The LM5170-Q1 requires an external bias supply of 9 V to 12 V at the VCC and VCCA pins to function. If an external supply voltage is greater than 12 V, a 10-V LDO or switching regulator must be used to produce 10 V for VCC and VCCA. Figure 8-1 shows typical connections of the bias supply. The VCC voltage is directly fed to the low-side MOSFET drivers. A 1-µF to 2.2-µF ceramic capacitor must be placed between the VCC and PGND pins to bypass the driver switching currents. The VCCA pin serves as the bias supply input for the internal logic and analog circuits for which the ground reference is the AGND pin. VCCA should be connected to VCC through a 25- to 50-Ω external resistor. A 0.1-µF to 1-µF bypass capacitor must be placed between the VCCA and AGND pins to filter out possible switching noise.

The internal VCC undervoltage (UV) detection circuit monitors the VCC voltage. When the VCC voltage falls below 8 V on the falling edge, the LM5170-Q1 is held in the shutdown state. For normal operation, the VCC and VCCA voltages must be greater than 8.5 V on a rising edge.

Figure 8-1 VCC Bias Supply Connections