Half Bridge Gate Driver IC Circuit
Half Bridge Gate Driver IC Circuit
(OP)
I am looking at the Fairchild FAN7382 half bridge gate driver. On page 2 of their data sheet (attached) they show a typical application circuit. In this diagram, there is a resistor R2 from the gate of Q1 (the high side MOSFET) to the source of Q1. Similarly, there is a resistor R4 from the gate of Q2 (the low side MOSFET) to the source of Q2.
What is the purpose of these resistors? Are there any rules of thumb for determining values to use for these?
Ed
What is the purpose of these resistors? Are there any rules of thumb for determining values to use for these?
Ed





RE: Half Bridge Gate Driver IC Circuit
Furthermore as the system is powered up they provide a 'brainless' solution to transient charge from briefly turning ON the devices.
Value: Generally you look at the leakage that can be expected from the design, in this case the driver chip. If there is a stated amount of leakage at the LOW output state, the value of the resistors must be low enough to preclude the FETs from turning ON. If no spec exists you start at something like 47k and go from there. Too low a value and you will affect the drive current negatively, and the resistors will dissipate too much power.
Keith Cress
kcress - http://www.flaminsystems.com
RE: Half Bridge Gate Driver IC Circuit
Using a micro-controller to drive the gate driver IC, it could take tens or even hundreds of microseconds after power is applied to drive the gate output signals. Pulling Q2's gate high while tying Q1's gate to its source through the resistor R2 would put the half bridge into the desired initial state while the micro-controller was going through its power on sequence. If the micro-controller failed for some reason, the switch would then return to this initial state. Although it might take a while to charge up Q2's gate through R4 if R4 is something like 47K.
Ed
RE: Half Bridge Gate Driver IC Circuit
Dan - Owner

http://www.Hi-TecDesigns.com
RE: Half Bridge Gate Driver IC Circuit
RE: Half Bridge Gate Driver IC Circuit
RE: Half Bridge Gate Driver IC Circuit
http://
Dan - Owner

http://www.Hi-TecDesigns.com
RE: Half Bridge Gate Driver IC Circuit
Keith Cress
kcress - http://www.flaminsystems.com