Flying Capacitor (C1)

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

regulation and output resistance of the charge pump. A

C1 value that is too small degrades the device’s ability to

provide sufficient current drive. Increasing the value of

C1 improves load regulation and reduces the charge-

pump output resistance to an extent. Above 1µF, the on-

resistance of the switches and the ESR of C1 and C2

dominate.

Output Capacitor (C2)

The output capacitor value and ESR directly affect the

ripple at CHOLD. Increasing C2 reduces output ripple.

Likewise, decreasing the ESR of C2 reduces both rip-

ple and output resistance. Lower capacitance values

can be used in systems with low maximum output

power levels.

Output Filter

The MAX9713/MAX9714 do not require an output filter.

The device passes FCC emissions standards with

36cm of unshielded speaker cables. However, output

filtering can be used if a design is failing radiated emis-

sions due to board layout or cable length, or the circuit

is near EMI-sensitive devices. Use a ferrite bead filter

when radiated frequencies above 10MHz are of con-

cern. Use an LC filter when radiated frequencies below

10MHz are of concern, or when long leads connect the

amplifier to the speaker. Refer to the MAX9714

Evaluation Kit schematic for details of this filter.

Sharing Input Sources

In certain systems, a single audio source can be shared

by multiple devices (speaker and headphone ampli-

fiers). When sharing inputs, it is common to mute the

unused device, rather than completely shutting it down,

preventing the unused device inputs from distorting the

input signal. Mute the MAX9713/MAX9714 by driving SS

low through an open-drain output or MOSFET (see the

System Diagram). Driving SS low turns off the Class D

output stage, but does not affect the input bias levels of

the MAX9713/MAX9714. Be aware that during normal

operation, the voltage at SS can be up to 7V, depending

on the MAX9713/MAX9714 supply.

Supply Bypassing/Layout

Proper power-supply bypassing ensures low distortion

operation. For optimum performance, bypass VDD to

PGND with a 0.1µF capacitor as close to each VDD pin

as possible. A low-impedance, high-current power-sup-

ply connection to VDD is assumed. Additional bulk

capacitance should be added as required depending on

the application and power-supply characteristics. AGND

and PGND should be star connected to system ground.

Refer to the MAX9714 Evaluation Kit for layout guidance.

6W, Filterless, Spread-Spectrum

Mono/Stereo Class D Amplifiers

______________________________________________________________________________________

11

9

10

11

12

13

14

15

REG.

AGND

IN-

IN+

SS

SHDN

G1

32

31

30

29

28

27

26

N.C.

N.C.

OUT+

OUT+

OUT-

OUT-

N.C.

MAX9713

25

1

23

4

5

67

8

24

+

+

23

22

21

20

19

18

17

N.C.

16

G2

TOP VIEW

TQFN (5mm x 5mm)

TQFN (7mm x 7mm)

9

10

11

12

13

14

15

INL-

INL+

SHDN

SS

AGND

REG.

INR-

32

31

30

29

28

27

26

OUTL+

OUTL+

OUTL-

OUTL-

OUTR+

OUTR+

OUTR-

MAX9714

25

1

23

4

5

67

8

24

23

22

21

20

19

18

17

OUTR-

16

INR+

Pin Configurations

Chip Information

MAX9713 TRANSISTOR COUNT: 3093

MAX9714 TRANSISTOR COUNT: 4630

PROCESS: BiCMOS