Datasheet

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General Description

The MAX17014A multiple-output power-supply con-

troller generates all the supply rails for thin-film transis-

tor (TFT) liquid-crystal display (LCD) panels in TVs and

monitors operating from a regulated 12V input. It

includes a step-down and a step-up regulator, a posi-

tive and a negative charge pump, two operational

amplifiers, and a Dual Mode™ logic-controlled high-

voltage switch control block. The MAX17014A can

operate from 8V to 16.5V input voltages and is opti-

mized for LCD TV panel and LCD monitor applications

running directly from 12V supplies.

The step-up and step-down regulators feature internal

power MOSFETs and high-frequency operation allow-

ing the use of small inductors and capacitors, resulting

in a compact solution. Both switching regulators use

fixed-frequency current-mode control architectures,

providing fast load-transient response and easy com-

pensation. A current-limit function for internal switches

and output-fault shutdown protect the step-up and

step-down power supplies against fault conditions. The

MAX17014A provides soft-start functions to limit inrush

current during startup. The MAX17014A provides

adjustable power-up timing.

The positive and negative charge-pump regulators pro-

vide TFT gate driver supply voltages. Both output volt-

ages can be adjusted with external resistive

voltage-dividers. The switch control block allows the

manipulation of the positive TFT gate driver voltage.

The MAX17014A includes two high-current operational

amplifiers designed to drive the LCD backplane

(VCOM). The amplifier features high output current

(±150mA), fast slew rate (100V/µs), wide bandwidth

(20MHz), and rail-to-rail inputs and outputs. A series

p-channel MOSFET is integrated to sequence power to

after the MAX17014A has proceeded through

normal startup, and provides True Shutdown™.

The MAX17014A is available in a small (7mm x 7mm),

low-profile (0.8mm), 48-pin thin QFN package and

operates over a -40°C to +85°C temperature range.

Applications

LCD TV Panels

LCD Monitor Panels

Features

o Optimized for 10.8V to 13.2V Input Supply

o 8V to 16.5V Input Supply Range

o Selectable Frequency (600kHz/1.2MHz)

o Current-Mode Step-Up Regulator

Built-In 20V, 3.7A, 110mΩ n-Channel MOSFET

High-Accuracy Output Voltage (1%)

True Shutdown

Fast Load-Transient Response

High Efficiency

3ms Internal Soft-Start

o Current-Mode Step-Down Regulator

Built-In 20V, 2.5A, 120mΩ n-Channel MOSFET

Fast Load-Transient Response

Adjustable Output Voltage Down to 1.25V

Skip Mode at Light Load

High Efficiency

3ms Internal Soft-Start

o Adjustable Positive and Negative Charge-Pump

Regulators

o Soft-Start and Timer-Delay Fault Latch for All

Outputs

o Logic-Controlled High-Voltage Integrated

Switches with Adjustable Delay

o Two High-Speed Operational Amplifiers

±150mA Short-Circuit Current

100V/µs Slew Rate

20MHz, -3dB Bandwidth

o 120mΩ p-Channel FET for AV

Sequencing

o Input Undervoltage Lockout and Thermal-

Overload Protection

o 48-Pin, 7mm x 7mm Thin QFN Package

MAX17014A

Low-Cost Multiple-Output

Power Supply for LCD TVs

________________________________________________________________

Maxim Integrated Products

Ordering Information

19-4192; Rev 0; 8/08

For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642,

or visit Maxim’s website at www.maxim-ic.com.

Denotes a lead-free/RoHS-compatible package.

EVALUATION KIT

AVAILABLE

PART TEMP RANGE PIN-PACKAGE

MAX17014AETM+ -40°C to +85°C 48 Thin QFN

Dual Mode is a trademark of Maxim Integrated Products, Inc.

True Shutdown is a trademark of Maxim Integrated Products, Inc.

Simplified Operating Circuit and Pin Configuration appear

at end of data sheet.

Summary of content (32 pages)

PAGE 1
9-4192; Rev 0; 8/08 KIT ATION EVALU E L B A IL AVA Low-Cost Multiple-Output Power Supply for LCD TVs The MAX17014A multiple-output power-supply controller generates all the supply rails for thin-film transistor (TFT) liquid-crystal display (LCD) panels in TVs and monitors operating from a regulated 12V input. It includes a step-down and a step-up regulator, a positive and a negative charge pump, two operational amplifiers, and a Dual Mode™ logic-controlled highvoltage switch control block.
PAGE 2
MAX17014A Low-Cost Multiple-Output Power Supply for LCD TVs ABSOLUTE MAXIMUM RATINGS VIN, IN2, OVIN, SUP, EN1, EN2, FSEL to GND ......-0.3V to +24V GND1, OGND, CPGND to GND .........................................±0.3V MODE, DLP, CTL, THR, DEL1, DEL2, VL to GND ...-0.3V to +7.5V REF, FBP, FBN, FB1, FB2, COMP, OUT to GND ...........................................-0.3V to (VVL + 0.3V) SWI, SWO to GND ..................................................-0.3V to +24V LX1 to GND1 ...............................
PAGE 3
Low-Cost Multiple-Output Power Supply for LCD TVs (Circuit of Figure 1, VIN = IN2 = 12V, AVDD = OVIN = SUP = 15V, TA = 0°C to +85°C. Typical values are at TA = +25°C, unless otherwise noted.) PARAMETER CONDITIONS MIN TYP MAX UNITS 1.235 1.250 1.265 V 10 mV REFERENCE REF Output Voltage No external load REF Load Regulation 0 < ILOAD < 50μA REF Sink Current In regulation REF Undervoltage Lockout Threshold Rising edge; 20mV typical hysteresis 10 μA 1.0 1.
PAGE 4
MAX17014A Low-Cost Multiple-Output Power Supply for LCD TVs ELECTRICAL CHARACTERISTICS (continued) (Circuit of Figure 1, VIN = IN2 = 12V, AVDD = OVIN = SUP = 15V, TA = 0°C to +85°C. Typical values are at TA = +25°C, unless otherwise noted.) PARAMETER FB1 Load Regulation CONDITIONS FB1 Line Regulation 0 < ILOAD < full, transient only 10.8V < V VIN < 13.2V FB1 Input Bias Current VFB1 = 1.25V FB1 Transconductance I = ±2.
PAGE 5
Low-Cost Multiple-Output Power Supply for LCD TVs (Circuit of Figure 1, VIN = IN2 = 12V, AVDD = OVIN = SUP = 15V, TA = 0°C to +85°C. Typical values are at TA = +25°C, unless otherwise noted.) PARAMETER CONDITIONS AVDD SWITCH SWI Supply Range MIN TYP 8.0 SWI Overvoltage Fault Threshold SWI rising edge, 250mV typical hysteresis (Note 3) 18.50 SWI-SWO Switch Resistance MAX UNITS 18.5 V 19.25 20.
PAGE 6
MAX17014A Low-Cost Multiple-Output Power Supply for LCD TVs ELECTRICAL CHARACTERISTICS (continued) (Circuit of Figure 1, VIN = IN2 = 12V, AVDD = OVIN = SUP = 15V, TA = 0°C to +85°C. Typical values are at TA = +25°C, unless otherwise noted.) PARAMETER CONDITIONS MIN TYP MAX UNITS 1k from DRN to GND, CTL = GND to VL step, no load CTL-to-GON Rising Propagation Delay on GON, measured from VCTL = 2V to GON = 20% 100 ns 1k from DRN to GND, CTL = VL to GND step, no load on GON, measured from VCTL = 0.
PAGE 7
Low-Cost Multiple-Output Power Supply for LCD TVs (Circuit of Figure 1, VIN = IN2 = 12V, AVDD = OVIN = SUP = 15V, TA = -40°C to +85°C. Typical values are at TA = +25°C, unless otherwise noted.) (Note 4) PARAMETER CONDITIONS MIN TYP MAX UNITS V GENERAL VIN, IN2 Input Voltage Range 8.0 16.5 FSEL = VIN 1020 1380 FSEL = GND 510 690 VIN rising edge, 200mV typical hysteresis 6.0 8.0 V VL Output Voltage I VL = 25mA, VFB1 = VFB2 = VFBP = 1.1V, VFBN = 0.4V (all regulators switching) 4.9 5.
PAGE 8
MAX17014A Low-Cost Multiple-Output Power Supply for LCD TVs ELECTRICAL CHARACTERISTICS (continued) (Circuit of Figure 1, VIN = IN2 = 12V, AVDD = OVIN = SUP = 15V, TA = -40°C to +85°C. Typical values are at TA = +25°C, unless otherwise noted.) (Note 4) PARAMETER CONDITIONS MIN TYP MAX UNITS V POSITIVE- AND NEGATIVE-CHARGE-PUMP REGULATORS SUP Input Supply Range 8 18.5 18.5 20 V 1.23 1.
PAGE 9
Low-Cost Multiple-Output Power Supply for LCD TVs (Circuit of Figure 1, VIN = IN2 = 12V, AVDD = OVIN = SUP = 15V, TA = -40°C to +85°C. Typical values are at TA = +25°C, unless otherwise noted.) (Note 4) PARAMETER CONDITIONS MODE Voltage Threshold for Enabling DRN Switch Control in Mode 2 GON connects to DRN MODE Current-Source Stop Voltage Threshold MODE rising edge MIN THR-to-GON Voltage Gain TYP MAX UNITS 1.2 1.3 V 2 3 V 9.4 10.6 V/V 0.
PAGE 10
Typical Operating Characteristics (continued) (Circuit of Figure 1. VIN = VINL = VSUPP = 12V, AVDD = 16V, VGON = 34.5V, VGOFF = -6V, VOUT1 = 3.3V, TA = +25°C, unless otherwise noted.) MAX17014A toc04 0V C 95 90 85 80 75 70 65 60 55 50 D 0V 45 40 0.001 STEP-UP REGULATOR SOFT-START (HEAVY LOAD) MAX17014A toc07 16.06 16.04 0A 4.00ms/div C: INDUCTOR CURRENT, 500mA/div D: VLX2, 10V/div 16.08 AVDD (V) 0V 16.
PAGE 11
Low-Cost Multiple-Output Power Supply for LCD TVs STEP-UP REGULATOR CURRENT LIMIT vs. INPUT VOLTAGE MAX17014A toc11 5.5 1.200 A 0V 5.0 AVDD = 16V B 4.5 0V C 0V D 4.0 3.5 MAX17014A toc12 L1 = 4.7µH (CDEP134NP-4R8M, ISAT = 9.3A) SWITCHING FREQUENCY (MHz) MAX17014A toc10 6.0 STEP-UP CURRENT LIMIT (A) SWITCHING FREQUENCY vs. INPUT VOLTAGE TIME-DELAY LATCH RESPONSE TO OVERLOAD 1.198 1.196 1.194 1.192 3.0 E 0V 9 10 11 12 13 14 15 INPUT VOLTAGE (V) VL (V) 5.02 EN1 = EN2 = VL 5.
PAGE 12
Typical Operating Characteristics (continued) (Circuit of Figure 1. VIN = VINL = VSUPP = 12V, AVDD = 16V, VGON = 34.5V, VGOFF = -6V, VOUT1 = 3.3V, TA = +25°C, unless otherwise noted.) MAX17014A toc17 0 0.25 A 34.8V -0.4 -0.8 70mA -1.2 B -1.6 0.05 -0.15 -0.35 -0.55 10mA -0.75 -2.0 0 25 50 75 100 125 150 9 40.
PAGE 13
Low-Cost Multiple-Output Power Supply for LCD TVs MAX17014A toc22 MAX17014A toc24 MAX17014A toc23 50mA A 0mA A A -50mA 0V 0V B 8V B B 0V 0V 400ns/div A: INPUT SIGNAL, 5V/div B: OUTPUT SIGNAL, 5V/div 200ns/div A: OUTPUT CURRENT, 50mA/div B: OUTPUT VOLTAGE, 500mV/div OPERATIONAL AMPLIFIER SMALL-SIGNAL RESPONSE INL SUPPLY CURRENT vs. TEMPERATURE VIN SUPPLY CURRENT vs. VIN VOLTAGE MAX17014A toc26 6 EN1 = EN2 = VL A 0V B 0V VIN SUPPLY CURRENT (mA) 5 4 3 2 EN1 = EN2 = GND 1 3.0 2.5 2.
PAGE 14
Low-Cost Multiple-Output Power Supply for LCD TVs MAX17014A Pin Description 14 PIN NAME 1 POS1 Operational Amplifier 1 Noninverting Input FUNCTION 2 OUT1 Operational Amplifier 1 Output 3 THR GON Low-Level Regulation Set-Point Input. Connect THR to the center of a resistive voltage-divider between AVDD and GND to set the V GON falling regulation level. The regulation level is 10 x VTHR. See the High-Voltage Switch Control section for details.
PAGE 15
Low-Cost Multiple-Output Power Supply for LCD TVs PIN NAME FUNCTION 23, 24 LX2 Step-Down Regulator Switching Node. LX2 is the source of the internal n-channel MOSFET connected between IN2 and LX2. Connect the inductor and Schottky catch diode close to both LX2 pins to minimize the trace area for low EMI. 25, 26 IN2 Step-Down Regulator Power Input. Drain of the internal n-channel MOSFET connected between IN2 and LX2. 27 VIN Input of the Internal 5V Linear Regulator and the Startup Circuitry.
PAGE 16
MAX17014A Low-Cost Multiple-Output Power Supply for LCD TVs L1 4.7μH VIN 12V C1 10μF 0.1μF 25 C3 10μF 26 35 36 GND1 GND1 IN2 IN2 22 OUT 3.3V 2A C2 10μF 37 LX1 SUI 23 SWO LX2 24 LX2 L2 2.6μH 21 27 VIN SWI C14 0.1μF 40 C24 10μF AVDD 16V 1.5A 42 C15 10μF C16 10μF R3 158kΩ FB1 41 31 COMP OUT R5 82kΩ FB2 OVIN OGND 30 VL 28 FSEL 4 MODE 17 REF C7 1μF REF C8 0.22μF 15 29 C9 0.1μF POS1 THR MAX17014A NEG1 GND OUT1 NEG2 DEL2 CTL DEL1 DRN C10 0.
PAGE 17
Low-Cost Multiple-Output Power Supply for LCD TVs Detailed Description The typical operating circuit (Figure 1) of the MAX17014A is a complete power-supply system for TFT LCD panels in monitors and TVs. The circuit generates a +3.3V logic supply, a +16V source driver supply, a +34.5V positive gate driver supply, and a -6V negative gate driver supply from a 12V ±10% input supply. Table 1 lists some selected components and Table 2 lists the contact information for component suppliers.
PAGE 18
MAX17014A Low-Cost Multiple-Output Power Supply for LCD TVs VIN (12V) BST VL IN2 LX1 3.3V 2A STEP-DOWN LX2 OSC STEP-UP GND1 FB1 COMP CPGND OUT FSEL VL SWI P AVDD 16V 1.
PAGE 19
Low-Cost Multiple-Output Power Supply for LCD TVs where VFB2 = 1.25V, and VOUT can vary from 1.25V to 5V. Because of FB2’s (pin 21) close proximity to the noisy BST (pin 22), a noise filter is required for FB2 adjustable-mode operation. Place a 100pF capacitor from FB2 to GND to prevent unstable operation. No filter is required for 3.3V fixed-mode operation. When EN1 is high and EN2 is low, the controller operates in skip mode.
PAGE 20
MAX17014A Low-Cost Multiple-Output Power Supply for LCD TVs 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 currentfeedback signal and the slope compensation exceed the COMP voltage, the controller resets the flip-flop and turns off the MOSFET.
PAGE 21
Low-Cost Multiple-Output Power Supply for LCD TVs Negative Charge-Pump Regulator The negative charge-pump regulator is typically used to generate the negative supply rail for the TFT LCD gate driver ICs. The output voltage is set with an external resistive voltage-divider from its output to REF with the midpoint connected to FBN. The number of chargepump stages and the setting of the feedback divider determine the output of the negative charge-pump regulator.
PAGE 22
MAX17014A Low-Cost Multiple-Output Power Supply for LCD TVs High-Voltage Switch Control The MAX17014A’s high-voltage switch control block (Figure 5) consists of two high-voltage p-channel MOSFETs: Q1, between SRC and GON and Q2, between GON and DRN. The switch control block is enabled when VDLP exceeds VREF. Q1 and Q2 are controlled by CTL and MODE. There are two different modes of operation (see the Typical Operating Characteristics).
PAGE 23
Low-Cost Multiple-Output Power Supply for LCD TVs Operational Amplifiers The MAX17014A has two operational amplifiers. The operational amplifiers are typically used to drive the LCD backplane (VCOM) or the gamma-correction divider string. They feature ±150mA output short-circuit current, 100V/µs slew rate, and 20MHz, -3dB bandwidth. While the op amp is a rail-to-rail input and output design, its accuracy is significantly degraded for input voltages within 2V of its supply rails (OVIN, OGND).
PAGE 24
MAX17014A Low-Cost Multiple-Output Power Supply for LCD TVs Driving Pure Capacitive Load The operational amplifiers are typically used to drive the LCD backplane (VCOM) or the gamma-correction divider string. The LCD backplane consists of a distributed series capacitance and resistance, a load that can be easily driven by the operational amplifier. However, if the operational amplifier is used in an application with a pure capacitive load, steps must be taken to ensure stable operation.
PAGE 25
Low-Cost Multiple-Output Power Supply for LCD TVs EN1 VL/REF VIN UVLO DEL1 BUCK OUTPUT REF tSS TIME NEGATIVE CHARGE-PUMP REGULATOR OUTPUT EN2 tSS DEL2 REF TIME DEL2 STARTS CHARGING WHEN EN2 IS HIGH AND THE BUCK SOFT-START IS FINISHED. POSITIVE CHARGE-PUMP REGULATOR OUTPUT AVDD SUI SUI_DONE TIME tSS DLP REF TIME VGON DEPENDS ON CTL VGON TIME Figure 7.
PAGE 26
MAX17014A Low-Cost Multiple-Output Power Supply for LCD TVs Fault Protection During steady-state operation, if any output of the four regulators (step-down regulator, step-up regulator, positive charge-pump regulator, and negative chargepump regulator) does not exceed its respective faultdetection threshold, the MAX17014A activates an internal fault timer.
PAGE 27
Low-Cost Multiple-Output Power Supply for LCD TVs For most applications, ceramic capacitors are used because of their high ripple current and surge current capabilities. For optimal circuit long-term reliability, choose an input capacitor that exhibits less than +10°C temperature rise at the RMS input current corresponding to the maximum load current.
PAGE 28
MAX17014A Low-Cost Multiple-Output Power Supply for LCD TVs 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 I2R losses in the entire power path.
PAGE 29
Low-Cost Multiple-Output Power Supply for LCD TVs Input Capacitor Selection The input capacitor reduces the current peaks drawn from the input supply and reduces noise injection into the IC. A 22µF ceramic capacitor is used in the typical operating circuit (Figure 1) 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.
PAGE 30
MAX17014A Low-Cost Multiple-Output Power Supply for LCD TVs Flying Capacitors Increasing the flying capacitors (connected to DRVN and DRVP) value lowers the effective source impedance and increases the output-current capability. Increasing the capacitance indefinitely has a negligible effect on output-current capability because the internal switch resistance and the diode impedance place a lower limit on the source impedance. A 0.1µF ceramic capacitor works well in most low-current applications.
PAGE 31
Low-Cost Multiple-Output Power Supply for LCD TVs • 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. Care should be taken to avoid running any feedback trace near LX1, LX2, DRVP, or DRVN. Place VIN pin, VL pin, and REF pin bypass capacitors as close to the device as possible.
PAGE 32
IN2 IN2 VIN FSEL DEL2 VL COMP EN2 EN1 GND GND1 TOP VIEW GND1 Pin Configuration 36 35 34 33 32 31 30 29 28 27 26 25 LX1 37 24 LX2 LX1 38 23 LX2 SWI 39 22 BST SUI 40 21 FB2 FB1 41 20 OUT SWO 42 19 N.C.