BQ24296_15 Datasheet, PDF (18/55 Pages) Texas Instruments – bq2429x I2C Controlled 3-A Single Cell USB Charger With Narrow VDC Power Path Management and Adjustable Voltage USB OTG

bq24296, bq24297
SLUSBP6B – SEPTEMBER 2013 – REVISED NOVEMBER 2014
Feature Description (continued)
VDP_SRC
VLGC_HI
CHG_DET
D+
IDP_SRC
IDM_SINK
VDAC_REF
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D-
RDM_DWN
Figure 12. USB D+/D- Detection
DCD (Data Contact Detection) uses a current source to detect when the D+/D– pins have made contact during
an attach event. The protocol for data contact detect is as follows:
• Detect VBUS present and REG08[2] = 1 (power good)
• Turn on D+ I_{DP_SRC} and the D– pull-down resistor R_{DM_DWN} for 40 ms
• If the USB connector is properly attached, the D+ line goes from HIGH to LOW, wait up to 0.5 sec.
• Turn off I_{DP_SRC} and disconnect R_{DM_DWN}
The primary detection is used to distinguish between USB host (Standard Down Stream Port, or SDP) and
different type of charging ports (Charging Down Stream Port, or CDP, and Dedicated Charging Port, or DCP).
The protocol for primary detection is as follows:
• Turn on V_{DP_SRC} on D+ and I_{DM_SINK} on D– for 40 ms
• If PD is attached to a USB host (SDP), the D– is low. If PD is attached to a charging port (CDP or DCP), the
D– is high
• Turn off V_{DP_SRC} and I_{DM_SINK}
Table 2 shows the input current limit setting after D+/D– detection.
Table 2. bq24297 USB D+/D– Detection
D+/D– DETECTION
0.5 sec timer expired in DCD
(D+/D- floating)
USB host
USB host
Charging port
OTG
—
LOW
HIGH
—
INPUT CURRENT LIMIT
Proceed to non-standard
adapter detection
100 mA
500 mA
3A
REG08[7:6]
00
01
01
10
18
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