LM293A: Worst Case Output Saturation Voltage Curve

Shinichi Inoue

Guru 18781 points

Part Number: LM293A
Other Parts Discussed in Thread: LM193, LM393, LM293

Dear Specialists,

My customer is considering LM293A and has a request.

I would be grateful if you could advise.

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Datasheet P.11　Figure 6-3 shows the output characteristics when the LM293A output is at L level. As the current draws in, the saturation voltage increases, and the output voltage jumps when it exceeds 10mA. Perhaps this characteristic is a typical value.

On the other hand, the data sheet P.8 6.10 Electrical Characteristics for LM193, LM293, and LM393 (without A suffix) specifies the IOL Low-level output current at 6mAmin.

Due to product deviation, when the output drive capability is low(6mA min), the slope change point circled attached graph will shift to the left?

Is it correct this understanding?

Could you please provide the data below.
(1) Could you give me a graph of the worst value (IOL 6mA)?
(2) If possible, I would like the data to be driven by the comparator supply voltage of 5V.

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I appreciate your great help in advance.

Best regards,

Shinichi

3 months ago

+1 Clemens Ladisch 3 months ago

Guru 212930 points

The output of the comparator is an NPN transistor. Figure 6-3 just shows the typical characteristics of this transistor.

The datasheet gives a guaranteed value only for 4 mA. This implies that the transistor is guaranteed to not go out of saturation at this current, but it might happen at any larger current.

1. Move the line up from 130 mV to 700 mV.

2. The transistor has a constant base current (see the functional block diagram); this behaviour does not depend on the supply voltage.

+1 Chuck Sins 3 months ago in reply to Clemens Ladisch

TI__Mastermind 22970 points

Thanks Clemens for answering and Shinichi for your post.

Chuck

0 Shinichi Inoue 3 months ago in reply to Chuck Sins

Guru 18781 points

Hi Clemens and Chuck,

Thank you for your reply.

I’d like to confirm your suggestion.

Does 130mV indicate the voltage at Io 4mA.

When the output current is 6mA, the voltage will be 700mV.

The line move up?

I appreciate your great help and cooperation.

Best regards,

Shinichi

+1 Clemens Ladisch 3 months ago in reply to Shinichi Inoue

Guru 212930 points

Yes.

+1 Chuck Sins 3 months ago in reply to Clemens Ladisch

TI__Mastermind 22970 points

Thanks again for quickly resolving

Chuck

0 Shinichi Inoue 3 months ago in reply to Chuck Sins

Guru 18781 points

Hi Clemens and Chuck,

Thank you for your reply.

I have organized your advice.

The minimum value is IOL = 4mA, which is listed in VOL of the electrical characteristics.

At this time, VOL(maximum) is 700mV.

In other words, the slope of the graph changes at the point of IOL=4mA and VOL=700mV.

Could you please comment if there is any misunderstanding.

I appreciate your great help and cooperation.

Best regards,

Shinichi

+1 Chi Nguyen1 3 months ago in reply to Shinichi Inoue

TI__Expert 8026 points

Hi Shinichi,

Thanks for reaching out. As mentioned before, the only value we can warranty is the VOL at IOL = 4mA. The linear approximation approach can be valid for estimations but we cant really warranty that the behavior of the output current will perform like that or exactly how the slope changes. It may be that at IOL = 6 mA, the VOL is 700mV but its possible you may need to add some process variation of about 15-20% to get the worst case value.

0 Shinichi Inoue 3 months ago in reply to Chi Nguyen1

Guru 18781 points

Hi Chi,

Thank you for your reply.

I understand and keep in mind your suggestion.

I appreciate your great help and cooperation.

Best regards,

Shinichi

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LM293A: Worst Case Output Saturation Voltage Curve