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RT8901 Datasheet(PDF) 8 Page - Richtek Technology Corporation

Part No. RT8901
Description  35V Gate Pulse Modulator for LCD Panels
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Maker  RICHTEK [Richtek Technology Corporation]
Homepage  http://www.richtek.com
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RT8901 Datasheet(HTML) 8 Page - Richtek Technology Corporation

 
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RT8901
8
DS8901-03 October 2013
www.richtek.com
©
Copyright 2013 Richtek Technology Corporation. All rights reserved.
is a registered trademark of Richtek Technology Corporation.
Applications Information
The GPM consists of two high-voltage MOSFETs which
include P1 between VGH and VGHM and P2 between
VGHM and RE. The switch-control block is enabled when
VDPM exceeds VREF and then P1 and P2 are controlled
by VFLK and CD. There are three different modes of
operation (see the Typical Application Circuit and Timing
Diagram).
Activate the Mode A by connecting CD to 5V. When VFLK
is logic high, P1 turns on and P2 turns off, VGHM is
connected to VGH. When VFLK is logic low, P1 turns off
and P2 turns on, VGHM is connected to RE, and VGHM
is discharged through the resistor between RE and GND.
P2 turns off and stops discharging VGHM when VGHM
reaches 10 times the voltage of the VD pin.
When CD is connected with a capacitor, the switch control
block works in the Mode B. The rising edge of the VFLK
will turns on P1 and turns off P2, connecting VGHM to
VGH. An internal N-MOSFET Q3 between CDO and GND
is also turned on to discharge the external capacitor
between CD and GND. The falling edge of VFLK turns off
Q3, and an internal 50
μA current source starts charging
the CD capacitor. Once VCD exceeds VREF, the switch
control circuit turns off P1 and turns on P2, connecting
VGHM to RE. VGHM is discharged through the resistor
connected between RE and GND. P2 turns off and stops
discharging VGHM when VGHM reaches 10 times the
voltage of the VD pin.
Activate the Mode C by connecting CD to 3.3V. P1 will be
turned on, P2 will be turned off and Q3 will be turned on
respectively when VFLK is high. When VFLK is low, Q3
will be turned off and CDO will be pull to the same voltage
level as CD through a 1k
Ω resistor. P1 and P2 will be turn
off and on respectively when comparator detects CDO
voltage is greater than 2.5V. VGHM is discharged through
the resistor connected between RE and GND. P2 turns
off and stops discharging VGHM when VGHM reaches 10
times the voltage of VD pin.
The timing of enabling the switch control block can be
adjusted with an external capacitor connected between
VDPM and GND. An internal 5
μA current source starts
charging the VDPM capacitor if all internal power is ready.
The voltage on the VDPM linearly rises because of the
constant-charging current. When VDPM goes above VREF,
the switch control block is enabled.
Output Current Maximum Rating (rms value)
TheGPM output current is RMS value and the RMS current
boundary depends on ambient temperature with fixed P1
and P2 on-resistance. In figure 6, the test condition is
VGH = 30V with R1 = 0
Ω and R1 = 43Ω. The boundary is
located at 125
°C junction temperature for safe operation
in SOP-8 package.
Figure 6. Output Current Maximum Rating vs. Ambient
Temperature with R1 = 0
Ω and R1 = 43Ω
Thermal Considerations
For continuous operation, do not exceed absolute
maximum operation junction temperature. The maximum
power dissipation depends on the thermal resistance of
IC package, PCB layout, the rate of surroundings airflow
and temperature difference between junction to ambient.
The maximum power dissipation can be calculated by
following formula :
PD(MAX) = ( TJ(MAX) - TA ) /
θJA
Where TJ(MAX) is the maximum operation junction
temperature, TA is the ambient temperature and the
θJAis
the junction to ambient thermal resistance.
RMS Current vs. Ambient Temperature
0
20
40
60
80
100
120
140
160
180
0
20406080
100
120
140
Ambient Temperature (°C)
R1 = 0
Ω
R1 = 43
Ω
RMS Curent vs. Ambient Temperature


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