參數(shù)資料
型號: MAX9725DETC+T
廠商: Maxim Integrated Products
文件頁數(shù): 2/17頁
文件大小: 0K
描述: IC AMP AUDIO .025W STER 12TQFN
產(chǎn)品培訓模塊: Lead (SnPb) Finish for COTS
Obsolescence Mitigation Program
標準包裝: 2,500
系列: DirectDrive®
類型: AB 類
輸出類型: 耳機,2-通道(立體聲)
在某負載時最大輸出功率 x 通道數(shù)量: 25mW x 2 @ 16 歐姆
電源電壓: 900 mV ~ 1.8 V
特點: 消除爆音,短路保護,關機
安裝類型: 表面貼裝
供應商設備封裝: 12-TQFN-EP(4x4)
封裝/外殼: 12-WQFN 裸露焊盤
包裝: 帶卷 (TR)
MAX9725
1V, Low-Power, DirectDrive, Stereo Headphone
Amplifier with Shutdown
10
______________________________________________________________________________________
Click-and-Pop Suppression
In conventional single-supply audio drivers, the output-
coupling capacitor is a major contributor of audible
clicks and pops. Upon startup, the driver charges the
coupling capacitor to its bias voltage, typically half the
supply. Likewise, on shutdown, the capacitor is dis-
charged to GND. This results in a DC shift across the
capacitor that appears as an audible transient at the
speaker. The MAX9725’s DirectDrive technology elimi-
nates the need for output-coupling capacitors.
The MAX9725 also features extensive click-and-pop
suppression that eliminates any audible transient
sources internal to the device. The Power-Up/-Down
Waveform in the
Typical Operating Characteristics
shows minimal DC shift and no spurious transients at
the output upon startup or shutdown.
In most applications, the output of the preamplifier dri-
ving the MAX9725 has a DC bias of typically half the
supply. At startup, the input-coupling capacitor is
charged to the preamplifier’s DC bias voltage through
the internal input resistor (25k
Ω for MAX9725A-
MAX9725D, minimum 10k
Ω for MAX9725E) causing an
audible click and pop. Delaying the rise of
SHDN 4 or 5
time constants, based on RIN x CIN, relative to the start-
up of the preamplifier eliminates any click and pop
caused by the input filter (see the
Functional Diagrams).
Applications Information
Power Dissipation
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 TJ(MAX) is +150
°C, TA is the ambient tempera-
ture, and
θJA is the reciprocal of the derating factor in
°C/W as specified in the Absolute Maximum Ratings
section. For example,
θJA for the thin QFN package is
+59.3
°C/W.
The MAX9725 has two power dissipation sources, the
charge pump and the two amplifiers. If the power dissi-
pation exceeds the rated package dissipation, reduce
VDD, increase load impedance, decrease the ambient
temperature, or add heatsinking to the device. Large
output, supply, and ground traces decrease
θJA, allow-
ing more heat to be transferred from the package to
surrounding air.
Output Power
The MAX9725’s output power increases when the left
and right audio signals differ in magnitude and/or
phase. Figure 4 shows the two extreme cases for in-
and out-of-phase input signals. The output power of a
typical stereo application lies between the two extremes
shown in Figure 4. The MAX9725 is specified to output
20mW per channel when both inputs are in-phase.
Powering Other Circuits from
the Negative Supply
The MAX9725 internally generates a negative supply
voltage (PVSS) to provide the ground-referenced output
signal. Other devices can be powered from PVSS pro-
vided the current drawn from the charge pump does
not exceed 1mA. Headphone driver output power and
THD+N will be adversely affected if more than 1mA is
drawn from PVSS. Using PVSS as an LCD bias is a typi-
cal application for the negative supply.
PVSS is unregulated and proportional to VDD. Connect
a 1F capacitor from C1P to C1N for best charge-pump
operation.
P
T- T
DISSPKG(MAX)
J(MAX)
A
JA
=
θ
Figure 4. Output Power vs. Supply Voltage with Inputs In-/Out-
of-Phase
0
15
10
5
20
25
30
35
40
45
50
0.9
1.1
1.3
1.5
OUTPUT POWER vs. SUPPLY VOLTAGE
WITH INPUTS IN- AND OUT-OF-PHASE
SUPPLY VOLTAGE (V)
OUTPUT
POWER
(mW)
fIN = 1kHz
RL = 16
Ω
THD+N = 1%
INPUTS 180° OUT-OF-PHASE
INPUTS IN-PHASE
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