Sharp LC-40LE361E Service Manual ▷ View online
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LC-32/40LE361
LC-32/40LE360
LC-32/40LE362
LC-32/40LE363
3. POWER STAGE
Figure 5: Power socket and power options
Power socket is used for taking voltages which are 3.3V, 12V, 5V and 24V (VDD_Audio). These
voltages are produced in power card. Also socket is used for giving dimming, backlight and standby
signals with power card. İt is shown in figure 5.
voltages are produced in power card. Also socket is used for giving dimming, backlight and standby
signals with power card. İt is shown in figure 5.
24V (VDD_Audio) goes directly to the audio side, through power socket other incoming voltages
from power card are converted several voltages.
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LC-32/40LE363
Figure 6: Power steps
FDC642P
a. General Description and Features
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LC-32/40LE361
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LC-32/40LE363
TPS65251
a. General Description
The TPS65251 features three synchronous wide input range high efficiency buck converters. The
converters are designed to simplify its application while giving the designer the option to optimize their
usage according to the target application.
The converters can operate in 5-, 9-, 12- or 15-V systems and have integrated power transistors. The
output voltage can be set externally using a resistor divider to any value between 0.8 V and close to the
input supply. Each converter features enable pin that allows a delayed start-up for sequencing purposes,
soft start pin that allows adjustable soft-start time by choosing the soft-start capacitor, and a current limit
(RLIMx) pin that enables designer to adjust current limit by selecting an external resistor and optimize
the choice of inductor. The current mode control allows a simple RC compensation.
The switching frequency of the converters can either be set with an external resistor connected to
ROSC pin or can be synchronized to an external clock connected to SYNC pin if needed. The switching
regulators are designed to operate from 300 kHz to 2.2 MHz. 180° out of phase operation between Buck 1
and Buck 2, 3 (Buck 2 and 3 run in phase) minimizes the input filter requirements.
TPS65251 features a supervisor circuit that monitors each converter output. The PGOOD pin is
asserted once sequencing is done, all PG signals are reported and a selectable end of reset time lapses.
The polarity of the PGOOD signal is active high.
TPS65251 also features a light load pulse skipping mode (PSM) by allowing the LOW_P pin tied to
V3V. The PSM mode allows for a reduction on the input power supplied to the system when the host
processor is in stand-by (low activity) mode.
b. Features
•
Wide Input Supply Voltage Range (4.5 V - 18 V)
•
0.8 V, 1% Accuracy Reference
•
Continuous Loading: 3 A (Buck 1), 2 A (Buck 2 and 3)
•
Maximum Current: 3.5 A (Buck 1), 2.5 A (Buck 2 and 3)
•
Adjustable Switching Frequency 300 kHz - 2.2 MHz Set By External Resistor
•
Dedicated Enable for Each Buck
•
External Synchronization Pin for Oscillator
•
External Enable/Sequencing and Soft Start Pins
•
Adjustable Current Limit Set By External Resistor
•
Soft Start Pins
•
Current-Mode Control With Simple Compensation Circuit
•
Power Good
•
Optional Low Power Mode Operation for Light Loads
•
QFN Package, 40-Pin 6 mm x 6 mm RHA
APPLICATIONS
•
Set Top Boxes
•
Blu-ray DVD
•
Security Camera
•
Car Audio/Video
•
DTV
•
DVR
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Table 5: Recommended operating conditions
Figure 7: Pin description
NAME
NO.
I/O
DESCRIPTION
RLIME
1
I
Current limit settings for buck 3 Fit a resistor from this pin to ground to set the peak current limit
on the output inductor
SS3
2
I
Soft start pin for Buck 3. Fit a small ceramic capacitor to this pin to set the converter soft start
time.
COMP3
3
O
Compensation for Buck 3. Fit a series RC circuit to this pin to complete the compensation circuit of
this converter.
FB3
4
I
Feedback input to Buck 3. Connect a divider set to 0,8V from the output of the converter to ground.
SYNC
5
I
Synchronous clock input. If there is a sync clock in the system connect to the pin. When not used
connect to GND.
ROSC
6
I
Oscillator set. This resistor sets the frequency of internal autonomous clock. If external
synchronization is used resistor should be fitted and set to
~ 70% of external clock frequency.
FB1
7
I
Feedback pin for Buck 1. Connect a divider set to 0.8V from the output of the converter to ground.
COMP1
8
O
Compensation pin for Buck 1 Fit a series RC circuit to this pin to complete the compensation circuit
of this converter.
SS1
9
I
Soft start pin for buck 1. Fit a small ceramic capacitor to this pin to set the converter soft start time.
RLIM1
10
I
Current limit setting pin for Buck 1. Fit resistor from this pin to ground to set the peak current limit
on the output inductor.
EN1
11
I
Enable pin for Buck 1. A low level signal on this pin disables it. If pin is left open a weak internal
pull-up to V3V will allow for automatic enable for a delayed star-up add a small ceramic capacitor
from this pin to ground.
BST1
12
I
Bootstrap capacitor for Buck 1. Fit a 47-nF ceramic capacitor from this pin to the switching node.
VIN1
13
I
Input supply for Buck 1. Fit a 10-
µF ceramic capacitor close to this pin.
LX1
14,15
O
Switching node for Buck 1.
LX2
16,17
O
Switching node for Buck 2.
VIN2
18
I
Input supply for Buck 2. Fit a 10-
µF ceramic capacitor close to this pin.
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