MAX1513 datasheet(13/28 Pages) MAXIM

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TFT-LCD Power-Supply Controllers

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Typical Operating Circuit

The typical operating circuit of the MAX1513 (Figure 1) is

a complete power-supply system for TFT LCDs. The cir-

cuit generates a +15V source-driver supply, +25V and

-10V gate-driver supplies, a +3.3V logic supply for the

timing controller, a 14.7V gamma-correction string supply

and a VCOM buffer. The typical operating circuit of the

MAX1514 (Figure 2) is similar to that of the MAX1513

except the gamma-correction string supply and the

VCOM buffer have been eliminated. The input voltage

range for the IC is from +2.7V to +5.5V. The typical oper-

ating circuits’ listed load currents are available from a

+4.5V to +5.5V supply. Table 1 lists recommended com-

ponent options, and Table 2 lists the component suppli-

ers’ contact information.

Detailed Description

The MAX1513 and MAX1514 contain a high-perfor-

mance, step-up switching-regulator controller and three

linear-regulator controllers (two positive and one nega-

tive). The MAX1513 also includes an additional linear-reg-

ulator controller and a high-current buffer amplifier. Figure

3 shows the MAX1513/MAX1514 functional diagram.

Main Step-Up Regulator Controller

The main step-up regulator controller drives an external

N-channel power MOSFET to generate the TFT-LCD

source-driver supply. The controller employs a current-

mode, fixed-frequency PWM architecture to maximize

loop bandwidth and provide fast transient response to

pulsed loads found in source-driver applications. The

multilevel control input SDFR sets the switching fre-

quency to 430kHz, 750kHz, or 1.5MHz. The high

switching frequency allows the use of low-profile induc-

tors and ceramic capacitors to minimize the thickness

of LCD panel designs, while maintaining high efficiency

using a lossless current-sense method. The IC’s built-in

soft-start function reduces the inrush current during

startup.

The controller regulates the output voltage and the

power delivered to the output by modulating the duty

cycle (D) of the power MOSFET in each switching cycle.

The duty cycle of the MOSFET is approximated by:

Figure 4 shows the functional diagram of the step-up

regulator controller. The core of the controller is a multi-

input summing comparator that sums three signals: the

output-voltage error signal with respect to the reference

voltage, the current-sense signal, and the slope-com-

pensation ramp. On the rising edge of the internal

clock, the controller sets a flip-flop, which turns on the

external N-channel MOSFET, 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 feedback voltage error, slope

compensation, and current-sense signals trip the multi-

MAIN

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Table 1. Component List

Table 2. Component Suppliers

DESIGNATION

DESCRIPTION

22µF ±20%, 6.3V X5R ceramic capacitor (1206)

Taiyo Yuden JMK316BJ226ML

10µF ±20%, 16V POSCAP (D10)

Sanyo 16AQU10M

1A, 30V Schottky diode (S-Flat)

Toshiba CRS02

D2, D3

200mA, 100V diodes (SOT23)

Fairchild MMBT4148SE

2.2µH, 3.3A inductor

Sumida CLS7D16NP-2R2NC

3A, 20V N-channel MOSFET (SOT23)

Fairchild FDN339AN

3A, 60V PNP bipolar transistor (SOT23)

Fairchild NZT660

200mA, 40V NPN bipolar transistor (SOT23)

Fairchild MMBT3904

Q3, Q4

200mA, 40V PNP bipolar transistors (SOT23)

Fairchild MMBT3906

SUPPLIER

PHONE

FAX

WEBSITE

Fairchild Semiconductor

408-822-2000

408-822-2102

www.fairchildsemi.com

Sumida

847-545-6700

847-545-6720

www.sumida.com

Taiyo Yuden

800-348-2496

847-925-0899

www.t-yuden.com

TDK

847-803-6100

847-390-4405

www.component.tdk.com

Toshiba

949-455-2000

949-859-3963

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