www.austriamicrosystems.com/Audio/Amps/AS1702-05 Revision 1.48 11 - 20
AS1702 - AS1705
Datasheet - Detailed Description
8 Detailed Description
The AS1702 - AS1705 are 1.8W high output-current audio amplifiers (configured as BTL amplifiers), and contain integrated 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:
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 shutdown 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.
Click-and-Pop Suppression
During power-up, the device common-mode bias voltage (VBIAS (see page 4)) ramps to the DC bias point. When entering shutdown, the device
outputs are driven high impedance to 100k
Ω between both outputs minimizing the energy present in the audio band, thus preventing clicks and
pops.
Table 6. Shutdown Mode Selection Configurations
SHDM SHDN Mode
0 0 Shutdown Mode Enabled
0 1 Normal Operation Enabled
1 0 Normal Operation Enabled
1 1 Shutdown Mode Enabled
