MAX9789 MAXIM [Maxim Integrated Products], MAX9789 Datasheet - Page 20

• Manufacturer Part Number: MAX9789
• Description: Windows Vista-Compliant, Stereo Class AB Speaker Amplifiers and DirectDrive Headphone Amplifiers
• Manufacturer: MAXIM [Maxim Integrated Products]

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 MAX9789/MAX9790’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
Amplifiers and DirectDrive Headphone Amplifiers
20
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DD
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 4Ω load through a 100mΩ trace, 49mW is con-
sumed in the trace. If power is delivered through a
10mΩ trace, only 5mW is consumed in the trace. Large
output, supply and GND traces also improve the power
dissipation of the device.
The MAX9789/MAX9790 thin QFN package features an
exposed thermal pad on its underside. This pad lowers
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.
SS
together at C2. Place the charge-pump
DD
with a 0.1µF capacitor to
SS