• State
  • Locked Locked
  • Replies 4 replies
  • Subscribers 32 subscribers
  • Views 1230 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.

TPL7407LA: About OUT7 diode removing

Kazuya Nakai59
Guru 20540 points
Part Number: TPL7407LA
Other Parts Discussed in Thread: TPL7407L,

 Hello guys,

 One of our customers is considering to evaluate TPL7407LA released May/2017 because it seems that the device is improved version of TPL7407L. On TPL7407LA datasheet, they knew that a external diode was not required to be attached between OUT7 and GND in case of inductive driving though it is required in TPL7407L case. Then they had a question about the new device, TPL7407LA as the follow.

Q1. Why the external diode is not required in case of TPL7407LA?

Has the device OUT7 tolerant level against minus surge genarated by any inductive load been improved compare with TPL7407L?

Also they have a few questions about TPL7407LA as the follows.

Q2. The absolute max rating of TPL7407LA OUT1-OUT7 has been degraded from 42V to 32V. But it is no problem for the customer because their load voltage is 12V or 5V DC.

 However they want to know whether OUTn tolerant level against any plus surge is similar with TPL7407L or not. For example, I think that TPL7407L is probably no problem if 100ns pulse of 50V is applied to OUTn.

 How about TPL7407LA?

Q3. It seems that TPL7407LA typlical Vol is almost same as TPL7407L one. But TPL7407LA maximum Vol is bigger than TPL7407L one. So I think that the graphs of Maximum Collector Current vs Duty Cycle (Fig 3/4) show that the duty cycle deleting is started at lower duty cycle than TPL7407L.

 But if the customer apply short pulse (5ms~100ms) to the input for turning on/off of OUTn with long interval (ex. 1~10seconds). In case of this, how much pulse width is allowed in thermal wise as the maximum? And is the pulse width similar with TPL7407L case?

 Your reply would be appreciated.

 Best regards,

 Kazuya Nakai.   

  • 0
    TI__Genius 15740 points

    Hi Kazuya,

    Please find the answers to your questions below:

    Q1. The external diode is not needed because the layout of the device was changed to better protect OUT7 from inductive transients. The tolerance against a negative transient has been improved from the L version.

    Q2. The changes made to the device protects the outputs from negative transients, but it also affects the COM and OUT pin voltage capability when inductive loads are driven. Instead of 40V, the device is rated for 32V. However, this is also dependent on the negative current transients put on the device during over voltage events, so it is difficult to say whether or not the device can withstand a specific higher voltage transient. 

    Q3. Yes, the VOL voltage is higher on the LA version vs. the L version, and this does have an impact on the power dissipation across the device. Without a given current and the amount of channels active, it is difficult to find the "maximum pulse width" allowed for the device. Figures 3 and 4 should be a good guide for this if the "long interval" is known.

    Thanks,

    Alek Kaknevicius

  • 0 in reply to Aleksandras_Kaknevicius
    Guru 20540 points
    Hi Alek,

    Thank you for your prompt reply.
    Could I ask you a few additional questions?

    About your answer to Q1, could you please tell me the specific value how much TPL7407LA OUT7 tolerance against a negative is improved from L one for a just reference? For examlpe, TPL7407L has a problem when OUT7 voltage is down to -0.7V by the current flowing from OUT7 to the outside. But LA is no problem even if OUT7 is -1.5V .
    Or TPL7407L has a problem when 100mA is pulled out from OUT7 but LA is no problem even if 150mA is pull out from OUT7 .
    The specific value would be very helpful because we can explain to our customer easily how much LA is improved.

    About your answer to Q3, in same condition (same current value, same on time, same on duty), is TPL7407LA temperature always higher than L one?

    Thank you and best regards,
    Kazuya Nakai.
  • 0 in reply to Kazuya Nakai59
    TI__Genius 15740 points

    Hi Kazuya,

    Q1. Low negative DC current applied to the channel OUT7 (~2mA) was enough to destroy the channel 7 of the device, whereas now the LA device can handle >250 mA of reverse current peaks. That is a pretty significant difference!

    Q3. You are correct, the TPL7407LA temperature will always be higher than the TPL7407L. However, the difference should be very minimal since the typical VOL numbers did not change significantly.

    Thanks,

    Alek Kaknevicius

  • 0 in reply to Aleksandras_Kaknevicius
    Guru 20540 points
    Hi Alek,

    Thank you very much for your answers.

    Best regards,
    Kazuya Nakai.