TPS3840-Q1: Query regarding review of design

Nitesh Bhurke

Part Number: TPS3840-Q1
Other Parts Discussed in Thread: TPS3842-Q1, TPS3840, TPS3842, TPS3808

Tool/software:

Hello,

We are using TPS3840DL32DBVRQ1 in one of our design, I have attached the image of our design to review, as per design we are using the EC25 microcontroller. When the EC25 is in power-down mode, it can be turned on to normal mode by driving the PWRKEY pin to a low level for at least 500ms.

For this, we have designed an ON-OFF circuit (refer to the attached image). V_ORING is a supply voltage that may vary from 7.4V to 12V. We are planning to use a resistor divider to provide VDD to the TPS3840DL32DBVRQ1. Is this approach acceptable?

When VDD rises from the threshold (6.8V), the RESETN will go high. As a result, one input of the X-OR gate will be high and the other will be low for the capacitor charge time (660ms). Therefore, the output of the X-OR gate will be high for 660ms. This will generate a 660ms pulse on the transistor’s base, which will subsequently drive the PWRKEY pin of the EC25 low for 660ms.

When VDD goes below 6.4V then the RESETN will go low, as a result one input of the X-OR gate will be low but as we have provided D25 diode it will provide the discharge path to reduce the discharge time. as we do not require pulse for turning off.

So can you please review the design and please confirm if our approach is electrically and functionally correct?

In the attached image we are using 74AUP1G58GW,125 IC as an X-or gate.

Regards,

Nitesh

over 1 year ago

0 Sila Atalar over 1 year ago

TI__Genius 9640 points

Hi Nitesh,

Thanks for your question!

I will get back to you by the end of Wednesday (pacific time)

Best

0 Sila Atalar over 1 year ago in reply to Sila Atalar

TI__Genius 9640 points

Hi Nitesh,

When I look at over all system it logically make sense to me. But please let me highlight that our customers are responsible from their design and TI products are helping meet their objectives and requirements.

When I look at TPS3840-Q1, it seems a good fit. VDD and VReset seems as in datasheet specification according to this schematic, and Ireset is less than 5 mA.

I hope this helps. Please let me know if you have further question.

Best Regards,

Sila Atalar

0 Nitesh Bhurke over 1 year ago in reply to Sila Atalar

Intellectual 260 points

Hello Sila,

Thank you for the clarification. Referring to the image of schematic attached, we have a resistor divider circuit at the VDD pin, where V_ORING ranges between 6-12V, can the VDD pin be able to resist if any surge occurs while turning ON the board? Is the 0.1uF enough between VDD and GND pins?

Regards,

Nitesh

0 Sila Atalar over 1 year ago in reply to Nitesh Bhurke

TI__Genius 9640 points

Hi Nitesh,

The recommended operation condition for TPS3840-Q1 VDD is 10V. We have supervisors that can directly connect 12V, 24V, and 48V batteries and are capable of handling surges.

I'd like to inform you about a new device we have TPS3842-Q1, Automotive,42V, small size nano-power undervoltage supervisor, and it could be a better fit for your requirements.

And, generally 0.1 uF capacitor should be enough for most application.

Best,

Sila

0 Nitesh Bhurke over 1 year ago in reply to Sila Atalar

Intellectual 260 points

Hello Sila,

Thanks for the response, do you have any supervisor IC with hysteresis greater than or equal to 400mV?

0 Sila Atalar over 1 year ago in reply to Nitesh Bhurke

TI__Genius 9640 points

Hi Nitesh,

Yes we do have supervisors that has hysteresis greater than 400mV. Please find TPS3760-Q1, TPS3762-Q1 which they both can be connected directly to 12 V / 24 V automotive battery system for continuous monitoring of over (OV) or under (UV) voltage conditions.

Are you looking for using a hysteresis greater than 400 mV for the above system or do you need in elsewhere?

0 Nitesh Bhurke over 1 year ago in reply to Sila Atalar

Intellectual 260 points

Helllo Sila,

As per our new design requirement when Vin is above around 7V Resetn should be high and when Vin drops below around 6V Resetn should be asserted Low. The hysteresis should be 0.8V to 1V.

If we use resistor divider circuit at the input to half the the input voltage same as we have used earlier in the above diagram, then the supervisor IC with threshold voltage 3V and hysteresis 800mV to 1V can also be suitable for our application.

Regards,

Nitesh

0 Sila Atalar over 1 year ago in reply to Nitesh Bhurke

TI__Genius 9640 points

Hi Nitesh,

Thanks for explaining your hysteresis requirement.

Could you please provide your project timeline and expected volume for this project? I would like to check with our backend team to see how can I support with this better.

Thanks,

Sila

0 Nitesh Bhurke over 1 year ago in reply to Sila Atalar

Intellectual 260 points

Project timeline: September end and expected volume: 10

0 Sila Atalar over 1 year ago in reply to Nitesh Bhurke

TI__Genius 9640 points

Hi Nitesh,

I think still TPS3842-Q1 may be a better fit due to surges.

Best,

Sila

0 Nitesh Bhurke over 1 year ago in reply to Sila Atalar

Intellectual 260 points

Yes, I agree but TPS3842-Q1 has maximum 10% hysteresis, we require at least 15% hysteresis. Can you please check if you are having supervisory IC similar to TPS3840 with buit in hysteresis greater than 400mV or 15%.

Regards,

Nitesh

0 Sila Atalar over 1 year ago in reply to Nitesh Bhurke

TI__Genius 9640 points

Hi Nitesh,

I found an App note after checking with my team. I learned that you can add additional input voltage hysteresis can to the SVS. Please check this app note: https://www.ti.com/lit/an/slva360/slva360.pdf?ts=1724364831512

I believe this way TPS3842-Q1 can meet your hysteresis.

Best,

Sila

0 Nitesh Bhurke over 1 year ago in reply to Sila Atalar

Intellectual 260 points

Hello Sila,

TPS3842-Q1 part number is not available with any distributors, kindly suggest us any alternative that provides the same function or suggest us any distributor that will provide us this part TPS3842-Q1

0 Sila Atalar over 1 year ago in reply to Nitesh Bhurke

TI__Genius 9640 points

Hi Nitesh,

You can get it from TI.com. It's available on the TPS3842-Q1 product page.

You can ordering option at the bottom of the page.

Best,

Sila

0 Nitesh Bhurke over 1 year ago in reply to Sila Atalar

Intellectual 260 points

Hello Sila,

Thanks for suggestion and sharing the application note, we have referred the app note, By following the app note for increasing hysteresis we have designed the attached circuit using the TPS3808G33QDBVRQ1. Could you please review the design?

We have selected value of R1 and R2 such that we can have VT- at 6V and VT+ at 7V. Can you please check if our design/calculations are correct and whether it is suitable for our application or not?

0 Nitesh Bhurke over 1 year ago in reply to Nitesh Bhurke

Intellectual 260 points

Also, is it possible to increase the hysteresis of TPS3840-Q1 using the resistor as mentioned in application note? if possible please advice.

0 Sila Atalar over 1 year ago in reply to Nitesh Bhurke

TI__Genius 9640 points

Hi Nitesh,

I will test the resistor values you provide on the EVM for you to see if you are getting the expected hysteresis by the end of this week.

Best,

Sila

0 Nitesh Bhurke over 1 year ago in reply to Sila Atalar

Intellectual 260 points

Hello Sila,

Thanks for the response, we have also designed circuit with TPS3842. I have attaches the image of circuit. Please verify the design and please suggest if any changes are required.

Also please check if TPS3842300DRLR is active and available.

0 Sila Atalar over 1 year ago in reply to Nitesh Bhurke

TI__Genius 9640 points

Hi Nitesh,

Sila Atalar said:
You can get it from TI.com. It's available on the TPS3842-Q1 product page.

You can ordering option at the bottom of the page.

Currently we have only adjustable variant released on TI.com. The orderable part number is PTPS3842A011DRLRQ1.

the internal reference voltage Vt is set to 0.7V, and the typical hysteresis is set at 1% Vt.

Vs– = 0.7 V

Vs+ = 0.707 V

And I think you want to keep Rp = 100 kΩ. Rh = 1 MΩ as in the app note. Please update your design

0 Nitesh Bhurke over 1 year ago in reply to Sila Atalar

Intellectual 260 points

Hello Sila,

We are having the following queries:

1. What is the threshold of PTPS3842A011DRLRQ1? as per datasheet it is showing 0.7V. If we want reset low on 6V and reset high on 7V, is it possible to design using PTPS3842A011DRLRQ1?

2. So, if we use PTPS3842A011DRLRQ1 what will be the values for R1 and R2?

3. Our idea was to use TPS3842300DRLR, as it has threshold voltage 3V. so we were thinking to use as shown in the image I have shared on Aug 27. Is TPS3842300DRLR available? Is it possible that we can have few as sample for testing?

4. Also, is it possible to increase the hysteresis of TPS3840-Q1 using the resistor as mentioned in application note? if possible please advice.

0 Sila Atalar over 1 year ago in reply to Nitesh Bhurke

TI__Genius 9640 points

Hi Nitesh,

Please find my answers in below;

Yes, it's possible that you can increase the hysteresis of any supervisor (it could be TPS3840, TPS3842 or TPS3808.) According the App note, the concept should be the same, of course you need to consider the different reference voltages for the different supervisor.

TPS3842 is a new supervisor and we haven't released the different variants yet. Currently the only variant for TPS3842 is the adjustable variant. When I checked with my team, I learned that 3V variant is not currently planning to release. But 6.5V fix threshold variant with 10% hysteresis will be on TI.com on September. Do you think this helps?

PTPS3842A011DRLRQ1 has 0.7V threshold. I will need some time to find and verify the R1 and R2 values. I can share my result by early next week.

Best,

Sila

0 Nitesh Bhurke over 1 year ago in reply to Sila Atalar

Intellectual 260 points

Hello Sila,

Thanks for the response, I just want to confirm that, is the scheme for increasing hysteresis also applicable for the ICs do not have sense pin? or it is necessary to have sense pin, as TPS3840 do not have sense pin.

Also, can you please check if you can provide me the TINA library model for TPS3840, TPS3842 or TPS3808 so I can also verify by simulating, I tried with pspice model for TPS3840 but I am not able to simulate it or get the results.

0 Sila Atalar over 1 year ago in reply to Nitesh Bhurke

TI__Genius 9640 points

Hi Nitesh,

For external hysteresis, internally what we need is the Sense feature as in high level of block diagram. For TPS3840-Q1, the VDD and Sense pins are combined. So it should work.

I need to check for the model. I'm not sure if we can simulate the behavior when there Rh resistor. Let me check with my team on this.

Best, Sila

0 Nitesh Bhurke over 1 year ago in reply to Sila Atalar

Intellectual 260 points

Hello Sila,

Any updates on this?

0 Nitesh Bhurke over 1 year ago in reply to Nitesh Bhurke

Intellectual 260 points

Hello Sila,

I have tried to simulate TPS3840 design in PSpice for TI, but i am not able to get output. I am attaching my schematic file. Could you please verify if everything is correct or if any changes are needed? If the design is correct, could you simulate it and provide me with the output?

DESIGN1.DSN

0 Sila Atalar over 1 year ago in reply to Nitesh Bhurke

TI__Genius 9640 points

Hi Nitesh,

I will reach out to via email to support you better on your inquiry by the end of today. I think this will be easier and faster for us to align.

Best Regards,

Sila Atalar

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TPS3840-Q1: Query regarding review of design