OPA615ID datasheet(23/26 Pages) TI

23 / 26 page

www.ti.com

BOARD LAYOUT GUIDELINES

INPUT AND ESD PROTECTION

External

−V

Internal

Circuitry

OPA615

SBOS299B – FEBRUARY 2004 – REVISED JULY 2005

d) Connections to other wideband devices on the

board may be made with short direct traces or

Achieving optimum performance with a high- fre-

through onboard transmission lines. For short

quency amplifier like the OPA615 requires careful

connections, consider the trace and the input to the

attention to printed circuit board (PCB) layout para-

next device as a lumped capacitive load. Relatively

sitics and external component types. Recommen-

wide traces (50mils to 100mils) should be used,

dations that will optimize performance include:

preferably with ground and power planes opened up

around them.

a) Minimize parasitic capacitance to any AC

ground for all of the signal I/O pins. Parasitic

e) Socketing a high-speed part like the OPA615 is

capacitance on the output and inverting input pins

not recommended. The additional lead length and

can cause instability; on the non-inverting input, it can

pin-to-pin capacitance introduced by the socket can

react with the source impedance to cause uninten-

create an extremely troublesome parasitic network

tional bandlimiting. To reduce unwanted capacitance,

which can make it almost impossible to achieve a

a window around the signal I/O pins should be

smooth, stable frequency response. Best results are

opened in all of the ground and power planes around

obtained by soldering the OPA615 directly onto the

those pins. Otherwise, ground and power planes

PCB.

should be unbroken elsewhere on the board.

b) Minimize the distance (< 0.25") from the power

supply pins to high frequency 0.1

µF decoupling

The OPA615 is built using a very high-speed, comp-

capacitors. At the device pins, the ground and power

lementary bipolar process. The internal junction

plane layout should not be in close proximity to the

breakdown voltages are relatively low for these very

signal I/O pins. Avoid narrow power and ground

small geometry devices. These breakdowns are re-

traces to minimize inductance between the pins and

flected in the Absolute Maximum Ratings table where

the decoupling capacitors. The power-supply connec-

an absolute maximum

±6.5V supply is reported. All

tions should always be decoupled with these capaci-

device pins have limited ESD protection using internal

tors. An optional supply-decoupling capacitor across

diodes to the power supplies, as shown in Figure 53.

the two power supplies (for bipolar operation) will

improve 2nd-harmonic distortion performance. Larger

(2.2

µF to 6.8µF) decoupling capacitors, effective at a

lower frequency, should also be used on the main

supply pins. These may be placed somewhat farther

from the device and may be shared among several

devices in the same area of the PCB.

c) Careful selection and placement of external

components will preserve the high frequency

performance of the OPA615. Resistors should be a

very low reactance type. Surface-mount resistors

Figure 53. Internal ESD Protection

work best and allow a tighter overall layout. Metal-film

and carbon composition, axially-leaded resistors can

also provide good high frequency performance.

These diodes also provide moderate protection to

Again, keep these leads and PCB trace length as

input overdrive voltages above the supplies. The

short as possible. Never use wirewound-type re-

protection diodes can typically support 30mA continu-

sistors in a high frequency application. Other network

ous current. Where higher currents are possible (for

components, such as noninverting input termination

example, in systems with

±15V supply parts driving

resistors, should also be placed close to the package.

into the OPA615), 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 re-

sponse.

OPA615ID Datasheet(PDF) 23 Page - Texas Instruments

OPA615ID Datasheet(HTML) 23 Page - Texas Instruments

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26

Datasheet Download

Link URL