Rainbow Electronics MAX9729 - Manual (Page 21)

Charge-Pump Flying Capacitor (C1)
The charge-pump flying capacitor connected between
C1N and C1P affects the charge pump’s load regula-
tion and output impedance. Choosing too small a flying
capacitor degrades the MAX9729’s ability to provide
sufficient current drive and leads to a loss of output
voltage. Increasing the value of the flying capacitor
improves load regulation and reduces the charge-
pump output impedance. See the Output Power vs.
Charge-Pump Capacitance and Load Resistance
graph in the Typical Operating Characteristics . Place
C1 physically close to C1P and C1N. Use a 1µF capac-
itor for C1 in most applications.
Charge-Pump Hold Capacitor (C2)
The hold capacitor’s value and ESR directly affect the
ripple at PV
SS . Ripple is reduced by increasing the
value of the hold capacitor. Choosing a capacitor with
lower ESR reduces ripple and output impedance. Lower
capacitance values can be used in systems with low
maximum output power levels. See the Output Power vs.
Charge-Pump Capacitance and Load Resistance graph
in the
Typical Operating Characteristics . C2 should be
equal to the value of C1. Place C2 physically close to
PV
SS and SV SS . Connect PV SS and SV SS together at
C2. Use a 1µF capacitor for C2 in most applications.
PV DD Bypass Capacitor (C3)
The PV DD bypass capacitor lowers the output imped-
ance of the power supply and reduces the impact of
the MAX9729’s charge-pump switching transients. C3
should be greater than or equal to C1. Place C3 physi-
cally close to PV
DD
.
MAX9729
Stereo Headphone Amplifier with BassMax,
Volume Control, and Input Mux
______________________________________________________________________________________ 21
100
70
80
90
50
60
10
20
30
40
0
0 5 10 15 20 25 30 35
MAX9729 VOLUME CONTROL
TRANSFER FUNCTION
CODE (DECIMAL)
ATTENUATION (dB)
Figure 8. MAX9729 Volume Control Transfer Function
B7 B6 B5 BEEP LEVEL (dBV)
0 0 0 -10
0 0 1 -20
0 1 0 -30
0 1 1 -40
1 0 0 -50
1 0 1 -52
1 1 0 -54
1 1 1 -56
Table 6. Beep Level (Register 0x01)
BEEP level referenced to a 3V BEEP input.
B3 MODE
0 BassMax Disabled
1 BassMax Enabled
Table 7. BassMax Control (Register 0x01)
B2 B1 B0 MAXIMUM GAIN (dB)
0 0 0 3.5
0 0 1 6
0 1 0 8
0 1 1 10
1 0 0 19.5
1 0 1 22
1 1 0 24
1 1 1 26
Table 8. Maximum Gain Control
(Register 0x01)
Table 9. Initial Power-Up Command Register Status
REGISTER B7 B6 B5 B4 B3 B2 B1 B0 POR SETTINGS
0x00 1 0 0 0 1 0 1 1
Shutdown mode disabled (assuming V SHDN = V DD ), INL1 and
INR1 inputs selected, ATTEN = 16dB (A V_TOTAL = -10dB)
0x01 1 1 1 1 1 0 0 1 Beep input attenuation = 56dB, BassMax enabled, A V_MAX = 6dB