MAX9776 Maxim Integrated Products, MAX9776 Datasheet - Page 33

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MAX9776

Manufacturer Part Number
MAX9776
Description
(MAX9775 / MAX9776) Stereo Class D Audio Subsystem
Manufacturer
Maxim Integrated Products
Datasheet

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Use capacitors with an ESR less than 100mΩ for opti-
mum performance. Low-ESR ceramic capacitors mini-
mize the output resistance of the charge pump. Most
surface-mount ceramic capacitors satisfy the ESR
requirement. For best performance over the extended
temperature range, select capacitors with an X7R dielec-
tric or better. Table 12 lists suggested manufacturers.
The value of the flying capacitor (C1) affects the output
resistance of the charge pump. A C1 value that is too
small degrades the device’s ability to provide sufficient
current drive, which leads to a loss of output voltage.
Increasing the value of C1 reduces the charge-pump out-
put resistance to an extent. Above 1µF, the on-resistance
of the switches and the ESR of C1 and C2 dominate.
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. See the Output Power
vs. Load Resistance and Charge-Pump Capacitor Size
graph in the Typical Operating Characteristics .
The CPV
impedance of the power supply and reduces the
impact of the MAX9775/MAX9776’s charge-pump
switching transients. Bypass CPV
and place it physically close to the CPV
Use a value for C3 that is equal to C1.
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. Large traces also aid in mov-
ing heat away from the package. Proper grounding
improves audio performance, minimizes crosstalk
between channels, and prevents any switching noise
from coupling into the audio signal. Connect PGND and
GND together at a single point on the PCB. Route all
Table 12. Suggested Capacitor Manufacturers
Taiyo Yuden
TDK
Supply Bypassing, Layout, and Grounding
DD
SUPPLIER
bypass capacitor (C3) lowers the output
2 x 1.5W, Stereo Class D Audio Subsystem
SS
. Increasing the value of C2 reduces
______________________________________________________________________________________
Charge-Pump Capacitor Selection
CPV
with DirectDrive Headphone Amplifier
DD
Bypass Capacitor (C3)
Output Capacitor (C2)
Flying Capacitor (C1)
DD
800-348-2496
807-803-6100
with C3 to PGND
PHONE
DD
and PGND.
traces that carry switching transients away from GND
and the traces/components in the audio signal path.
Connect all of the power-supply inputs (CPV
and PV
tor to CPGND. Bypass V
Bypass PV
0.1µF capacitor to PGND. Place the bypass capacitors
as close to the MAX9775/MAX9776 as possible. Place
a bulk capacitor between PV
Use large, low-resistance output traces. Current drawn
from the outputs increases as load impedance
decreases. High output trace resistance decreases the
power delivered to the load. Large output, supply, and
GND traces also allow more heat to move from the
MAX9775/MAX9776 to the PCB, decreasing the thermal
impedance of the circuit.
The MAX9775/MAX9776 TQFN-EP package features an
exposed thermal pad on its underside. This pad lowers
the package’s thermal impedance by providing a direct
heat conduction path from the die to the PCB. The
exposed pad is internally connected to GND. Connect
the exposed thermal pad to the PCB GND plane.
For the latest application details on UCSP construction,
dimensions, tape carrier information, PCB techniques,
bump-pad layout, and recommended reflow tempera-
ture profile, as well as the latest information of reliability
testing results, refer to Application Note: UCSP—A
Wafer-Level Chip-Scale Package available on Maxim’s
website at www.maxim-ic.com/ucsp.
When operating at maximum output power, the UCSP
thermal dissipation can become a limiting factor. The
UCSP package does not dissipate as much power as a
TQFN and as a result will operate at a higher tempera-
ture. At peak output power into a 4Ω load, the
MAX9775/MAX9776 can exceed its thermal limit, trig-
gering thermal protection. As a result, do not choose
the UCSP package when maximum output power into
4Ω is required.
UCSP Applications Information
847-925-0899
847-390-4405
DD
) together. Bypass CPV
FAX
DD
with a 1µF capacitor in parallel with a
TQFN Applications Information
UCSP Thermal Consideration
DD
www.t-yuden.com
www.component.tdk.com
with 1µF capacitor to GND.
DD
and PGND if needed.
DD
with a 1µF capaci-
WEBSITE
DD
, V
DD
33
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