Bourns
®
TBU
®
Product Overview
Basic TBU
®
Device Operation
Bourns® TBU® high-speed protectors are circuit
protection devices constructed using MOSFET
semiconductor technology. When placed in series in the
system, the TBU® protector monitors the current flowing
through the line. If the current exceeds a preset level, the
TBU® device triggers, providing an effective barrier to
large, destructive voltages or currents during surge events,
thereby protecting sensitive electronics.
The TBU® device operates in approximately 1 μs - once
line current exceeds the TBU® device’s trigger current
I
trigger
. When operated, the TBU® device restricts line
current to less than 1 mA typically, and blocks voltages
including the surge up to rated limits.
After the surge, the TBU® automatically resets itself when
the voltage across the TBU® device falls to the V
reset
or
below. Therefore, the TBU® device will automatically reset
on lines which have no DC bias or have DC bias below
V
reset
(such as unpowered signal lines).
If the line has a normal DC bias above V
reset
, the voltage
across the TBU® device may not fall below V
reset
after
the surge. In such cases, special care needs to be taken
to ensure that the TBU® device will reset; software
monitoring may be used to accomplish this task. Bourns
application engineers can provide further assistance.
Key Features:
• TBU® device is used in series with the line
• TBU® device is triggered by current rise
• TBU® device can block voltages up to 850 V, enabling
easy coordination
• TBU® device provides superior protection in less than 1 µs
• TBU® device resets on voltage
• TBU® device offers an extremely low capacitance per line
•
•
•
•
•
•
•
•
•
High-speed performance
Blocks voltages and currents
Extremely low let-through energy of 100 nJ
Self-resetting on non-DC biased lines
Very high bandwidth up to 3 GHz
Small size in DFN package
TBU-PL & TBU-PK series offer voltage triggering
Smallest PCB area
Ultra low profile
Key Benefits:
TBU-VI Curve
I
I
OP
Forward
Trigger
Current
Reset
Voltage
Threshold
1/R
Residual
Reset
Current
Reset
Voltage
Threshold
V
TBU-based Solution Device Selection
Reverse
Trigger
Current
-I
OP
Step 1:
Current characterization:
Determine the peak system operating current and maximum operating ambient temperature. Use the TBU®
device data sheet’s “trigger current versus temperature” derating curve to determine the TBU® device derating value.
Step 2:
Overvoltage selection:
Select an overvoltage device that has the lowest available DC breakdown voltage greater than the normal system
voltages and any expected AC power faults. The selected device must also be capable of handling the required
lightning current.
Step 3:
TBU® device selection:
Choose a TBU® device with a maximum impulse voltage (V
imp
) greater than the maximum impulse breakover
or clamping voltage of the selected overvoltage protector. The selected TBU® device must also have a minimum
specified I
trigger
above the maximum peak system operating current compensating for the temperature derating.
Step 4:
Tertiary protection:
In most applications, the protected circuit sources sufficient current to trigger the TBU® device. If the protected
circuit impedance is high, a small avalanche diode to ground or small signal diodes clamping to the power
supply rails may be placed after the TBU® device. This will ensure that the TBU® device triggers, preventing
the voltage at the interface from rising to unsafe levels.
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Bourns
®
TBU
®
Product Examples
VOICE
GND
Line 1
SLIC
TBU
Line 2
SLIC
TBU-PL060-100-WH
Line 1
MOV-10D201K
MOV-10D201K
Line 2
VOICE Protection Solution Selection Guide
Bourns® TBU® Device Selection
Industry Standard
Telcordia GR-1089-CORE
Intra-building
Port Type 4
Telcordia GR-1089-CORE
Intra-building
Port Type 4a
Surge & AC Withstand
1500 V, 100 A 2/10 µs
120 V
rms
, 25 A, 900 s
1000 V, 100 A 10/1000 µs
120 V
rms
, 25 A, 900 s
5000 V, 500 A 2/10 µs
230 V
rms
, 25 A, 900 s
1500 V, 100 A 2/10 µs
275 V
rms
, 25 A, 900 s
4000 V, 40 Ω 10/700 µs
230 V
rms
10 Ω - 1000 Ω, 900 s
600 V
rms
600 Ω, 0.2 s
4000 V, 40 Ω 10/700 µs
230 V
rms
10 Ω -1000 Ω, 900 s
600 V
rms
600 Ω, 0.1 s
6000 V, 40 Ω 10/700 µs
240 V
rms
10 Ω - 1000 Ω, 900 s
600 V
rms
600 Ω, 0.2 s
600 V
rms
600 Ω, 1 s*
1500 V
rms
, 200 Ω, 2 s*
6000 V, 40 Ω 10/700 µs
240 V
rms
10 Ω - 1000 Ω, 900 s
600 V
rms
600 Ω, 1 s
1500 V
rms
, 200 Ω, 2 s
TBU® Device Part
Qty
Number
TBU-PL050-100-WH
OVP Device
Part Number
MOV-07D201K
Qty
2
1
TBU-PL060-100-WH
1
MOV-10D201K
2
-VBAT
Review VOICE Protection Solution Selection Guide to select TBU®
and overvoltage part numbers to meet protection industry standard.
TBU-PL085-100-WH
1
1
MOV-10D361K
2
2
Non-GR-1089-CORE Intra-
building Specifications
VDSL
VDSL
Driver
C1a
TBU-PL085-100-WH
MOV-10D431K
TBU-PL075-100-WH
1
MOV-10D361K
2
ITU-T Basic K.20, K.21, K.45
2031-15T-SM
TBU-PL060-100-WH
1
TISP4400M3BJ
2
TBU-CA050-500-WH
TBU-PL085-100-WH
1
MOV-10D391K
2
C1b
ITU-T Enhanced K.20, K.21, K.45
T1/E1 Interface
T1a
Transformer
TBU1
TBU-PL060-100-WH
1
TISP4500H3BJ
2
TTIP
P850-U
T1b
CM Transformer
1
2
3
4
8
7
6
5
1.25 A
Fuse
Tx Tip
2031-42T-SM
T1/E1
TRING
Physical Line
Interface
RTIP
Unit
1
* GDT Special Test Protector with DC breakdown (DCBD) of less than 330 V.
Fuse
1.25 A
TBU1
Tx Ring
1.25 A
Fuse Rx Tip
2031-42T-SM
P850-U
RRING
1
Fuse Rx Ring
1.25 A
Notes:
1) The Le9500, Le9520 and Le9530 (VE950 series) require a 200 mA Itrigger TBU
®
device for normal operation. Other SLIC types should use
the 100 mA device.
2) The MOV maximum continuous rms voltage rating should not be exceeded. The exception is where the data sheet highlights withstand
capability such as the 600 V rms, 1 A for 0.2 s, for example.
3) If EN55024 EMC compliance is required, the TBU
®
device may require capacitors to be fitted between the Tip and Ring connections and
ground (i.e. in parallel with the MOV device). The capacitance value can be chosen to meet levels as follows:
• 10 nF for EN55024 Level 1
• 20 nF for EN55024 Level 2
• 47 nF for EN55024 Level 3
Selection of capacitor voltage rating depends upon TBU
®
part number selection. Recommendations include:
• TBU-PL050 & TBU-PL060 Series: 120 VAC, 500 V Peak Surge Rated
• TBU-PL075 & TBU-PL085 Series: 240 VAC, 750 V Peak Surge Rated
Depending upon the SLIC type, it is usually possible to remove any EMI capacitors present between the output of the SLIC and ground
when using capacitors C1 and C2 in parallel with the MOVs.
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