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AS1702, AS1703, AS1704, AS1705

Data Sheet

Bias

6 Detailed Description

The AS1702, AS1703, AS1704, and AS1705 are 1.6W high output-current audio amplifiers (configured as BTL ampli-

fiers), 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 Section 6.2 Shutdown Mode on

page 5).

Each device has either adjustable or fixed gains (0dB, 3dB, 6dB) (see Section 9 Ordering Information on page 12).

6.1 Bias

The devices operate from a single 2.7 to 5.5V supply and contain an internally generated, common-mode bias voltage

of:

(EQ 1)

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 7.4.3 BIAS Capacitor on page 9.

Note: Do not connect external loads to BIAS as this can adversely affect overall device performance.

6.2 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.

6.3 Click-and-Pop Suppression

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 4. 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