max9789a Maxim Integrated Products, Inc., max9789a Datasheet - Page 19

• Manufacturer Part Number: max9789a
• Description: Windows Vista-compliant, Stereo Class Ab Speaker Amplifiers And Directdrive Headphone Amplifiers Integrated Products
• Manufacturer: Maxim Integrated Products, Inc.

The output capacitor value and ESR directly affect the
ripple at CPV
output ripple. Likewise, decreasing the ESR of C2
reduces both ripple and output resistance. Lower
capacitance values can be used in systems with low
maximum output power levels.
The CPV
impedance of the power supply and reduces the
impact of the MAX9789A/MAX9790A’s charge-pump
switching transients. Bypass CPV
value as C1, and place it physically close to the CPV
and CPGND pins.
Proper layout and grounding are essential for optimum
performance. Use large traces for the power-supply
inputs and amplifier outputs to minimize losses due to
parasitic trace resistance, as well as route heat away
from the device. Good grounding improves audio per-
formance, minimizes crosstalk between channels, and
prevents switching noise from coupling into the audio
signal. Connect PGND and GND together at a single
point on the PC board. Route PGND and all traces that
carry switching transients away from GND and the
traces and components in the audio signal path.
Windows Vista-Compliant, Stereo Class AB Speaker
DD
Amplifiers and DirectDrive Headphone Amplifiers
bypass capacitor (C3) lowers the output
SS
. Increasing the value of C2 reduces
______________________________________________________________________________________
CPV
Layout and Grounding
DD
Bypass Capacitor (C3)
Output Capacitor (C2)
DD
with 1µF, the same
DD
Connect C2 and C3 to the PGND plane. Connect PV
and CPV
capacitors (C1, C2, and C3) as close as possible to
the device. Bypass PV
PGND. Place the bypass capacitors as close as possi-
ble to the device.
Use large, low-resistance output traces. As load imped-
ance decreases, the current drawn from the device out-
puts increase. At higher current, the resistance of the
output traces decrease the power delivered to the load.
For example, if 2W is delivered from the speaker output
to a 4
sumed in the trace. If power is delivered through a
10m
output, supply and GND traces also improve the power
dissipation of the device.
The MAX9789A/MAX9790A thin QFN package features
an exposed thermal pad on its underside. This pad low-
ers the package’s thermal resistance by providing a
direct heat conduction path from the die to the printed
circuit board. Connect the exposed thermal pad to GND
by using a large pad and multiple vias to the GND plane.
trace, only 5mW is consumed in the trace. Large
load through a 100m
SS
together at C2. Place the charge-pump
DD
with a 0.1µF capacitor to
trace, 49mW is con-
SS
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