PCA9306-Q1: PCA9306TDCURQ1 Vref2 resistor value

sundararao yanamala

Part Number: PCA9306-Q1

Hi,

(PCA9306TDCURQ1)

I would like to know, what is the Reference-transistor current (Iref = 5uA) given in the Design Parameters table2?

And like to know, what is the EN pin input leakage current requirements? because we are considering 200K is only for limit leakage current between Vref2 and Vref1.

Thanks

over 6 years ago

0 fhoude over 6 years ago

TI__Genius 17205 points

Hello Sundararao,

This is the current travelling through 200k resistor. Here is a post that explains how the reference voltage is generated for the pass fets. The resistor sets the bias current and also limits current that passes through reference fet during startup and shutdown phases.

https://e2e.ti.com/support/interface/i2c/f/390/t/589374?tisearch=e2e-quicksearch&keymatch=pca9306

Let me know if you still have questions after reading the post.

-Francis Houde

0 sundararao yanamala over 6 years ago in reply to fhoude

Intellectual 260 points

Thanks Francis for your information.

Now I understood operation more clearly from Normal Setup circuit in shared link than datasheet.

And I have two questions please answer them too,

1. EN is used for many FET's switching purpose here, what is total current drawn by EN pin in worst case?

2. Suppose if we use 158K in place of 200K, what consequences we will face?

Sundar

0 fhoude over 6 years ago in reply to sundararao yanamala

TI__Genius 17205 points

Hello Sundar,
The EN pins don't draw much current, most of the current is from REF2 to REF1. The current is basically: (Vdpu - Vref2)/(R=200k), Vref2 is approximately Vref1 + Vth. The current going through R is always there, so changing the value changing it directly.
-Francis Houde

0 sundararao yanamala over 6 years ago in reply to fhoude

Intellectual 260 points

Hello Francis Houde,

Thanks for information,

Taking datasheet Reference-transistor current (IREF = 5uA typ) into consideration, we have replaced 200K with 158K in TRW ADAS system schematic.

So, could you please confirm is it OK to use 158K?

Regards,

Sundar

0 fhoude over 6 years ago in reply to sundararao yanamala

TI__Genius 17205 points

Hello Sundar,
Yes this is ok.
-Francis Houde

0 sundararao yanamala over 6 years ago in reply to fhoude

Intellectual 260 points

Thanks Francis,

Last question on this topic, because on BOM concern we like to change 158K to some standard resistor value.
Could you please suggest range of this pull up resistor. I mean, what are the min and max value of resistor?

Regards,
Sundar

0 Max Robertson over 6 years ago in reply to sundararao yanamala

TI__Guru 62910 points

Hi Sundar,

A good guideline for this resistor value is to keep it between 50 kOhm and 300 kOhm. Lower values result in higher static ICC currents (based on the equation that Francis provided). Values below this range would give current values that are unnecessarily high, and above this range the currents will be too low for the device to function reliably.

Best regards,
Max

0 sundararao yanamala over 6 years ago in reply to Max Robertson

Intellectual 260 points

Thanks Max for your information.

Regards,

Sundar

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PCA9306-Q1: PCA9306TDCURQ1 Vref2 resistor value