AS1702-T datasheet(8/13 Pages) AMSCO

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AS1702, AS1703, AS1704, AS1705

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Data Sheet

Fixed Differential Gain (AS1703, AS1704, and AS1705)

If the internal power dissipation exceeds the maximum allowed for a given package, power dissipation should be

reduced by increasing the ground plane heat-sinking capabilities and increasing the size of the device traces (see Sec-

tion 7.5 Layout and Grounding Considerations on page 9). Additionally, reducing VCC, increasing load impedance, and

decreasing ambient temperature can reduce device power dissipation.

The integrated thermal-overload protection circuitry limits the total device power dissipation. Note that if the junction

temperature is

≥ +145°C, the integrated thermal-overload protection circuitry will disable the amplifier output stage. If

the junction temperature is reduced by 9°, the amplifiers will be re-enabled.

Note: A pulsing output under continuous thermal overload results as the device heats and cools.

7.3 Fixed Differential Gain (AS1703, AS1704, and AS1705)

The AS1703, AS1704, and AS1705 contain different internally-fixed gains (see Ordering Information on page 12). A

fixed gain facilitates simplified designs, decreased footprint size, and elimination of external gain-setting resistors.

The fixed gain values are achieved using resistors R1 and R2 (see Figure 3 on page 6).

7.4 Adjustable Differential Gain (AS1702)

7.4.1 Gain-Setting Resistors

The AS1702 uses external feedback resistors, RF and RIN (Figure 5), to set the gain of the device as:

where AV is the desired voltage gain. For example, RIN = 10k

Ω, RF = 20kΩ yields a gain of 2V/V, or 6dB.

Note: RF can be either fixed or variable, allowing the gain to be controlled by software (using a AS150x digital poten-

tiometer. For more information on the AS1500 family of digital potentiometers, refer to the latest version of the

AS150x data sheet, available from the austriamicrosystems website http://www.austriamicrosystems.com.)

Figure 5. Setting the AS1702 Gain

AV =

RIN

(EQ 7)

AS1702

–

OUT+

OUT-

20k

Ω

20k

Ω

Bias

Generator

Inverting Differential

Input

Non-Inverting Differential

Input

CIN*

10µF

CIN*

10µF

RIN

10k

Ω

RIN

10k

Ω

* Optional

CBIAS

0.1µF

IN+

IN-

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