External

Pin

+V

CC

−V

CC

Internal

Circuitry

OPA830-EP

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SBOS655 – MARCH 2014

Layout Guidelines (continued)

phase margin). If a long trace is required, and the 6dB signal loss intrinsic to a doubly-terminated

transmission line is acceptable, implement a matched impedance transmission line using microstrip or

stripline techniques (consult an ECL design handbook for microstrip and stripline layout techniques). A 50

Ω

environment is normally not necessary onboard, and in fact, a higher impedance environment will improve

distortion as shown in the distortion versus load plots. With a characteristic board trace impedance defined

(based on board material and trace dimensions), a matching series resistor into the trace from the output of

the OPA830 is used as well as a terminating shunt resistor at the input of the destination device. Remember

also that the terminating impedance will be the parallel combination of the shunt resistor and the input

impedance of the destination device; this total effective impedance should be set to match the trace

impedance. If the 6dB attenuation of a doubly-terminated transmission line is unacceptable, a long trace can

be series-terminated at the source end only. Treat the trace as a capacitive load in this case and set the

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.

5. Socketing a high-speed part is not recommended. The additional lead length and terminal-to-terminal

capacitance introduced by the socket can create an extremely troublesome parasitic network which can

make it almost impossible to achieve a smooth, stable frequency response. Best results are obtained by

soldering the OPA830 onto the board.

10.2 Input and ESD Protection

The OPA830 is built using a very high-speed complementary bipolar process. The internal junction breakdown

voltages are relatively low for these very small geometry devices. These breakdowns are reflected in the

Absolute Maximum Ratings table. All device terminals are protected with internal ESD protection diodes to the

power supplies, as shown in Figure 60.

Figure 60. Internal ESD Protection

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 (that is, in systems

with ±15V supply parts driving into the OPA830), 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 © 2014, Texas Instruments Incorporated

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