BQ24257 Datasheet, PDF (20/45 Pages) Texas Instruments – 2A Single Input I2C, Standalone Switch-Mode Li-Ion Battery Charger with Integrated Current Sense Resistor

bq24257
bq24258
SLUSBG0B – FEBRUARY 2013 – REVISED JULY 2013
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If resistors are not desired for BOM count reduction, the VDPM and the ILIM pins can be shorted to set the
internal defaults. However, the ISET resistor must be populated as this will be interpreted as a fault. Table 2
summarizes the settings when the ILIM, ISET, and V_{IN_DPM} pins are shorted to GND.
Table 2. ILIM, VDPM, and ISET Short Behaviors
PIN SHORTED
ILIM
VDPM
ISET
BEHAVIOR
Input current limit = 2A
V_{IN_DPM} = 4.36V
Fault—Charging Suspended
BC1.2 D+/D– DETECTION
The bq24257 includes a fully BC1.2 compatible D+/D– source detection. This detection supports the following
types of ports:
• DCP (dedicated charge port)
• CDP (charging downstream port)
• SDP (standard downstream port)
• Apple™/TomTom™ ports
This D+/D– detection algorithm does not support ACA (accessory charge adapter) identification, but the input
current will default to 500mA when a charge port is attached to the ACA and bq24257 is connected to the OTG
port.
The D+/D– detection algorithm is only active when the device is in standalone mode (e.g. the host is not
communicating with the device and the watch dog timer has expired). However, when the device is in host mode
(that is, host is communicating via i2c to the device) writing a ‘1’ to register 0x04 bit location 4 (DPDM_EN)
forces the device to perform a D+/D– detection on the next power port insertion. This allows the D+/D– detection
to be enabled in both host mode and default mode.
The D+/D– detection algorithm has 5 primary states. These states are termed the following:
1. Data Contact Detect
2. Primary Detection
3. Secondary Detection
4. Non-standard Adapter Detection (for Apple™ / TomTom™)
5. Detection Configuration
The DCD state determines if the device has properly connected to the D+/D– lines. If the device is not in host
mode and VBUS is inserted (or DPDM_EN is true) the device will enter the DCD state and enable the
appropriate algorithm. If the DCD timer expires, the device will enter the Non-standard Adapter Detection (for
Apple™ / TomTom™) state. Otherwise it will enter the Primary Detection state.
When entering the Primary Detection state, the appropriate algorithm is enabled to determine whether to enter
the secondary detection state for DCP and CDP or the secondary detection state for SDP/Non-Standard
adaptors.
The non-standard adapter detection state for Apple™ / TomTom™ tests for the unique conditions for these non-
standard adapters. If the algorithm passes the unique conditions found with these adapters, it will proceed to the
Detection Configuration state. Otherwise it will revert back to the primary detection state.
The secondary detection state determines whether the input port is a DCP, CDP, SDP, or other non-standard
adapters. If the Primary Detection state indicated that the input port is either a DCP or CDP, the device will
enable the appropriate algorithm to differentiate between the two. If the Primary Detection state indicated that the
input port is either a SDP or non-standard adapter, the device will enable the appropriate algorithm to
differentiate between these two ports. Once complete, the device will continue to the Detection Configuration
state.
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