TBU-PL datasheet(2/7 Pages) BOURNS

2 / 7 page

Specificationsaresubjecttochangewithoutnotice.

Thedevicecharacteristicsandparametersinthisdatasheetcananddovaryindifferentapplicationsandactualdeviceperformancemayvaryovertime.

Usersshouldverifyactualdeviceperformanceintheirspecificapplications.

TBU-PL Series - TBU® High-Speed Protectors

Functional Block Diagram

Reference Application

The TBU-PL Series are high-speed protectors used in voice/

VoIP SLIC applications.The maximum voltage rating of the TBU®

device should never be exceeded. Where necessary, an OVP

device should be employed to limit the maximum voltage. A cost-

effective protection solution combines Bourns® TBU® protection

devices with a pair of Bourns® MOVs. For bandwidth sensitive

applications, a Bourns® GDT may be substituted for the MOV. If

EN55024 EMC compliance is required, the TBU® device

may require capacitors to be fitted between the Tip and Ring

connections and ground.

MOV

TBU®

Device

GND

-VBAT

Line 1

SLIC

Vdd

Vss

Line 2

SLIC

Line 1

Line 2

The TBU® device, constructed using MOSFET semiconductor

technology, placed in the system circuit will monitor the

current with the MOSFET detection circuit triggering to provide

an effective barrier behind which sensitive electronics are not

exposed to large voltages or currents during surge events. The

TBU® device operates in approximately 1 µs - once line current

exceeds the TBU® device’s trigger current Itrigger. When operat-

ed, the TBU® device will limit the current to less than the Itrigger

value within the tblock duration. If voltage above Vreset is contin-

uously sustained, the TBU® device will subsequently reduce the

current to a quiescent current level within a period of time that is

dependent upon the applied voltage.

When the voltage on the SLIC output is driven below

(Vbat – Vto) the TBU-PL series device switches to the

blocking state, regardless of output current in the device.

After the surge, the TBU® device resets when the voltage

across the TBU® device falls to the Vreset level. The TBU®

device will automatically reset on lines which have no DC bias

or have DC bias below Vreset (such as unpowered signal lines).

If the line has a normal DC bias above Vreset, the voltage

across the TBU® device may not fall below Vreset after the

surge. In such cases, special care needs to be taken to ensure

that the TBU® device will reset, with software monitoring as one

method used to accomplish this. Bourns application

engineers can provide further assistance.

Basic TBU Operation

Line 1

HIGH

VOLTAGE

SWITCH

Line 1 SLIC

Vss

Line 2

Line 2 SLIC

CURRENT

SENSE

VOLTAGE

COMPARATOR

HIGH

VOLTAGE

SWITCH

CURRENT

SENSE

VOLTAGE

COMPARATOR

Vss

Vdd

Vss

Vdd

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