It would be also possible to use some other, cheaper RSPECL comparators (are there any? Maxim has something) to build lower performance logic probe. Even for VCCO it is 2.4V to ground + 2.4V to VEE so 4.8V in total which should be close enough. The scope supplies 4V on VCCI and -2.4V on VEE so total supply voltage is 6.4V for VCCI. One more thing - the LMH7332 comparators get pretty hot - I've measured over 60 C when the pod case was open. Probably, PLA2216 has slightly different input attenuator to allow 200 MHz signals (RPL1116 is rated for 100 MHz). It should be easy to make a converter to attach RPL1116 to MSO5000 (that's what I'm interested in). 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). It is connected to resistor divider between VCCI and GND (division factor 3/4). There is one mysterious pin which I've named CONF. Reference voltages from the scope are divided by 10 since input attenuator also divides the signal by 10. 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. The measurements should be quite accurate. I've desoldered elements and measured them using RLC meter. Reverse engineering of RPL116 completed:D I've drawn schematic of pod's single channel.
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