Datasheet

where R
IN
is a minimum of 10kΩ. Choose C
IN
such
that f
-3dB
is well below the lowest frequency of interest.
Setting f
-3dB
too high affects the amplifier’s low-frequency
response. Use capacitors with low-voltage coefficient
dielectrics. Film or C0G dielectric capacitors are good
choices for AC-coupling capacitors. Capacitors with high-
voltage coefficients, such as ceramics, can result in
increased distortion at low frequencies.
Charge-Pump Flying Capacitor
The charge-pump flying capacitor connected between
C1N and C1P affects the charge pump’s load regulation
and output impedance. Choosing a flying capacitor that
is too small degrades the MAX9723’s ability to provide
sufficient current drive and leads to a loss of output volt-
age. Increasing the value of the flying capacitor improves
load regulation and reduces the chargepump output
impedance. See the Output Power vs. Charge-Pump
Capacitance and Load Resistance graph in the Typical
Operating Characteristics.
Figure 7. MAX9723A/MAX9723B Transfer Function with B5 = 1
Figure 8. MAX9723A/MAX9723B Transfer Function with B5 = 0
Figure 9. MAX9723C/MAX9723D Transfer Function with B5 = 1
Figure 10. MAX9723C/MAX9723D Transfer Function with B5 = 0
MAX9723A AND MAX9723B
TRANSFER FUNCTION (B5 = 1)
CODE
GAIN (dB)
-20
-30
-40
10
0
-10
-50
0 6 12 18 24 30
MAX9723A AND MAX9723B
TRANSFER FUNCTION (B5 = 0)
CODE
GAIN (dB)
-40
-50
-60
-70
-80
0
-10
-30
-20
-90
0 6 12 18 24 30
GAIN PROFILE WITH AND
WITHOUT BassMax
FREQUENCY (Hz)
A
V
(dB)
1k10010
-8
-6
-4
-2
0
2
4
6
8
10
-10
1 10k
MAX9723A
CMD REGISTER
CODE = 0xFF
R1 = 47kΩ
R2 = 22kΩ
C3 = 0.1mF
f
POLE
f
ZERO
WITH
BassMax
WITHOUT
BassMax
MAX9723C AND MAX9723D
TRANSFER FUNCTION (B5 = 0)
CODE
0 6 12 18 24 30
GAIN (dB)
-30
-40
-50
-60
-70
10
0
-20
-10
-80
MAX9723 Stereo DirectDrive Headphone Amplier
with BassMax, Volume Control, and I
2
C
www.maximintegrated.com
Maxim Integrated │ 17