October, 20, 2011.

Techcode Semiconductor Limited

www.techcodesemi.com

14

USB Power-Distribution Switches

TD9516/TD9517/TD9518/TD9519

DATASHEET

Application Information

Input Capacitor

the TD951X, is strongly recommended to suppress the ringing

during short circuit fault event. Without the bypass capacitor,

the output short may cause sufficient ringing on the input

(from supply lead inductance) to damage internal control

circuitry.

Output Capacitor

A low-ESR 10F aluminum electrolytic or tantalum between

drop during hot-attachment of downstream peripheral. (Per

USB 2.0, output ports must have a minimum 120F of

low-ESR bulk capacitance per hub).

Higher-value output capacitor is better when the output load

is heavy. Additionally, bypassing the output with a 0.1F

ceramic capacitor improves the immunity of the device to

short-circuit transients.

Layout Consideration

The PCB layout should be carefully performed to maximize

thermal dissipation and to minimize voltage drop, droop and

EMI. The following guidelines must be considered:

1. Please place the input capacitors near the VIN pin as close

as possible.

2. Output decoupling capacitors for load must be placed near

the load as close as possible for decoupling highfrequency

ripples.

3. Locate TD951X and output capacitors near the load to

reduce parasitic resistance and inductance for excellent load

transient performance.

4. The negative pins of the input and output capacitors and

the GND pin must be connected to the ground plane of the

load.