SLUSBC8C December 2013 – July 2018
Figure 38 is an example application that shows the bq51003 used as a wireless power receiver that can power mutliplex between wired or wireless power for the down-system electronics. In the default operating mode pins EN1 and EN2 are low, which activates the adapter enable functionality. In this mode, if an adapter is not present the AD pin will be low, and AD-EN pin will be pulled to the higher of the OUT and AD pins so that the PMOS between OUT and AD will be turned off. If an adapter is plugged in and the voltage at the AD pin goes above
3.6 V then wireless charging is disabled and the AD-EN pin will be pulled approximately 4 V below the AD pin to connect AD to the secondary charger. The difference between AD and AD-EN is regulated to a maximum of 7 V to ensure the VGS of the external PMOS is protected.
The EN1 and EN2 pins include internal 200-kΩ pulldown resistors, so that if these pins are not connected bq51003 defaults to AD-EN control mode. However, these pins can be pulled high to enable other operating modes as described in Table 3:
|0||0||Adapter control enabled. If adapter is present then secondary charger is powered by adapter, otherwise wireless charging is enabled when wireless power is available. Communication current limit is enabled.|
|0||1||Disables communication current limit.|
|1||0||AD-EN is pulled low, whether or not adapter voltage is present. This feature can be used, for example, for USB OTG applications.|
|1||1||Adapter and wireless charging are disabled, that is, power will never be delivered by the OUT pin in this mode.|
|EN1||EN2||WIRELESS POWER||WIRED POWER||OTG MODE||ADAPTIVE COMMUNICATION LIMIT||EPT|
|0||0||Enabled||Priority(1)||Disabled||Enabled||Not Sent to Tx|
|0||1||Priority(1)||Enabled||Disabled||Disabled||Not Sent to Tx|
|1||0||Disabled||Enabled||Enabled(2)||N/A||EPT 0x00, Unknown|
|1||1||Disabled||Disabled||Disabled||N/A||EPT 0x01, Charge Complete|
As described in Table 4, pulling EN2 high disables the adapter mode and only allows wireless charging. In this mode the adapter voltage will always be blocked from the OUT pin. An application example where this mode is useful is when USB power is present at AD, but the USB is in suspend mode so that no power can be taken from the USB supply. Pulling EN1 high enables the off-chip PMOS regardless of the presence of a voltage. This function can be used in USB OTG mode to allow a charger connected to the OUT pin to power the AD pin. Finally, pulling both EN1 and EN2 high disables both wired and wireless charging.
It is required to connect a back-to-back PMOS between AD and OUT so that voltage is blocked in both directions. Also, when AD mode is enabled no load can be pulled from the RECT pin as this could cause an internal device overvoltage in bq51003.