Texas Instruments BQ24392EVM, User Manual, Page: 4 / 22

BQ24392 Implementation Guidelines
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3 BQ24392 Implementation Guidelines
3.1 Detection Overview
After accessory insertion and once VBUS is greater than VBUS_VALID threshold, the device proceeds
onto data contact detection. This state has a 600 ms timeout feature specified in the BCDv1.2
specification. If the device passes DCD, a 130 ms de-bounce period is started and the BQ24392 proceeds
to primary detection and then secondary detection to determine if a DCP, SDP, or CDP is attached to the
USB port. Detection time for a DCP, SDP, and CDP is – at a minimum – 130 ms, and can be as long as
600 ms, due to the slow plug in effect.
If data contact detection fails, the BQ24392 proceeds to detect whether an Apple or TomTom charger is
detected. Thus, for Apple and TomTom chargers, detection time typically takes ~600 ms.
The 3 output pins change their status at the end of detection. Table 1 is the detection table with the GPIO
status for each type of supported accessory. More information on how to use the GPIOs is available in
Section 5 .
Table 1. Detection Table
GOOD_BAT CHG_AL_N CHG_DET SW_OPEN Switch
Device Type VBUS DP_CON (D+) DM_CON (D–)
(Input) (Output) (Output) (Output) Status
HIGH LOW LOW LOW Connected
Standard Downstream Port > 3.5 V Pull-down R to GND Pull-down R to GND
LOW LOW LOW Hi-Z Not connected
HIGH LOW HIGH LOW Connected
Charging Downstream Port > 3.5 V Pull-down R to GND V
DM_SRC
LOW LOW HIGH Hi-Z Not connected
HIGH LOW HIGH Hi-Z Not connected
Dedicated Charging Port > 3.5 V Short to D– Short to D+
LOW LOW HIGH Hi-Z Not connected
HIGH LOW HIGH Hi-Z Not connected
Apple Charger > 3.5 V 2.0 < V
DP
< 2.8 2.0 < V
DP
< 2.8
LOW LOW HIGH Hi-Z Not connected
HIGH LOW HIGH Hi-Z Not connected
TomTom Charger > 3.5 V 2.0 < V
DP
< 3.1 2.0 < V
DP
< 3.1
LOW LOW HIGH Hi-Z Not connected
PS/2 Charger > 3.5 V Pull-up R to VBUS Pull-up R to VBUS X LOW LOW Hi-Z Not connected
Noncompliant USB Charger > 3.5 V Open Open X LOW LOW Hi-Z Not connected
Any Device < 3.5 V Open Open X Hi-Z LOW Hi-Z Not connected
Any Device DBP Timer
> 3.5 V x x LOW Hi-Z LOW Hi-Z Not connected
Expired
4 BQ24392EVM User's Guide SLVUA61 – April 2014
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