Need help driving two IPS1031 Low-Side MOSFETs from a PIC

[[email protected]]

The IPS1031 is a Low-Side MOSFET Driver that drives its own MOSFET. I
am planning on incorporating it into my design, but most of its spec
sheet is total gibberish to me.
I am driving two of them off of a single PIC output which can sink
3.7-5V @ 25mA.
The IPS1031 datasheet:
http://www.irf.com/product-info/datasheets/data/ips1031.pdf

Attached is a schem I used for its simulations purposes. Through the
use of "OR" diodes, only two IPS1031s are on at any single time; Q2 is
saturated when either Q1 or Q3 is saturated. S1 and S2 signafy two
different PIC Outputs.
Schematic is located at:
http://www.myfilehut.com/userfiles/155002/Switch3.JPG

 

[[email protected]]

The IPS1031 is a Low-Side MOSFET Driver that drives its own MOSFET. I
am planning on incorporating it into my design, but most of its spec
sheet is total gibberish to me.
I am driving two of them off of a single PIC output which can sink
3.7-5V @ 25mA.
The IPS1031 datasheet:
http://www.irf.com/product-info/datasheets/data/ips1031.pdf

Attached is a schem I used for its simulations purposes. Through the
use of "OR" diodes, only two IPS1031s are on at any single time; Q2 is
saturated when either Q1 or Q3 is saturated. S1 and S2 signafy two
different PIC Outputs.
Schematic is located at:
http://www.myfilehut.com/userfiles/155002/Switch3.JPG

LMAO, I forgot to mention what it was that I needed help on. I was
concerned about the required voltage to turn on the mosfet, and if in
combination with the diode and the pic output, if it would even see
this voltage.

 

[Chris]

LMAO, I forgot to mention what it was that I needed help on. I was
concerned about the required voltage to turn on the mosfet, and if in
combination with the diode and the pic output, if it would even see
this voltage.

Hi, Jed. The 1N5282 is a controlled forward voltage silicon diode, and
will have a Vf of 0.55 to 0.6V at 1mA forward current. The IR Low Side
Switch IC requires a minimum of 4.5V for guaranteed operation. If your
power supply is 5.0V, and your PIC output was exactly 5.0V, that means
the IN terminal will see 4.45V to 4.4V -- not quite enough for
guaranteed operation. And there will be a voltage drop of a tenth of a
volt or so at the PIC output with 1mA output.

Of course, 4.4V or even 4.3V should be enough. But if you want to be
sure, you might want to replace the 1N5282s with schottky diodes. That
way, your diode "Wired-OR" configuration will be guaranteed to work.
Schottkys have a typical forward voltage of less than 0.3V at low
forward current.

You might want to use standard transistors, though -- the PIC output
pin can certainly source the current, and a 2N3904 will cost a lot less
than your low side switch ICs (view in fixed font or M$ Notepad):

|
| .--------------------------------------o--------------.
| | +12V +12V +12V | |
| | | | | | |
| | ~ V | | | |
| | ~ - | | | V
| | | | | | -
| | .-. | - | |
| | | | C| ^ .-. .-.
| | | | C| | | | | |
| | '-' C| | | | | |
| | | | | '-' '-'
| | '----o----' | |
| | | | |
| | _/ ___ |/ ___ |/ ___ |/
| o--o/ o-o-|___|-o-| .--|___|-o-| .-|___|-o-|
| | | 470 | |> | 2.2K | |> | 2.2K | |>
| | D V .-. | | .-. | | .-. |
| | - 4.7K| | | | 2.2K| | | | 2.2K| | |
| | | | | === | | | === | | | ===
| | o---. '-' GND | '-' GND | '-' GND
| | | | | | | | |
| | D - | === | === | ===
| | ^ | GND | GND | GND
| | _/ | '------------' |
| o--o/ o-o -------------------------------'
| |
| |
| +|
| ---
| -
| |
| ===
| GND
|
(created by AACircuit v1.28.6 beta 04/19/05 www.tech-chat.de)

With 2N3904s or other standard NPN small signal switching transistors
and shottky diodes for D, this will work well for any 12V relay with a
coil requiring less than 100mA.

Good luck
Chris