ISL97645(2006) Просмотр технического описания (PDF) - Intersil
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ISL97645 Datasheet PDF : 14 Pages
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Typical Application Diagram
VIN
C1
22µF
C3
2.2nF
COMP
C4
10nF SS
S1 ENABLE
S2 FREQ-
S3 VDPM
VFLK
C5
470P CE
AVDD
VCOM
+4.0V
R6
130k
R7
80k
C6
0.1µF
RE
R3
2K POS
C11
1µF
NEG-
OUT
VIN
AGND
GND
ISL97645
L1
10µH
BOOST
D1
LX
C2
47µF
FB
PGND
AVDD
R1
10K
R2
1.3K
GPM
CIRCUIT
VGH
VDD_1
VON
VGH_M
VDD2
0.47µF
TO ROW DRIVER
NC
NC
FIGURE 12. TYPICAL APPLICATION DIAGRAM
Applications Information
The ISL97645 provides a complete power solution for TFT
LCD applications. The system consists of one boost
converter to generate AVDD voltage for column drivers, one
integrated VCOM buffer which can provide up to 400mA peak
current. This part also integrates Gate Pulse Modulator
circuit that can help to optimize the picture quality.
Enable Control
When enable pin is pulling down, the ISL97645 is shut down
reducing the supply current to <10µA. When the voltage at
enable pin reaches 2.2V, the ISL97645 is on.
Boost Converter
Frequency Selection
The ISL97645 switching frequency can be user selected to
operate at either constant 650kHz or 1.2MHz. Lower
switching frequency can save power dissipation, while
higher switching frequency can allow smaller external
components like inductor and output capacitors, etc.
Connecting FREQ pin to ground sets the PWM switching
frequency to 650MHz, or connecting FREQ pin to VIN for
1.2MHz.
Soft-Start
The soft-start is provided by an internal 2.5µA current source
to charge the external soft start capacitor. The ISL97645
ramps up current limit from 0A up to full value, as the voltage
at SS pin ramps from 0 to 1.2V. Hence the soft-start time is
4.8ms when the soft-start capacitor is 10nF, 22.6ms for 47nF
and 48ms for 100nF.
Operation
The boost converter is a current mode PWM converter
operating at either a 650kHz or 1.2MHz. It can operate in
both discontinuous conduction mode (DCM) at light load and
8
FN9263.0
April 11, 2006
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