LTC4270SLASH datasheet(28/32 Pages) LINER

28 / 32 page

LTC4290/LTC4271

429071f

APPLICATIONS INFORMATION

Figure 16. LTC4290 Discharge Protection

ESD/Cable Discharge Protection

Ethernet ports can be subject to significant ESD events

when long data cables, each potentially charged to thou-

sands of volts, are plugged into the low impedance of the

RJ45 jack. To protect against damage, each port requires a

pair of clamp diodes; one to AGND and one to VEE (Figure

16). An additional surge suppressor is required for each

LTC4290 chip from VEE to AGND. The diodes at the ports

steer harmful surges into the supply rails, where they are

absorbed by the surge suppressor and the VEE bypass

capacitance. The surge suppressor has the additional

benefit of protecting the LTC4290 from transients on the

VEE supply.

S1B diodes work well as port clamp diodes, and an

SMAJ58A or equivalent is recommended for the VEEsurge

suppressor.

LAYOUT GUIDELINES

Strict adherence to board layout, parts placement and

routing guidelines is critical for optimal current read-

ing accuracy, IEEE compliance, system robustness, and

thermal dissipation. Refer to the DC1842A Demo Board

as a layout reference. Contact LTC Applications to obtain

a full set of layout guidelines, example layouts and BOMs.

0.22µF

0.25

S1B PORTn

OUTn

GATEn

SENSEn

AGND

VEE

S1B

429071 F16

–54V

SMAJ58A

LTC4290

0.1µF

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