NUP4202W1
www.onsemi.com
5
APPLICATIONS INFORMATION
The new NUP4202W1 is a low capacitance surge
protection diode array designed to protect sensitive
electronics such as communications systems, computers,
and computer peripherals against damage due to ESD events
or transient overvoltage conditions. Because of its low
capacitance, it can be used in high speed I/O data lines. The
integrated design of the NUP4202W1 offers surge rated, low
capacitance steering diodes and a surge protection diode
integrated in a single package (SC−88). If a transient
condition occurs, the steering diodes will drive the transient
to the positive rail of the power supply or to ground. The
surge protection device protects the power line against
overvoltage conditions to avoid damage to the power supply
and any downstream components.
NUP4202W1 Configuration Options
The NUP4202W1 is able to protect up to four data lines
against transient overvoltage conditions by driving them to
a fixed reference point for clamping purposes. The steering
diodes will be forward biased whenever the voltage on the
protected line exceeds the reference voltage (Vf or V
CC
+
Vf). The diodes will force the transient current to bypass the
sensitive circuit.
Data lines are connected at pins 1, 3, 4 and 6. The negative
reference is connected at pin 2. This pin must be connected
directly to ground by using a ground plane to minimize the
PCB’s ground inductance. It is very important to reduce the
PCB trace lengths as much as possible to minimize parasitic
inductances.
Option 1
Protection of four data lines and the power supply using
V
CC
as reference.
6
5
4
1
2
3
I/O 1
I/O 2
I/O 3
I/O 4
V
CC
For this configuration, connect pin 5 directly to the
positive supply rail (V
CC
), the data lines are referenced to
the supply voltage. The internal surge protection diode
prevents overvoltage on the supply rail. Biasing of the
steering diodes reduces their capacitance.
Option 2
Protection of four data lines with bias and power supply
isolation resistor.
V
CC
10 k
6
5
4
1
2
3
I/O 1
I/O 2
I/O 3
I/O 4
The NUP4202W1 can be isolated from the power supply
by connecting a series resistor between pin 5 and V
CC
. A
10 kW resistor is recommended for this application. This
will maintain a bias on the internal surge protection and
steering diodes, reducing their capacitance.
Option 3
Protection of four data lines using the internal surge
protection diode as reference.
6
5
4
1
2
3
I/O 1
I/O 2
I/O 3
I/O 4
NC
In applications lacking a positive supply reference or
those cases in which a fully isolated power supply is
required, the internal surge protection can be used as the
reference. For these applications, pin 5 is not connected. In
this configuration, the steering diodes will conduct
whenever the voltage on the protected line exceeds the
working voltage of the surge protection plus one diode drop
(Vc = Vf + V
RWM
).
ESD Protection of Power Supply Lines
When using diodes for data line protection, referencing to
a supply rail provides advantages. Biasing the diodes
reduces their capacitance and minimizes signal distortion.
Implementing this topology with discrete devices does have
disadvantages. This configuration is shown below:
