Datasheet

USB

Transceiver

GND

SN65220

USB

Connector

GND

27O

15kO

D+

D-

GND

VBUS

27O

15kO

VIA to Power Ground Plane

VIA to Power Supply Plane

SN65220

SN65240

SN75240

SLLS266H –FEBRUARY 1997–REVISED MAY 2015

www.ti.com

12 Power Supply Recommendations

Unlike other semiconductor components that require a supply voltage to operate, the SN65220, SN65240, and

SN75240 transient suppressors are combinations of multiple p-n diodes, activated by transient voltages.

Therefore, these transient suppressors do not require external voltage supplies.

13 Layout

13.1 Layout Guidelines

The multiple ground pins provided lower the connection resistance to ground. In order to improve circuit

operation, a connection to all ground pins must be provided on the system printed circuit board. Without proper

device connection to ground, the speed and protection capability of the device will be degraded.

• The ground termination pads should be connected directly to a ground plane on the board for optimum

performance. A single trace ground conductor will not provide an effective path for fast rise-time transient

events including ESD due to parasitic inductance.

• Nominal inductive values of a PCB trace are approximately 20 nH/cm. This value may seem small, but an

apparent “short length” of trace may be sufficient to produce significant L(di/dt) effects with fast rise-time ESD

spikes.

• Mount the TVS as close as possible to the I/O socket to reduce radiation originating from the transient as it is

routed to ground.

NOTE

Direct connective paths of the traces are taken to the suppressor mounting pads to

minimize parasitic inductance in the surge-current conductive path, thus minimizing

L(di/dt) effects.

13.2 Layout Example

Figure 7. Layout Example of a 4-Layer Board With SN65220

Product Folder Links: SN65220 SN65240 SN75240