LMC6442: Leakage Current input/output pin to (V+)/(V-) pin

Hey Shinichi, 

I believe this article provides the illustrations you are asking for: 

All the best,
Carolina 

Hi Carolina,

Thank you for your reply.

I read the article and have several question.

I would be grateful if you could advise.

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(1) Is the internal circuit of the LMC6442 similar to Figure 1 in the article?

(2) Is an clamp diode connected between the output pin and the V + / V- pin?

(3) The absolute maximum rating of the input/output voltage of LMC6442 is (V-)-0.3V (V +) + 0.3V.

Does this mean that the Vf of the internal diode is 0.3V?

(4) Even when 0 to 1.8V is input, does the input exceeding (V-)-0.3V (V +) + 0.3V flow out to V + and V-?

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I appreciate your great help.

Best regards,

Shinichi

Hello Shinichi, 

I am not sure about the specific internal circuitry of the LMC6642 since the datasheet is not very descriptive. However, I also found this article that may also prove useful about your customer questions: 

Why does the customer need to know the internal circuitry? What are they trying to accomplish?

Hi Carolina,

Thank you for your reply.

According to the datasheet, I guess the input pin and output pin have protection clamp diodes to V+/V- pin.

This is very important for the customer.

Could you please confirm to other members.

I appreciate your great help and cooperation.

Best regards,

Shinichi

Shinichi,

For input or output voltage outside of the supply rail, current will be split between V+ and V-.  For both >V+ and <V- cases, current will flow through both pins. I do not have data for the split percentages. In semiconductor there is a saying "there is no such thing as a diode". That means every diode prefers to act as a bipolar transistor with the '3rd lead' being any nearby node.     

The AMR table is 5mA, so it is better to keep this current below 500uA. The actual diode voltage varies with the temperature.

Hi Ron,

Thank you for your reply.

I thought there were clamp diodes on the input and output pins.

The absolute maximum ratings of the input and output pins are (V +) + 0.3V and (V-) -0.3V.
It was thought that when a voltage exceeding (V +) + 0.3V and (V-)-0.3V was applied, the voltage would exceed Vf of the diode and current would flow toward V + and V-.

You mentioned that when <(V-) is input with> (V +), current flows through both rails.

In the case of LMC6442, does it mean that there are no clamp diodes on the input and output pins?

I appreciater your great help.

Best regards,

Shinichi 

Hi Shinichi,

yes, there ARE ESD clamps from the inputs and outputs to the rails and they are very probably ESD diodes. But they can interact with the intrinsic substrat diodes or can be part of a more complex circuit interacting or not with the substrat diodes. So thinking of having simple diodes there might be a too simplistic assumption and can cause trouble when treating them as simple diodes.

Kai  

Shinichi,

For when current flows, think of a diode. For where the current flows, be prepared for it to go to V+ or V- 

300mV is the specified voltage because little (safe) current will flow even at the highest allowed temperature.  

We could help better if the factor that lead to this question was explained.

Hi Kai and Ron,

Thank you for your reply.

I'm sorry for the late reply because I was off on the weekend.

I understand internal clamp diode can act as another circuit.

I'll share this information with the customer.

Also I confirm the background of this question.

I'll feedback to you when I obtain.

I appreciate your great help and cooperation.

Best regards,

Shinichi 

Hi Ron,

I could obtain the background of the customer's question.

---background
When the power of amplifier circuit ​​is turned off in the state of the circuit configuration,
I am concerned that the electric charge remaining in the ceramic capacitor mounted on the circuit may destroy the amplifier.

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Would you please confirm the schematic.

Could you please contact my e-mail  address listed below.

<email address removed>

I appreciate your great help and cooperation.

Best regards,

Shinichi

Shinichi,

I sent a friend request. Once we are "friends" we can share privately.

Hi Ron,

Thank you for your reply.

I just accepted friendship.

I'm preparing the materials.

Then I send you.

Could you please wait for a while.

I appreciate your great help and cooperation.

Best regards,

Shinichi

Hi Ron,

Thank you for your reply.

I understand capacitor and resistor value look good.

I'll share this information with the customer.

I appreciate your great help and cooperation.

Best regards,

Shinichi