accuracy. The bypass capacitors should include a

0.1µF ceramic capacitor between each supply pin and

the ground plane, located as close to the package as

possible. Additionally, place a 1µF to 10µF ceramic or

tantalum capacitor in parallel with each 0.1µF capacitor,

and as close to them as possible. Place a 10µF to 15µF

power-supply points of entry to the PC board. Place a

power-supply point of entry to the PC board. The power-

supply traces should lead directly from the board input

tance, keep PC traces short and use surface-mount

components. Wire-wrapped boards are much too induc-

tive, and breadboards are much too capacitive; neither

should be used. Power-supply sequencing is required;

apply ±5.0 before applying ±2.5V.

Exposed-Pad Connection

For optimum electrical performance, the EP of the

MAX9480/MAX9481/MAX9482 should be soldered to

wide a trace as possible. If using the EP, the 100µF to

220µF low-ESR tantalum capacitor should be used to

decouple the EP to the ground plane of the PC board

as close to the EP region as possible. For optimum

thermal performance, the EP should be additionally

connected to a heat sink, as described in the Thermal

Protection and Power Dissipation section.

Preamp Output Bypassing

In addition to the above layout considerations, and inde-

pendent of the gain setting, some high-frequency

bypassing of the preamp outputs is necessary to prevent

instability arising from the high-frequency input imped-

ance characteristics of the buffers. A 50

Ω resistor in

series with a 2200pF ceramic capacitor should be con-

nected between POUT_ and DGND, with a 47pF capaci-

tor connected directly between POUT_ and DGND.

Choosing Feedback and Gain Resistors

The MAX9480/MAX9481/MAX9482 use current-feed-

back amplifiers. Figure 2 shows the standard inverting

and noninverting configurations. Notice that the gain of

the noninverting circuit, Figure 2(b), is 1 plus the mag-

nitude of the inverting closed-loop gain. Increasing

feedback resistor values decreases peaking. Use the

Do not use feedback capacitance.

DC and Noise Errors

There are several error sources to consider when using

any operational amplifier, and this applies to the

MAX9480/MAX9481/MAX9482 as well. Offset-error

terms are given by equations 3 and 4. Voltage and cur-

rent-noise errors are root-square summed and there-

fore computed separately. In Figure 3, the total output

offset voltage is determined by:

Ω), plus the nega-

amplifiers, the input bias currents may flow into or

out of the device. For this reason, there is no benefit

to matching the resistance at both inputs, as is com-

mon in voltage-feedback amplifiers.

Low-Power, Low-Distortion, Central-Office

ADSL Drivers and Integrated Drivers/Receivers

_______________________________________________________________________________________

9

MAX9480

MAX9481

MAX9482

( )

)

(a)

(b)

MAX9480

MAX9481

MAX9482

[ ( )]

( )

1+

Figure 2. Inverting Gain Configuration and Noninverting Gain

Configuration