Datasheet

MAX17103/AUO-P1721.14
DC-DC Converter with Integrated Scan Driver,
VGL Controller, Op Amp, and LDO for TFT LCD
16 ______________________________________________________________________________________
Typical Application Circuit
The MAX17103 typical application circuit (Figure 1)
generates a +8.5V source-driver supply and approxi-
mately +23V and -6V gate-driver supplies for TFT dis-
plays. The input-voltage range for the IC is from +2.3V
to +5.5V, but the circuit in Figure 1 is designed to run
from 2.5V to 3.6V. Table 1 lists the recommended com-
ponents and Table 2 lists the component suppliers.
Detailed Description
The MAX17103 includes a high-performance, step-up
regulator, a 350mA low-dropout (LDO) linear regulator, a
high-speed operational amplifier, a negative linear-regu-
lator controller, and a high-voltage, level-shifting scan dri-
ver. Figure 2 shows the MAX17103 functional diagram.
Step-Up Regulator
The step-up regulator employs a peak-current-mode
control architecture with a fixed 1.2MHz switching fre-
quency that maximizes loop bandwidth and provides a
fast-transient response to pulsed loads found in source
drivers of TFT LCD panels. The high 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
reduces the number of external components required.
The output voltage can be set from V
IN
to 15V 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:
Figure 3 shows the block diagram of the step-up regu-
lator. An error amplifier compares the signal at FB to
1.24V and changes the COMP output. The voltage at
COMP determines the current trip point each time the
internal MOSFET turns on. As the load varies, the error
amplifier sources or sinks current to the COMP output
accordingly to produce the inductor peak current nec-
essary 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 mag-
netic field. Once the sum of the current-feedback signal
and the slope compensation exceed 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.
D
VV
V
MAIN IN
MAIN
≈
-
DESIGNATION DESCRIPTION
C1, C2
1μF ±10%, 16V X5R ceramic capacitors (0603)
Murata GRM188R61C105K
TDK C1608X5R1C105K
C3
10μF ±10%, 10V X5R ceramic capacitor (0805)
TDK C2012X5R1A106K
Murata GRM21BR61A106K
C4, C5, C6
10μF ±10%, 16V X5R ceramic capacitors (1206)
Taiyo Yuden EMK316BJ106KL
Murata GRM31CR61C106K
D1
1A, 30V Schottky diode (S-Flat)
Central CMMSH1-40
Nihon EP10QY03
Toshiba CRS02(TE85L)
D2, D3, D4
200mA, 100V dual diodes (SOT23)
Fairchild MMBD4148SE
Central CMPD7000
L1
10μH, 1.85A, 74.4m inductor
(6mm x 6mm x 3mm)
Sumida CDRH5D28RHPNP-100M
Q1
npn surface-mount transistor (SOT23)
Diodes Inc. MMBT3904
Fairchild MMBT3904
Table 1. Component List
SUPPLIER WEBSITE
Central Semiconductor Corp. www.centralsemi.com
Diodes Inc. www.diodes.com
Fairchild Semiconductor www.fairchildsemi.com
Murata Electronics North
America, Inc.
www.murata-northamerica.com
Nihon Inter Electronics Corp. www.niec.co.jp
Sumida Corp. www.sumida.com
Taiyo Yuden www.t-yuden.com
TDK Corp. www.component.tdk.com
Toshiba America Electronic
Components, Inc.
www.toshiba.com/taec
Table 2. Component Suppliers