I'm *ASSUMING* your objective is still a 150KHz, 20V amplitude (40V peak to peak) squarewave, centered about 0V, capable of driving a load with 200mA, with no DC offset when its not being output. If not, please clarify your requirements immediately.
Ian, Why can't I just use one ltc4446? it is 0 to 100V mosfet drive capabilities, so 2x 4446's do not need to be used...
To produce the above waveform, a LTC4446 requires either two series connected PSUs or a fairly expensive dual output PSU to get the +20V and -20V rails centered about 0V (Gnd). It also requires level shifting on its inputs and a somewhat tricky circuit to provide deadtime to prevent shootthrough that is likely to require some file-tuning to get right (unless you have a MCU that can output a pair of antiphase PWM signals with added deadtime).
OTOH for the price of an extra chip and an extra pair of MOSFETs, the dual LTC4449 circuit has many advantages:
- It only needs a single 20V supply rail, so will run from a much cheaper single PSU.
- It doesn't need a fancy level shifter to get the logic signals down to the negative rail.
- It doesn't need a circuit to add deadtime to the drive waveforms as that's internal in the LTC4449 chips.
You need to balance the costs vs benefits for the project as a whole, which will be dependent on the number of these drive circuits you require and on what other voltage rails your project needs. If you need lots of these drivers, and other circuits need +/-20V rails (or low current +/-18V or lower rails that can reasonably be provided from the +/-20V rails by linear regulators, you'll probably want to go for something like the LTC4446 circuit. OTOH for only four pumps, the dual LTC4449 circuit for each is probably still cheaper, even though it requires four logic level MOSFETs per pump rather than the two ordinary MOSFETs required by the LTC4446 circuit.
A further note here: at 150KHz with an inductive load you probably cant rely on the MOSFET internal body diodes for clamping the resulting inductive spikes when it switches, as their reverse recovery time will be too long and you'll get a massive current spike as charge is cleared out of the junction when it gets suddenly reverse biassed when the opposing MOSFET switches on. Therefore each MOSFET will require a Schottky diode across it in parallel with its body diode.
I don't have a circuit simulator so idk if there are atomic intricacies that make this have to be done this way.
Errrr. . . . . you seem to be opening
LTspice schematics OK. LTspice *IS* a circuit simulator, free to use unless you are designing ICs (silicon chips) commercially. For any of my posted circuits in LTspice .asc format, simply click the 'Run' icon on its toolbar, then click any of the nodes (signals) in the circuit to plot them.
Also, Ian, in your dual 4449 circuit, What is the difference between V2 and v4??
V2 and V4 provide input signals to control the simulated circuit. V2 provides 'In' the 150KHz logic level squarewave signal. V4 provides 'Gate' which is the signal to switch the pump on or off (Logic '1' = On).
Also, side topic, does anyone know where I can buy or make a 5V 1uA power supply for the 4446? I don't want to use a 7805 then amp limiter then 2 resistors, because the 1uA would be uncertain and there will be voltage drop. Sorry I am noob. Thanks
You don't need a 5V 1uA supply for the LTC4446 and if you had one it probably wouldn't work. In fact, that circuit doesn't even need a 5V rail. It does however need a supply in the 9V to 12V range to provide the Vcc supply to the LTC4446 and the CD4030. A single LM7812 would be suitable to power *all* your pump drivers Vcc supplies. It draws an approx 2A transient from Vcc when the output switches low, to charge the boost capacitor, so the Vcc supply must be very well decoupled right at each LTC4446 chip - I'd suggest a 22uF ceramic with a 0.1uF in parallel if you are building the drivers on sepeate boards, or 100uF output capacitor on the LM7812 and 0.1uF ceramic at each LTC4446 if you are building all four drivers on a single board with a groundplane.
The LTC4449 based circuits do need a 5V supply, but not a 1uA one. They'll also need a high transient current from the 5V rail when the output switches low. A LM7805 is the easiest option to meet their 5V supply requirements.
Neither circuit needs a heatsink on the LM78xx regulator as the average current consumption will be pretty low. Make sure you meet the minimum load current requirement for the regulator - you may need an extra load resistor on the regulator output, possibly feeding a 'power on' LED.