8.3.1 Battery Charging Features

The TUSB8042A provides support for USB Battery Charging (BC1.2) and custom charging. Battery charging support may be enabled on a per port basis through the REG_6h(batEn[3:0]) or the BATEN[4:1] pins.

USB Battery charging support includes both Charging Downstream Port (CDP) and Dedicated Charging Port (DCP) modes. The DCP mode is compliant with the Chinese Telecommunications Industry Standard YD/T 1591-2009. CDP is enabled when the upstream port has detected valid VBUS, configured, and host sets port power. When the upstream port is not connected and battery charging support is enabled, the TUSB8042A enables DCP mode once all other battery modes such as ACPx have failed or are disabled.

In addition to USB Battery charging (BC1.2), the TUSB8042A supports custom charging indications: Divider Charging (ACP3, ACP2, ACP1 modes), and Galaxy compatible charging. These custom charging modes are only supported when upstream port is unconnected and AUTOMODE is enabled. AUTOMODE can be enabled either thru AUTOENz pin or from Reg_0Ah bit 1 (autoModeEnz) . When in AUTOMODE and upstream port is disconnected, the port automatically transitions from ACP mode to the DCP mode depending on the portable device connected. The divided mode places a fixed DC voltage on the ports DP and DM signals which allows some devices to identify the capabilities of the charger. The default divider mode indicates support for up to 10W (ACP3). The divider mode can be configured to report a lower-current setting (up to 5 W) through REG_0Ah (HiCurAcpModeEn).

When the upstream port is not connected and battery charging support is enabled for a port, the TUSB8042A drives the port power enable active. If AUTOMODE is disabled, then DCP mode is used. If AUTOMODE is enabled and fully automatic mode is disabled (FullAutoEn bit is cleared (Reg_25h Bit 0) or FULLAUTOz pin = 0), then TUSB8042A starts with highest enabled divider current mode (ACPx). The TUSB8042A remains in highest current mode as long as a pull-up is not detected on DP pin. If an pull-up is detected on DP pin, then TUSB8042A drives the port power enable inactive and switch to Galaxy mode, if enabled, or to DCP mode if Galaxy mode is disabled. The TUSB8042A again drives the port power enable active. The TUSB8042A remains in Galaxy mode as long as no pull-up is detected on DP pin. If an pull-up is detected on DP pin, then TUSB8042A drives the port power enable inactive and transition to DCP mode. The TUSB8042A again drives the port power enable active. In DCP mode, the TUSB8042A looks for a pull-up detected on DP pin or RxVdat. If a pull-up or RxVdat is detected on DP, the TUSB8042A remains in DCP mode. If no pull-up or RxVdat is detected on DP pin after 2 seconds, the TUSB8042A drives the port power enable inactive and transition back to ACPx mode. This sequence repeats until upstream port is connected.

When Automatic mode is enabled and full automatic mode is enabled (FullAutoEn Reg_25h bit 0 is set or FULLAUTOz pin = 1), TUSB8042A performs same sequence described in previous paragraph with the addition of attempting all supported ACPx modes before sequencing to Galaxy Mode (if enabled) or DCP mode.

The supported battery charging modes when TUSB8042A configured for SMBus or external EEPROM is detailed in Battery Charging Modes with SMBus/EEPROM Table.

The supported battery charging modes when TUSB8042A configured for I2C but without an external EEPROM is determined by the sampled state of the pins. These modes are detailed in Battery Charging Modes without EEPROM Table.