THS7002 datasheet(30/40 Pages) TI

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THS6002

DUAL DIFFERENTIAL LINE DRIVERS AND RECEIVERS

SLOS202D– JANUARY 1998– REVISED JULY 1999

POST OFFICE BOX 655303

• DALLAS, TEXAS 75265

APPLICATION INFORMATION

PCB design considerations

Proper PCB design techniques in two areas are important to assure proper operation of the THS6002. These

areas are high-speed layout techniques and thermal-management techniques. Because the THS6002 is a

high-speed part, the following guidelines are recommended.

D Ground plane – It is essential that a ground plane be used on the board to provide all components with a

low inductive ground connection. Although a ground connection directly to a terminal of the THS6002 is not

necessarily required, it is recommended that the thermal pad of the package be tied to ground. This serves

two functions. It provides a low inductive ground to the device substrate to minimize internal crosstalk and

it provides the path for heat removal.

D Input stray capacitance – To minimize potential problems with amplifier oscillation, the capacitance at the

inverting input of the amplifiers must be kept to a minimum. To do this, PCB trace runs to the inverting input

must be as short as possible, the ground plane must be removed under any etch runs connected to the

inverting input, and external components should be placed as close as possible to the inverting input. This

is especially true in the noninverting configuration. An example of this can be seen in Figure 56, which shows

what happens when 1.8 pF is added to the inverting input terminal in the noninverting configuration. The

bandwidth increases dramatically at the expense of peaking. This is because some of the error current is

flowing through the stray capacitor instead of the inverting node of the amplifier. Although, in the inverting

mode, stray capacitance at the inverting input has little effect. This is because the inverting node is at a

virtual ground and the voltage does not fluctuate nearly as much as in the noninverting configuration.

f – Frequency – Hz

100

10M

100M

500M

–1

–3

–5

–7

–2

–4

–6

DRIVER

NORMALIZED FREQUENCY RESPONSE

FREQUENCY

VCC = ±15 V

VI = 200 mV

RL = 25 Ω

RF = 1 kΩ

Gain = 1

CI = 0 pF

(Stray C Only)

CI = 1.8 pF

–

1 k

Ω

RL =

Ω

Cin

Vin

Vout

Figure 56. Driver Normalized Frequency Response vs. Frequency

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