Hi m8!
The TXB and TXS level shifters are for logic, e.g. weak current. For example one of these cant even drive I2C coz of current limits.
I suspect fet input gate capacitance may have something to do with your issue. This capacitance may be significant. Perhaps your IC functions correctly and it just discharge the capacitance extremely slowly. But i would think its burned coz the peak current is so much higher than it would be rated for. Mosfet gate input capacitance is in range of 5000pF-10000pF. It is very high for power mosfets coz it needs to drive huge currents (&peaks), hence the geometry of the conducting channel needs to be big enough for that, and a big physical geometry equals big parasitic capacitance. In comparison, a small logic mosfet gate may have 4-10pF input capacitance, e.g. 1k times smaller, coz a logic mosfet is designed for small currents. Similarly, lets say a logic buffer IC is made for speed (60Mhz) and very small parasitic capacitance, at some extent perhaps its current capability may be even lower than the rating of uC pin itself.
Charging a gate with such capacitance makes high peak currents, blindly say it can get in range of 3-6A (peak). Some time ago the TC drivers i chose for that board we made had 9A and 12A peak ratings, good for up to 10nF load capacitance. Bit overkill but good to have it capable to dissipate enough for driving in range of some 10s of kilohertz, coz after one cycle the frequency matters directly for power dissiapation. The TXS/TXB dont even give peak ratings, they say just continious +/-50mA, lets say a peak would be around 0.5A rating so the power mosfet capacitance may be too much. Hence, i wouldnt use these logic buffers for mosfet driving.
For example IRL8743 using some datasheet values for peak charging current:
Peak current (I) = Q / dt = MOSFET gate charge 36(typ) to 54(max) nC / Turn-on/turn-off time 23 ns = 2.35A(max) to 1.56A(typ).
Q is also C * V, so can be 5110pF*5V ~ 25.55 so Peak I = (C*V)/dt = 1,11A. Again, these are one-time peaks and not continious values. After these math out, the power dissipation needs to do same in relation to switching frequency, then it should be all good.
The TXB and TXS level shifters are for logic, e.g. weak current. For example one of these cant even drive I2C coz of current limits.
I suspect fet input gate capacitance may have something to do with your issue. This capacitance may be significant. Perhaps your IC functions correctly and it just discharge the capacitance extremely slowly. But i would think its burned coz the peak current is so much higher than it would be rated for. Mosfet gate input capacitance is in range of 5000pF-10000pF. It is very high for power mosfets coz it needs to drive huge currents (&peaks), hence the geometry of the conducting channel needs to be big enough for that, and a big physical geometry equals big parasitic capacitance. In comparison, a small logic mosfet gate may have 4-10pF input capacitance, e.g. 1k times smaller, coz a logic mosfet is designed for small currents. Similarly, lets say a logic buffer IC is made for speed (60Mhz) and very small parasitic capacitance, at some extent perhaps its current capability may be even lower than the rating of uC pin itself.
Charging a gate with such capacitance makes high peak currents, blindly say it can get in range of 3-6A (peak). Some time ago the TC drivers i chose for that board we made had 9A and 12A peak ratings, good for up to 10nF load capacitance. Bit overkill but good to have it capable to dissipate enough for driving in range of some 10s of kilohertz, coz after one cycle the frequency matters directly for power dissiapation. The TXS/TXB dont even give peak ratings, they say just continious +/-50mA, lets say a peak would be around 0.5A rating so the power mosfet capacitance may be too much. Hence, i wouldnt use these logic buffers for mosfet driving.
For example IRL8743 using some datasheet values for peak charging current:
Peak current (I) = Q / dt = MOSFET gate charge 36(typ) to 54(max) nC / Turn-on/turn-off time 23 ns = 2.35A(max) to 1.56A(typ).
Q is also C * V, so can be 5110pF*5V ~ 25.55 so Peak I = (C*V)/dt = 1,11A. Again, these are one-time peaks and not continious values. After these math out, the power dissipation needs to do same in relation to switching frequency, then it should be all good.
