RPL1116 (MSO1000Z) and PLA2216 (MSO5000) Active Logic Probe teardown

[Vtech]

Here are some photos of RPL1116 Active Logic Probe pod used in MSO1000Z series scope.

Scope has 16 channel logic probe. The probe pod uses 8x LMH7322 (Dual 700ps High Speed Comparator with RSPECL Outputs). 4 comparators on each side. The pod is connected to the scope using 68 pin connector and flat cable. Reference voltage is generated inside the scope.
Cable connector has:
16x2 pins for PECL signals,
22x GND between diff pairs + some extra,
6 pins for VCC
2x2 pins for +/- supply voltage
Some 4 more signals (reference voltage??)


Most likely, the same design is used in new pod for MSO5000 series - PLA2216 Active logic probe. Here are some x-rays of the new pod: https://www.eevblog.com/forum/testgear/hacking-the-rigol-mso5000-series-oscilloscopes/msg2055715/#msg2055715

[wulfman]

get me some dimensions and i can reproduce the board for everybody.
If i make some preliminary schematics, maybe you can fill in the blanks with a ohm meter ?

[oliv3r]

Here's some links to the PLA2216 X-Ray's. Attached is the close-up from the second link

https://www.eevblog.com/forum/testgear/hacking-the-rigol-mso5000-series-oscilloscopes/msg2055715/#msg2055715
https://www.eevblog.com/forum/testgear/hacking-the-rigol-mso5000-series-oscilloscopes/msg2055778/#msg2055778
https://www.eevblog.com/forum/testgear/hacking-the-rigol-mso5000-series-oscilloscopes/msg2057401/#msg2057401

So I reccon to rename the topic to add the PLA2216 for the MSO[5789]000 series

Was looking at pricing of the LMH73222's and TI says they are 4.35 USD per 1 Ku! 
Digikey had them for 8 something a piece!
So with the need of 8, that's 35 to 65 USD! just for the chips

[TK]

Was looking at pricing of the LMH73222's and TI says they are 4.35 USD per 1 Ku! 
Digikey had them for 8 something a piece!
So with the need of 8, that's 35 to 65 USD! just for the chips

You can use 4 LMH7324 instead and save some $$

[TopLoser]

i think it will be useless without the LA daughter board inside, thats where the dso recognize the LA existant, or am i missing something on the newer rigol model?

The board just contains the comparators, scope is ready and waiting for the digital outputs from the comparators and outputs threshold voltages for the comparators as selected on the scope. I think there’s an input to be pulled low to indicate to the scope that the pod is plugged in. That’s certainly the case with the 5000 series and this looks exactly the same but different pinout and connector.

[Vtech]

I've changed the topic to include PLA2216 as this is now more desired version. I'm going to do full reverse of RPL1116 including measurement of passives. I hope we can make DIY logic pod for all Rigols.

The board is 4 layer so not exactly cheap to make. To cut the price we can switch to LMH7324 as Oliv3r said (4 would be reqired). Mayby order samples from TI

[TopLoser]

madmac posted this about the 50 pin 0.1 pitch good old cheap and cheerful IDC connector:

Had a quick look at the 50 way logic connector while having coffee

0V     X    X    D7P
D7N   X    X    D6P
D6N   X    X    D15P
D15N  X    X    D14P
D14N  X    X    D0V

0V     X    X    D5P
D5N   X    X    D4P
D4N   X    X    D13P
D13N  X    X    D12P
D12N  X    X    0V

0V     X    X    D3P
D3N   X    X    D2P
D2N   X    X    D11P
D11N  X    X    D10P
D10N  X    X    0V

0V     X    X    D1P
D1N   X    X    D0P
D0N   X    X    D9P
D9N   X    X    D8P
D8N   X    X    0V

4V0    X    X    0V
4V0    X    X    2V4
D0-7V X    X    D8-15 VREF   10:1 INPUT  +/- 1V5
-2V5   X    X    0V
0V     X    X    DETECT  LOW FOR PROBE ATTACHED

Input range is +/- 15 volts.

Top of table is power switch on/off side and   lower pin  X   X  upper pin

https://www.eevblog.com/forum/testgear/hacking-the-rigol-mso5000-series-oscilloscopes/msg2057401/#msg2057401

[joeyjoejoe]

Another nice option is that those needing fewer channels can just populate fewer comparators! With that in mind, it might also be possible to create a board with 2 layers only.

Another option for 2 layers would be to increase the size of the PCB if that eases the routing.

[oliv3r]

i think it will be useless without the LA daughter board inside, thats where the dso recognize the LA existant, or am i missing something on the newer rigol model?

For the DS1000Z series; yeah it's not that usefull ...

[dren.dk]

The reason this subject is interesting is that the MSO5000 series is trivially upgradeable and even the cheapest one comes with all of the hardware, except for probes:
https://www.eevblog.com/forum/testgear/hacking-the-rigol-mso5000-series-oscilloscopes/msg2057338/

I think a lot of us that have an MSO5072 in the mail without the LA option would really like to be able to roll our own LA pod cheaper than what Rigol wants for one, even if performance is a bit more modest.

[Vtech]

Reverse engineering of RPL116 completed:D

I've drawn schematic of pod's single channel. Every channel is identical. I've desoldered elements and measured them using RLC meter. The measurements should be quite accurate.

The probe has 3 supply voltages:
VCCO = 2.4 V under load (when pod is connected, no load 2.5 V)
VCCI = 4.0 V (no load 4.1 V)
VEE = -2.4 V (no load -2.5 V)

IN- of channels 1-8 and 9-16 are connected together to common reference voltages delivered by the scope. Reference voltages from the scope are divided by 10 since input attenuator also divides the signal by 10.

There is one mysterious pin which I've named CONF.  It is connected to resistor divider between VCCI and GND (division factor 3/4). It is either some configuration pin so the scope knows that the pod is connected or it is simply measurement of VCCI voltage (now when I think about it, this is more likely the case).

Here is the pinout of the 68 pin connector:

1   GND      35   VEE
2   VEE      36   VCCI
3   VCCI   37   REF9-16
4   NC      38   REF1-8
5   VCCO   39   VCCO
6   VCCO   40   VCCO
7   VCCO   41   VCCO
8   D16Q+   42   D16Q-
9   GND      43   D15Q+
10   D15Q-   44   GND
11   D14Q+   45   D14Q-
12   GND      46   D13Q+
13   D13Q-   47   GND
14   D12Q+   48   D12Q-
15   GND      49   D11Q+
16   D11Q-   50   GND
17   D10Q+   51   D10Q-
18   GND      52   D9Q+
19   D9Q-   53   GND
20   GND      54   GND
21   CONF   55   GND
22   GND      56   GND
23   D8Q+   57   D8Q-
24   GND      58   D7Q+
25   D7Q-   59   GND
26   D6Q+   60   D6Q-
27   GND      61   D5Q+
28   D5Q-   62   GND
29   D4Q+   63   D4Q-
30   GND      64   D3Q+
31   D3Q-   65   GND
32   D2Q+   66   D2Q-
33   GND      67   D1Q+
34   D1Q-   68   GND

Comparing this with TopLoser's findings, looks like the RPL1116 and PLA2216 pods are nearly identical. It should be easy to make a converter to attach RPL1116 to MSO5000 (that's what I'm interested in). Probably, PLA2216 has slightly different input attenuator to allow 200 MHz signals (RPL1116 is rated for 100 MHz).

One more thing - the LMH7332 comparators get pretty hot  - I've measured over 60 C when the pod case was open.

[madmac]

The LMH7324 is only spec'ed down to 5V VCC. The scope supplies 4V

The other difference is hysteresis is adjustable on the LMH7322 and set to around 15mV. On the LMH7324 it is fixed at 25mV. Should not make much difference unless trying to probe very low logic swings.

[Vtech]

Supply voltage should not be a problem. The scope supplies 4V on VCCI and -2.4V on VEE so total supply voltage is 6.4V for VCCI. Even for VCCO it is 2.4V to ground + 2.4V to VEE so 4.8V in total which should be close enough .
It would be also possible to use some other, cheaper RSPECL comparators (are there any? Maxim has something) to build lower performance logic probe. These RPL1116 logis probes are a bit over engineered in my opinion. LMH7322 are specified up to 4GHz so quite an overkill for 100MHz probe.

According to datasheet, sampling rate of digital channels on MSO5000 is 1Gsps. 700ps propagation delay on LMH7322 ensures that the sampling time lags no more than 1 clock behind actual data. But this is only for the comparator itself. What about input attenuator and propagation through connector cable and scope's internal circuitry?

MSO5000 datasheet says:
Min. Detectable Pulse Width: 5 ns
Maximum Input Frequency: 200 MHz
Inter-channel Time Delay: 2 ns (typical), 5 ns (maximum)

Am I right that any LVDS comparator should work with RSPECL inputs at this voltage levels (2.4V)?
From LMH7322 datasheet: "When used in combination with a VCCO supply voltage of 2.5V the outputs have LVDS compatible levels."

[oliv3r]

So I took your pics and overlayed them; just for fun and got the following
I also added the X-Ray from ian, but it was immediatly obvious, while similar (the chips on the same spots) the traces and mounting holes where fastly different.



As for the 'overratedness' I do think they used the same probe cable in all of their earlier MSO's and use the PLA2216 for all the new high-end scopes. So you would have to look at the specs of the MSO7000 or MS9000 when it arrives what the logic probes will have to endure. And then; it was probably cheaper to do one for all is my guess.

[Vtech]

As for the 'overratedness' I do think they used the same probe cable in all of their earlier MSO's and use the PLA2216 for all the new high-end scopes. So you would have to look at the specs of the MSO7000 or MS9000 when it arrives what the logic probes will have to endure. And then; it was probably cheaper to do one for all is my guess.

MSO7000 uses its own logic probe RPL2316. I can't find exact bandwidth spec of this logic pod but it is probably identical to RPL2216 except for the connector.

[suj]

MSO7000 uses its own logic probe RPL2316...

My MSO2072A also uses RPL2316 probe. If I remember correctly, they are of the passive type - the comparators are on the oscilloscope PCB.

[helmy]

what would happen if we feed a 5v p-p signal using a homemade passive probe into the MSO5000 without the comparators?

also is there anyone working on making their own active probe to use with the MSO5000, and getting it made in china to be sold for cheap?

[Vtech]

what would happen if we feed a 5v p-p signal using a homemade passive probe into the MSO5000 without the comparators?

The scope would blow up  At least if there was enough current provided.

Logic pod inputs in MSO5000 accept RSPECL differential signals. Typical levels are Vo-1.1V for high and Vo-1.5V for low line. Since Vo is about 2.4V, H=1.3V, L=0.9V (remember this is differential signal so one line is L and the other is H at the same time).
At this voltage levels it is compatible with LVDS levels so it is possible to use "something" with that type of outputs but you would lose ability to watch negative voltages (not very useful anyway, is anyone still using ECL logic?)

[dren.dk]

I'm in the process of drawing up a LA pod using LMH7324 ICs, I hope to be able to whack it on a 2 layer board and make a couple of units for me and a friend.

I don't have the time to stick it on gitlab right now, but it will end up there when it's a little more complete.

[Noy]

I got 10 samples from ti and will also start of i have a bit more time .
I don't think that a 2 layer board is a good Idea for differential rspecl signals.

[dren.dk]

Yeah, 2-layer is not the best, but the differential signals are destined for a long flat ribbon cable anyway, so I doubt a couple of mm on a two layer board will mean anything in comparison.

[dren.dk]

Well, I just took at look at the pinout of LMH7324 and it's a huge bitch to lay out on a two-layer PCB, so I have re-drawn the entire pod using LMH7322.

The complete schematic is now on gitlab, feel free to critique and/or steal it outright:
https://gitlab.com/dren.dk/mso5k-la-pod/tree/master

[oliv3r]

That's looking great! And on gitlab as well yay!

One question though, Rigol splits each of those comparators 'far' apart, e.g. on chip1, it's ch0 and 8, on chip2, it's ch1 and 9, right?

Is there any downside to having it like ch0 and ch4; ch1 and ch5. That would indeed allow your plan, to have them split in 2 pods, which has many advantages (cheap bastards can only get the 1

But what does that mean to the backend? Do they have more memory/bandwith if you only use chn 0 - 7. Further more, if you do ch0 - 4 on chip 1, pin-out wise, that would mean that on the UI, it would still be chan 0 - 8; so that could be quite confusing?

[dren.dk]

I had actually not considered the distribution of channels vs. comparators, I have no idea if it matters, but my guess is that it's only a matter of layout.

[Noy]

I think its better to build a small but long pod. Put female 50pin straight  connectors in the pcb edge (Pad 1 top, Pad 2 bot, ..).
Then you can Plug it directly in the scope and If you put a second connector in the Others side  you can use jumperwires ...
And If you want, you can use a ribbon cable instead If you use a male header in both pcb sides.
For the cheap guys: Just solder the amount of chips you have/want on the pcb.. You only have to watch out for the correct pin.

Edit:
Why aren't there any protection diodes or others stuff?
Maybe we should add some usb3 (High speed, low capacity) tvs/esd protection diodes?