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PDF EUP2644 Data sheet ( Hoja de datos )
| Número de pieza | EUP2644 | |
| Descripción | TFT LCD DC-DC Converter | |
| Fabricantes | Eutech Microelectronics | |
| Logotipo |  |
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Hay una vista previa y un enlace de descarga de EUP2644 (archivo pdf) en la parte inferior de esta página. Total 14 Páginas | ||
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Preliminary
EUP2644
TFT LCD DC-DC Converter with Integrated
LDO, OP-AMP and GPM Switch
DESCRIPTION
The EUP2644 generates power supply rails for thin-film
transistor (TFT) liquid-crystal display (LCD) panels in
monitors and notebooks operation from 3V to 5.5V input
supply. The device integrates a step-up converter, a high
speed VCOM buffer, a 400mA low dropout (LDO) linear
regulator, and a Gate Pulse Modulator (GPM).
The external compensated step up converter features an
internal power MOSFET and high frequency operation
allowing the use of small inductors and capacitors. The step
up converter uses fixed-frequency, current mode control
architecture which provides fast load-transient response and
easy compensation. A 2.9A peak current limit for the
internal switch protects power supply fault condition.
The GPM provides a modulated voltage to the gate driver
circuitry of a TFT LCD display. It allows shaping of the
gate high voltage to improve image quality. It also can
delay the gate high voltage while power on. Both the
power-on delay time and the falling time of the gate high
voltage are programmable by external resistor and
capacitor.
The high speed VCOM butter features continues output
current (±100mA), 20MHz bandwidth, fast slew rate
70V/µs, and rail-to-rail inputs and outputs.
The LDO regulator provides up to 400mA current to the
external digital circuitry.
FEATURES
z 3V to 5.5V Input Supply Range
z Current Mode Step Up Converter
- Selectable Frequency (650kHz/1.2MHz)
- Built-In 20V, 2.9A, 0.15Ω N-MOSFET
- High Efficiency Up to 90%
- Programmable Soft-Start
- Fast Transient Response to Pulsed Load
z Gate Pulse Modulator Circuit
- Adjustable Falling Time and Delay
- Flicker Compensation
z High Speed High Output Current VCOM Buffer
- 20MHz BW
- 70V/µS Slew Rate
- 400mA Peak Output Current
z 400mA LDO Regulator for VLOGIC
- Adjustable Output Voltage2.5V, 2.85V, 3.3V
z Input Under Voltage Lockout and Thermal Protection
z 24 pin 4mm × 4mm TQFN Package
z RoHS Compliant and 100% Lead (Pb)-Free
APPLICATIONS
z LCD Monitors
z Notebook Display
DS2644 Ver0.1 June 2008
1
1 page  
Tel: 0755-8398 3377 / 135 9011 2223
http://www.gofotech.com
Preliminary
EUP2644
Absolute Maximum Ratings
LX to GND, AGND and PGND ------------------------------------------------------ -0.5V to 25V
VDD, OUT, NEG and POS to GND, AGND and PGND---------------------------- -0.5V to 25V
VGL, VGH and VGHM to GND, AGND and PGND-------------------------------- -0.5V to 32V
Differential Voltage Between POS and NEG ----------------------------------------- ±6V
Voltage Between GND, AGND and PGND ------------------------------------------- ±0.5V
All Other Pins to GND, AGND and PGND ------------------------------------------- -0.5V to 6.5V
Input ,Output, or I/O Voltage ---------------------------------------------- GND-0.3V to VIN+0.3V
Junction Temperature ------------------------------------------------------------------ 150°C
Lead Temp (Soldering, 10sec) --- --------------------------------------------------- 260°C
Operating Conditions
Operating Temperature --------------------------------------------------------- -40°C to 85°C
Input Voltage Range, VIN --------------------------------------------------------------- 3V to 5.5V
Step up Output Voltage Range----------------------------------------------------------- 8V to 20V
Electrical Characteristics
Specifications in standard type face are for TA=25 and those with boldface type apply over the full Operating
Temperature Range (TA=-40 to +85 ), LVIN=VIN=5V,VGL=VDD=14V,VGH=25V,AVDD=10V,
GND=AGND=PGND=0, unless otherwise noted.
Symbol
Parameter
Conditions
EUP2644
Unit
Min. Typ. Max.
GENERAL
VS
IS_DIS
IS
LVIN,VIN Input Voltage Range
Sum Of LVIN, VIN Supply
Currents when Disabled
Sum Of LVIN ,VIIN Supply
Currents
See separate LDO specifications
EN=0V
EN=5V,LX not switching,
LDO not loaded
3
5 5.5 V
0.2 2 uA
0.65 mA
UVLO
Rising
Undervoltage Lockout Threshold
Falling
2.25 2.45 2.65
2.15 2.35 2.55
V
V
OTR
Temperature Rising
Thermal Shutdown Temperature
OTF Temperature Falling
160
120
LOGIC INPUT CHARACTERISTICS-EN,CTRL,FSEL,VDPM
VIL Low Voltage Threshold
VIH High Voltage Threshold
RIL Pull-Down Resistor
STEP-UP SWITCHING REGULATOR
Enabled, Input at VIN
0.8 V
2.2 V
150 250 400 V
AVDD Output Voltage Range
A VDD/VAVDD Load Regulation
A VDD/V IN Line Regulation
50mA<ILOAD<250mA
ILOAD=150mA,
3.0V<LVIN<5.5V
ACCAVDD
Overall Accuracy (Line, Load, 10mA<ILOAD<300mA, 3.0V<
Temperature)
LVIN <5.5V,-40<T A<85
VFB Feedback Voltage(VFB)
ILOAD=100mA, TA=25
ILOAD=100mA, TA=-40 to
+85
IFB FB Input Bias Current
-3
1.248
1.23
0.2
0.05
1.260
1.26
100
20
0.12
3
1.273
1.29
200
V
%
%/V
%
V
V
nA
DS2644 Ver0.1 June 2008
5
5 Page 
Tel: 0755-8398 3377 / 135 9011 2223
http://www.gofotech.com
Preliminary
EUP2644
Application Information
The EUP2644 provides a complete power solution for TFT
LCD applications. The system consists of one boost
converter to generate AVDD voltage for column drivers, one
logic LDO regulator to provide voltage to logic circuit in
the LCD panel, 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.
into the feedback pin. The boost converter output voltage
is determined by the following equation:
VSTEP −UP
=
R1 + R
R2
2
×
VFB
(EQ. 2)
The current through the MOSFET is limited to 2.9 APEAK.
This restricts the maximum output current (average) based
on the following equation:
Enable Control
When EN pin is pulling down, the EUP2644 is shut down
reducing the supply current to <10µA. When the voltage at
EN pin reaches 2.2V, the EUP2644 is on.
Step Up Converter
Frequency Selection
The EUP2644 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 FSEL pin to ground sets the PWM switching
frequency to 650kHz, or connecting FSEL pin to VIN for
1.2MHz.
Soft-Start
The soft-start is provided by an internal 3µA current
source to charge the external soft start capacitor. The
EUP2644 ramps up current limit from 0A up to full value,
as the voltage at SS pin ramps from 0 to 0.6V. Hence the
soft-start time is 2ms when the soft-start capacitor is 10nF,
9.42ms for 47nF and 20ms for 100nF.
Operation
The step up 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 flows continuously in the inductor during the entire
switching cycle in steady state operation. The voltage
conversion ratio in continuous current mode is given by:
VSTEP −UP = 1
VIN 1 − D
(EQ.1)
Where D is the duty cycle of the switching MOSFET.
Figure 2 shows the block diagram of the boost regulator. It
uses a error amplifier architecture consisting of gm stages
for voltage feedback. A comparator looks at the peak
inductor current cycle by cycle and terminates the PWM
cycle if the current limit is reached.
An external resistor divider is required to divide the output
voltage down to the nominal reference voltage. Current
drawn by the resistor network should be limited to
maintain the overall converter efficiency. The maximum
value of the resistor network is limited by the feedback
input bias current and the potential for noise being coupled
IOMAX
=
ILMT
−
∆IL
2
×
VIN
VO
(EQ.3)
Where ∆IL is peak to peak inductor ripple current, and is
set by:
∆IL
=
VIN
L
×
D
fS
(EQ.4)
where fS is the switching frequency (650kHz or 1.2MHz).
The Table 1 gives typical values (margins are considered
10%, 3%, 20%, 10% and 15% on VIN, VO, L, fS and
IOMAX).
Table 1. Maximum Output Current Calculation
VIN(V)
3
3
3
5
5
5
3
3
3
5
5
5
VO(V)
9
12
15
9
12
15
9
12
15
9
12
15
L(uH)
10
10
10
10
10
10
10
10
10
10
10
10
FS(MHz)
0.65
0.65
0.65
0.65
0.65
0.65
1.2
1.2
1.2
1.2
1.2
1.2
IOMAX(mA)
553
400
319
1110
838
675
486
342
226
1066
779
610
Capacitor
An input capacitor is used to suppress the voltage ripple
injected into the boost converter. The ceramic capacitor
with capacitance larger than 10µF is recommended. The
voltage rating of input capacitor should be larger than the
maximum input voltage.
Inductor
The boost inductor is a critical part which influences the
output voltage ripple, transient response, and efficiency.
Values of 3.3µH to 10µH are used to match the internal
slope compensation. The inductor must be able to handle
the following average and peak current:
I LAVG
= IO
1− D
ILPK
= ILAVG
+
∆IL
2
(EQ.5)
DS2644 Ver0.1 June 2008
11
11 Page | ||
| Páginas | Total 14 Páginas | |
| PDF Descargar | [ Datasheet EUP2644.PDF ] | |
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