DT8211 查看數據表（PDF） - Unspecified
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DT8211 Datasheet PDF : 10 Pages
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DMB Technology
DT8211
LCD Back Light Inverter Drive IC
9. Block Diagram
VFB 11
VCMP ICMP
13
12
Fast Response
OTA
EN
VCC
2
18
Startup
and
Voltage Reference
6.0V
Internal Bias
1 VREF
IFB 10
ADIM 3
Positive & Negative
Control Block
2.0V
0.8V
BDIM 4
Positive & Negative
Control Block
2V Ref.
OTA
LTA
2V Ref.
Burst
On/Off
COMP
EN
Open Lamp
Detection
and
Frequency
Shift Block
5
RTS
Pulse Distributor
GD
COMP
and
Dead Time
Generator
GD
3.0V
1.2V
High Precision
Dual Oscillator
Block
(Main/Burst)
2.0V
VREF
0.5uA
R
FF Q
S
COMP
3V Ref.
7
8
6
9
CT
CTB
RT
PROT
17 HOUT
16 LOUT
15 GND
14 GND
10. Functional Description
Internal Regulator
To supply a stable power to internal and external circuit, a high precise regulator is
included. It makes 6.0V over the full range of input supply voltage. This also supplies
a stable voltage to internal analog critical circuit, to make stable operation. VREF is
an output of internal regulator, and can supply over 30mA to external circuit.
Chip Enable
When EN pin is over VEN,ON, the internal regulator is turned on. Therefore internal
and external circuits begin to operate. Since it has over 100mV hysteresis,
unpredictable operation is protected.
Main Frequency Oscillator
To generate clear PWM pulse, DT8211 includes a precise triangular waveform
generator circuit. The voltage of RT pin is fixed at 2.0V and the current of RT pin is
flow through the resistor which is connected between RT pin and GND. This current
makes charging and discharging current of a capacitor which is connected to CT pin
and GND. Triangular wave is generated at CT pin by charging and discharging
(repeated operation) to this capacitor. This triangular wave is one of reference signal
to generate PWM. The frequency of triangular wave can be calculated approximately
as below and is 2 times of lamp frequency.
fMain [Hz]
=
0.232
RT • CT
Rev1.1– 11 July 2008
© 2007 DMB Tech. All Rights Reserved
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