E-CMOS EC9219 Tft- lcd dc-dc converters with operational amplifier Datasheet

TFT- LCD DC-DC Converters with Operational Amplifiers
EC9219
General Description
The EC9219 include a high-performance step-up regulator, and high-current operational amplifiers for active-matrix
thin-film transistor (TFT) liquid-crystal displays (LCDs).
The step-up DC-DC converter provides the regulated supply voltage for the panel source driver ICs. The converter is
a high-frequency (1.2MHz or 640KHZ) current-mode regulator with an integrated 18V n-channel MOSFET that
allows the use of ultra-small inductors and ceramic capacitors. It provides fast transient response to pulsed loads
while achieving efficiencies over 85%.
The EC9219 includes one operational amplifier. These amplifiers are designed to drive the LCD backplane (VCOM)
and/or the gamma-correction divider string. The devices feature high output current (±150mA), fast slew rate
(17V/μs), wide bandwidth (12MHz), and rail-to-rail inputs and outputs
The EC9219 are available in 14- pin thin TSOP packages with a maximum thickness of 1mm for ultra-thin LCD
panels.
Features
Applications
2.6V to 5.5V Input Supply Range
z
z
1.2MHz or 640KHZ Current-Mode Step-Up Regulator
z
z
Fast Transient Response to Pulsed Load
z
High-Accuracy Output Voltage ( 2% )
z
Built-In 18V, 1.6A, 0.16Ω N-Channel MOSFET
z
High Efficiency (90%)
z
High-Performance Operational Amplifiers
z
17V/μs Slew Rate
z
12MHz, -3dB Bandwidth
z
Rail-to-Rail Inputs/Outputs
z
Thermal-Overload Protection
z
z
Notebook Computer Displays ,
LCD Monitor Panels ,
Automotive Displays
Ordering information
PART NO
MARKING
PACKAGE
EC9219I-G
EC9219-G
TSSOP14 Green Package
EC9219G-G
EC9219G
TQFN16 Green Package
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TFT- LCD DC-DC Converters with Operational Amplifiers
EC9219
NAME
Function
OUT Operational-Amplifier Output
IN + Operational-Amplifier Non-inverting Input
SGND Analog ground.
Comp Compensation pin. Output of the internal error amplifier. Capacitor and resistor from COMP pin to ground.
Voltage feedback pin. Internal reference is 1.228V nominal. Connect a resistor divider from VOUT. VOUT =1.228V (1 + R3 / R8). See Typical
FB
Application Circuit.
/SD Shutdown control pin. Pull SHDN low to turn off the device, and Soft-start Internal reference voltage control pin, Connect RC Delay circuit.
PGND Power ground.
LX
Switch Pin. Connect the inductor/catch diode to LX and minimize the trace area for lowest EMI.
Vin Analog power supply input pin.
Freq Frequency Select Input. When FREQ is low, the oscillator frequency is set to 640kHz. When FREQ is high the frequency is 1.2MHz.
SS
Soft-start control pin. Connect a capacitor to control the converter start-up.
Operational-Amplifier Power Input. Positive supply rail for the operational amplifiers.
SUP
Typically connected to DC-DC converter Output. Bypass SUP to SGND with a 0.1µF capacitor.
NC
IN - Operational-Amplifier Inverting Input
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TFT- LCD DC-DC Converters with Operational Amplifiers
EC9219
Absolute Maximum rating ( TA = 25℃ )
VIN to SGND......................................................-0.3V to +6V
Comp, FB, SD , Freq to SGND ........................-0.3V to +6V
PGND to SGND .......................................................... ±0.3V
LX to PGND ....................................................-0.3V to +18V
SUP,IN+,IN- to SGND .....................................-0.3V to +18V
Out Maximum Continuous Output Current ...... ±150mA
RMS LX Pin Current......................................................1.6A
Operating Ambient Temperature ......... -40℃ to +85℃
Operating Junction Temperature........................ +125℃
Storage temperature ......................... -65℃ to +150℃
Lead Temperature ............................................+260℃
Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress
ratings only, and functional operation of the device at these or any other conditions beyond those indicated in the operational sections
of the specifications is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability.
Electrical Specifications
VIN = 3V, VSUP = 10V ,FSEL = GND, TA =25℃ unless otherwise specified
PARAMETER
VIN Supply Range
VIN Under voltage-Lockout
Threshold
SYMBOL
VIN
VUVLO
Quiescent Current
IIN
Shutdown Supply Current
IIN
Input Low Level
Input High Level
VIL
CONDITIONS
MIN
2.6
TYP
MAX
5.5
UNIT
V
2.25
2.38
2.52
V
SD = VIN,VFB=1.3, not switching
0.4
1
mA
SD = VIN,VFB=COMP, switching
4
0.1
5
1
mA
uA
0.3VIN
V
VIN rising ,typical hysteresis = 40mV
SD = SGND include OP.
SD , Freq ;VIN=3V to 5.5V
VIH
SD , Freq ;VIN=3V to 5.5V
Hysteresis
0.7VIN
SD , Freq ;VIN=3V to 5.5V
Freq =VIN
SD =VIN
Temperature rising
Freq Input Current
SD Input Current
Thermal Shutdown
Hysteresis
V
0.1VIN
V
1
1
nA
nA
130
30
°C
°C
Main STEP-UP REGULATOR
Output Voltage Range
Frequency
Vmain
fosc
Maximum Duty Cycle
D
FB Regulation Voltage
FB Line Regulation
FB Input Bias Current
Voltage Gain
Swicth On-Resistance
LX Leakage Current
LX Current Limit
Current-Sense
Tran conductance
VFB
VIN
500
1000
85
85
1.222
Freq=GND
Freq= VIN,
Freq=GND
Freq= VIN,
load=50mA
VIN=2.6V to 5.5V
VFB=1.4
Av
Rds(on)
ILX
FB to Comp
VLX=18V
Rcs
640
1200
90
90
1.24
18
750
1500
95
95
1.258
0.5
1
1000
160
1.8
2
250
0.047
V
kHz
kHz
%
%
V
%
nA
V/V
mΩ
uA
A
V/A
OPEATIONAL AMPLIFERS
SUP Supply Range
SUP Supply Current
Input Offset Voltage
Input Bias Current
Input Common-Mode Range
Common-Mode Rejection Ratio
Open-Loop Gain
Output Voltage Swing ,High
Output Voltage Swing ,Low
Power-Supply Rejection Ratio
Vsup
Isup
VOS
IBIAS
VCM
CMRR
AV
VOH
VOL
PSRR
4.5
Buffer configuration ,no load
OUT=4V,Vsup=8V
OUT= Vsup/2
OUT= Vsup/2
0
50
75
Vsup-150
IOUT=5mA
IOUT=-5mA
60
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18
V
2.8
4
mA
2
20
50
Vsup
mV
nA
V
dB
dB
mV
mV
dB
70
100
Vsup-80
70
70
150
2009/09/29
TFT- LCD DC-DC Converters with Operational Amplifiers
EC9219
PARAMETER
Slew Rate
SYMBOL
SR
-3dB Bandwidth
Gain-Bandwidth Product
GBP
CONDITIONS
Vin=4V,VIN+=6V,RL=2kΩ,CL=100 pF
,buffer configuration
RL=2kΩ,CL=100 pF
,buffer configuration
RL=2kΩ,CL=100pF
buffer configuration
MIN
TYP
MAX
10
17
V/µs
12
MHz
8
MHz
Block Diagram
EC9219
Figure 1
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UNIT
TFT- LCD DC-DC Converters with Operational Amplifiers
EC9219
Typical Application Circuit
Q1 2N3906
D1
3
3
1
1
R1
2
0.1uF
J1
1
VGFF= -6V/20mA
2
C1
1K
C2
C3
0.1uF
BAT54S
0.22uF
D2
6.8V
D3
Q2 2N3904
2
C4
3
J2
1
1
1
R2
2
3
0.1uF
VGON= +18V/20mA
270
BAT54S
C5
C6
0.1uF
0.22uF
D4
18.8V
VIN
VDD=9.6V
±0.2VVDD
2
FM220
R3
87.6K_1%
U1
LX
VIN
C14
0.1UF
R7
NC
R10
0
J5
1
CON1
J7
C15
47nF
8
9
FSLC
10
SS
11
VDD
12
13
14
LX
GND
IN
/SHDN
FREQ
SS
OPVCC
OPVSUP
INEC9219
J6
1
FB
COMP
OPGND
IN+
OPOUT
R4
NC
7
6
/SHDN
5
FB
4
COMP
R6 0
R5
10.5K_1%
1
3
C17
0.1uF
C10
C11
C12
C13
1 J4
CON1
VIN
3
2
C9
10uF/16V/1206
10UH
D5
10uF/16V/1206
1
10uF/16V/1206
C8
LX
10uF/16V/1206
C7
10uF/10V/1206
10uF/10V/1206
CON1
L1
VIN
1
R13
12K_1%
R11
1
R12
13K_1%
2
J3
VDD
R9
20K
C16
R8
13K_1%
10pF
C18
6.8nF
VCOM
CON1
1
CON1
Figure 2
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TFT- LCD DC-DC Converters with Operational Amplifiers
EC9219
Typical operating Characteristics
Typical Application Circuit, Vin=3.3V, VMAIN=9.6 ,VGON=18V , VGOFF=-6V , OUT=6V , Freq=Vin TA=25℃
unless otherwise noted.)
No-Load Supply Current vs. Input Voltage Freq=640kHz
No-Load Supply Current vs. Input Voltage
Freq=1.2MHz
0.8
0.8
0.7
0.6
No-Load Supply Current(mA)
No-Load Supply Current(mA)
0.7
0.5
0.4
0.3
0.2
0.1
0.6
0.5
0.4
0.3
0.2
0.1
0
0
2.5
3
3.5
4
4.5
5
5.5
2.5
3
3.5
Input Voltage(V)
4
4.5
5
5.5
Input Voltage
Output Voltage vs. Output Curren
Efficiency vs. Output Current
10.1
95.00%
90.00%
10.05
85.00%
Efficiency (%)
Output Voltage(V)
10
9.95
80.00%
75.00%
3.3V
70.00%
5V
65.00%
9.9
60.00%
55.00%
9.85
50.00%
1
9.8
0
50
100
150
200
250
300
Output Current(mA)
Vout=10V,Vin=3.3V,L=10uH, Freq=640KHz
10
100
1000
Output Current (mA)
Vout=9.6V,L=10uH,Freq=640kHz
FB Voltage vs. Temperature
1.257
FB Voltage(V)
1.252
1.247
1.242
1.237
1.232
1.227
1.222
-40
-20
0
20
40
60
80
100
120
140
Temperature(℃)
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TFT- LCD DC-DC Converters with Operational Amplifiers
EC9219
Start-up Waveform with Soft-start
Start-up Waveform with Soft-start
CH1: Vin
CH1:Vin
CH2:Output Voltage
CH2:Output Voltage
CH3:Inductor Current
CH3:Inductor Current
Vin=3.3V,Iout=10mA,Freq=640KHz,
Vin=3.3V,Iout=200mA,Freq=640KHz,
Vout=10.6V,Cout=30uF
Start-up Waveform with Soft-start
Vout=10.6V,Cout=30uF
Start-up Waveform with Soft-start
CH4: SHDN
CH1:SHDN
CH2:Output Voltage
CH2:Output Voltage
CH3:Inductor Current
CH3:Inductor Current
Vin=3.3V,Iout=10mA,Freq=640KHz,
Vin=3.3V,Iout=200mA,Freq=640KHz,
Vout=9.6V,Cout=30uF
Vout=9.6V,Cout=30uF
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TFT- LCD DC-DC Converters with Operational Amplifiers
EC9219
Load-Transient Response
SWITCHING WAVEFORM
CH2: Output Voltage,AC-Coupled
CH1:Output Voltage,AC-Coupled
CH3:Load Current
Ch3:Inductor Current
Vin=3.3V,Vout=10V,Freq=640KHz
Ch2:LX Switching Waveform
Figure 7. Start-up Waveform with Soft-start
Vin=3.3V,Vout=10V,Iout=200mA,Freq=640KHz,L=10uH
Operational-Amplifier RAIL-TO-RAIL INPUT/OUTPU
Operational-Amplifier Large-Signal Step Response
CH1: Input signal
CH1: Input signal
CH2:Output signal
CH2:Output signal
VSUP:12V,RL:2K,CL:100P
VSUP:12V,RL:2K,CL:100P
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TFT- LCD DC-DC Converters with Operational Amplifiers
EC9219
Typical Operating Circuit
The EC9219 Typical Operating Circuit (Figure 2) is a complete power-supply system for TFT LCDs. The
circuit generates a +9.6V source-driver supply and +18V and -6V gate-driver supplies. The input voltage
range for the IC is from +2.6V to +5.5V. The listed load currents in Figure 1 are available from a +4.5V to
+5.5V supply. Typical Operating Circuit recommended components,.
Applications Information
The EC9219 is a high frequency, high efficiency boost regulator operated at constant frequency PWM
mode. The boost converter stores energy from an input voltage source and deliver it to a higher output
voltage. The input voltage range is 2.6V to 5.5V and output voltage range is 5V to 18V The switching
frequency is selectable between 640KHz and 1.2MHz allowing smaller inductors and faster transient
response. An external compensation pin gives the user greater flexibility in setting output transient
response and tighter load regulation. The converter soft-start characteristic can also be controlled by
external C08 capacitor. The SHDN pin allows the user to completely shut-down the device.
Main Step-Up Regulator
The main step-up regulator employs a current-mode, fixed-frequency PWM architecture to maximize loop
bandwidth and provide fast transient response to pulsed loads typical of TFT-LCD panel source drivers.
The 1.2MHz switching frequency allows the use of low profile inductors and ceramic capacitors to
minimize the thickness of LCD panel designs. The integrated high-efficiency MOSFET and soft-start
function controls inrush currents. The output voltage can be set from VIN to 13V with an external resistive
voltage-divider. The regulator controls the output voltage and the power delivered to the output by
modulating the duty cycle (D) of the internal power MOSFET in each switching cycle. The duty cycle of the
MOSFET is approximated by:
D=
VMAIN − VIN
VMAIN
Figure 1 shows the Functional Diagram of the step-up regulator. An error amplifier compares the signal at
FB to 1.228V and changes the COMP output. The voltage at COMP sets the peak inductor current. As the
load varies, the error amplifier sources or sinks current to the COMP output accordingly to produce the
inductor peak current necessary to service the load. To maintain stability at high duty cycles, a
slope-compensation signal is summed with the current-sense signal. On the rising edge of the internal
clock, the controller sets a flip-flop, turning on the n-channel MOSFET and applying the input voltage
across the inductor. The current through the inductor ramps up linearly, storing energy in its magnetic field.
Once the sum of the current-feedback signal and the lope compensation exceeds the COMP voltage, the
controller resets the flip-flop and turns off the MOSFET. Since the inductor current is continuous, a
transverse potential develops across the inductor that turns on the diode (D1). The voltage across the
inductor then becomes the difference between the output voltage and the input voltage. This discharge
condition forces the current through the inductor to ramp back down, transferring the energy stored in the
magnetic field to the output capacitor and the load. The MOSFET remains off for the rest of the clock cycle.
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TFT- LCD DC-DC Converters with Operational Amplifiers
EC9219
Operational Amplifiers
The EC9219 has one operational amplifier. The operational amplifiers are typically used to drive the LCD
backplane (VCOM) or the gamma-correction divider string. They feature 150mA output current, 17V/µs
slew rate, and 12MHz bandwidth. The rail-to-rail input and output capability maximizes system flexibility.
Frequency Selection
The EC9219’s frequency can be user selected to operate at either 640kHz or 1.2MHz. Tie FREQ to GND for
640kHz operation. For a 1.2MHz switching frequency, tie FREQ to VIN.
Under voltage Lockout (UVLO)
The under voltage-lockout (UVLO) circuit compares the input voltage at VIN with the UVLO threshold to
ensure the input voltage is high enough for reliable operation. The 100mV (typ) hysteresis prevents supply
transients from causing a restart. Once the input voltage exceeds the UVLO rising threshold, startup
begins. When the input voltage falls below the UVLO falling threshold, the controller turns off the main
step-up regulator, turns off the outputs, and disables the switch control block; the operational amplifier
outputs are high impedance.
Thermal-Overload Protection
Thermal-overload protection prevents excessive power dissipation from overheating the EC9219. When
the junction temperature exceeds TJ = +135℃, a thermal sensor immediately activates the fault protection,
which shuts down all outputs except the reference, allowing the device to cool down. Once the device
cools down by approximately 30℃, and reactivate the device. The thermal-overload protection protects the
controller in the event of fault conditions. For continuous operation, do not exceed the absolute maximum
junction temperature rating of TJ = +125℃.
Design Procedure Main Step-Up Regulator Inductor Selection
The minimum inductance value, peak current rating, and series resistance are factors to consider when
selecting the inductor. These factors influence the converter’s efficiency, maximum output load capability,
transient-response time, and output voltage ripple. Size and cost are also important factors to consider.
The maximum output current, input voltage, output voltage, and switching frequency determine the
inductor value. Very high inductance values minimize the current ripple and therefore reduce the peak
current, which decreases core losses in the inductor and RL losses in the entire power path. However,
large inductor values also require more energy storage and more turns of wire, which increases size and
can increase winding resistance losses in the inductor. Low inductance values decrease the size but
increase the current ripple and peak current. Finding the best inductor involves choosing the best
compromise between circuit efficiency, inductor size, and cost. The equations used here include a
constant ICR(Inductor current ripple rate), which is the ratio of the inductor peak-to-peak ripple current to
the average DC inductor current at the full load current. The best trade-off between inductor size and
circuit efficiency for step-up regulators generally has an ICR between 0.3 and 0.5. However, depending on
the AC characteristics of the inductor core material and ratio of inductor resistance to other power-path
resistances, the best ICR can shift up or down. If the inductor resistance is relatively high, more ripple can
be accepted to reduce the number of turns required and increase the wire diameter. If the inductor
resistance is relatively low, increasing inductance to lower the peak current can decrease losses
throughout the power path. If extremely thin high-resistance inductors are used, as is common for
LCD-panel applications, the best ICR can increase to between 0.5 and 1.0. Once a physical inductor is
chosen, higher and lower values of the inductor should be evaluated for efficiency improvements in typical
operating regions. Calculate the approximate inductor value using the typical input voltage (VIN), the
maximum output current (IMAIN(MAX)), the expected efficiency ( η TYP) taken from an appropriate curve
in the Typical Operating Characteristics section, and an estimate of ICR based on the above discussion:
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TFT- LCD DC-DC Converters with Operational Amplifiers
EC9219
I2R is a registered trademark of Instruments for Research and Industry, Inc.
Choose an available inductor value from an appropriate inductor family. Calculate the maximum DC input
current at the minimum input voltage (VIN(MIN)) using conservation of energy and the expected efficiency at that
operating point (⎜MIN) taken from the appropriate curve in the Typical Operating Characteristics:
Calculate the ripple current at that operating point and the peak current required for the inductor:
The inductor’s saturation current rating and the EC9219s’ LX current limit (ILIM) should exceed IPEAK,
and the inductor’s DC current rating should exceed IIN(DC,MAX). For good efficiency, choose an
inductor with less than 0.1Ω series resistance. Considering the Typical Operating Circuit, the maximum
load current (IMAIN(MAX)) is 500mA with a 13V output and a typical input voltage of 5V. Choosing an ICR
of 0.5 and estimating efficiency of 85% at this operating point:
Using the circuit’s minimum input voltage (4.5V) and estimating efficiency of 80% at that operating point:
The ripple current and the peak current are:
Output-Capacitor Selection
The total output voltage ripple has two components: the capacitive ripple caused by the charging and
discharging of the output capacitance, and the ohmic ripple due to the capacitor’s equivalent series
resistance (ESR).
where IPEAK is the peak inductor current (see the Inductor Selection section). For ceramic capacitors, the
output voltage ripple is typically dominated by VRIPPLE(C). The voltage rating and temperature
characteristics of the output capacitor must also be considered.
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TFT- LCD DC-DC Converters with Operational Amplifiers
EC9219
Input-Capacitor Selection
The input capacitor (CIN) reduces the current peaks drawn from the input supply and reduces noise
injection into the IC. A 10μF ceramic capacitor is used in the Typical Applications Circuit (Figure 2)
because of the high source impedance seen in typical lab setups. Actual applications usually have much
lower source impedance since the step-up regulator often runs directly from the output of another
regulated supply. Typically, CIN can be reduced below the values used in the Typical Applications Circuit.
Ensure a low-noise supply at VIN by using adequate CIN. Alternately, greater voltage variation can be
tolerated on CIN if VIN is decoupled from CIN using an RC low-pass filter.
Rectifier Diode
The EC9219s’ high switching frequency demands a high-speed rectifier. Schottky diodes are recommended for
most applications because of their fast recovery time and low forward voltage. In general, a 2A Schottky diode
complements the internal MOSFET well.
Output-Voltage Selection
The output voltage of the main step-up regulator can be adjusted by connecting a resistive voltage-divider
from the output (VMAIN) to AGND with the center tap connected to FB (see Figure 2). Select R2 in the
10kΩ to 50kΩ range. Calculate R1 with the following equation:
R3 = R8 × (
Vmain
- 1)
VFB
where VFB, the step-up regulator’s feedback set point, is 1.228V. Place R3 and R8 close to the IC.
Loop Compensation
The EC9219 incorporates an trans conductance amplifier in its feedback path to allow the user some
adjustment on the transient response and better regulation. The EC9219 uses current mode control
architecture which has a fast current sense loop and a slow voltage feedback loop. The fast current
feedback loop does not require any compensation. The slow voltage loop must be compensated for stable
operation. The compensation network is a series RC network from COMP pin to ground. The resistor sets
the high frequency integrator gain for fast transient response and the capacitor sets the integrator zero to
ensure loop stability. For most applications, the compensation resistor in the range of 10K to 100K and the
compensation capacitor in the range of 1nF to 0.22uF.
PC Board Layout and Grounding
Careful PC board layout is important for proper operation. Use the following guidelines for good PC board
layout:
z
Minimize the area of high-current loops by placing the inductor, the output diode, and the output
capacitors near the input capacitors and near the LX and PGND pins. The high-current input loop goes
from the positive terminal of the input capacitor to the inductor, to the IC’s LX pin, out of PGND, and to
the input capacitor’s negative terminal. The high-current output loop is from the positive terminal of the
input capacitor to the inductor, to the output diode (D5), and to the positive terminal of the output
capacitors, reconnecting between the output capacitor and input capacitor ground terminals. Connect
these loop components with short, wide connections. Avoid using vias in the high-current paths. If vias
are unavoidable, use many vias in parallel to reduce resistance and inductance.
z
Create a power-ground island (PGND) consisting of the input and output capacitor grounds, PGND pin,
and any charge-pump components. Connect all of these together with short, wide traces or a small
ground plane. Maximizing the width of the power-ground traces improves efficiency and reduces output
voltage ripple and noise spikes. Create an analog ground plane (SGND) consisting of the SGND pin, all
the feedback-divider ground connections, the COMP and SS capacitor ground connections. Connect
the SGND and PGND islands. Make no other connections between these separate ground planes.
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TFT- LCD DC-DC Converters with Operational Amplifiers
EC9219
z
z
z
z
Place all feedback voltage-divider resistors as close to their respective feedback pins as possible. The
divider’s center trace should be kept short. Placing the resistors far away causes their FB traces to
become antennas that can pick up switching noise. Take care to avoid running any feedback trace near
LX or the switching nodes in the charge pumps.
Place the VIN pin bypass capacitors as close to the device as possible. The ground connection of the
VIN bypass capacitor should be connected directly to the SGND pin with a wide trace.
Minimize the length and maximize the width of the traces between the output capacitors and the load
for best transient responses.
Minimize the size of the LX node while keeping it wide and short. Keep the LX node away from
feedback nodes (FB) and analog ground. Use DC traces to shield if necessary.
Refer to the EC9219 DEMO BOARD for an example of proper PC board layout.
Package Dimension
TSSOP-14
Unit:mm
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TFT- LCD DC-DC Converters with Operational Amplifiers
EC9219
TQFN-16
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