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APA2177 Datasheet(PDF) 13 Page - Anpec Electronics Coropration

No. de Pieza. APA2177
Descripción  25mW Stereo Cap-Free Headphone Driver
Descarga  20 Pages
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Fabricante  ANPEC [Anpec Electronics Coropration]
Página de inicio  http://www.anpec.com.tw
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APA2177 Datasheet(HTML) 13 Page - Anpec Electronics Coropration

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Copyright
© ANPEC Electronics Corp.
Rev. A.1 - Jul., 2012
APA2177
www.anpec.com.tw
13
Headphone Driver Operation
Function Description
The APA2177’s headphone drivers use a charge pump
to invert the positive power supply (V
DD) to negative power
supply (V
SS), see figure1. The headphone drivers oper-
ate at this bipolar power supply (V
DD and VSS) and the out-
puts reference refers to the ground. This feature elimi-
nates the output capacitor that is using in conventional
single-ended headphone drive amplifier. Compare with
the single power supply amplifier, the power supply range
has almost doubled.
Figure 1. Cap-free Operation
Thermal Protection
The thermal protection circuit limits the junction tempera-
ture of the APA2177. When the junction temperature ex-
ceeds T
J = +150
oC, a thermal sensor turns off the driver,
allowing the devices to cool. The thermal sensor allows
the driver to start-up after the junction temperature down
about 125oC. The thermal protection is designed with a
25oC hysteresis to lower the average T
J during continu-
ous thermal overload conditions, increasing lifetime of
the ICs.
Shutdown Function
In order to reduce power consumption while not in use,
the APA2177 contains shutdown controllers to externally
turns off the amplifier bias circuitry. This shutdown fea-
ture turns the amplifier off when logic low is placed on the
SDN pins for the APA2177. The trigger point between a
logic high is 1.0V and logic low level is 0.35V. It is recom-
mended to switch between ground and the supply volt-
age V
DD to provide maximum device performance. By
switching the SDN pins to a low level, the amplifier enters
a low-consumption current circumstance, charge pump
is disabled, and I
DD for the APA2177 is in shutdown mode.
In normal operating, the APA2177’s SDN pins should be
pulled to a high level to keep the IC out of the shutdown
mode. The SDN pins should be tied to a definite voltage
to avoid unwanted circumstance changes.
V
DD
V
DD/2
GND
V
OUT
V
DD
V
SS
GND
V
OUT
Conventional Headphone Driver
Cap-free Headphone Driver


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