AS1702 - AS1705
Data Sheet - Detailed Description
8 Detailed Description
The AS1702 - AS1705 are 1.8W high output-current audio amplifiers (configured as BTL amplifiers), and contain inte-
grated low-power shutdown and click- and pop-suppression circuitry. Two inputs (SHDM and SHDN) allow shutdown
mode to be configured as active-high or active-low (see Shutdown Mode on page 11).
Each device has either adjustable or fixed gains (0dB, 3dB, 6dB) (see Ordering Information on page 19).
Bias
The devices operate from a single 2.7 to 5.5V supply and contain an internally generated, common-mode bias voltage
of:
VCC
(EQ 1)
2
referenced to ground. Bias provides click-and-pop suppression and sets the DC bias level for the audio outputs. Select
the value of the bias bypass capacitor as described in Section BIAS Capacitor on page 15.
Note: Do not connect external loads to BIAS as this can adversely affect overall device performance.
Shutdown Mode
All devices implement a 100nA, low-power shutdown circuit which reduces quiescent current consumption. As shut-
down mode commences, the bias circuitry is automatically disabled, the device outputs go high impedance, and bias is
driven to GND.
The SHDM input controls the polarity of SHDN:
ꢀ
Drive SHDM high for an active-low SHDN input.
Drive SHDM low for an active-high SHDN input.
ꢀ
Table 6. Shutdown Mode Selection Configurations
SHDM
SHDN
Mode
0
0
1
1
0
1
0
1
Shutdown Mode Enabled
Normal Operation Enabled
Normal Operation Enabled
Shutdown Mode Enabled
Click-and-Pop Suppression
During power-up, the device common-mode bias voltage (VBIAS (see page 4)) ramps to the DC bias point. When enter-
ing shutdown, the device outputs are driven high impedance to 100kΩ between both outputs minimizing the energy
present in the audio band, thus preventing clicks and pops.
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