Schematic for a 48VDC Battery Low Volt Disconnect

[ElectronsFlow]

he electronics industry has made a complete hash of the pin outs and case descriptions with about 10 different reference numbers for the same package.

Tell me about it! I found this out when browsing for the TLV3001. You'd be forgiven for thinking people who have the smarts to design these IC's could at least do a decent job being united with pinouts.

I believe this is the pinout for that link I sent you a couple messages ago. It matches the pinout you posted, So provided I stick with that exact unit everything should be fine

 

[spec]

Tell me about it! I found this out when browsing for the TLV3001. You'd be forgiven for thinking people who have the smarts to design these IC's could at least do a decent job being united with pinouts.

I believe this is the pinout for that link I sent you a couple messages ago. It matches the pinout you posted, So provided I stick with that exact unit everything should be fine

View attachment 102161

Correct.

By the way, you do know that the SOIC-8 is very small- are you able fit that size package?

spec

 

[ElectronsFlow]

By the way, you do know that the SOIC-8 is very small- are you able fit that size package?

I've got some experience with surface mount components. But certainly not a pro. I'll be sure to apply enough solder to connect and short all the pins together

 

[spec]

I've got some experience with surface mount components. But certainly not a pro. I'll be sure to apply enough solder to connect and short all the pins together

Ha Ha- that is what I do too- if I can find the f@*%$!? component in the first place that is.

spec

 

[ElectronsFlow]

Hey Spec, I've ordered all of the components last night apart from the MAX6008 shunts, I can get my hands on them, between shipping costs/minimum order quantities they work out rather expensive for what they are. I think I found a suitable substitute from Texas Instruments but I wanted to ask you if they are suitable?

Texas Instruments LM4040AIM3-2.5/NOPB

https://nz.rs-online.com/web/p/voltage-references/5338445/


EDIT: Just a thought Spec, When my custom PCB is made I don't mind using the surface mount shunts, But for the first prototype surface mount can be a pain. Could I substitute the 2 MAX6008 shunts for 2x 2.5v zener diodes?

 

[evovi]

Cool design

 

[spec]

Hi EF

Hey Spec, I've ordered all of the components last night apart from the MAX6008 shunts, I can get my hands on them, between shipping costs/minimum order quantities they work out rather expensive for what they are. I think I found a suitable substitute from Texas Instruments but I wanted to ask you if they are suitable?

Texas Instruments LM4040AIM3-2.5/NOPB

They will work OK but, in the schematic of post #21, you would need to change R21 to 470K. The circuit performance will be just as good but the circuit current consumption would increase to 100uA. Note that the objective is to generate a precision 5V reference voltage. The two MAX6008 shunt voltage references are just a means to that end, so a single 5V shunt reference would be just as good (the MAX6008 was specified because it has an exceptional performance at very low currents and will regulate the voltage to 2.5V at 1uA forward current).

EDIT: Just a thought Spec, When my custom PCB is made I don't mind using the surface mount shunts, But for the first prototype surface mount can be a pain. Could I substitute the 2 MAX6008 shunts for 2x 2.5v zener diodes?

Not really EF. An ordinary Zener diode is not up to the job for a couple of reasons- sorry.

I will have a look and see if RS has got a good micro power shunt voltage reference in stock, and get back.

spec

 

[spec]

Hi again EF,

This single TO92, thru-hole 5V version will replace both Zener diodes without loss of performance (R21 will still need to be reduced to 470K and the cut-off circuit will still consume 100uA):
LM4040DIZ-5.0/NOPB https://nz.rs-online.com/web/p/voltage-references/5343065/

Don't worry about the lower initial accuracy. That is not important because you will be setting the cut off voltage yourself. The change with temperature and other characteristics will be just as good as the higher accuracy part (they are the same chips in fact).

spec

DATA SHEET
https://www.ti.com/lit/ds/symlink/lm4040-n.pdf

 

[ElectronsFlow]

Hey Spec,
Sweet, I've just ordered some. I should have all the parts arrive early next week.

Thanks again man!

 

[spec]

Hey Spec,
Sweet, I've just ordered some. I should have all the parts arrive early next week.

Thanks again man!

Good move- look forward to learning how it all goes.

My pleasure EF.

spec

 

[ElectronsFlow]

Hey Spec, Just thought I'd give you an update to the going's on. RS ended up having the TLV3701's delayed in shipping. I've received an email today that they have been dispatched, should receive them tomorrow or the day after. After reading the data sheet for the LM4040DIZ-5.0 Am I right that only 2 out of the 3 pins are used? I've never used a shunt like this unit before. In layman terms it's not too dissimilar to a zener, however where the similarities end is this shunt only putouts a fixed voltage, rather than a voltage drop correct?

 

[spec]

Hi EF,

Thanks for the update. I like RS, and have used them a lot, especially at work. But they are a bit of a shambles sometimes. They got into a complete tangle with one order and in the end they just re-sent the whole order and did not want the incorrect parts back.

After reading the data sheet for the LM4040DIZ-5.0 Am I right that only 2 out of the 3 pins are used? I've never used a shunt like this unit before. In layman terms it's not too dissimilar to a zener, however where the similarities end is this shunt only putouts a fixed voltage, rather than a voltage drop correct?

That is correct, just leave the third pin open circuit- it is used by the factory for testing/calibration.

You are also correct when you say that a shunt voltage reference is like a Zener diode. You are also right in saying that they are different but not in the way that you say. In the forward direction a Zener diode and a shunt precision voltage reference are functionally the same. They are not the same functionally in the reverse direction though. In the reverse direction a Zener diode behaves like a normal diode (in the forward direction), if that makes sense. The characteristics of an integrated circuit shunt references, in the reverse direction, depends on the particulart part's design. But you can always put a normal diode in parallel with the integrated shunt referece to get a similar characteristic to a Zener diode (but check the data sheet to ensure the integrated shunt brference will stand 1V reverse connection).

Some shunt precision voltage references are just accurate Zener diodes, but the manufacturers can achieve far superior performance by using an integrated circuit containing active components.

spec

 

[ElectronsFlow]

Thanks for taking the time to inform me Spec! I'll be sure to update you once I've got all the components together

 

[ElectronsFlow]

Quick Update, I received the last of the parts on friday, While I was tempted to assemble this circuit on a breadboard, in the back of my mind I knew my custom PCB would arrive early~mid this week. Since the TLV3701 is rather a little beast to hand solder wires to, I figured I'll wait a couple more days for the PCB to show up.

 

[spec]

Quick Update, I received the last of the parts on friday, While I was tempted to assemble this circuit on a breadboard, in the back of my mind I knew my custom PCB would arrive early~mid this week. Since the TLV3701 is rather a little beast to hand solder wires to, I figured I'll wait a couple more days for the PCB to show up.

Good move EF.

spec

 

[ElectronsFlow]

Hey Spec, Finally got my hands on the PCB. Ended up having a week long delay during manufacturing. Could I trouble you to update the schematic to include LM4040DIZ-5.0 shunt? I think I made a muck up with my schematic I sent to the PCB maker with regards to the shunt. So if I have your version to compare I'll see if I got it wrong/right. If I got it wrong its a pretty easy fix. Rather not release the blue smoke unnecessarily

 

[spec]

POST ISSUE 3 of 2016_12_03 (also see the schematic of post #2 for a version of the cutoff circuit using two very low current shunt voltage references)

Hi EF,

No problem.

Below is the version of the cutoff circuit of post #2, using the LM404DIZ-5.0 shunt voltage reference in place of the two MAX6008 shunt voltage references.

spec

​

NOTES
see post #2

DATASHEETS
see post #2
LM4040: https://www.ti.com/lit/ds/symlink/lm4040-n.pdf

 

[ElectronsFlow]

Hey Spec, Phew I got it right! looks like they (PCB manufacturer) stuffed up on the pinout though, however lease its an easy fix. Quick question I forgot to ask before, I couldn't find the SQM100P06 mosfet from any of my usual suppliers. I've got some IRF9510 on hand in my bag of tricks. They be a substitute or no?

I might be mistaken? but is Q3 drain and source correct orientation?

 

[spec]

Hi EF,

Phew I got it right! looks like they (PCB manufacturer) stuffed up on the pinout though, however lease its an easy fix.

Glad you have a handle on it- in life there is always something trying to stop you succeeding.

I couldn't find the SQM100P06 MOSFET from any of my usual suppliers. I've got some IRF9510 on hand in my bag of tricks. They be a substitute or no?

Afraid no: The IRF9510, gate threshold voltage is too high and the Rdss is way too high- sorry. But there are many other PMOSFETs that will suit. It is just that the SQM100P06 is particularly good for this application. If you have any other PMOSFETs in your spares box, just list them and I will check them for suitability. Also if you post a link to your preferred supplier, I will see if they have a suitable PMOSFET.

I might be mistaken? but is Q3 drain and source correct orientation?

The PMOSFET connections may look odd if you are used to NMOSFETs, but yes, the PMOSFET connections shown on both schematics are correct (schematic of post #37 has been updated to indicate the drain, source, and gate).

spec

 

[ElectronsFlow]

e PMOSFET connections may look odd if you are used to NMOSFETs, but yes, the PMOSFET connections shown on both schematics are correct (schematic of post #37 has been updated to indicate the drain, source, and gate).

Thanks for the info Spec!

I'm afraid the only other P-mosfet's I own are too lower voltage for this circuit I don't surpose I could trouble you to find a suitable substitute on RS?? If you're even in NZ I'll take you to the local pub for a beer