• State TI Thinks Resolved
  • Locked Locked
  • Replies 7 replies
  • Answers 3 answers
  • Subscribers 63 subscribers
  • Views 288 views
  • Users 0 members are here
Support feedback
Options
Options
Similar topics

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

TPS2H000-Q1: Open Load Operating issue

Woo Sungchul
Prodigy 10 points
Part Number: TPS2H000-Q1

We use TPSH000-Q1 (version A)

2-Channel Output Load are LED Module. 

Chip support Open Load Detecting function.

But. We don't use open load function because  it can't perform certain function. 

So. Diag_EN : Disable 

Diag_EN : Disable Status. 

 : Channel1 : OFF  //  Channle1  Output Load (connected),

  Channel2 : OFF // Channel 1 Output Load (Connected) 

    

  Diag EN : Disable

 : Channel1 : ON  //  Channle1  Output Load (connected),

  Channel2 : ON // Channel 1 Output Load (Connected) 

  Diag EN : Disable

 : Channel1 : OFF//  Channle1  Output Load (connected),

  Channel2 : OFF // Channel 1 Output Lfoad (not Connected)  <-- Open Load

Open Load Voltage is 5.2V (Vbat : 12V) // Output load voltage changes according to the value of Vbat

 

  Diag EN : Enable

 : Channel1 : OFF//  Channle1  Output Load (connected),

  Channel2 : OFF // Channel 1 Output Lfoad (not Connected)  <-- Open Load

Diag En : Disable --> Enable 

Output2 (Open Load) Voltage Change  5.2 V --> 2.2V 

 

Problem 

  Diag EN : Disable

 : Channel1 : ON  //  Channle1  Output Load (connected),

  Channel2 : OFF // Channel 1 Output Lfoad (not Connected)  <-- Open Load

if you turn on channel1 LED, the output2 channel voltage changes 5.2 V --> 2.4V ( Same as Diag EN : Enable When channel2 open load voltage) 

We want to hold channel 2 voltage level  (5.2V)

thank you

  • 0
    TI__Mastermind 32650 points

    Hello,

    When the device is enabled, the open load circuitry works. DIAG_EN is inconsequential here as far as the output being on/off is concerned. DIAG_EN only affects what signals are reported on the STx pins and would not cause outputs to go low/high.

    To maintain a high voltage on the output during open load, we recommend adding an external resistor as described in section 8.3.6.2 in the datasheet.

    Thanks,

    Shreyas

  • 0 in reply to Shreyas Dmello
    Prodigy 10 points

    I know that it is recommended to use 20kohm external resistor for openload detection. 

    But, I can't use 20kohm because of sleep current issue. 

    So we use 1Mohm external resistor and ADC circuit is used to find the open load 

    (MCU supports ADC circuit // Detection Voltage Level) 

    The current problem is as follows 

      - External Resistor : 1Mohm

     -  Diag Enable Status : Disable 

     - Channel_1 Open Load / Channel 2 Closed Load and LED ON (Channel_2 : PWM Signal input) 

        Channel _1 : 5.5V --> 1.7V     @ 12V supply  //  Voltage Drop occurs.

    In the vehicle environment. Openload Detection Voltage level is 9V ~ 16V 

    In the past, there was no problem using only 1 Channel. 

    Currently, both channels  muse be used. 

    However, when one channel is openload and a PWM signal is applied to the other channel, 

    Voltage drop occurs. 

    The Open Load Voltage has been changed like this. 

      @Vbat : 9V  // 4V ---> 750mV  

       @Vbat 12V : 5.5V --> 1.3~1.5V

       @ Vbat 16V : 7.2V --> 3.1V

    When using the existing 1 Channel. 

    Even if the GEN of the vehicle was shaken, there seemed to be no problem in detecting it with the ADC because there was a voltage margin.

    In the state where voltage drop occurs, there is a risk of false detection. 

    So, Even if the Diag_EN pin is disabled. 

    Like using 1 Channel, I want to have a voltage value that does not cause a voltage drop. 

  • 0 in reply to Woo Sungchul
    TI__Mastermind 32650 points

    Hi Woo,

    I think the issue is that with two channels there is more I,ol,off current that is sinking into the device. As such the options are to either reduce the resistance or change the detection threshold. 

    I would recommend changing the resistor to a smaller value(not necessarily 20kOhm) but lower and lower than 1MOhm to find a sweet spot that results in okay sleep current but also holds the voltage on the output high.

    Another system could be used where the resistor is connected through a FET that only turns on when DIAG_EN is high. Therefore in the controller or software system, it could be set up to ignore the output unless DIAG_EN is high. 

    Unfortunately we are working around the specifications of the older device and we have integrated the resistor internally into our new devices with such kind of switch which only turns on when DIAG_EN is high.

    Thanks,

    Shreyas

  • 0 in reply to Shreyas Dmello
    Prodigy 10 points

    Hi Shreyas. Thank you for your advice. 

    I alse want to use a resistor value lower than 1 Mohm. 

    OEM Sleep Current Spec. is very tight. 

    For 1M Ohm. 1 Channel consumes 12uA. 

    The 2 Channel Diver consumes 24uA. 

    I will try to evaluate by changing the resistance, but it is not a fundamental problem-solving method. 

    The only solution is that no voltage drop occurs when the PWM signal is applied. 

    Please rate  if the sampe symptoms appear on the EVB Board. 

    When the resistance value is changed from 20K to 1M. 

    And if the voltage drop does not occur in the chip that I would lkie you to check if it is possible to control.

    Thanks,.

    Woo.

  • 0 in reply to Woo Sungchul
    TI__Mastermind 32650 points

    Hi Woo,

    As specified on the datasheet, the leakage into the VOUT pin can be at minimum 75uA. We expect similar behavior on the EVM but exact behavior may be only achieved with your system and your load. Please feel free to order samples of the EVM for testing with your load if required.

    For our newer generation and next generation devices, we have integrated a system that disconnects the open load detection when the DIAG_EN pin is low.

    Is it possible to use devices like TPS1HC100 for this application? If not, then a lower resistance is required.

    Thanks,

    Shreyas

  • 0 in reply to Shreyas Dmello
    Prodigy 10 points

    I'am currently working for an automotive tier 1 company. 

    It is being mass-produced as TPS2H000-Q1 (Var. A)

    Previously, Only one of the two channels was used, 

    but as the function to use the remaining 1 channel was added, the open load undetected issue occurred due to the voltage drop.

    Other models cannot be reviewed. 

    Based on your opinion, the evaluation was conducted while changing the external resistor value. 

    However, the resistance value that satisfies the sleep current is only 1Mohm. 

    The only solution is to eliminate the voltage drop problem. 

    Thanks.

  • 0 in reply to Woo Sungchul
    TI__Mastermind 32650 points

    Hi Woo,

    The value on the datasheet is a recommended method buy which this can be solved but we do note that it causes high leakage for your system. It may be possible to use a newer device like TPS1HC100 which can disengage the open load when DIAG_EN is pulled low.

    Thanks,

    Shreyas