AS1702 - AS1705
Data Sheet - Application Information
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 Lay-
out and Grounding Considerations on page 15). Additionally, reducing VCC, increasing load impedance, and decreas-
ing 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 ≥ +145ºC, 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.
Fixed Differential Gain (AS1703, AS1704, and AS1705)
The AS1703, AS1704, and AS1705 contain different internally-fixed gains (see Ordering Information on page 19). 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 31 on page 12).
Adjustable Differential Gain (AS1702)
Gain-Setting Resistors
The AS1702 uses external feedback resistors, RF and RIN (Figure 33), to set the gain of the device as:
RF
(EQ 7)
AV =
RIN
where AV is the desired voltage gain. For example, RIN = 10kΩ, 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 33. Setting the AS1702 Gain
RF
20kΩ
RF
20kΩ
RIN
CIN*
10kΩ
10µF
2
10
Inverting
Differential Input
–
+
IN-
4
OUT+
6
Non-Inverting
Differential Input
RIN
10kΩ
IN+
OUT-
CIN*
10µF
5
Bias
Generator
* Optional
BIAS
CBIAS
0.1µF
AS1702
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