MAX1517ETJ+ Maxim Integrated Products, MAX1517ETJ+ Datasheet - Page 12

• Manufacturer Part Number: MAX1517ETJ+
• Description: IC DC/DC CONV TFT-LCD 32-TQFN
• Manufacturer: Maxim Integrated Products

Specifications of MAX1517ETJ+

• Applications: LCD Display, Automotive
• Voltage - Supply: 2.6 V ~ 5.5 V
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 32-TQFN Exposed Pad
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Current - Supply: -
• Lead Free Status / Rohs Status: Lead free / RoHS Compliant

TFT-LCD DC-DC Converters with
Operational Amplifiers
The MAX1518
complete power-supply system for TFT LCDs. The cir-
cuit generates a +13V source-driver supply and +24V
and -8V gate-driver supplies. The input voltage range
for the IC is from +2.6V to +5.5V. The listed load cur-
rents in Figure 1 are available from a +4.5V to +5.5V
supply. Table 1 lists some recommended components,
and Table 2 lists the contact information of component
suppliers.
The MAX1516/MAX1517/MAX1518 contain a high-
performance step-up switching regulator, two low-cost
linear-regulator controllers, multiple high-current opera-
tional amplifiers, and startup timing and level-shifting
functionality useful for active-matrix TFT LCDs. Figure 2
shows the MAX1518 Functional Diagram.
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 the IC’s built-in digital
soft-start functions reduce the number of external com-
ponents required while controlling inrush currents. The
output voltage can be set from V
nal resistive voltage-divider. To generate an output volt-
age greater than 13V, an external cascoded MOSFET
is needed. See the Generating Output Voltages > 13V
section in the Design Procedures.
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:
Table 2. Component Suppliers
12
Fairchild
Sumida
TDK
Toshiba
______________________________________________________________________________________
SUPPLIER
Typical Operating Circuit (Figure 1) is a
Typical Operating Circuit
D
≈
V
Detailed Description
MAIN
V
Main Step-Up Regulator
MAIN
−
V
408-822-2000
847-545-6700
847-803-6100
949-455-2000
IN
IN
PHONE
to 13V with an exter-
408-822-2102
847-545-6720
847-390-4405
949-859-3963
FAX
Figure 3 shows the Functional Diagram of the step-up
regulator. An error amplifier compares the signal at FB
to 1.236V 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 sta-
bility 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 cur-
rent through the inductor ramps up linearly, storing
energy in its magnetic field. Once the sum of the cur-
rent-feedback signal and the slope 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 differ-
ence between the output voltage and the input voltage.
Table 1. Component List
DESIGNATION
D2, D3
Q1
Q2
C1
C2
D1
L1
www.fairchildsemi.com
www.sumida.com
www.component.tdk.com
www.toshiba.com/taec
22µF, 6.3V X5R ceramic capacitor (1210)
TDK C3225X5R0J227M
22µF, 16V X5R ceramic capacitor (1812)
TDK C4532X5X1C226M
3A, 30V Schottky diode (M-flat)
Toshiba CMS02
200mA, 100V, dual ultra-fast diodes (SOT23)
Fairchild MMBD4148SE
3.0µH, 3A inductor
Sumida CDRH6D28-3R0
200mA, 40V pnp bipolar transistor (SOT23)
Fairchild MMBT3906
200mA, 40V npn bipolar transistor (SOT23)
Fairchild MMBT3904
DESCRIPTION
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