Copyright © 2013 Future Technology Devices International Limited

26

FT240X USB 8-BIT FIFO IC Datasheet

Version 1.3

Document No.: FT_000626 Clearance No.:

FTDI# 259

7.2 Battery Charge 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 FT240X 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.

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

GND

SLD

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

LTC4053EDD

GND

3V3OUT

3V3OUT

4.7uF

0.1uF

GND

VBUS

VBUS

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%

DP

DM

3V3OUT

RESET#

CBUS0

FT240X

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 7.2 USB Battery Charging Detection (1 pin)

To use the FT240X 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

above is 1A as defined by the resistance on the PROG 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 above the charge current would need to be limited to 0.4A to ensure that the USB

host power limit is not exceeded.