Texas Instruments BQ24392EVM User Manual
User's Guide
SLVUA61–April 2014
BQ24392EVM User's Guide
This document is the EVM user guide for the BQ24392. The BQ24392 is a charger detection IC with an
integrated USB 2.0 high-speed isolation switch for use with a micro- or mini-USB port. The device is
compatible with all BC1.2 chargers and detects both Apple®and TomTom™ chargers.
NOTE: This board is not designed to support high-current charging.
Contents
1 About this Manual............................................................................................................ 2
1.1 Information about Cautions and Warnings ...................................................................... 2
2 Introduction ................................................................................................................... 2
2.1 List of Hardware Items for Operation ............................................................................ 3
3 BQ24392 Implementation Guidelines..................................................................................... 4
3.1 Detection Overview................................................................................................. 4
3.2 Slow Plug-in Event.................................................................................................. 5
3.3 DBP Timer........................................................................................................... 5
3.4 Using the BQ24932 GPIOS ....................................................................................... 5
3.5 EVM Overview ...................................................................................................... 6
3.6 BQ24392 Quick Start Evaluation ................................................................................. 8
4 Board Documentation...................................................................................................... 12
4.1 Bill of Materials .................................................................................................... 12
4.2 Schematic .......................................................................................................... 13
4.3 Board Layout....................................................................................................... 14
5 Board Stackup and Layout Guidelines .................................................................................. 17
6 Related Documentation.................................................................................................... 17
List of Figures
1 EVM Block Diagram......................................................................................................... 3
2 Data Connections Recessed from Power Connections ................................................................ 5
3 Schematic for 3.3-V Output LDO .......................................................................................... 6
4 Schematic for GOOD_BAT Selection Header ........................................................................... 7
5 GOOD_BAT Selection Header on EVM .................................................................................. 7
6 Test Point Locations......................................................................................................... 7
7 LED Output Schematic...................................................................................................... 8
8 Device and USB Connections.............................................................................................. 8
9 EVM After High-Current Charger Attached............................................................................... 9
10 SDP with GOOD_BAT Low or Nonstandard Charger................................................................. 10
11 SDP with GOOD_BAT = High ............................................................................................ 10
12 USB Communication with Thumb Drive Through BQ24392.......................................................... 11
13 BQ24392EVM Schematic ................................................................................................. 13
14 Top Overlay................................................................................................................. 14
15 Top Layer.................................................................................................................... 14
16 Ground Layer ............................................................................................................... 15
17 Power Layer................................................................................................................. 15
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About this Manual
18 Bottom Layer................................................................................................................ 16
19 Bottom Overlay ............................................................................................................. 16
20 Board Stackup.............................................................................................................. 17
List of Tables
1 Detection Table .............................................................................................................. 4
2 BQ24392 Outputs............................................................................................................ 5
3 LED State After Inserting Charger......................................................................................... 9
4 Output Status for Different Low-Current Charger Attachments........................................................ 9
5 bq24392 EVM Bill of Materials ........................................................................................... 12
1 About this Manual
This user’s guide describes the BQ24392 evaluation module (EVM) and its intended use. This guide
contains the bill of materials (BOM), EVM schematics, printed-circuit-board (PCB) layout information, and
an implementation guide.
1.1 Information about Cautions and Warnings
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The information in a caution or a warning is provided for your protection. Please read each caution and
warning carefully.
2 Introduction
The BQ24932EVM is an evaluation module for TI's BC1.2-compatible charger detection IC with an
integrated USB 2.0 high-speed isolation switch. In addition to detecting BC1.2-compliant chargers, the
BQ24932 is also able to detect Apple and TomTom chargers, allowing the system containing the
BQ24392 to charge from more types of chargers, enhancing the end-user experience.
The evaluation module is designed to easily demonstrate the capabilities of the BQ24392 without the need
for external supplies or metering equipment through the use of status indicator LEDs. See Figure 1 for the
EVM block diagram.
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Common
MHL
DUT
Output LED
Indictaors
J1
J2
J5
J4
BQ24392EVM
TP9_CHG_AL_N
Through
Path
TP10_SW_OPEN
TP11_CHG_DET
TP12_GOOD_BAT
J3
GND
High
GOOD_BAT
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Figure 1. EVM Block Diagram
2.1 List of Hardware Items for Operation
The following items are required for EVM evaluation:
• BQ24392 EVM
• BC1.2-compliant charger
• PC with USB port
• USB cable
• USB peripheral to connect to the PC
Introduction
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BQ24392 Implementation Guidelines
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
Device Type VBUS DP_CON (D+) DM_CON (D–)
Standard Downstream Port >3.5 V Pull-down R to GND Pull-down R to GND
Charging Downstream Port >3.5 V Pull-down R to GND V
Dedicated Charging Port > 3.5 V Short to D– Short to D+
Apple Charger > 3.5 V 2.0 < VDP< 2.8 2.0 < VDP< 2.8
TomTom Charger > 3.5 V 2.0 < VDP< 3.1 2.0 < VDP< 3.1
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
Expired
> 3.5 V x x LOW Hi-Z LOW Hi-Z Not connected
DM_SRC
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GOOD_BAT CHG_AL_N CHG_DET SW_OPEN Switch
(Input) (Output) (Output) (Output) Status
HIGH LOW LOW LOW Connected
LOW LOW LOW Hi-Z Not connected
HIGH LOW HIGH LOW Connected
LOW LOW HIGH Hi-Z Not connected
HIGH LOW HIGH Hi-Z Not connected
LOW LOW HIGH Hi-Z Not connected
HIGH LOW HIGH Hi-Z Not connected
LOW LOW HIGH Hi-Z Not connected
HIGH LOW HIGH Hi-Z Not connected
LOW LOW HIGH Hi-Z Not connected
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Data Lines
VBUS and
Ground
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3.2 Slow Plug-in Event
As you insert a charger into the USB receptacle, the pins are configured so that the VBUS and GND pins
make contact first. This presents a problem as the BQ24392 (or any other charger detection IC) requires
access to the D+ D– lines to run detection. This is why the BQ24392 has a standard 130 ms de-bounce
time after VBUS valid to run the detection algorithm. This delay helps minimize the effects of the D+ D–
lines making contact after VBUS and GND.
Figure 2 is from the datasheet of a standard male micro-USB connector and shows how the data
connections (red line) are slightly recessed from the power connections (blue line).
BQ24392 Implementation Guidelines
Figure 2. Data Connections Recessed from Power Connections
However, in some cases the charger is inserted very slowly, causing the VBUS and GND to make contact
long before D+ D–. Due to this effect, there is no guaranteed detection time as the detection time can vary
based on how long it takes to insert the charger. If longer than 600 ms is taken to insert the charger into
the USB receptacle, the detection algorithm of the BQ24392 will timeout and instead of the charger being
detected as a DCP, it is now detected as a nonstandard charger (D+ and D– floating).
3.3 DBP Timer
The BQ24392 features a dead battery provision timer per the BC1.2 specification. Once a charger has
been detected and the GOOD_BAT pin is low, a dead battery timer is initiated. If the GOOD_BAT
continues to be LOW for 30 minutes (maximum of 45 minutes), charging is disabled and CHG_AL_N goes
into the High-Z state to indicate this. Toggling GOOD_BAT high after the DBP timer expires re-starts
detection and the DBP timer.
3.4 Using the BQ24932 GPIOS
3.4.1 CHG_AL and CHG_DET
The BQ24392 has 2 outputs, CHG_AL_N and CHG_DET, that the host can used to determine whether it
can charge and if it can charge at a low or high current. Table 2 demonstrates how these outputs should
be interpreted. CHG_AL_N is an open drain output and is active when the output of the pin is low.
CHG_DET is a push-pull output and is high in the active state.
Table 2. BQ24392 Outputs
CHG_AL_N CHG_DET
High-Z X Charging is not allowed
Low Low Low-current charging is allowed
Low High High-current charging is allowed
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BQ24392 Implementation Guidelines
The system must define what is meant by low- and high-current charging. If CHG_DET is high, a system
could try to draw 2 A, 1.5 A, or 1.0 A. If the system is trying to support > 1.5-A chargers, then the system
has to use a charger IC that is capable of monitoring the VBUS voltage as it tries to pull the higher current
values. If the voltage on VBUS starts to drop because that high of a current is supported then the system
has to back down on how much current it is trying to draw until it finds a stable state with VBUS not
dropping.
3.4.2 SW_OPEN
SW_OPEN is an open drain output that indicates whether the USB switches are opened or closed. In the
High-Z state the switches are open and in the active, or low state, the switches are closed. The host
should monitor this pin to know when the switches are closed or open.
3.4.3 GOOD_BAT
GOOD_BAT is used by the host controller to indicate the status of the battery to the BQ24392. This pin
affects the switch status for a SDP or CDP, and it also affects the DBP timer as discussed in the DBP
timer section.
3.5 EVM Overview
The EVM for the BQ24392 is designed to be self-contained so no use of lab equipment is required to
evaluate the functionality of the battery charging detection or the USB communication capabilities.
However, there are test points available for more detailed analysis of the detection timings.
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3.5.1 Board Power
The EVM is fully supplied by VBUS from the charger or PC connected to the board with test points for
monitoring VBUS as a device is attached. The EVM also has an LED output indicating when VBUS is
present as depicted in the following figure:
The EVM contains a 3.3-V output LDO for the SW_OPEN output and GOOD_BAT input as these pins
must not be connected to VBUS. Figure 3 is the schematic for this portion of the design.
Figure 3. Schematic for 3.3-V Output LDO
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3.5.2 GOOD_BAT Selection Jumper
There is a 3-pin header (J3) on the EVM to select the GOOD_BAT input to be high or low. The jumper
positioning is fully labeled on the EVM itself for ease of use. Figure 4 and Figure 5 illustrate the schematic
and the EVM board labeling.
Figure 4. Schematic for GOOD_BAT Selection Header
BQ24392 Implementation Guidelines
3.5.3 Test Points
The EVM also contains test point for the 3 outputs, 1 input, and the D+ D– pins. Figure 6 shows the
schematic for these test points and the locations on the EVM.
Figure 5. GOOD_BAT Selection Header on EVM
Figure 6. Test Point Locations
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