ZHCSQ40C January 2023 – September 2023 LM2105
PRODUCTION DATA
In most applications, the body diode of the external low-side power MOSFET clamps the SH node to ground. In some situations, board capacitance and inductance can cause the SH node to transiently swing several volts below ground, before the body diode of the external low-side MOSFET clamps this swing. The SH pin in the LM2105 is allowed to swing below ground as long as specifications are not violated and conditions mentioned in this section are followed.
SH must always be at a lower potential than GH. Pulling GH more negative than specified conditions can activate parasitic transistors which may result in excessive current flow from the BST supply. This may result in damage to the device. The same relationship is true with GL and GND. If necessary, a Schottky diode can be placed externally between GH and SH or GL and GND to protect the device from this type of transient. The diode must be placed as close to the device pins as possible in order to be effective.
Low ESR bypass capacitors from BST to SH and from GVDD to GND are essential for proper operation of the gate driver device. The capacitor should be located at the leads of the device to minimize series inductance. The peak currents from GL and GH can be quite large. Any series inductance with the bypass capacitor causes voltage ringing at the leads of the device which must be avoided for reliable operation.