Figure 3.2.7.1 Reset circuit diagram
2. Working principle: after power on, voltage of DV33 increases to 3.3V, main chip power supply is
normal. Now, voltage of TC81 to DV33 cannot change suddenly to make base electrode of Q80 has
current flow in, Q80 is saturation on, URST is low level. DV33 charges TC81 in two paths through emitter
junction of R97 and Q80 make negative pole voltage of TC81 decrease slowly. When this voltage
decreases below 0.7V, Q80 cuts off, URST changes into high level, the process for URST from low to
high is called effective reset signal of low level by us. After power off, voltage of DV33 decreases, TC81
decreases together with DV33 voltage, VD3 performs suge discharge and clamping to TC81.
R87
10K
R117
1K
URST#
DV33
C98
104
R86
10K
R116
1K
TC81
16uF/10V
Q80
2SC1815-YS
VD3
1N4148
This machine type has no separate mute circuit. Mute signal SCMUTE is emitted by PCA9555,
which is a serial to parallel converter adopting I2C bus control and converting I2C signal into parallel
signal to output. When machine is mute, pin 17 of PCA9555 release a low level signal and input to pin 15
of DSP chip TAS5508. Cut off audio signal output to realize mute function. Circuit diagram is shown in
figure 3.2.8.1
3.2.8 Mute circuit
N85 PCA9555
N509 TAS5508
SCMUTE
14
17
Figure 3.2.8.1 MT1389 SCMUTE signal block diagram
- 25 -
Summary of Contents for DK2810HD
Page 1: ...DK2810HD service manual DK2871HD DK2870HD...
Page 89: ...Chapter Cinque PCB board Circuit diagram Section One PCB board 5 1 1 Surface layer of Panel 85...
Page 90: ...5 1 2 Bottom layer of Panel 86...
Page 91: ...5 1 3 Surface layer of DECODE SERVO Board 87...
Page 92: ...5 1 4 Power Board 98...
