1858-0044 ?

[brouhaha]

(09-29-2023 10:22 PM)teenix Wrote:  PBHV8110DA, NPN, 1A, 0.4V VceSat, 1.25W in a SOT-23. Still need to get rid of the heat though, 25mm square pads suggested at that power.

That Vce(sat) spec seems impressive, until one looks at Note1, whcih says that it's at pulse width <=300us, duty cycle<=2%. If that characteristic isn't similar at a much higher duty cycle, then it's not going to be better than an MMBT2222A. Given how much more this costs than the MMBT2222A, it might be worth prototyping with this part and measuring what saturation voltage you actually observe.

Also if you have less Vce(sat) in your transistors, and want to run the printhead at the same current, the delta in voltage drop for the transistor has to be made up somewhere else, so the heat dissipation will be transferred there. That's the reason for not switching to nFETs, which would lower the dissipation in the transistors even more than the PBHV might.

The 1.25W power dissipation is for 1 in^2 copper pad, so the limit on the DIP PCB is going to be much lower, probably not too different than the power dissipation limit of the MMBT2222A.

Quote:The PIK IC must have the drive circuitry incorporated inside as it directly connects to the transistor bases. I think the Anode Driver has an external resistor common to each segment drive on the Vcc pin (5).

It probably does have beefier output transistors. In PMOS, pulling high works well, but you can't generally get much current pulling low. That's convenient for driving the bases of NPN transistors. I don't know how many mA they can drive without the Vout going too low, but I'd guess it's probably not much more than 15mA, and they probably count on the transistor hFE being 40 or better at the 500mA collector current. (That's the 2222A hFE spec.)