max9726aetpt Maxim Integrated Products, Inc., max9726aetpt Datasheet - Page 17

• Manufacturer Part Number: max9726aetpt
• Description: Max9726 Directdrive, Headphone Amplifier With Bassmax, I?c, Volume And Gain Control
• Manufacturer: Maxim Integrated Products, Inc.

The contents of the MAX9726’s command register at
power-on are as shown in Table 6.
Linear power amplifiers can dissipate a significant
amount of power under normal operating conditions.
The maximum power dissipation for each package is
given in the Absolute Maximum Ratings section under
Continuous Power Dissipation or can be calculated by
the following equation:
where T
ture, and θ
°C/W as specified in the Absolute Maximum Ratings
section. For example, θ
+39°C/W.
If the power dissipation exceeds the rated package
dissipation, reduce V
decrease the ambient temperature, or add heatsinking.
Large output, supply, and ground traces decrease θ
allowing more heat to be transferred from the package
to surrounding air.
Dynamic range is the difference between the noise
floor of the system and the output level at 1% THD+N. It
is essential that a system’s dynamic range be known
before setting the maximum output gain. Output clip-
ping occurs if the output signal is greater than the
dynamic range of the system. The DirectDrive architec-
ture of the MAX9726 has increased dynamic range (for
a given V
fiers. Due to the absolute maximum ratings of the
MAX9726 and to limit power dissipation, the MAX9726
includes internal circuitry that limits the output voltage
to approximately ±2.5V.
Use the THD+N vs. Output Power graphs in the Typical
Operating Characteristics section to identify the sys-
tem’s dynamic range. Find the output power that caus-
es 1% THD+N for a given load. This point indicates the
output power that causes the output to begin to clip.
Table 6. Initial Power-Up Command Register Status
Power-On Reset
MODE
J(MAX)
DD
Power Dissipation and Heatsinking
JA
) compared to other single-supply ampli-
is the reciprocal of the derating factor in
Applications Information
is +150°C, T
P
D MAX
______________________________________________________________________________________
(
BassMax, I
DirectDrive, Headphone Amplifier with
DD
B7
)
1
=
JA
Output Dynamic Range
, increase load impedance,
T
J MAX
(
A
for the TQFN package is
θ
is the ambient tempera-
JA
)
−
B6
T
1
A
Power-On Reset
2
B5
1
C, Volume and Gain Control
JA
,
B4
1
Use the following equation to determine the peak-to-
peak output voltage that causes 1% THD+N for a given
load.
where P
THD+N, R
peak-to-peak output voltage. Determine the voltage
gain (A
on the maximum peak-to-peak input voltage (V
The maximum voltage gain setting is determined by
external components (see the Gain-Setting Components
section).
The MAX9726 features an undervoltage lockout (UVLO)
function that prevents the device from operating if the
supply voltage is less than 2.7V. This feature ensures
proper operation during brownout conditions and pre-
vents deep battery discharge. Once the supply voltage
exceeds the UVLO threshold, the MAX9726 charge
pump is turned on and the amplifiers are powered, pro-
vided that SHDN is high and B7 in the command regis-
ter is set to 1.
Use ceramic capacitors with a low ESR for optimum
performance. For optimal performance over the extend-
ed temperature range, select capacitors with an X7R
dielectric.
The charge-pump flying capacitor connected between
C1N and C1P affects the charge pump’s load regula-
tion and output impedance. Choosing a flying capacitor
that is too small degrades the MAX9726’s ability to pro-
vide sufficient current drive and leads to a loss of out-
put 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
graphs in the Typical Operating Characteristics .
V
OUT_1%
) necessary to attain this output voltage based
L
B3
V
is the load resistance, and V
1
OUT P P
(
is the output power that causes 1%
Charge-Pump Flying Capacitor (C1)
−
Charge-Pump Capacitor Selection
A
)
V
=
=
B2
2 2
1
V
V
OUT P P
IN P P
Component Selection
(
P
(
OUT
(
−
−
)
_ %
)
1
B1
1
×
R
OUT(P-P)
L
IN(P-P)
UVLO
B0
1
is the
):
17