Datasheet

Input and ESD Protection
External
Pin
Internal
Circuitry
-V
CC
+V
CC
PowerPAD™ Information
OPA659
SBOS342B – DECEMBER 2008 – REVISED AUGUST 2009 ............................................................................................................................................ www.ti.com
well as a doubly-terminated line. If the input shown in the EVM layer views (see Figure 41 ). For
impedance of the destination device is low, there will more general data and detailed information about the
be some signal attenuation as a result of the voltage PowerPAD package, refer to the PowerPAD™
divider formed by the series output into the Thermally Enhanced Package application note
terminating impedance. (SLMA002 ).
e) Socketing a high-speed part such as the
OPA659 is not recommended. The additional lead
length and pin-to-pin capacitance introduced by the
The OPA659 is built using a very high-speed
socket can create an extremely troublesome parasitic
complementary bipolar process. The internal junction
network that can make it almost impossible to
breakdown voltages are relatively low for these very
achieve a smooth, stable frequency response. Best
small geometry devices. These breakdowns are
results are obtained by soldering the OPA659 directly
reflected in the Absolute Maximum Ratings table. All
onto the board.
device pins are protected with internal ESD protection
diodes to the power supplies, as Figure 39 shows.
f) The thermal slug on bottom of OPA659 DRB
package must be tied to the most negative
supply. The DRB package is a PowerPAD
thermally-enhanced package. Best results are
obtained by soldering the exposed metal tab on the
bottom of the OPA659 DRB directly to a metal plane
on the PCB that is connected to the most negative
supply voltage of the op amp. General layout
guidelines can be found in the application reports,
PowerPAD™ Layout Guidelines (SLOA120 ) and
PowerPAD™ Made Easy (SLMA004 ) , both available
Figure 39. Internal ESD Protection
for download from the TI web site at www.ti.com . It
may also be helpful to copy the EVM layout shown in
These diodes provide moderate protection to input
the Evaluation Module section.
overdrive voltages above the supplies as well. The
protection diodes can typically support 30mA
continuous current. Where higher currents are
The DRB package option is a PowerPAD™ package
possible (for example, in systems with ± 12V supply
that includes a thermal pad for increased thermal
parts driving into the OPA659), current limiting series
performance. When using this package, it is
resistors should be added into the two inputs. Keep
recommended to distribute the negative supply as a
these resistor values as low as possible because high
power plane, and tie the PowerPAD to this supply
values degrade both noise performance and
with multiple vias for proper power dissipation. For
frequency response.
proper operation, the PowerPAD must be tied to the
most negative supply voltage. It is recommended to
use five evenly-spaced vias under the device as
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