OPA1622 Datasheet, PDF (18/36 Pages) Texas Instruments – OPA1622 SoundPlus™ High-Fidelity, Bipolar-Input, Audio Operational Amplifier

OPA1622
SBOS727A – NOVEMBER 2015 – REVISED NOVEMBER 2015
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Device Functional Modes (continued)
7.4.1 Shutdown Mode
When the enable pin voltage is below the logic low threshold, the OPA1622 enters a shutdown mode with
minimal power consumption. In this state the output transistors of the amplifier are not powered on. However, do
not consider the amplifier output to be high-impedance. Applying signals to the output of the OPA1622 while the
device is in the shutdown mode may parasitically power the output stage, causing the OPA1622 output to draw
current.
The OPA1622 enable circuitry limits transients at the output when transitioning into or out of shutdown mode.
However, small output transients do still accompany this transition, as illustrated in Figure 46 and Figure 47. Note
that in both figures the time scale is 1 µs per division, indicating that the output transients are extremely brief in
nature, and therefore not likely to be audible in headphone applications.
Enable (2 V/div)
Enable (2 V/div)
Output (20 mV/div)
Output (20 mV/div)
Time (1 s/div)
C001
Figure 46. OPA1622 Output Voltage When Enable Pin
Transitions High (32-Ω Load Connected)
Time (1 s/div)
C002
Figure 47. OPA1622 Output Voltage When Enable Pin
Transitions Low (32-Ω Load Connected)
7.4.2 Output Transients During Power Up and Power Down
To minimize the possibility of output transients that might produce an audible click or pop, ramp the supply
voltages for the OPA1622 symmetrically to their nominal values. Asymmetrical supply ramping can cause output
transients during power up that may be audible in headphone applications. If possible, hold the enable pin low
while the power supplies are ramping up or down. If the enable pin is not being independently controlled (for
example, by a GPIO pin), use a voltage divider to hold the enable pin voltage below the logic-high threshold until
the power supplies reach the specified minimum voltage, as shown in Figure 48.
VCC
22.1 k
To enable
pin on IC
10.7 k
Figure 48. Voltage Divider Used to Hold Enable Low at Power Up or Power Down.
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