific circuit configuration. For example, I do not know what you mean by "Icntrl only jumpered" but if I had your schematic I would know exactly what the connection is at Icntrl.

    Note that the current limit and thermal sharing equations are dependent on the Rcntrl and Rref resistor values.

    Please provide your detailed schematic for my reference.

    Thanks,

    Zach

  • 0 in reply to Zach Olson
    Intellectual 320 points

    Hi Zach,

    There is no other circuit designed..

    The 2 crocodile clips one is connected to OUT1 and other one is connected to GND of the LED schematic which I sent you in the above post..

    No other design circuit is there or no other components used either..

    Only RES1 and SNS1 values changed.. 

    Remaining all values are initial values of the EV kit..

    ICTRL2 value is 165.8 Ohms

    Regards,

    Tex

  • +1 in reply to Tex
    TI__Genius 11765 points

    Hi Tex,

    If I understand correctly, you are using the EVM schematic with the following resistor values:

    R15 (Rref) R16 (Rctrl1) R17 (Rctrl2) R3 (Rsns1) R1 (Rres1)
    6190 44.2 165.8 2.3 134

    The 2.3Ω resistor (R3) was calculated based on a total series resistance of 544.2Ω at the ICTRL pin. If you have reduced the potentiometer resistance (R17), you will need to adjust the R3 resistor according to equation 10. See table below.

    R15 (Rref) R16 (Rctrl1) R17 (Rctrl2) R3 (Rsns1) R1 (Rres1)
    6190 44.2 165.8 0.88 134

    I see you accounted for ~500mV dropout voltage to determine 134Ω for R1, this should be an appropriate value.

    Regards,

    Zach

  • 0 in reply to Zach Olson
    Intellectual 320 points

    Hi Zach,

    Zach Olson said:
    R15 (Rref) R16 (Rctrl1) R17 (Rctrl2) R3 (Rsns1) R1 (Rres1)
    6190 44.2 165.8 0.88 134

    Yes! you are correct as per our previous discussions, I kept these values.. and i confirm that these are the current resistor values..

    Tex said:
    I need to achieve 25V at OUT1 when i give 30V as input supply.. and the IC should turn off the string only after reaching 30V and current consumption should not exceed 70mA

    After setting the above values, i'm still not getting this output from the board..

    Present situation,

    Actually 8 LEDs should turn ON when the forward is ~24V at OUT1, But all the LEDs are turning ON at 20V and when we try to give input voltage of 21V all LEDs are turning off and 0V at OUT1.. throughout this current consumption is 3mA

    Please Look at the below image..

    This is the 2D Design which is given in EV Kit Guide.. If i change any resistance value, that will be modified in the middle pin but that is connected nowhere and 3rd pin where i'm getting 485Ω is connected to GND.. so, as per the connections in EVKIT ICTRL2 value is 485Ω.. Is My doubt correct or should need to use that R17 resistor in a different way to change the value ? 

    Please suggest more debugging steps..

    Kind regards,

    Tex

  • +1 in reply to Tex
    TI__Genius 11765 points

    Hi Tex,

    I have verified the R17 connection on my EVM and you are correct, there is a bug in the potentiometer routing and the wiper is left floating. My apologies for the confusion, in this configuration the Rctrl2 (R17) value is fixed at 500Ω. I will submit to revise the EVM layout and correct this bug.

    I recommend one of the two following solutions:

    Option 1.) Remove J12 shunt and connect 165Ω resistor from J12 terminal pin 2 to ground. This can be done easily with a through-hole resistor.

    Option 2.) Keep J2 shunt populated and replace R3 with a 2.3Ω resistor as calculated by R17 = 500Ω

    Please let me know if this works.

    If you require further debugging please provide a table showing multiple test values of input voltage, output voltage, voltage at RES pin, and the differential voltage across the sense resistor R3 (see table below). Please also confirm the resistor values used as per the tables above.

    Vin Vout1 Vres1 Vdiff (R3)
    x x x x
    x x x x
    x x x x
    x x x x

    Thanks,

    Zach

  • 0 in reply to Zach Olson
    Intellectual 320 points

    Hi Zach,

    Zach Olson said:
    I have verified the R17 connection on my EVM and you are correct, there is a bug in the potentiometer routing and the wiper is left floating.

    Thanks for your confirmation,

    Zach Olson said:

    Option 1.) Remove J12 shunt and connect 165Ω resistor from J12 terminal pin 2 to ground. This can be done easily with a through-hole resistor.

    Option 2.) Keep J2 shunt populated and replace R3 with a 2.3Ω resistor as calculated by R17 = 500Ω

    I tried both the options one after another,

    Also tried soldering R17 Resistor on the LED board and checked but still, when the input voltage is more than 21V the OUT1 string is turning off.

    The values which I tried,

    LEDs Vf(required) Vin Vout Vres1 Rsns1 Rres1 Rictrl2 Current in string
    8 24.8V 30V 0V 0V 0.88Ω 134Ω 165Ω 1mA
    8 24.8V 21V 21V 21V 0.88Ω 134Ω 165Ω 5mA
    8 24.8V 30V 0V 0v 2.3Ω 134Ω 165Ω 4mA
    4 12.4V 15V 0V 0v 2.3Ω 134Ω 165Ω 4mA
    4 12.4V 10.8V 10.8V 10.8V 2.3Ω 20Ω 165Ω 5mA
    2 6.2V 7V 6.3V 6.3V 1.7Ω 100Ω 500Ω 50mA

    Current control is happening but the voltage control is not happening when we change Rres1..

    Zach Olson said:
    I will submit to revise the EVM layout and correct this bug.

    Also i request the team to include the 40V input design requirement for this IC..

    Even in the TPS92633-Q1 Calculation tool also not having the calculations with 40V.. it consists only 20V for 3 strings..

    Please include this thing also..

    Best regards,

    Tex

  • +1 in reply to Tex
    TI__Genius 11765 points

    Hi Tex,

    With an input voltage of 30V, I am able to configure my EVM with 12 LEDs in series resulting in a total forward voltage of 24.66V with 67mA of current sourced from channel 1. You may refer to the table below for my exact configuration values.

    R15 (Rref) R16 (Rctrl1) Rexternal (Rctrl2) R3 (Rsns1) R1 (Rres1) Vin Vout1 Vres1 I_total
    6190 44.2 220 1.15 100 30 24.66 29.43 0.067

    I recommend you double check your connections, the forward voltage of your LEDs @70mA, and equations 8-11 from the TPS92633-Q1 from the datasheet.

    I also notice in your previous setup picture that you have removed the shunts from J8 and J9, but you have left the PWM pins floating. I recommend connecting pin 1 of J8 and J9 to ground to ensure that channels 2 and 3 are in the off state. If the PWM pins float high, the device will detect an open-circuit error at the LED output (J3 and J5 shunts removed) and will disable the output of all channels.

    Good luck with your debugging.

    Regards,

    Zach

  • +1 in reply to Zach Olson
    Intellectual 320 points

    Hi Zach..

    IC is now working just as expected..

    Zach Olson said:
    I also notice in your previous setup picture that you have removed the shunts from J8 and J9, but you have left the PWM pins floating. I recommend connecting pin 1 of J8 and J9 to ground to ensure that channels 2 and 3 are in the off state. If the PWM pins float high, the device will detect an open-circuit error at the LED output (J3 and J5 shunts removed) and will disable the output of all channels.

    You are correct!

    All of my settings are working.. only because i left pwm pins floating, the whole circuit was not working.. 

    I found helpful information in all of your replies..

    thank you so much for all of your help..

    Best regards,

    Tex

  • 0 in reply to Zach Olson
    Intellectual 320 points

    Hi Zach,

    One small doubt on the calculation of the R1(Rres1)..

    when i do calculation as per the datasheet as per the equation 11,

    The res1 value for 24.66V is 152Ω.. could you please explain how you have done the calculation and how i should do this in future !?

    Kind regards,

    Tex

  • 0 in reply to Tex
    TI__Genius 11765 points

    Hi Tex,

    You are correct, Equation 11 will provide a Rres value of 152Ω based on a supply of 30V, and an output current of 70mA. This equation is designed to split the output current equally between the RES pin and the OUT pin to reduce the internal power dissipation of the IC.

    I used 100Ω in my example because this was the default populated value on my EVM, this is not necessarily the value that should be chosen for optimal thermal performance.

    Regards,

    Zach

  • 0 in reply to Zach Olson
    Intellectual 320 points

    Hi zach,

    Thanks for your reply, 

    please clarify these doubts..

    Zach Olson said:
    I used 100Ω in my example because this was the default populated value on my EVM, this is not necessarily the value that should be chosen for optimal thermal performance.

    Then can we keep the resistor unchanged for all voltage values ?

    How is that the circuit is taking only 24V while 30V is the input power supply with your settings which are shared previously ?

    One small doubt with respect to my personal design.. please try to suggest if you know about this kind of circuits..

    The distance between Micro controller and TPS92633-Q1 IC is 5 meter or more.. i'm connecting the controller GPIO pins (6 pins) to this IC EN/PWM pins so, i might need to use a 5 meter cable.. 

    Is there any best way to do this task ? like is there any TI integrated circuits which can help me to do this ? 

    Regards,

    Tex

  • +1 in reply to Tex
    TI__Genius 11765 points

    Hi Tex,

    I recommend using Equation 11 in the TPS92633-Q1 datasheet to determine your Rresx value for each channel.

    How is that the circuit is taking only 24V while 30V is the input power supply with your settings which are shared previously ?

    My series LED load produces a total forward voltage of 24.66V for a current of ~70mA.

    I'm connecting the controller GPIO pins (6 pins) to this IC EN/PWM pins so, i might need to use a 5 meter cable.. Is there any best way to do this task ? like is there any TI integrated circuits which can help me to do this ? 

    I am not sure what the cable-driving capabilities of your microcontroller are. If this is a TI microcontroller, you may create a new thread directed to the microcontrollers E2E forum and the proper team will be able to provide support.

    I am aware that TI offers cable drivers and other signal conditioners, however these are typically only necessary for high-speed data lines. 

    https://www.ti.com/interface/serial-digital-interface/overview.html 

    Regards,

    Zach