Author Topic: Replacement for Fluke 700013 IC (quad SPST analog switch)  (Read 5353 times)

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Offline richipedia

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Replacement for Fluke 700013 IC (quad SPST analog switch)
« on: May 03, 2018, 03:46:45 pm »
Hello everybody,

I recently bought a broken Fluke 8842A bench multimeter. As it turns out, two Fluke specific ICs with Fluke stock number "700013" are broken. Those are quad SPST analog switches with some integrated logic (latches and NAND gates) to accomplish the input voltage scaling and the current source switching for the resistance measurement - see images below or see the users manual at assets.fluke.com/manuals/8842a___imeng0300.pdf.

I tried to find a genuine replacement IC, but was not successful. From the 8842A users manual, I can deduce that Fluke stock number "803478" is a similar device, but I have no success either in finding one of these. After so much frustration, buying another broken Fluke 8842A or Fluke 8840A (both contain said ICs) seems too few of a challenge to me  ;), so why not design a replacement, that can replace any of the five 700013s in use in a 8842A? And why not share it with you? I already figured there are some guys also looking for a suitable replacement.

The logic functions can easily be replicated using standard 74xxnnn CMOS logic gates, I believe. As far as I'm aware, I need to consider for those...
  • supply voltage
  • propagation delay
  • digital logic level voltages (inputs need to match levels at hand on the PCB, outputs of the (N)AND gates need to match levels required by the analog switches)
  • latch must be transparent while the signal not(L) at pin 3 is low

The analog switch function can be implemented using analog switch ICs (who would have thought?). Jelly bean ICs like the Intersil DG411 or the Analog Devices ADG411 (better specs) are readily available for hobbyists like me, but I'm not familiar with all the peculiarites of these devices, I believe. Anything to consider for this purpose other than the following?
  • supply voltage: must run off analog voltages -8,2V / +7,5V and -5V / +7,5V and 0V / +15V
  • current consumption
  • propagation delay
  • on-resistance
  • off-resistance a.k.a. leakage current
  • charge injection

The values of most of the requirements above need to be extracted from the PCB and from the two working 700013s I have. This is where I'm at so far. Just start screaming at me if there are some horrible mistakes :)
  • digital logic levels: using my humble DS1054Z, I measured clean square waves at the digital signals with low levels close to 0,0 V and high levels at 4,0V or above.
  • propagation delay: tbd
  • latch transparent while not(L) is low: should be easily obtainable using a standard 74xx373 or 74xx573 and an inverter in front of the latch input
  • current consumption: if I draw more than 4 mA from either the -8,2V rail or the +7,5V rail, the voltage drops dramatically. Haven't tested the +15V rail yet. The +5V rail seems to be very stable - no wonder as it is supplied by a standard 7805 voltage regulator IC.
  • on resistance: plots in the DG411 data sheet show that on-resistance is dependent on the bias voltage at the switch nodes. So I closed a 700013 switch, put a DC voltage on one of the switch pins using a trim pot, and measured DC resistance using a measly multimeter. Is that sufficient? Seems like a very casual, unsophisticated approach to me.
  • off-resistance a.k.a. leakage current: similar to the above, I opened a 700013 switch and measured DC resistance using my measly multimeter. Result: infinite ohms. Bummer, leakage current is too low. Next try: put a high voltage on one of the switch pins, connect the other pin to the multimeter in DC-voltage-mode connected to ground. From the measured voltage and the (not very precisely specified) input impedance of the multimeter, I can calculate that leakage current must be in the order of 10 pA
  • charge injection: there is a nice Analog Devices appnote showing how to measure charge injection. Put a cap with known capacitance at one of the switch nodes, open and close the analog switch using a function gen at a rate of 10 kHz, and track the capacitor voltage using an oscilloscope. There should be a significant voltage rise when the switch is turned off. Result using a 10 nF cap: there is no voltage rise. Apparently, the capacitance is too large. Using no capacitor at all (so that just the probe input capacitance affects the circuit), I can see and measure the charge injection voltage rise. Any ideas on how to measure probe input impedance?

Well... enough ideas and questions for now. Or is it? Ah, wait!

Bonus question: what might be the root cause for the 700013s failing in so many Fluke DMMs? Is there a way to prevent my little replacement from suffering the same painful death? I would guess that there might be an unfortunate condition at power up, causing multiple switches which act on the same node to be closed at the same time, resulting in a short circuit.
 

Offline mlefe

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Re: Replacement for Fluke 700013 IC (quad SPST analog switch)
« Reply #1 on: July 15, 2019, 07:56:30 am »
Hi Richipedia,
      I'm exactly in the same place as you are... did you make any progress?

Thanks,
Martin.-
 

Offline richipedia

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Re: Replacement for Fluke 700013 IC (quad SPST analog switch)
« Reply #2 on: July 15, 2019, 09:20:02 am »
Hi mlefe,
I did build a replacement for the 700013 IC, but have not yet put any effort in testing if the analog switch IC I use (DG411) has similar performance as the originial ASIC.
I will provide my schematic later to share with the forum.
 
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Offline mlefe

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Re: Replacement for Fluke 700013 IC (quad SPST analog switch)
« Reply #3 on: July 15, 2019, 01:28:31 pm »
Excellent!! Thank you very much :)
 

Offline Kleinstein

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Re: Replacement for Fluke 700013 IC (quad SPST analog switch)
« Reply #4 on: July 15, 2019, 04:52:17 pm »
The DG411 is a relatively low ohms switch, but with relatively high leakage current. In cases where leakage is critical (e.g. ohms circuit), the DG211B should be the more suitable replacement.  At least DG211 and DG411 use the same pin-out.
 

Offline mlefe

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Re: Replacement for Fluke 700013 IC (quad SPST analog switch)
« Reply #5 on: July 16, 2019, 04:46:05 am »
Do you know if HEF4066BD could be used as well?
Here is the datasheet: https://pdf1.alldatasheet.com/datasheet-pdf/view/17724/PHILIPS/HEF4066BD.html
I'm sorry for the question, I never played with analog switches before and I'm not sure what to look at...  :-//
 

Offline Kleinstein

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Re: Replacement for Fluke 700013 IC (quad SPST analog switch)
« Reply #6 on: July 16, 2019, 09:20:30 pm »
HEF4066 and similar would be tricky, as the control voltage likely uses only 5 V logic level. So it would need extra level shifters. In addition the supply at some 15 V is close to the maximum, depending on the exact version.

The 4066 CMOS switches can be used for analog functions in principle, but the chips are not well tested - this is more like the very cheap version, many may be OK, but not guarantied.
 
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Online edavid

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Re: Replacement for Fluke 700013 IC (quad SPST analog switch)
« Reply #7 on: July 16, 2019, 11:06:50 pm »
I think 74HC4316 would be a better choice than 4066.

The question is whether the Fluke IC uses CMOS or JFET switches.  Are there any clues in the manual?

 
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Offline mlefe

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Re: Replacement for Fluke 700013 IC (quad SPST analog switch)
« Reply #8 on: July 18, 2019, 01:13:55 am »
They're CMOS, this is the description: IC CMOS, QAS, PLASTIC, HIGH, B GRADE
 

Offline mlefe

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Re: Replacement for Fluke 700013 IC (quad SPST analog switch)
« Reply #9 on: July 26, 2019, 01:38:55 am »
After reading and studying a bit, I finally came up with a couple of circuits using HEF4066B on one ocasion and max399 in a different version.
Unfortunately, I still can't figure out the 'latch part'.
Can you help me understand the purpose of it?
When I put a probe on pin 3 looks like it's always low... am I missing something?
Thanks!
 

Offline Kleinstein

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Re: Replacement for Fluke 700013 IC (quad SPST analog switch)
« Reply #10 on: July 26, 2019, 08:00:04 am »
The latch function is a kind of memory function. A 74HC75 could probably do the job. For U403/402, they seem to no use the extra logic AND function. So one could for these positions get away without that extra functions.

A hef4066 would make like more difficult with the logic levels. The 74HC4316 (suggested by EDavid)  and similar would make things easier. For higher supply it might take DG201B or similar.
« Last Edit: July 26, 2019, 08:02:51 am by Kleinstein »
 

Offline softfoot

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Re: Replacement for Fluke 700013 IC (quad SPST analog switch)
« Reply #11 on: May 29, 2020, 08:57:06 pm »
Hi, I'm yet another Fluke user looking for a solution ...

Did you make any progress on a replacement for the 700013 ??

If you did I'd love to see what you did.

BTW is the 700013 normally open (ie if an input is LOW is the switch OPEN) ??? 
If that is the case then the DG212B (normally open) would be best because the DH211B is normally closed.

Best regards,
Dave
« Last Edit: May 30, 2020, 04:25:28 pm by softfoot »
Grumpy Old Software/Hardware Engineering Git
Dave
 

Offline Kjo

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Re: Replacement for Fluke 700013 IC (quad SPST analog switch)
« Reply #12 on: August 23, 2020, 02:39:51 am »
The 700013 and it’s variants are very special devices. First, they are evidently unobtanium.
The latching function reduces the number of signals required from the ADC chip and in-guard uprocessor. Some 700013 switches are used in rather static applications, such as the precision current source. Others are VERY dynamic, such as the DC scaling circuit.
It would be informative in we knew prop delay for digital to analog. It would also be good to know the on and off capacitance presented by analog switch nodes.
The bus between the DC scaling and Sample-hold amp is a very sensitive node. It has like 5 switch nodes in common.
Anyone with a 700013 to spare for testing I would be appreciative.
PM me if so.
I have actually build several prototype 700013 with no success.
 

Offline g0rsq

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Re: Replacement for Fluke 700013 IC (quad SPST analog switch)
« Reply #13 on: December 22, 2020, 10:49:49 pm »
Hi

I am now at the same position as others here, and looking for a solution to the 700013 issue.

I have just made a replacement LCD using a GLCD, only to find one faulty 700013  :-[

Is anyone willing to share their work so far, before I sart looking into building a 700013, as I dont want to go down a blind alley if someone else has already been there!

In the next few days I will be testing the bad 700013 in case it is just one switch that has died (301C).

Then I will put a logic alayser on my good 8840A and work out the timing issues through the chip. I dont want to remove any good 700013's to test though.

Peter
 

Offline richipedia

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Re: Replacement for Fluke 700013 IC (quad SPST analog switch)
« Reply #14 on: December 27, 2020, 02:58:47 pm »
Oh well... 1 year and 9 months since I started my yet unfinished project. Still, glad to see that there are people interested in seeing how far I've come.

The 8842A's manual clearly shows the internal functional blocks of the 700013 IC's:
[attachimg=2]

The logic part consists of 4 2-input AND gates, each having one input connected to a latch and the other input connected to the 8842's electronics either directly or through an inverter.
Mimicking that part using standard logic gates should be easy.

The 700013 is supplied using 3 different voltages:
  • Pin 6: This is connected to +5V for all 5 700013 ICs. Seems to be digital supply VDD.
  • Pin 10: GND
  • Pin 20: +7.5 V for U301, U302, U303 (DC scaling, sampling etc); +15 V for U402 and U403 (precision current source). Seems to be the positive supply voltage V+ for the analog switch.
  • Pin 11: -5V for U301, U302; -8.2 V for U303, GND for U402 and U403. Negative supply voltage V- for the analog part, obviously.

For the analog switch, I figured I could use a DG411. Supply voltage is +5V ... +20V for V+ and -5V ... -20V for V-. (Probably made a mistake here, because U402 and U403 use V- = GND, but more on that later.) I do not remember more on why I chose this one, nor do I have a note.
I ruled out the 4066 analog switch. If I remember correctly, the supply voltage requirements did not match at all.

Be aware that the DG411 is active-low (enabled using a low input signal), contradictory to how the 700013's internals are presented in the manual.

For the digital part, I figured I use mostly 74AC logic devices.
With the DG411 having active-low inputs, the AND is replaced with a NAND 74HC00.
For the latch, I chose a 74AC175D. To ensure all analog switches are turned off when the unit is powered on, a little reset circuit is provided.
For the inverter, TI offers the 74LVC2G14 in a handy SOT23-6 package, which is 5V tolerant, so I chose this one.

And there's the schematic:
[attach=1]

 
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Offline richipedia

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Re: Replacement for Fluke 700013 IC (quad SPST analog switch)
« Reply #15 on: December 27, 2020, 03:13:22 pm »
I cobbled together a simple test interface to be controlled by a RasPi. It helped my to get my understanding of the workings of the 700013 right and to see which of my ICs are broken.
[attach=2]

The RasPi provides the logic control signals. The outputs are connected to just a bunch of resistor dividers, so see if the analog switches can be enabled and disabled. This is basically a DC test, though, not taking care of digital timing or any of the properties I mentioned in my initial post.
[attach=1]


« Last Edit: December 27, 2020, 03:21:43 pm by richipedia »
 

Offline richipedia

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Re: Replacement for Fluke 700013 IC (quad SPST analog switch)
« Reply #16 on: December 27, 2020, 03:23:49 pm »
Just to feed your interest, here's prototype 0 on a breadboard (while it's in the making), shoved into my test adapter.  :)
 

Offline richipedia

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Re: Replacement for Fluke 700013 IC (quad SPST analog switch)
« Reply #17 on: December 27, 2020, 03:25:51 pm »
Prototype 0 was already built to fit into the original PCB, so that's what I did.
With the 8842's PCB populated my working 700013 ICs and the prototype in the right places for the right measuring mode, it kind of works.
 

Offline richipedia

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Re: Replacement for Fluke 700013 IC (quad SPST analog switch)
« Reply #18 on: December 27, 2020, 03:29:29 pm »
For some reason, I built prototype 1 on veroboard. It plugs nicely into the 8842.
 

Offline richipedia

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Re: Replacement for Fluke 700013 IC (quad SPST analog switch)
« Reply #19 on: December 27, 2020, 03:56:14 pm »
The 8842 has 5 700013 ICs. There is one IC in my unit which I believe is fully functional. The remaining 4 are somewhere between "suspiciously high current consumption/input loading" and "completely dead". I didn't quite like the idea of making a total of 5 hand-wired veroboard replacements, so I ordered some PCBs.

Eagle files are attached.

I tried to recreate the solder mask keep-outs I found on the 8842 PCB on my PCBs, although I am not completely aware of what I am doing here and how to get it right  :-//

With U301, U302 and U303 populated with my replacement PCB and using two of the original 700013 for U402 and U403, the DMM kind of works. I tried calibrating it at work.
  • Some of the higher VDC ranges did calibrate correctly. Success!  :box:
  • Some of the lower VDC ranges did not calibrate. Probably it was the 20mV and the 200mV ranges, but would have to check again to be sure.
  • Most Ohms ranges did not calibrate correctly.
  • The ADC ranges did calibrate correctly. Yay! :box:
« Last Edit: December 27, 2020, 04:00:11 pm by richipedia »
 
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Offline Kleinstein

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Re: Replacement for Fluke 700013 IC (quad SPST analog switch)
« Reply #20 on: December 27, 2020, 06:27:02 pm »
The DG411 is low resistance, but also has more leakage. The DG211 should be a lower leakage counterpart - AFAIK with the same pin-out  :-*. Leakage can be a problem with the higher resistors.
 
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Offline softfoot

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Re: Replacement for Fluke 700013 IC (quad SPST analog switch)
« Reply #21 on: December 29, 2020, 10:37:32 am »

I am following this project with great interest,  and look forward to a working solution.
Regards,
David.
Grumpy Old Software/Hardware Engineering Git
Dave
 

Offline Noopy

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Re: Replacement for Fluke 700013 IC (quad SPST analog switch)
« Reply #22 on: April 17, 2021, 07:28:10 pm »
Hi all!

TiN had sent me a 700013 and I have taken some pictures of the die.  :-/O






Well you know what it does...




The die is 2,6mm x 2,3mm.




A 1982 Fluke design.
QAS-B seems to be the name of the switch. In the servicemanual of the 8842A the chip is named "IC CMOS, QAS, PLASTIC, HIGH, B Grade". Sounds feasible!  :-+




Fluke used eight masks to manufacture the switch.






Some test structures.
On the right side there are three different type of the resistors.
On the left side it seems like there are complementary MOS transistors. You can see the small spot in the middle of the cross where the thin gate oxide is placed.
In the middle perhaps some bipolar transistors?




Let the music play!  ;D




The four switches are easy to spot.
You can see that the left control side is supplied with +5V and 0V while the right switching side is supplied with +7,5V and -5V (of course other voltages are possible).




Some protection at the input pins.




On both sides of the analog switches there are metal lines to isolate the switches. On the left side +5V/0V and on the right side +7,5V/-5V.




The inputs without the latches are fed into a kind of a push-pull-stage before reaching the control circuit.




The control circuit contains the latch, the AND gate and the chip select.
The upper area is connected to +5V, the lower area is connected to 0V.
On the right side of the picture there is the transition from +5V/0V to +7,5V/-5V.




To control the analog switch quite a big differential push-pull-stage was integrated.
It seems like the transistor areas were optimized for ideal switching behaviour.






Now that is interesting: There are two small MOSFETs doing the switching of the analog channel. But there are two additional bigger MOSFETs connected to two unused bondpads. It seems like you can choose which transistor you like: a big one with low resistance but with a high leackage current and parasitiv capacitance or a small one with a higher resistance but with lower leackage and capacitance.  :-/O


https://www.richis-lab.de/aswitch01.htm

 :-/O
« Last Edit: April 17, 2021, 07:33:34 pm by Noopy »
 
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Offline JoergR

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Re: Replacement for Fluke 700013 IC (quad SPST analog switch)
« Reply #23 on: May 26, 2021, 06:06:34 pm »
Hi all,

This is my first post on the EEVBlog - pls be gentle. ;-)

I believe I too have a Fluke 8840 with a faulty 700013 - but before I venture to desolder everything, I wanted to know:

How did you ascertained that this was indeed the faulty chip?

Background:
All DC readings are garbage, no autoranging. Display works. I removed the AC unit and placed it in another meter where it works just fine.
All self tests except 11 fail. Voltages appear within specs, so the power supply seems ok.
Following the manual, I can get correct voltages displayed when placing a voltage directly between TP103 and common low and I get a zero reading when shorting TP103 to common low. The front panel switches allow me to switch the ranges of the display, i.e. I can display 1.3V as 13V, 130V etc. So the ADC and the Voltage reference appear ok. With a short on the input, all ranges _do not_ display zeros. The manual says:

If zero is not displayed for r3 and r5 with HI and LO shorted, then Z301 or U302-D is probably bad.

Now, I also checked track and hold. The voltages on the chips are ok, but the waveforms are off - They don't extend below 0 far enough. The shape is similar, though.

Hence, my question: Can you suggest another procedure to test whether U302 Chip, the Fluke 700013, is really at fault? I haven't given up the hope that the fault lies somewhere else ;-)
Thanks in advance!
Joerg
 

Offline Kleinstein

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Re: Replacement for Fluke 700013 IC (quad SPST analog switch)
« Reply #24 on: May 26, 2021, 06:49:03 pm »
One should be able to test the input amplifier part up to the S&H stage separately. So set a range and check the result from a signal at the input at TP302 and directly at the S&H input (e.g. pin 17=18 of U301). There can be a little offset, but should not be much.

When seeing which range does not work and how it fails one could than do a more specific test.
 
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