5.3 Charge Pumps (CP1 and CP2)

The ATA6847/ATA6847L supports 100% duty cycle operation by using two charge pumps. CP1 supplies the low-side gate drivers, and its input voltage is generated from the battery supply pin VDH. CP2 supplies the high-side gate drivers and is generated out of the charge pump output of VG. Each charge pump (CP1 and CP2) charges from its input supply via an external flying capacitor into an external storage capacitor. VG is the output pin of CP1, whereas VCP is the output pin of CP2.

After the GDU transitions into Standby mode, CP1 is turned on if VDH < VCP_START to power the 12V LDO. In case VDH > VCP_STOP, the 12V LDO will be supplied directly from VDH, bypassing the charge pump to limit VG voltage to 12V.

The second charge pump, CP2, provides the high-side gate driver biasing and is active when the GDU is in Standby or Normal mode.

The module monitors the output voltages and delivers an undervoltage detection event, which is notified in the SIR3 Register, through the VCPUV and VGUV bits.

The output of CP2 may serve as a control output pin for a reverse voltage polarity protection MOSFET, see Figure 1-1.