AFE4403 interface with NJL5501R

praba karan

Other Parts Discussed in Thread: MSP430FR5959, AFE4403, AFE4490, AFE4403EVM, AFE4400, AFE4400SPO2EVM

Hello,

I am trying to implement a pulse oximeter using AFE4403 with MSP430FR5959. I have came across a forum post by Praveen Aroul , telling about interfacing AFE44X0 with NJL5501R. based on that forum pose i have came up with a schematic for AFE4403. My doubt is , will this implementation works fine.

6607.AFE4403.pdf

The attached schematic is based on AFE44X0 forum post ( http://e2e.ti.com/support/applications/high_reliability/f/30/p/285068/995576.aspx#995576 ).

If the above is not working,then can i follow the same approach for AFE4490. Will that works fine.

I have seen ACLK of MSP430 is connected to XIN of AFE4490. does is needed anyway. because ACLK of MSP is an output signal and it is connected to an oscillator input of AFE4490. I feel like it is giving two lock signals same pins. am i missing anything in this point. The ACLK can be divided by 2,4.. factors, so we can provide clock to the AFE4490 from MSP430. If it is possible then what is the need of connecting an 8Mhz resonators ti that XIN. can anyone kindly clarify my doubts

Thanks in advance

over 9 years ago

0 Amy Schnoor over 9 years ago

TI__Mastermind 18275 points

Praba,

We have received your post and should have a response back to you soon.

0 praba karan over 9 years ago in reply to Amy Schnoor

Prodigy 120 points

Thank you Amy Ball, I will be waiting for your reply.

Regards

E.Prabakaran

0 Praveen Aroul over 9 years ago

TI__Mastermind 49146 points

Hello Prabakaran,

AFE44xx family of devices has been designed to work with photodiodes.

Since we do not recommend NJL5501R (phototransistor) based pulse oximeter solution using AFE4403 or AFE4490, we cannot guarantee that your implementation will work successfully.

The purpose of having both ACLK of MSP430 and a resonator connected to XIN of the device is to provide an ability to choose either the external clock from MSP430 or the clock from the resonator.

If you plan to use the resonator, then R11 should not be installed.

If ACLK from MSP430 is providing the clock to AFE44xx, then Y1, R9 and R10 should not be installed, R11 should be installed and XTALDIS bit (CONTROL2 register bit 9) must be set to disable the crystal module.

0 praba karan over 9 years ago in reply to Praveen Aroul

Prodigy 120 points

Dear Praveen,

Thank you for the reply. I would like to know that, have you evaluated any new senors with AFE44X0 series. I have gone through your post related to this same question. But that was very old post. so i just wanted to know that have you evaluated any new sensors in recent time.

Thanks in Advance

E.Prabakaran

0 Praveen Aroul over 9 years ago in reply to praba karan

TI__Mastermind 49146 points

Hello Prabakaran,

We have also evaluated reflective sensors like SFH7050 from OSRAM and NJL5310R from NJRC.

These sensors are currently shipped with AFE4403EVM.

Regards

Praveen.

0 Scott Brenneman over 8 years ago in reply to Praveen Aroul

Genius 3265 points

Hi Praveen,

Sorry to jump in on this thread after it's been quiet for months, but it's relevant to our design. Has the NJL5501R been tested and found not to work, or is it just unknown if it will work?

What is it about a phototransistor-based detector which makes it less suitable for the AFE4403? The NJL5501R is smaller than the SFH7050 or DCM05, and thus it's attractive to us.

The NJL5310R you recommend doesn't appear to be designed for SpO2 measurement since it contains two green LEDs, not red + IR. Am I interpreting that correctly?

Thanks,
Scott

0 Praveen Aroul over 8 years ago in reply to Scott Brenneman

TI__Mastermind 49146 points

Scott,

The NJL5501R has been tested and not found to work reliably with AFE44xx.

NJRC have other PD based optical sensors with small form factor that could be used for SpO2 measurement.
You may want to check with NJRC.

0 Scott Brenneman over 8 years ago in reply to Praveen Aroul

Genius 3265 points

Thank you for confirming that.

0 Balajy Kumar over 8 years ago in reply to Praveen Aroul

Prodigy 90 points

Hi Praveen,

I am using AFE4400 (Integrated Analog Front-End for Heart Rate Monitors and Low-Cost Pulse Oximeters ) in my design. During Design phase TI is suggested to use NJL5501R-TE1 Photo Reflector for AFE4400.But in the above conversation it seems like this part is not reliable to the AFE.During our testing phase we found issue with the PD.Its not giving any datas.
Can you suggest the Drop in replacement alternate Photo Reflector part for AFE4400 with the same functionality?

Thanks
Balajy

0 Praveen Aroul over 8 years ago in reply to Balajy Kumar

TI__Mastermind 49146 points

Hello Balajy,

I don't remember a drop in replacement for NJL5501R.

You may want to check with the manufacturer NJRC for the alternate part.

0 Vijayan Sivamani26 over 8 years ago in reply to Praveen Aroul

Prodigy 25 points

Hi Praveen,

In my design, I have used AFE4400 with NJL5501R as per previous recommendation along with the discretes (Resistors and capacitors) as in reference design.
My question is,
1. Is replacing the part NJL5501R by other device will be only option to make the circuit work reliably or is there any option to tune the discretes in the circuit to make the circuit work and retained 'NJL5501R ' ?
2. What are the other recommended devices for NJL5501R replacement ? which are evaluated and worked reliably.

Regards,
Vijayan

0 Amy Schnoor over 8 years ago in reply to Vijayan Sivamani26

TI__Mastermind 18275 points

Vijayan,

1. We do not currently have a discrete solution that has been proven to work.
2. Our recommendations that we make can be found on our FAQ (Question #3) posted here: e2e.ti.com/.../369445

0 Balajy Kumar over 8 years ago in reply to Praveen Aroul

Prodigy 90 points

Hi Praveen,

I have requested NJRC for the replacement of NJL5501R parts. They dont have a direct replacement.But They have suggested to use NJL5510R part. which can support to measure both pulse rate and SPO2. Have you tested these Photo sensor with AFE4400RHAT?

Can you confirm it?

Thanks

Balajy

0 Praveen Aroul over 8 years ago in reply to Balajy Kumar

TI__Mastermind 49146 points

Hello Balajy,

No we have not tested the NJL5510R with AFE4400.

If the photosensor is a photodiode, the optical sensor should work fine with the AFE.

0 Balajy Kumar over 8 years ago in reply to Praveen Aroul

Prodigy 90 points

Hi Praveen,

I am planning to use NJL5510R with AFE4400. The schematics connection would be same as NJL5501R ( assuming) since its has photo diode instead of transistor or do u have any reference schematics for this sensor?.

please give your suggestions because i have to do rework in the existing board.

Thanks

Balajy

0 Praveen Aroul over 8 years ago in reply to Balajy Kumar

TI__Mastermind 49146 points

Hello Balajy,

I have shown the AFE interface (H bridge configuration) to the NJL5510R sensor in the image below.

0 Balajy Kumar over 8 years ago in reply to Praveen Aroul

Prodigy 90 points

Praveen,

In AFE4403 reference schematics, I have seen the clamp Diode and EMI filter in the photo sensor interface. Does it need for this part NJL5510R?

Do I need to add that connection in the rework? or can i connect it directly with AFE without any additional circuit?

Thanks

Balajy

0 Praveen Aroul over 8 years ago in reply to Balajy Kumar

TI__Mastermind 49146 points

Balajy,

If you expect to see accidental higher voltages at the INN, INP, DETP and DETM lines, it is recommended to use clamp diodes to supply and ground to protect the AFE4490 / AFE4400. For battery operated systems this might not be necessary.

For the EMI filters, in wearable systems with wireless capability, RF energy can attenuate the signals on the INN and INP channels. It is recommended to use the common mode choke coils to suppress common mode noise.

0 Balajy Kumar over 8 years ago in reply to Praveen Aroul

Prodigy 90 points

Praveen,

Can you share the schematics file of the reference board part AFE4400SPO2EVM?

Thanks

Balajy

0 Amy Schnoor over 8 years ago in reply to Balajy Kumar

TI__Mastermind 18275 points

Balajy,

The schematics can be found on page 55 of the User's Guide.

www.ti.com/.../slau480c.pdf

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AFE4403 interface with NJL5501R