Teclast X21, Руководство по обслуживанию

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U3
TPS62200/FAN5307* SOT23-5
VI
1
GND
2
EN
3
FB
4
SW
5
R5
120K¡À1%
C10
101
L1
CDRH3D16/HP-100
VCC18
C9
106/X5R
C7
47PF R4
300K¡À1%
C8
106/X5R
P_GND P_GND
VCC18
P_GND
P_VDD
EN
C41
104 U7
PQ1X281M2ZP
VI
1
GND
2
EN
3
BYPASS
4
VOUT
5
C39
106/X5R
C40
106/X5R
D_GND
VCC33
P_GND D_GND
2.8V
Figure 3.2.9.2 2.8V power circuit schematic diagram
Figure 3.2.9.3 1.8V power circuit schematic diagram
2. Working principle: seen from the figure 3.2.9.1, 3.3V power is supplied by IC TPS79301 and
peripheral circuit. TPS79301 is a linear voltage stabilizing module (LDO also called), EN pin is
theenable pin that controls normal working, high level is effective; BYPASS has a resistor inside that can
composes low pass filter together with external 103 capacitor C4 to decrease output noise; the setup of
TPS79301 output voltage is decided by the resistance value of the two externally-connected resistors of
FB pin and the relationship is shown as follows:
Seen from the above , VOUT is about 3.2V.
1.8V power of the working of the player is provided by IC TPS62200 and peripheral circuit.
TPS62200 is high efficiency voltage drop DC-DC converter. EN is enable pin and high level is effective.
The relationship between TPS62200 output voltage and FB pin feedback resistor is shown as follows:
Seen from the above, the output voltage is about 1.75V.
To improve sound quality of Mp3 and effect of FM and microphone, we introduce 2.8V power to
supply power for audio system of PNX0101 and FM and microphone, feature of this channel 2.8V power
is: it is outputted by LDO PQ1X281, power is very pure with low ripple voltage. PQ1X281 may output
fixed voltage 2.8V, EN is the enable end.
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