LG 42LB7DF (CHASSIS:LJ81A) Service Manual ▷ View online
- 49 -
Power-on
Reset
Not Gate
BCM7412
Active Low
Active High
BCM3553
Active Low
Flash
Tuner
PLD
Reset Design
54M
Crystal
BCM3553
33MHz
BCM7412
Main Clock
27MHz Clock is Recovered From The STC Values
BCM3553
BCM7412
VCXO 27M
Clock Design
BCM3553
3.3V
CH 0
NIM TUNER
(0xC2, 0x30)
5V
Audio
Switch
(0x9A)
CH 1
3.3V
HDCP Key
EEPROM
(0xA8)
CH 2
3.3V
Micom
(0x50)
CH 3
NVRAM
(0xA6)
Audio
AMP
(0x54)
I2C Design
BLOCK DIAGRAM
- 50 -
BCM3553
- A Controlled power-up sequence is necessary to establish the two core voltages before the pad voltage is
applied
BCM7412
- Recommends the following power-up sequence: 1.2V -> 2.5V -> 3.3V
- Recommends no more than 5ms between different supplies
All Voltages should regulate at their nominal output voltages no later than 10ms
So, Power-up is Controlled by
Micom
- These 3 voltages should ramp up within 20ms total in any order, no sequence required, supplying
- 1.2V/2.6V/3.3V simultaneously is meet our requirement too.
D3.3V, D1.2V.jpg
Power-Up Sequence
BLOCK DIAGRAM
- 51 -
Power-Up Sequence
2)
Result
-
Initially 1.2V, 2.6V, 3.3V ramp up in 10ms.(Spec. : within 20ms)e
-
Actually Reset time is approximately 100ms(considering the variation of R, C)
after power on.(Spec. : after 75ms)
1) Power Sequence measurement waveform
D1.2_BCM
D2.6_BCM
D3.3_BCM
BCM_Reset
BLOCK DIAGRAM
- 52 -
Reserved
23
Board Revision 2
Input
REV_SEL2
62
RGB Auto Detect
Input
RGB_SW
56
S-Video 2 Auto Detect
Input
S-VIDEO2_SW
55
Reserved
41
Reserved
40
Reserved
39
Reserved
38
RF Switch Control
Output
RF_SWITCH_CTRL
31
HDMI Source 1 Select
Output
HDMI_SEL_1
30
HDMI Source 0 Select
Output
HDMI_SEL_0
29
Composite 1 Auto Detect
Input
COMPOSITE1_SW
26
Composite 2 Auto Detect
Input
COMPOSITE2_SW
24
Board Revision 1
Input
REV_SEL1
17
Board Revision 0
Input
REV_SEL0
16
Component 2 Auto Detect
Input
COMP2_SW
15
Component 1 Auto Detect
Input
COMP1_SW
14
HDMI 2 Hot Plug Detect
Output
HDMI_HPD_2
11
HDMI 1 Hot Plug Detect
Output
HDMI_HPD_1
10
HDMI 0 Hot Plug Detect
Output
HDMI_HPD_0
9
HDMI 2 Power Detect
Input
HDMI_POWER_2
8
HDMI 1 Power Detect
Input
HDMI_POWER_1
7
HDMI 0 Power Detect
Input
HDMI_POWER_0
6
S-Video 1 Auto Detect
Input
S-VIDEO1_SW
5
Description
Direction
Signal Name
GPIO
GPIO Structure
BLOCK DIAGRAM
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