Hello NXP Community,
I am planning to use the MC34GD3000 to drive a 24 V, 26 W motor.
In many reference circuits and examples, the VPWR supply of the MC34GD3000 appears to be connected to the same supply voltage as the motor supply. In my application, the motor supply voltage will be 24 V, so VPWR of the MC34GD3000 will also be 24 V.
I would like to clarify the gate drive output voltage level of the MC34GD3000.
In the datasheet absolute maximum ratings table, I found values such as:
- PX_HS_G to PX_HS_S: 3.0 V to 16.5 V
- PX_LS_G to PX_LS_S: 3.0 V to 16.5 V
- PX_BOOT to PX_HS_S: 3.0 V to 16.5 V
My question is:
When VPWR is 24 V, what is the actual PWM gate drive output voltage level of the MC34GD3000?
Does the gate drive output become 24 V because VPWR is 24 V, or is the gate drive output limited to approximately 16.5 V maximum with respect to each MOSFET source node?
For example, for the low-side MOSFET, should I understand that PX_LS_G to PX_LS_S is driven up to around 15 V, not 24 V?
And for the high-side MOSFET, should I understand that PX_HS_G is driven above the phase node, but the gate-to-source voltage PX_HS_G to PX_HS_S is still limited to around 15 V?
I would appreciate your confirmation.
Thank you.
Hello,
Yes, your understanding is correct. Even when VPWR is connected to a 24 V motor supply, the MC34GD3000 does not drive the MOSFET gates to 24 V with respect to their source terminals. The device generates an internal gate-drive supply (VLS), which is regulated to approximately 15 V.
Therefore:
For the low-side MOSFET, PX_LS_G is driven to approximately 15 V above PX_LS_S.
For the high-side MOSFET, PX_HS_G is driven above the phase node through the bootstrap circuit, but the gate-to-source voltage PX_HS_G − PX_HS_S remains approximately 15 V.
The limits shown in the datasheet (PX_HS_G to PX_HS_S and PX_LS_G to PX_LS_S) represent the effective gate-to-source drive voltage and indicate that the gate drive is not equal to the 24 V VPWR supply.
Hope this helps!