[FAQ] Can I use LMG1210 with a bipolar supply?

[FAQ] Can I use LMG1210 with a bipolar supply?

There are several considerations when designing for bipolar bus voltage to make sure that the specifications of the LMG1210 driver are not exceeded at any moment. In general, the main thing to keep in mind is that the reference of the bus voltage is going to be used as the ground reference of the driver, and therefore, the bias supplies, inputs and outputs of the driver need to use this reference as well to make sure the device is not stressed beyond its specified limits. These are some other key considerations:

• V_SS pin of the LMG1210 driver can be at a negative voltage as long as V_DD supply is level shifted to remain at 5V with respect to V_SS.
  • (e.g. if Vbus is +/-50V, then V_SS pin should be referenced to -50V and V_DD voltage should be at -45V to keep V_DD - V_SS = 5V).

• The voltage difference between the positive and negative bus voltage should not exceed the maximum recommended operating conditions of HS pin.
  • (e.g. If Vbus is +/-50V, then the maximum voltage at HS-V_SS is 100V which is within the specified limits).

• In most cases,  a bootstrap diode cannot be used since the maximum reverse voltage rating would be exceeded. Therefore, an isolated supply is needed to supply HB-HS and the BST pin needs to be left floating.  
  • (e.g. If Vbus is +/-100V, V_DD would be at -95V and when the high side FET is ON, HB pin would be at ~105V. The reverse voltage that the diode sees is 200V and this could damage the diode).

• The input signals (DHL, DLH, EN, PWM, VIN) also need to be level shifted in reference to the V_SS pin voltage.