BQ24257 Datasheet, PDF (21/45 Pages) Texas Instruments – 2A Single Input I2C, Standalone Switch-Mode Li-Ion Battery Charger with Integrated Current Sense Resistor

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DCP
Settings
CDP
Settings
bq24257
bq24258
SLUSBG0B – FEBRUARY 2013 – REVISED JULY 2013
SDP
Settings
Non
Standard
Adapter
No
VBAT > VBATGD?
Yes
Turn on V DP_SRC
And keep it on until
CLR_VDP is set to ‘1’ in i2c
DCP
External ILIM
Start 6 hr timer
CDP and
weak battery
IILIM=100mA
Start 45 min timer
CDP and
good battery
IILIM=1500mA
Start 6 hr timer
VBAT > VBATGD
No
Turn on VDP_SRC
And keep it on until
CLR_VDP is set to ‘1’
SDP and
weak battery
IILIM=100mA
Start 45 min timer
Yes
SDP and
good battery
Hi-Z mode
Apple/TT or
Non-Standard
IILIM=0.5A
Start 6 hr timer
Detection Done.
Set detection
status in register
Figure 17. Detection Configuration State
The detection configuration state sets the input current limit of the device along with the charge timer. The
exception to the CDP and the SDP settings are due to the Dead Battery Provision (DBP) clause for unconnected
devices. This clause states that the device can pull a maximum of 100mA when not connected due to a dead
battery. During the battery wakeup time, the device sources a voltage on the D+ pin in order to comply with the
DBP clause. Once the battery is good, the system can clear the D+ pin voltage by writing a ‘1’ to address 0x07
bit position 4 (CLR_VDP). The device must connect to the host within 1sec of clearing the D+ pin voltage per the
DPB clause.
A summary of the input current limits and timer configurations for each charge port type are found in Table 3.
Table 3. D+, D– Detection Results per Charge Port Type
CHARGE PORT TYPE
DCP
CDP Dead Battery
CDP Good Battery
SDP Dead Battery
SDP Good Battery
Non-Standard
INPUT CURRENT LIMIT
External ILIM
100 mA
1500 mA
100 mA
Hi-Z
500 mA
CHARGE TIMER
6 hours
45 minutes
6 hours
45 minutes
N/A
6 hours
TRANSIENT RESPONSE
The bq2425x includes an advanced hybrid switch mode control architecture. When the device is regulating the
charge current (fast-charge), a traditional voltage mode control loop is used with a Type-3 compensation
network. However, the bq2425x switches to a current mode control loop when the device enters voltage
regulation. Voltage regulation occurs in three charging conditions: 1) Minimum system voltage regulation, 2)
Battery voltage regulation (I_BAT < I_CHG), and 3) Charge Done. This architecture allows for superior transient
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