MAX8753ETI-T Maxim Integrated, MAX8753ETI-T Datasheet - Page 11

• Manufacturer Part Number: MAX8753ETI-T
• Description: LCD Drivers
• Manufacturer: Maxim Integrated

Table 2. Component Suppliers
The MAX8753 quadruple-output DC-DC converter pro-
vides the regulated voltages required by active-matrix,
TFT LCDs. Figure 1 shows the typical operating circuit.
It includes a high-power step-up regulator (V
low-power charge pumps (V
voltage, 300mA linear regulator (V
boost converter uses an internal n-channel MOSFET to
provide maximum efficiency and to minimize the num-
ber of external components. The output voltage of the
main boost converter (V
13V with external resistors. The positive charge pump
regulates a positive output (V
switches or diodes. The negative charge pump regu-
lates a negative output (V
proprietary regulation algorithm minimizes output rip-
ple, as well as capacitor sizes for both charge pumps.
Also included in the MAX8753 is a precision 1.25V ref-
erence that sources up to 50µA, logic shutdown, soft-
start, power-up sequencing, and fault detection. Figure
2 is the MAX8753 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 and TFT LCD panel source driver applica-
tions. The high switching frequency (1MHz) allows the
use of low-profile inductors and ceramic capacitors to
minimize the thickness of LCD panel designs. The inte-
grated high-efficiency MOSFET and the IC’s built-in,
digital, soft-start function reduces the number of exter-
nal components required while controlling inrush cur-
rent. The output voltage can be set from V
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:
Fairchild
Sumida
Taiyo Yuden
TDK
Toshiba
SUPPLIER
______________________________________________________________________________________
D
≈
Detailed Description
V
MAIN
Main Step-Up Regulator
MAIN
V
NEG
MAIN
408-822-2000
847-545-6700
408-573-4150
847-803-6100
949-455-2000
POS
) can be set from V
PHONE
−
) with external diodes. A
V
POS
IN
and V
LOGIC
) without external
NEG
TFT LCD DC-DC Converter with
). The primary
IN
), and a low-
to 13V with
MAIN
), two
IN
to
Integrated Charge Pumps
408-822-2102
847-545-6720
408-573-4159
847-390-4405
949-859-3963
FAX
Figure 3 shows the block diagram of the step-up regu-
lator. A transconductance 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 transconductance error amplifier sources or
sinks current to the COMP output accordingly to pro-
duce the inductor peak current necessary to service
the load. To maintain stability at high duty cycles, a
Figure 2. Functional Diagram
ONLCD
SHDN
OUTP
OUTL
DLP
C1N
C1P
C2N
C2P
FBP
FBL
IN
REGULATOR
LDO
CHARGE-
POSITIVE
PUMP
www.fairchildsemi.com
www.sumida.com
www.t-yuden.com
www.component.tdk.com
www.toshiba.com/taec
SUPP
REGULATOR
SEQ
STEP-UP
INTG
REGULATOR
NEGATIVE
CHARGE-
PUMP
WEBSITE
REF
LX
MAX8753
PGND
FB
GND
REF
SUPN
C3P
FBN
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