Datasheet

External
Pin
+V
CC
-V
CC
Internal
Circuitry
OPA2690
www.ti.com SBOS238G –JUNE 2002–REVISED MARCH 2010
the 6dB attenuation of a doubly-terminated INPUT AND ESD PROTECTION
transmission line is unacceptable, a long trace
The OPA2690 is built using a very high-speed
can be series-terminated at the source end only.
complementary bipolar process. The internal junction
Treat the trace as a capacitive load in this case
breakdown voltages are relatively low for these very
and set the series resistor value as shown in the
small geometry devices. These breakdowns are
plots of Recommended R
S
vs Capacitive Load
reflected in the Absolute Maximum Ratings table. All
(Figure 15 for ±5V and Figure 30 for +5V). This
device pins are protected with internal ESD protection
will not preserve signal integrity as well as a
diodes to the power supplies, as shown in Figure 54.
doubly-terminated line. If the input impedance of
the destination device is low, there will be some
signal attenuation due to the voltage divider
formed by the series output into the terminating
impedance.
e. Socketing a high-speed part like the OPA2690
is not recommended. The additional lead length
and pin-to-pin capacitance introduced by the
socket can create an extremely troublesome
parasitic network which can make it almost
Figure 54. Internal ESD Protection
impossible to achieve a smooth, stable frequency
response. Best results are obtained by soldering
the OPA2690 onto the board.
These diodes provide moderate protection to input
overdrive voltages above the supplies as well. The
protection diodes can typically support 30mA
continuous current. Where higher currents are
possible (for example, in systems with ±15V supply
parts driving into the OPA2690), current-limiting
series resistors should be added into the two inputs.
Keep these resistor values as low as possible since
high values degrade both noise performance and
frequency response.
Copyright © 2002–2010, Texas Instruments Incorporated 29
Product Folder Link(s): OPA2690