BQ24195 Datasheet, PDF (19/41 Pages) Texas Instruments – I2C Controlled 2.5A / 4.5A Single Cell USB/Adapter Charger With 5.1V at 1A / 5.1V at 2.1A Synchronous Boost Operation

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VDP_SRC
VLGC_HI
CHG_DET
D+
IDP_SRC
IDM_SINK
VDAC_REF
bq24195
bq24195L
SLUSB97 – OCTOBER 2012
D-
RDM_DWN
Figure 15. 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 40ms
• 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 40ms
• 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. bq24195L, bq24195 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
100 mA
100 mA
500 mA
1.5 A
REG08[7:6]
00
01
01
10
HIZ State wth 100mA USB Host
In battery charging spec, the good battery threshold is the minimum charge level of a battery to power up the
portable device successfully. When the input source is 100mA USB host, and the battery is above bat-good
threshold (V_BATGD), the device follows battery charging spec and enters high impedance state (HIZ). In HIZ state,
the device is in the lowest quiescent state with REGN LDO and the bias circuits off. The charger device sets
REG00[7] to 1, and the VBUS current during HIZ state will be less than 30µA. The system is supplied by the
battery.
Once the charger device enters HIZ state in host mode, it stays in HIZ until the host writes REG00[7]=0. When
the processor host wakes up, it is recommended to first check if the charger is in HIZ state.
Copyright © 2012, Texas Instruments Incorporated
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