Detailed Description
The MAX9890 provides click-and-pop suppression for
single-supply devices such as CODECs and other head-
phone amplifiers that do not have click-and-pop suppres-
sion. Single-supply audio amplifier outputs have a DC
bias voltage, VCC / 2, and require large output-coupling
capacitors to block the DC voltage from the speaker.
During startup or shutdown, the DC bias voltage is quickly
raised or lowered (Figure 1), resulting in an audible
transient through the headphone load. The MAX9890
prevents the audible transient by slowly ramping the DC
bias in an S-shaped waveform (Figure 2), suppressing
the large transient at the output of the coupling capacitor.
The S-shaped waveform shapes the frequency spectrum,
minimizing the amount of audible components present at
the output.
Internal switches couple the inputs to the outputs after
the coupling capacitors have fully charged to the input
common-mode bias voltage. When power is removed or
the device is put into shutdown, the internal switches in the
MAX9890 immediately disconnect the output and slowly
discharge the coupling capacitors through 220kΩ resistors.
The MAX9890 has an undervoltage lockout (UVLO)
that prevents device operation when VCC is below the
power-down threshold (2.5V, typ). The MAX9890 features
±8kV ESD (Human Body Model) protection on the audio
outputs.
Startup
The MAX9890 monitors VCC and SHDN. The UVLO holds
the device off when VCC is below the power-down thresh-
old (VUVLO) or SHDN is held low. The device needs both
VCC above the power-down threshold and SHDN = high
for the part to start up. Once the supply voltage is above
the power-down threshold and SHDN is high, the device
charges the coupling capacitors to the input DC bias volt-
age using CEXT to control the ramp. After the DC bias
ramp, the internal switches close, coupling the audio input
to the output. The MAX9890 provides click-pop suppres-
sion even if the output blocking capacitors are already
partially or fully charged.
The MAX9890A features a 200ms switch turn-on time,
enabling the use of up to 100μF coupling capacitors
at the output for applications requiring only a lim-
ited low-frequency response and a rapid turn-on time.
The MAX9890B features a 330ms switch turn-on time,
enabling the use of >100μF coupling capacitors at the
output for extended low-frequency response applications.
For optional click-pop suppression, mute the audio signal
until after the turn-on time has elapsed.
The internal switches stay closed as long as VCC is above
the power-down threshold voltage and SHDN is high.
Figures 1 and 2 show typical startup/power-up sequences
with and without click-pop suppression.
Shutdown
If the supply voltage falls below the UVLO threshold or
if SHDN is driven low, the device enters low-power shut-
down mode. In low-power shutdown mode, quiescent cur-
rent reduces to 0.001μA. The switches are immediately
turned off and 220kΩ resistors slowly bleed the charge
off the coupling capacitors. Figures 3 and 4 show typi-
cal shutdown/power-down sequences with and without
click-pop suppression. For optimal click-pop performance,
mute the audio signal before shutting down the MAX9890.
PIN/BUMP NAME FUNCTION
TDFN UCSP
1 C2 VCC Power Supply. VCC accepts 2.7V to 5.5V input supply. Bypass VCC to GND with a 1µF capacitor.
2 C1 SHDN Active-Low Shutdown. Connect SHDN to GND to enter a 0.1µA shutdown mode. Connect SHDN
to VCC for normal operation.
3B1 INL Left-Channel Audio Input. Connect to output of headphone amplier.
4 A1 OUTL Left-Channel Audio Output. AC couple to headphone.
5A2 GND Ground
6A3 OUTR Right-Channel Audio Output. AC couple to headphone.
7B3 INR Right-Channel Audio Input. Connect to output of headphone amplier.
8 C3 CEXT External Capacitor. Connect a 0.1µF capacitor from CEXT to GND.
MAX9890 Audio Click-Pop Suppressor
www.maximintegrated.com Maxim Integrated
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Pin Description