ISL97645 Просмотр технического описания (PDF) - Renesas Electronics
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ISL97645 Datasheet PDF : 14 Pages
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ISL97645
Typical Application Diagram
VIN
C1
22µF
C3
2.2nF
COMP
C4
10nF SS
AVDD
VCOM
+4.0V
R6
130k
R7
80k
C6
0.1µF
S1 ENABLE
S2 FREQ-
S3 VDPM
VFLK
C5
470P CE
RE
R3
2K POS
C11
1µF
NEG-
OUT
VIN
AGND
GND
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
continuous mode (CCM). In continuous current mode, current
FN9263 Rev 1.00
December 14, 2007
Page 8 of 14
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