BQ24392-Q1_16 Datasheet, PDF (12/22 Pages) Texas Instruments – Dual SPST USB 2.0 High Speed Switch

BQ24392-Q1
SLIS160C – AUGUST 2014 – REVISED JANUARY 2016
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Typical Application (continued)
8.2.1 Design Requirements
VBUS requires 1-μF – 10-μF and 0.1-μF bypass capacitors to reduce noise from circuit elements by providing a
low impedance path to ground for the unwanted high frequency content. The 0.1-μF capacitor filters out higher
frequencies and has a lower series inductance while the 1 μF ~ 10 μF capacitor filters out the lower frequencies
and has a much higher series inductance. Using both capacitors will provide better load regulation across the
frequency spectrum.
SW_OPEN and CHG_AL_N are open-drain outputs that require a 10-kΩ pull-up resistor to VDDIO and VBUS.
VBUS, DM_CON, and DP_CON are recommended to have an external resistor of 2.2 Ω to provide extra
ballasting to protect the chip and internal circuitry.
DM_CON and DP_CON are recommended to have a 1-pF external ESD protection diode rated for 8-kV IEC
protection to prevent failure in case of an 8-kV IEC contact discharge.
VBUS is recommended to have a 1-pF ~ 10-pF external ESD Protection Diode rated for 8-kV IEC protection to
prevent failure in case of an 8-kV IEC contact discharge
CHG_DET is a push-pull output pin. An external pull-up and diode are shown to depict a typical 3.3-V system.
The pull-up resistor and diode are optional. The pull-up range on the CHG_DET pin is from 3.5 V to V_VBUS. When
V_VBUS > 7 V, CHG_DET will be clamped to 7 V.
8.2.2 Detailed Design Procedure
The minimum pull-up resistance for the open-drain data lines is a function of the pull-up voltage V_PU, output logic
LOW voltage V_OL(max), and Output logic LOW current I_OL.
R_PU(MIN) = (V_PU – V_OL/MAX) / I_OL
(1)
The maximum pull-up resistance for the open-drain data lines is a function of the maximum rise time of the
desired signal, t_r, and the bus capacitance, C_b.
R_PU(MAX) = t_r / (0.8473 × C_b)
(2)
8.2.3 Application Curves
Figure 6. 480-Mbps USB 2.0 Eye Diagram with No Device
Figure 7. 480-Mbps USB 2.0 Eye Diagram with USB Switch
9 Power Supply Recommendations
Power to the device is supplied through the VBUS pin from the device that is inserted into the mini or micro-USB
port. The power from the inserted devices should follow BCv1.2 specification.
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