I am trying to switch between two sources with solid state relay, which seems to be more robust than mechanical relay. But I can't find a SSR that can guarantee to be break-before-make. The datasheet specs always show some potential overlap between turn-on time and turn off time like below (https://www.mouser.com/datasheet/2/240/lcc110-1546141.pdf). Does break-before-make single-pole-double-throw SSR exists? Thanks.
You are trying to make a DPST (NC/NO) switch into a SPDT switch with break before make.
This requirement is the same as a half bridge that demands no shootthru between Vdd and Vss or “dead-time” yet these are tolerant to high V isolation and high blocking voltage so the cross conduction of switches will occur yet be only a transient less than the max load. The chips themselves do not radiate EMI, but your interface wiring might.
All CMOS and this part included overlap at a higher resistance than fully on so during switching time the two sources have a controlled shoot-through current between sources that dictates using a d3coupling cap for each CMOS IC. In the logic case it is between Vdd and Vss. In your case it would be between Form-A and Form-B.
If you need such operation then define the circuit impedance and voltage being switched, the required On resistance, switching capacitance and load current and reactance and dead-time between each or more explicit design specs for this multiplexing.
Figure 1. With tON and tOFF rated at 4 ms max it looks like you have a region of about 2 ms where you will have shoot-through risk.
I suspect that any dual NO / NC package like this will suffer the same problem as there is no internal switching logic involved.
If you need to avoid overlap you may need to use two NO type and control them individually.
Generally speaking, it seems to be true for most, if not all, SSR relays with single diode controlling both switches.
The devices with separate LEDs might have the break-before-make functionality. For example this app note mentions Siemens LH1502 with built-in control circuitry that ensures OFF timing to be less than ON.
What is interesting, however, is that the datasheet for Vishay LH1502, which seems to be the same device, has no mention of break-before-make, only obscure reference to some "control circuity". You can see that typical timing data makes it possible to use these relays, if you are lucky.
You can also take a look at dual 1a1b relays with separate control inputs. As @DwayneReid suggested in comments you may find relays with suitable timing characteristics and wire them in SPDT (1c) configuration.
