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Inquiry about sensing solution

MJ Jeon
Genius 5240 points

Other Parts Discussed in Thread: INA240

Hi, TI support team

Inquiries about the current sensor to be applied to the concept below have been received from the customer.

Application: Low-frequency massage device

Detail : A product that delivers low-frequency stimulation with two pads connected to the device

The solution the customer is looking for: A sensing solution to stop the operation of the device when one or both of the two PADs fall off the skin.

The customer wants to know if sensing is possible through the current sensor (INA240).

I am attaching the block below.

It is a structure that outputs the frequency by loading it on the PWM.

Since the device has to stop operating even when one pad is dropped, sensing for each line of Ch1 and Ch2 shown in the block below seems necessary.

The reason (see waveforms below) is that the waveforms for 1 PAD drop and for all drop cases are the same as 1-2.

I share the waveform received from the customer.

This is the waveform when only PWM is output and when Frequency is output together.

1. PAD CH1, CH2 output: MAX Level + Frequency

1-1. [Max Level unplug PAD]

1-2. [Max Level plug PAD]

2. PWM output : MAX Level

2-1. [Max Level unplug PAD]

2-2. [Max Level plug PAD]

If there are other sensing methods applicable to this solution, please recommend them.

Can I use TI's current sensor (INA series, etc.) to sense the power signal such as the attached waveform?

Please let us know if you have additional questions.

I will answer you.

Thanks.

Regards,

MJ

  • 0
    TI__Mastermind 35890 points

    Hi MJ,

    At first glance, INA240 will be able to survive in this application. However before going too far,  you’d want to evaluate some important electrical parameters. Here are a couple I can think if:

    If the current into the pads are small (mA scale), it would be difficult for INA240 since its input bias current becomes significant relatively-speaking.

    The other is quiescent current – INA240 requires 1.8mA constant current which may be an issue if this is a low power handheld device.

    If none of these is a problem, then highly likely you could go with it.

    Regards, Guang