Datasheet

External
Pin
+V
CC
-V
CC
Internal
Circuitry
OPA690
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SBOS223F DECEMBER 2001REVISED FEBRUARY 2010
destination devices to be handled as separate INPUT AND ESD PROTECTION
transmission lines, each with their own series and
The OPA690 is built using a very high-speed
shunt terminations. If the 6dB attenuation of a
complementary bipolar process. The internal junction
doubly-terminated transmission line is
breakdown voltages are relatively low for these very
unacceptable, a long trace can be
small geometry devices. These breakdowns are
series-terminated at the source end only. Treat
reflected in the Absolute Maximum Ratings table. All
the trace as a capacitive load in this case and set
device pins are protected with internal ESD protection
the series resistor value as shown in the plot of
diodes to the power supplies, as shown in Figure 50.
Recommended R
S
vs Capacitive Load (Figure 15
for ±5V and Figure 30 for +5V). This will not
preserve signal integrity as well as a
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 OPA690
is not recommended. The additional lead length
Figure 50. Internal ESD Protection
and pin-to-pin capacitance introduced by the
socket can create an extremely troublesome
parasitic network which can make it almost
These diodes provide moderate protection to input
impossible to achieve a smooth, stable frequency
overdrive voltages above the supplies as well. The
response. Best results are obtained by soldering
protection diodes can typically support 30mA
the OPA690 onto the board.
continuous current. Where higher currents are
possible (e.g., in systems with ±15V supply parts
driving into the OPA690), 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 © 2001–2010, Texas Instruments Incorporated 27
Product Folder Link(s): OPA690