Data Sheet

Copyright © 2013 Future Technology Devices International Limited 28
FT231X USB TO FULL HANDSHAKE UART IC
Datasheet
Version 1.2
Document No.: FT_000565 Clearance No.: FTDI# 261
7.4 USB Battery Charging Detection
A recent addition to the USB specification (http://www.usb.org/developers/devclass_docs/BCv1.2_011912.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 FT231X 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 provided to allow external logic to switch to charging mode as opposed
to operation mode.
To use the FT231X with battery charging detection the CBUS pins must be reprogrammed to allow for the
BCD Charger output to switch the external charger circuitry on. The CBUS pins are configured in the
internal MTP memory with the free utility FTPROG. If the charging circuitry requires an active low signal
to enable it, the CBUS pin can be programmed to BCD Charger# as an alternative.
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 and the device suspended. The BCD charger signal will
bring the LTC4053 out of suspend and allow battery charging to start. The charge current in the example
below is 1A as defined by the resistance on the PROG pin.
X-Chip Pin Function
EEPROM Setting
CBUS0 BCD
Battery Options
Battery Charger Enable
Force Power Enable
De-acticate Sleep
X
GND
GND
0.1uF
0.1uF
GND
GND
600R/2A
10nF
VBUS 3V3OUT
0.1uF
0R
GNDSLD GND
27R
27R
VBUS
1
D-
2
D+
3
GND
5
ID
4
CN USB
VCC
2
FAULT
3
TIMER
4
GND
5
NTC
6
PROG
7
SHDN
8
BAT
9
ACPR
10
CHRG
1
GND
11
LTC4053EDD
GND
3V3OUT 3V3OUT
4.7uF
0.1uF
GND
VBUSVBUS
GND
VBATT
GND
GND
1K5
GND
1
TB3.5mm
VBUS VBUS
NTC
0.1uF
GND
VBUS
1uF
1R
GND
VBUS
BCD
2K2
GND
JP1
1-2
2-3
NCT Enabled
NCT Available
JP1
SIP-3
NTC
GND
NCT Disabled (Default)
JUMPER-2mm
4K32 1%
GND
DP
DM
3V3OUT
RESET#
VCC
GND
CBUS0
VCCIO
FT231X
BCD
1A when connected to a dedicated charger port
0A when enumerated
0A when in sleep
0A when not enumerated and not in sleep
+
-
NCT
N.F.
Figure 7.4 USB Battery Charging Detection (1 pin)
Alternatively the PWREN# And SLEEP pins may be used to control the LTC4053 such that a battery may
be charged from a standard host (low current) or from a dedicated charging port (high current). In such
a design as shown below the charge current would need to be limited to 0.4A to ensure that the USB host
power limit is not exceeded.