Datasheet

ManualsBrandsMAXIM INTEGRATED ManualsPMICsPMIC - voltage regulator - special purpose TQFN 32 EP (5x5)

General Description

The MAX1997/MAX1998 provide the voltages required for

active-matrix, thin-film transistor liquid-crystal displays

(TFT LCDs). Both combine a high-performance step-up

regulator with two linear-regulator controllers, input pro-

tection switch control, and flexible sequence program-

ming. The MAX1997 contains two additional linear-

regulator controllers and a VCOM buffer. The MAX1997/

MAX1998 can operate from input supplies of 2.7V to 5.5V

and feature multiple levels of protection circuitry, making

them complete power-supply systems for displays.

The main DC-DC converter provides the regulated supply

voltage for the display’s source-driver ICs. The converter

is a high-frequency (up to 1.5MHz) step-up regulator with

an integrated 14V N-channel MOSFET that allows the use

of ultra-small inductors and ceramic capacitors while

achieving efficiencies over 85%. Its current-mode control

architecture provides fast transient response to pulsed

loads. Internal soft-start and cycle-by-cycle current limit

help prevent input surge currents.

The positive and negative linear-regulator controllers

postregulate charge-pump outputs for TFT gate-on and

gate-off supplies. Both linear-regulator controllers, as well

as the step-up regulator, have supply-sequencing control

inputs. The three outputs can be sequenced in any order

by selecting the appropriate external components.

The MAX1997 features a high-current backplane driver

(VCOM). This buffer provides peak currents exceeding

300mA (typ) and requires only a 0.47µF output filter

capacitor. The MAX1997’s two additional linear-regulator

controllers can be used to build the gamma reference

voltage and a logic supply.

The MAX1997/MAX1998 have a unique input switch con-

trol that can replace the typical input supply fuse. When a

fault is detected, the regulator is disconnected from the

input supply. The fault detector monitors all the regulated

output voltages and the current from the input supply. In

addition, the MAX1997/MAX1998 enter shutdown when

the internal over-temperature threshold is reached.

The MAX1997 is available in a 32-pin thin QFN package

and the MAX1998 is available in a 20-pin thin QFN pack-

age. Both packages have a maximum thickness of

0.8mm suitable for ultra-thin LCD panels.

Applications

Notebook Computer Displays

LCD Monitors

Car Navigation Displays

Features

♦ 2.7V to 5.5V Input Supply Range

♦ Adjustable (Up to +13V) Output Voltage for

Source-Driver ICs

♦ Integrated High-Efficiency Power MOSFET

♦ Linear-Regulator Controllers for TFT Gate-On and

Gate-Off Supplies

♦ High-Current VCOM Buffer (MAX1997 Only)

♦ Two Additional Linear-Regulator Controllers

(MAX1997 Only)

♦ Programmable Power-Up Sequencing

♦ Multiple Overload Protection with Thermal

Shutdown

♦ 1µA Shutdown Current

♦ 32-Pin/20-Pin Thin QFN Packages

MAX1997/MAX1998

Quintuple/Triple-Output TFT LCD Power Supplies

with Fault Protection and VCOM Buffer

________________________________________________________________ Maxim Integrated Products 1

19-2638; Rev 0; 10/02

For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at

1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com.

Ordering Information

PART

TEMP RANGE

PIN-PACKAGE

MAX1997ETJ

-40°C to +85°C

32 Thin QFN 5mm x 5mm

MAX1998ETP

-40°C to +85°C

20 Thin QFN 5mm x 5mm

FREQ

GATE

OCP

OCN

DRVN

FBN

DRVA

REF

GND

FBP

DRVP

ON2

ONP

ONN

PGND

TGNDA

TOP VIEW

MAX1998

THIN QFN 5mm × 5mm

Pin Configurations

Pin Configurations continued at end of data sheet.

Summary of content (31 pages)

PAGE 1
9-2638; Rev 0; 10/02 Quintuple/Triple-Output TFT LCD Power Supplies with Fault Protection and VCOM Buffer LCD Monitors Car Navigation Displays ♦ Integrated High-Efficiency Power MOSFET ♦ Linear-Regulator Controllers for TFT Gate-On and Gate-Off Supplies ♦ High-Current VCOM Buffer (MAX1997 Only) ♦ Two Additional Linear-Regulator Controllers (MAX1997 Only) ♦ Programmable Power-Up Sequencing ♦ Multiple Overload Protection with Thermal Shutdown ♦ 1µA Shutdown Current ♦ 32-Pin/20-Pin Thin QFN Packages Order
PAGE 2
MAX1997/MAX1998 Quintuple/Triple-Output TFT LCD Power Supplies with Fault Protection and VCOM Buffer ABSOLUTE MAXIMUM RATINGS IN, SHDN, FB, FBP, FBN, FB1, FB2, ONDC, ONP, ONN, ON2, TGNDA, TGNDB to GND.............-0.3V to +6V PGND to GND .....................................................................±0.3V LX, VDDB to GND....................................................-0.3V to +14V DRVP, DRV1, DRV2, DRVA to GND .......................-0.3V to +30V REF, FREQ, GATE, OCN, OCP, CT, PFLT to GND .......
PAGE 3
Quintuple/Triple-Output TFT LCD Power Supplies with Fault Protection and VCOM Buffer (Circuit of Figure 1, VIN = 3V, VDDB = 10V, SHDN = ONDC = FREQ = IN, CREF = 0.22µF, PGND = GND, TA = 0°C to +85°C. Typical values are at TA = +25°C, unless otherwise noted.) PARAMETER CONDITIONS Oscillator Maximum Duty Cycle MIN TYP MAX UNITS 80 85 90 % FB Regulation Voltage ILX = 200mA 1.229 1.242 1.254 V FB Fault Trip Level VFB falling 0.96 1.00 1.04 V 0.
PAGE 4
MAX1997/MAX1998 Quintuple/Triple-Output TFT LCD Power Supplies with Fault Protection and VCOM Buffer ELECTRICAL CHARACTERISTICS (continued) (Circuit of Figure 1, VIN = 3V, VDDB = 10V, SHDN = ONDC = FREQ = IN, CREF = 0.22µF, PGND = GND, TA = 0°C to +85°C. Typical values are at TA = +25°C, unless otherwise noted.) PARAMETER CONDITIONS FBN Effective Load Regulation Error (Transconductance) VDRVN = -10V, IDRVN = 50µA to 1mA FBN Line (IN) Regulation Error IDRVN = 100µA, 2.7V < VIN < 5.
PAGE 5
Quintuple/Triple-Output TFT LCD Power Supplies with Fault Protection and VCOM Buffer (VIN = 3V, VDDB = 10V, SHDN = ONDC = FREQ = IN, CREF = 0.22µF, PGND = GND, TA = -40°C to +85°C, unless otherwise noted.) (Note 3) PARAMETER CONDITIONS IN Supply Range IN Undervoltage Lockout Threshold IN Quiescent Current (Note 1) 350mV typ hysteresis MIN MAX UNITS V 2.7 5.5 VIN rising 2.5 2.9 VIN falling 2.2 2.5 VFB = VFBP = VFB1 = VFB2 = 1.5V, VFBN = 0 (MAX1997 only) 1.25 VFB = VFBP = 1.
PAGE 6
MAX1997/MAX1998 Quintuple/Triple-Output TFT LCD Power Supplies with Fault Protection and VCOM Buffer ELECTRICAL CHARACTERISTICS (continued) (VIN = 3V, VDDB = 10V, SHDN = ONDC = FREQ = IN, CREF = 0.22µF, PGND = GND, TA = -40°C to +85°C, unless otherwise noted.
PAGE 7
Quintuple/Triple-Output TFT LCD Power Supplies with Fault Protection and VCOM Buffer 70 60 VIN = 2.7V 50 VIN = 3.3V 40 VIN = 5.5V 30 20 8.9 VIN = 2.7V 8.8 VIN = 3.3V VIN = 5.5V 8.7 90 VIN = 5.5V 80 70 VIN = 3.3V 60 VIN = 2.7V 50 40 30 20 8.6 10 10 0 8.5 0 10 100 10 1 1000 100 1 1000 10 100 1000 LOAD CURRENT (mA) LOAD CURRENT (mA) LOAD CURRENT (mA) STEP-UP REGULATOR EFFICIENCY vs. LOAD CURRENT STEP-UP REGULATOR SWITCHING FREQUENCY vs.
PAGE 8
MAX1997/MAX1998 Quintuple/Triple-Output TFT LCD Power Supplies with Fault Protection and VCOM Buffer Typical Operating Characteristics (continued) (Circuit of Figure 1, VIN = 3.3V, V MAIN = 9V, V G_ON = 20V, VG_OFF = -7V, V LOGIC = 2.5V, V GAMMA = 8.6V, T A = +25°C, unless otherwise noted.
PAGE 9
Quintuple/Triple-Output TFT LCD Power Supplies with Fault Protection and VCOM Buffer -0.10 -0.15 -0.20 -0.25 -0.16 -0.24 -0.32 1 10 -0.2 -0.4 -0.6 -0.8 -1.0 0.1 1 10 LOAD CURRENT (mA) LOAD CURRENT (mA) REG 2 (GAMMA REFERENCE) LOAD REGULATION REG 1 (LOGIC SUPPLY) LOAD TRANSIENT RESPONSE 1 MAX1997 toc17 -0.04 10 100 1000 LOAD CURRENT (mA) REG 2 (GAMMA REFERENCE) VMAIN TRANSIENT REJECTION MAX1997 toc18 0 MAX1997 toc16 -0.08 0 -0.40 0.
PAGE 10
Typical Operating Characteristics (continued) (Circuit of Figure 1, VIN = 3.3V, V MAIN = 9V, V G_ON = 20V, VG_OFF = -7V, V LOGIC = 2.5V, V GAMMA = 8.6V, T A = +25°C, unless otherwise noted.) MAX1997 toc21 10V 5V A 5V A 0 0 5V 5V B B 0 0 20V 20V 10V C 1.250 10V 10V C 0 D -10V -10V 20ms/div 1.248 1.247 1.246 LX CURRENT LIMIT vs. INPUT VOLTAGE VCOM BUFFER TRANSCONDUCTANCE vs. TEMPERATURE 1.9 1.8 LARGE-SIGNAL TRANSCONDUCTANCE 8 A 0 3.8V 6 B 3.6V 4 3.
PAGE 11
Quintuple/Triple-Output TFT LCD Power Supplies with Fault Protection and VCOM Buffer PIN MAX1997 MAX1998 4 — NAME FUNCTION FB1 Logic Linear-Regulator (REG 1) Feedback Input. FB1 regulates at 1.25V nominal. Connect FB1 to the center tap of a resistive voltage-divider between the REG 1 output and the analog ground (GND) to set the output voltage. Place the resistive voltage-divider close to the pin. 5 2 CT Sequence Timing Control Input. Connect a capacitor from this pin to GND.
PAGE 12
MAX1997/MAX1998 Quintuple/Triple-Output TFT LCD Power Supplies with Fault Protection and VCOM Buffer Pin Description (continued) PIN MAX1997 MAX1998 19 — 12 NAME FUNCTION DRV2 Gamma Linear-Regulator (REG 2) Base Drive. Open drain of an internal N-channel MOSFET. Connect DRV2 to the base of an external PNP linear regulator pass transistor. (See the Pass Transistor Selection section.) Main Step-Up Regulator Feedback Input.
PAGE 13
Quintuple/Triple-Output TFT LCD Power Supplies with Fault Protection and VCOM Buffer P1 C2 10µF 6.3V R1 10Ω C7 1000pF R2 51.1kΩ R24 150kΩ R4 43.2kΩ C8 100pF 27 R3 150kΩ 26 29 28 C1 0.47µF 32 30 31 R7 7.68kΩ LX OCN 3 R88 12.4kΩ C6 4.7µF 10V C9 0.01µF IN FB 20 PFLT SHDN VSOURCE 9V R8 1.21kΩ N1 ONDC C11 0.47µF FREQ 11 R10 2.2kΩ Q1 C5 4.7µF 10V D5 R9 1MΩ OCP DRVA C12 1µF DRV1 DRV2 19 R6 100kΩ Q2 VGAMMA 8.6V 4 FB1 C13 10µF R99 12.4kΩ 5 C16 0.1µF REF D6 12 C17 0.
PAGE 14
MAX1997/MAX1998 Quintuple/Triple-Output TFT LCD Power Supplies with Fault Protection and VCOM Buffer VIN CONTROL INPUTS VP VMAIN ONN ONP ON2 ONDC N SHDN DRVA VSOURCE IN UVLO AND GATE CONTROL SEQUENCE CONTROL GATE VC OCP CT OC OCN OVERCURRENT COMPARATOR VC DRV1 VLOGIC VMAIN LX REG 1 WITH SOFT-START AND FAULT COMPARATOR MAIN STEP-UP REGULATOR WITH SOFT-START AND FAULT COMPARATOR FB1 MAX1997 ONLY FB PGND CONTROL BLOCK VSOURCE DRV2 VGAMMA REG 2 WITH SOFT-START AND FAULT COMPARATOR VP FB
PAGE 15
Quintuple/Triple-Output TFT LCD Power Supplies with Fault Protection and VCOM Buffer MAX1997/MAX1998 Table 1. Selected Component List DESIGNATION C2, C13 DESCRIPTION 10µF, 6.3V X5R ceramic capacitors (1206), TDK C3216X5R0J106M C4, C5, C6 D1 4.7µF, 10V X7R ceramic capacitors (1210), Taiyo Yuden LMK352BJ475MF 1.0A, 30V Schottky diode (S-flat), Toshiba CRS02 D2, D3, D4 200mA, 25V dual-series Schottky diodes (SOT23), Fairchild BAT54S D5, D6 200mA, 75V diode (SOT23), Fairchild MMBD4148 L1 3.0µH, 1.
PAGE 16
MAX1997/MAX1998 Quintuple/Triple-Output TFT LCD Power Supplies with Fault Protection and VCOM Buffer FROM OSCILLATOR LX RESET DOMINANT S PGND R Q ILIM COMPARATOR VLIMIT CURRENT SENSE SLOPE_COMP ∑ FB TO FAULT LOGIC 1.0V REFOUT REFIN SOFT-START CLK REF Figure 3. Main Step-Up Converter Functional Diagram In addition, all outputs are monitored for fault conditions that last longer than the fault timer period.
PAGE 17
Quintuple/Triple-Output TFT LCD Power Supplies with Fault Protection and VCOM Buffer DRVP NPN CASCODE TRANSISTOR VN PNP PASS TRANSISTOR DRVN VG_ON FBP PNP CASCODE TRANSISTOR NPN PASS TRANSISTOR VG_OFF FBN REF Figure 4. Using Cascode NPN for Output Voltages > 28V Positive Linear-Regulator Controller, REG P The positive linear-regulator controller is an analog gain block with an open-drain N-channel output. It drives an external PNP pass transistor with a 6.8kΩ base-to-emitter resistor (Figure 1).
PAGE 18
MAX1997/MAX1998 Quintuple/Triple-Output TFT LCD Power Supplies with Fault Protection and VCOM Buffer VIN IN INPUT CAP VREF 2 GATE EXTERNAL PFET INDUCTOR INPUT CAP 10µA GATE ENABLE Figure 6. External P-Channel MOSFET Input Switch Control Linear-Regulator Controller REG 2 (MAX1997 Only) The linear-regulator controller REG 2 is an analog gain block with an open-drain N-channel output. It drives an external PNP pass transistor with a 2.2kΩ base-to-emitter resistor (Figure 1).
PAGE 19
Quintuple/Triple-Output TFT LCD Power Supplies with Fault Protection and VCOM Buffer Power-Up Sequencing and Inrush Current Control Once SHDN is pulled high and the input voltage on IN exceeds the rising input UVLO threshold (2.7V typ), the reference turns on. With a 0.22µF REF bypass capacitor, the reference reaches its regulation voltage of 1.25V in approximately 1ms. When the reference voltage is ready, the MAX1997/MAX1998 enable the oscillator and fault detector.
PAGE 20
MAX1997/MAX1998 Quintuple/Triple-Output TFT LCD Power Supplies with Fault Protection and VCOM Buffer Table 3. Fault Timer Duration FREQ PIN PFLT PIN* FAULT TIMER DURATION (CLOCK CYCLES) FAULT TIMER DURATION (ms) 13 21.8 GND GND 2 Unconnected GND 214 21.8 IN GND 215 21.8 GND Unconnected 214 43.6 Unconnected Unconnected 2 15 43.6 IN Unconnected 216 43.6 GND IN** 215 87.2 Unconnected IN** 2 16 87.2 IN IN** 217 87.2 *For MAX1997 only.
PAGE 21
Quintuple/Triple-Output TFT LCD Power Supplies with Fault Protection and VCOM Buffer MAX1997/MAX1998 ONDC SHDN UVLO R GATE Q REFERENCE READY THERMAL FAULT S FAULT LATCH GATE READY OVERCURRENT FAULT VCT > VON2 REG 2 FAULT REG 1 FAULT ENABLES REG 1 LINEAR-REGULATOR ENABLES REG 2 LINEAR-REGULATOR ENABLES STEP-UP REGULATOR REG P FAULT STEP-UP REGULATOR FAULT REG N FAULT fOSC/128 FREQ PFLT VCT > VONP R RIPPLE COUNTER CLK ENABLES REG P LINEAR-REGULATOR STEP-UP REGULATOR SOFT-START DONE FAULT TIME
PAGE 22
MAX1997/MAX1998 Quintuple/Triple-Output TFT LCD Power Supplies with Fault Protection and VCOM Buffer Output Capacitor The output capacitor affects the circuit’s stability and output-voltage ripple. A 15µF ceramic capacitor works well in most 1.5MHz applications. Depending on the output capacitor chosen, feedback compensation may be required or desirable to increase the loop phase margin or increase the loop bandwidth for transient response. (See the Feedback Compensation section.
PAGE 23
Quintuple/Triple-Output TFT LCD Power Supplies with Fault Protection and VCOM Buffer At high frequencies, R9 is effectively in parallel with R7, determining the amount of added high-frequency gain. If R9 is very large, there is no added gain and as R9 approaches zero, the added gain approaches the inverse of the feedback divider’s attenuation. A typical value for R9 is greater than half of R7. The value of C9 determines the frequency placement of the zero and pole.
PAGE 24
MAX1997/MAX1998 Quintuple/Triple-Output TFT LCD Power Supplies with Fault Protection and VCOM Buffer If the comparator and resistors are ideal, the threshold is at the current where both inputs are equal: R3 R5 VIN × = VIN - IL(MAX) × RDS(MAX) × R2 + R 3 R4 + R5 P1 RDS(ON) ( VIN R2 R4 IL(MAX) is the average inductor current at maximum load condition and minimum input voltage, and is given by: OCP 100pF IL(MAX) = OCN OC COMP R3 R5 Figure 10.
PAGE 25
Quintuple/Triple-Output TFT LCD Power Supplies with Fault Protection and VCOM Buffer R 3 × (1 + ε) + R2 × (1 + ε) + R 3 × (1 + ε) 5mV = (VIN(MIN) - IL(MAX) × RDS(MAX) ) × VIN(MIN) × R5 × (1 + ε) R4 × (1 + ε) + R5 × (1 + ε) where VIN(MIN) is the minimum expected value of the input voltage, ε is the tolerance of the resistors, and 5mV is the worst-case input offset voltage of the comparator.
PAGE 26
MAX1997/MAX1998 Quintuple/Triple-Output TFT LCD Power Supplies with Fault Protection and VCOM Buffer Flying Capacitors Increasing the flying capacitor (CX) value 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 limit the source impedance. A 0.1µF ceramic capacitor works well in most low-current applications.
PAGE 27
Quintuple/Triple-Output TFT LCD Power Supplies with Fault Protection and VCOM Buffer The transconductance amplifier regulates the output voltage by controlling the pass transistor’s base current. The total DC loop gain is approximately: 3) Next, calculate the pole set by the transistor’s input capacitance, the transistor’s input resistance, and the base-to-emitter pullup resistor: f POLE(CIN) = RBE = VBE IBIAS The output capacitor and the load resistance create the dominant pole in the system.
PAGE 28
MAX1997/MAX1998 Quintuple/Triple-Output TFT LCD Power Supplies with Fault Protection and VCOM Buffer VCOM BUFFER VGAMMA RB 0.47µF TO TFT LCD BACKPLANE CB Figure 11. Optimizing VCOM Buffer Drive Current L D VIN VOUT CIN COUT Figure 12. High-Current Loops of Step-Up Regulator VP VIN A capacitor connected between the regulator output and the feedback node can improve the transient response and reduce the noise coupled into the feedback loop (Figure 1).
PAGE 29
Quintuple/Triple-Output TFT LCD Power Supplies with Fault Protection and VCOM Buffer VN VIN 3.3V TO 5V VMAIN +9V IN LX FB GATE OCN OCP SWITCH CONTROL STEP-UP REGULATOR OCN PGND MAX1997 MAX1998 REF REF GND Figure 14. Disabling Input MOSFET Switch Applications Information PC Board Layout and Grounding Careful PC board layout is extremely important for proper operation.
PAGE 30
Quintuple/Triple-Output TFT LCD Power Supplies with Fault Protection and VCOM Buffer MAX1997/MAX1998 Pin Configurations (continued) Chip Information SHDN FREQ ONDC IN PFLT GATE OCP OCN 32 31 30 29 28 27 26 25 TRANSISTOR COUNT: 4704 TOP VIEW TGNDB 1 24 TGNDA PGND 2 23 LX DRV1 3 22 DRVP FB1 4 21 FBP CT 5 20 FB ONN 6 19 DRV2 ONP 7 18 FB2 ON2 8 17 FBPB 11 12 13 14 15 16 DRVA REF GND FBNB OUTB VDDB 9 10 DRVN FBN MAX1997 THIN QFN 5mm × 5mm 30
PAGE 31
Quintuple/Triple-Output TFT LCD Power Supplies with Fault Protection and VCOM Buffer b CL 0.10 M C A B D2/2 D/2 PIN # 1 I.D. QFN THIN 5x5x0.8 .EPS D2 0.15 C A D k 0.15 C B PIN # 1 I.D. 0.35x45 E/2 E2/2 CL (NE-1) X e E E2 k L DETAIL A e (ND-1) X e CL CL L L e e 0.10 C A C 0.08 C A1 A3 PROPRIETARY INFORMATION TITLE: PACKAGE OUTLINE 16, 20, 28, 32L, QFN THIN, 5x5x0.8 mm APPROVAL COMMON DIMENSIONS DOCUMENT CONTROL NO. REV. 21-0140 C 1 2 EXPOSED PAD VARIATIONS NOTES: 1.