MAX13331 datasheet(12/15 Pages) AD

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Flying Capacitor (C1)

The value of the flying capacitor (C1) affects the charge

pump’s load regulation and output resistance. 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 improves load regula-

tion and reduces the charge-pump output resistance to an

extent. See the Output Power vs. Load Resistance graph

in the Typical Operating Characteristics. Above 1μF, the

on-resistance of the switches and the ESR of C1 and C2

dominate.

Holding Capacitor (C2)

The hold capacitor value and ESR directly affect the ripple

at CPVSS. Increasing the value of C2 reduces 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 graph

in the Typical Operating Characteristics.

Power-Supply Bypass Capacitor (C3)

The power-supply bypass capacitor (C3) lowers the

output impedance of the power supply and reduces

the impact of the MAX13330/MAX13331 charge-pump

switching transients. Bypass CPVDD with C3, the same

value as C1, and place it physically close to the CPVDD

and PGND pins.

Layout and Grounding

Proper layout and grounding are essential for optimum

performance. Connect CPVDD and VDD together at the

device. Connect CPVSS and VSS together at the device.

Bypassing of both supplies is accomplished by charge-

pump capacitors C2 and C3 (see the Typical Application

Circuits). Place capacitors C2 and C3 as close to the

device as possible and bypass them to the PGND plane.

Keep PGND and all traces that carry switching transients

as short as possible to minimize EMI. Route them away

from SGND, the audio signal path, and the external feed-

back components (MAX13331). Connect the PGND plane

and the SGND plane together at a single point on the

PCB. Refer to the MAX13330/MAX13331 Evaluation Kit

for layout guidelines.

ESD Protection

To pass module level ESD requirements, it may be nec-

essary to add ESD diodes to the MAX13330/MAX13331

outputs. Connect the anode to the CPVSS supply, and

connect the cathode to an output pin, as shown in the

Typical Application Circuits.

MAX13330/MAX13331

Automotive DirectDrive Headphone Amplifiers

with Output Protection and Diagnostics

www.maximintegrated.com

Maxim Integrated │ 12

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