AS1701, AS1706
Data Sheet - Application Information
If the internal power dissipation exceeds the maximum allowed for a given package, power dissipation can be reduced
by increasing the ground plane heat-sinking capabilities and increasing the size of the traces to the device (see Layout
and Grounding Considerations on page 14). Additionally, reducing VDD, 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 9ºC, the amplifiers will be re-enabled.
Note: A pulsing output under continuous thermal overload results as the device heats and cools.
Efficiency
Efficiency of the AS1701/AS1706 is calculated by taking the ratio of the power delivered to the load, to the power con-
sumed from the power supply. Output power is calculated by:
2
VPEAK
(EQ 7)
POUT =
π2RL
where VPEAK is half the peak-to-peak output voltage. In BTL amplifier configurations, the supply current waveform is a
full-wave rectified sinusoid with the magnitude proportional to the peak output voltage and load.
Calculate the supply current and power drawn from the power supply by:
2VPEAK
(EQ 8)
(EQ 9)
IDD =
πRL
2VPEAK
PIN = VDD
πRL
The efficiency of the AS1701/AS1706 is:
(EQ 10)
POUT
POUTRL
η =
= π
RIN
2
2VDD
Component Selection
Gain-Setting Resistors
External feedback resistors RF and RIN (see Figure 1 on page 1) set the gain of the device as:
RF
AVD = 2 x
RIN
(EQ 11)
Optimum output offset is achieved when RF = 20kΩ. Device gain can be varied by changing the value of RIN.
If used in a high-gain configuration (greater than 8V/V), a feedback capacitor may be required to maintain stability (see
Figure 1 on page 1). CF and RF limit the bandwidth of the device, preventing high-frequency oscillations.
Note: Ensure that the pole created by CF and RF is not within the frequency band of interest.
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