FT4222HQ-C-R datasheet(35/49 Pages) FTDI

35 / 49 page

FT4222H USB2.0 TO QUADSPI/I2C BRIDGE IC

1.3

Document No.: FT_001011 Clearance No.: FTDI#405

7.5

USB Battery Charging Detection

An addition to the USB specification

(http://www.usb.org/developers/docs/devclass_docs/BCv1.2_070312.zip) is to allow for additional

charging profiles to be used for charging batteries in portable devices. These charging profiles do not

enumerate the USB port of the peripheral. The FT4222H device will detect that a USB compliant

dedicated charging port (DCP) is connected. Once detected while in suspend mode a battery charge

detection signal is then provided to allow external logic to switch to charging mode as opposed to

operation mode.

Figure 7.5 USB Battery Charging Detection

To use the FT4222H with battery charging detection, the BCD_DET pin acts as BCD Charger output to

switch the external charger circuitry on. If the charging circuitry requires an active low signal to enable it,

the polarity of BCD_DET can be configured in the vender configuration area of internal OTP memory.

When connected to a USB compliant dedicated charging port (DCP, as opposed to a standard USB host)

the device USB signals will be shorted together. The BCD charger signal will bring the LTC4053 out of

suspend and allow battery charging to start. The charge current in the example above is 1A as defined by

the resistance on the PROG pin.

To calculate the equivalent resistance on the LTC4053 PROG pin select a charge current, then Res =

1500V/Ichg

For more configuration options of the LTC4053 refer to :

Section4.3 Example with 1 CBUS pin in AN_175_Battery Charging Over USB

Note: If the FT4222H is connected to a standard host port such that the device is enumerated, the signal

BCD_DET is inactive, LTC4053 is in shut down condition and the charging function will not be enabled.

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