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General Description

The MAX1530/MAX1531 multiple-output power-supply

controllers generate all the supply rails for thin-film tran-

sistor (TFT) liquid-crystal display (LCD) monitors. Both

devices include a high-efficiency, fixed-frequency,

step-down regulator. The low-cost, all N-channel, syn-

chronous topology enables operation with efficiency as

high as 93%. High-frequency operation allows the use

of small inductors and capacitors, resulting in a com-

pact solution. The MAX1530 includes three linear regu-

lator controllers and the MAX1531 includes five linear

regulator controllers for supplying logic and LCD bias

voltages. A programmable startup sequence enables

easy control of the regulators.

The MAX1530/MAX1531 include soft-start functions to

limit inrush current during startup. An internal step-

down converter current-limit function and a versatile

overcurrent shutdown protect the power supplies against

fault conditions. The MAX1530/MAX1531 use a current-

mode control architecture, providing fast load transient

response and easy compensation. An internal linear

regulator provides MOSFET gate drive and can be

used to power small external loads.

The MAX1530/MAX1531 can operate from inputs as

high as 28V and are well suited for LCD monitor and TV

applications running directly from AC/DC wall adapters.

Both devices are available in a small (5mm x 5mm),

ultra-thin (0.8mm), 32-pin QFN package and operate

over the -40°C to +85°C temperature range.

Applications

LCD Monitors and TVs

Automotive LCDs

Features

♦ 4.5V to 28V Input Voltage Range

♦ 250kHz/500kHz Current-Mode Step-Down Converter

Small Inductor/Capacitors

No Sense Resistor

♦ Three Positive Linear Regulator Controllers

One Positive and One Negative Additional

Controller (MAX1531)

Small Input and Output Capacitors

♦ Timed Reset Output

♦ Uncommitted Overcurrent Protection (MAX1531)

♦ Soft-Start for All Regulators

♦ Programmable Input Undervoltage Comparator

♦ Programmable Startup Sequencing

MAX1530/MAX1531

Multiple-Output Power-Supply Controllers for

LCD Monitors

________________________________________________________________ Maxim Integrated Products 1

Ordering Information

RESET

GON

25V

GOFF

-9V

= 12V

ONL2

SOURCE

10V/500mA

GAMMA

9.7V

ONL5

ONL4

ONL3

SEQ

RSTIN

OUT

3.3V/1.5A

LOGIC

2.5V/500mA

OUT

DRV3

FBL3

FBL1

DRV1

BST

PGND

COMP

FBL2

DRV2

FBL5

DRV5

DRV4

FBL4

CSH

CSL

FREQ

ILIM

AGND

MAX1530

Minimal Operating Circuit

19-2866; Rev 0; 5/03

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.

Pin Configuration appears at end of data sheet.

PART TEMP RANGE PIN-PACKAGE

MAX1530ETJ -40°C to +85°C 32 Thin QFN

MAX1531ETJ -40°C to +85°C 32 Thin QFN

Summary of content (33 pages)

PAGE 1
9-2866; Rev 0; 5/03 Multiple-Output Power-Supply Controllers for LCD Monitors Features ♦ 4.
PAGE 2
MAX1530/MAX1531 Multiple-Output Power-Supply Controllers for LCD Monitors ABSOLUTE MAXIMUM RATINGS IN, DRV1, DRV2, DRV3, DRV4, CSH, CSL to AGND .....................................................-0.3V to +30V DRV5 to VL .............................................................-28V to +0.3V CSH to CSL ..............................................................-0.3V to +6V VL to AGND ..............................................................-0.3V to +6V PGND to AGND..............................
PAGE 3
Multiple-Output Power-Supply Controllers for LCD Monitors (Circuit of Figure 1, VIN = 12V, VEN = VSEQ = 5V, TA = 0°C to +85°C, unless otherwise noted. Typical values are at TA = +25°C.) PARAMETER Comparator Bandwidth CONDITIONS MIN For EN, FB, FBL_ TYP MAX 10 UNITS kHz Duration to Trigger Fault Latch For FB, FBL_ 51 64 77 ms Overcurrent Protection Threshold (VCSH - VCSL) 270 300 330 mV Overcurrent Sense CommonMode Range VCSH, VCSL 2.7 28.0 V CSH Input Current VCSH = 2.
PAGE 4
MAX1530/MAX1531 Multiple-Output Power-Supply Controllers for LCD Monitors ELECTRICAL CHARACTERISTICS (continued) (Circuit of Figure 1, VIN = 12V, VEN = VSEQ = 5V, TA = 0°C to +85°C, unless otherwise noted. Typical values are at TA = +25°C.) PARAMETER CONDITIONS MIN TYP MAX UNITS SOFT-START Step Size Period Measured at FB 1.
PAGE 5
Multiple-Output Power-Supply Controllers for LCD Monitors (Circuit of Figure 1, VIN = 12V, VEN = VSEQ = 5V, TA = 0°C to +85°C, unless otherwise noted. Typical values are at TA = +25°C.) PARAMETER Soft-Start Period CONDITIONS MIN TYP FREQ = GND 1024 / fOSC FREQ = VL 2048 / fOSC MAX UNITS s POSITIVE LINEAR REGULATOR (LR4) FBL4 Regulation Voltage VDRV4 = 5V, IDRV4 = 500µA FBL4 Input Bias Current VFBL4 = 1.
PAGE 6
MAX1530/MAX1531 Multiple-Output Power-Supply Controllers for LCD Monitors ELECTRICAL CHARACTERISTICS (continued) (Circuit of Figure 1, VIN = 12V, VEN = VSEQ = 5V, TA = -40°C to +85°C, unless otherwise noted.) (Note 3) PARAMETER CONDITIONS MIN TYP MAX UNITS CONTROL AND SEQUENCE ONL_ Input Threshold ONL_ rising, 25mV hysteresis 1.201 1.275 V EN Input Threshold EN rising, 5% hysteresis 1.201 1.
PAGE 7
Multiple-Output Power-Supply Controllers for LCD Monitors MAX1530/MAX1531 Typical Operating Characteristics (Circuit of Figure 1; including R5, R6, and D2; TA = +25°C, unless otherwise noted.) STEP-DOWN LOAD REGULATION VIN = 12V 80 VIN = 20V 70 60 MAX1530 toc02 520 515 -0.04 510 FREQUENCY (kHz) EFFICIENCY (%) 90 OUTPUT-VOLTAGE ERROR (%) MAX1530 toc01 fSW = 500kHz SWITCHING FREQUENCY vs. LOAD CURRENT 0 MAX1530 toc03 STEP-DOWN EFFICIENCY vs. LOAD CURRENT 100 -0.08 -0.
PAGE 8
Typical Operating Characteristics (continued) (Circuit of Figure 1; including R5, R6, and D2; TA = +25°C, unless otherwise noted.) LR1 NORMALIZED LOAD REGULATION -0.5 -1.0 -1.5 LR1 LOAD TRANSIENT MAX1530 toc12 MAX1530 toc11 MAX1530 toc10 LR1 NORMALIZED LINE REGULATION 0.2 OUTPUT-VOLTAGE ERROR (%) VOLTAGE ERROR (%) 0 0 A 2.5V -0.2 -0.4 -0.6 B -0.8 0mA 200mA LOAD CURRENT -2.0 -1.0 200 300 400 500 2 3 LOAD CURRENT (mA) LR2/LR3 BASE CURRENT vs.
PAGE 9
Multiple-Output Power-Supply Controllers for LCD Monitors LR4 NORMALIZED LINE REGULATION LR4 NORMALIZED LOAD REGULATION MAX1530 toc21 -0.2 -0.3 -0.4 MAX1530 toc20 OUTPUT-VOLTAGE ERROR (%) 0 A -0.2 10V -0.4 -0.6 B -0.8 -0.5 0mA 200mA LOAD CURRENT -1.
PAGE 10
Typical Operating Characteristics (continued) (Circuit of Figure 1; including R5, R6, and D2; TA = +25°C, unless otherwise noted.) LR5 NORMALIZED LOAD REGULATION LR5 NORMALIZED LINE REGULATION -0.4 -0.6 -0.8 MAX1530 toc26 -0.2 1.0 20mA LOAD CURRENT OUTPUT-VOLTAGE ERROR (%) MAX1530 toc25 0 VOLTAGE ERROR (%) MAX1530/MAX1531 Multiple-Output Power-Supply Controllers for LCD Monitors 0.8 0.6 0.4 0.2 0 -1.0 -0.
PAGE 11
Multiple-Output Power-Supply Controllers for LCD Monitors PIN MAX1530 MAX1531 NAME FUNCTION 12 12 RESET Open-Drain Reset Output. RESET asserts low when the monitored voltage is less than the reset trip threshold. RESET goes to a high-impedance state only after the monitored voltage remains above the reset trip threshold for the duration of the reset timeout period.
PAGE 12
MAX1530/MAX1531 Multiple-Output Power-Supply Controllers for LCD Monitors Pin Description (continued) PIN NAME FUNCTION MAX1530 MAX1531 23 23 DH High-Side Gate Driver Output. DH drives the main switch of the step-down regulator. DH swings from LX to BST. 24 24 BST Step-Down Regulator Boostrap Capacitor Connection for High-Side Gate Driver. Connect a 0.1µF ceramic capacitor from BST to LX. 25 25 SEQ Sequence Control Input for LR2, LR3, LR4, and LR5.
PAGE 13
Multiple-Output Power-Supply Controllers for LCD Monitors PIN NAME FUNCTION MAX1530 MAX1531 — 7 FBL4 Source Drive Linear Regulator (LR4) Feedback Input. FBL4 regulates at 1.245V nominal. Connect FBL4 to the center tap of a resistive voltage-divider between the LR4 output and AGND to set the output voltage. Place the divider close to the FBL4 pin. — 8 DRV4 Source Drive Linear Regulator (LR4) Base Drive. Open drain of an internal N-channel MOSFET.
PAGE 14
MAX1530/MAX1531 Multiple-Output Power-Supply Controllers for LCD Monitors VIN = 12V C3 4.7µF 25V R3 124kΩ 1% R4 20.0kΩ 1% D1 C5 0.1µF R5* 10Ω 30 VL 5V/30mA 28 C4 1µF 26 EN IN VL DH 25 R7 100kΩ 12 16 R14 121kΩ 1% R15 68.1kΩ 1% R16 43.2kΩ 1% DL PGND ONL2 ONL3 MAX1531 DRV1 18 RSTIN 19 ONL5 FB ILIM C20 0.1µF 1 R18 68.1kΩ 1% 2 21 R8 6.8kΩ 32 Q1 VLOGIC 2.5V/500mA 14 13 R12 300kΩ 15 C2, OPEN D4 C8 0.1µF R13 150kΩ C14 0.1µF 4 C6 0.1µF FBL3 3 8 C15 0.1µF R24 6.
PAGE 15
Multiple-Output Power-Supply Controllers for LCD Monitors MAX1530/MAX1531 VIN = 12V C3 4.7µF 25V D1 R3 124kΩ 1% R4 20.0kΩ 1% C5 0.1µF R5* 10Ω IN 24 30 EN IN VL DH 27 C1 1µF VL 5V/30mA 28 C4 1µF 26 25 R7 100kΩ 12 16 5 6 7 8 DL ONL2 MAX1530 PGND DRV1 20 1 2 N.C. RSTIN N.C. N.C. FB D2* R2 10.7kΩ 1% C22 2.2µF R8 6.8kΩ 32 Q1 R10 10kΩ 1% 11 VLOGIC 2.5V/500mA R9 10kΩ 1% C9 10µF 6.3V 14 VL C10 470pF R11 100kΩ R12 300kΩ C2, OPEN 15 DRV2 VIN C21 2.2µF R24 6.
PAGE 16
MAX1530/MAX1531 Multiple-Output Power-Supply Controllers for LCD Monitors Table 1. Selected Component List DESIGNATION C3 C7 22µF, 6.3V X7R ceramic capacitor TDK C3216X7R0J226M C9 10µF, 6.3V X5R ceramic capacitor TDK C2012X5R0J106M C12, C19* DESIGNATION DESCRIPTION 4.7µF, 25V X7R ceramic capacitor (1210) TDK C3225X7R1E475K D3*, D4*, D5* C21, C22 D1, D6* L1 10µH, 2.3A (DC) inductor Sumida CDR7D28MN-100 N1 2.5A, 30V dual N-channel MOSFET (6-pin Super SOT) Fairchild FDC6561AN 0.
PAGE 17
Multiple-Output Power-Supply Controllers for LCD Monitors OSC VREF REF MAX1530/MAX1531 THERMAL FREQ EN RSTIN RESET MAX1531 IN VLOK VL VL TIMER GND CLOCK SLOPE HIGH-SIDE DRIVER IN COMP COMP STEP-DOWN CONTROLLER FB FB DH LX LX ILIM ILIM BST DH VL DL PGND SS DONE DC-DC EN FLTM DL LOW-SIDE DRIVER PGND DRV3 ONL2 ONL3 ONL4 ONL5 SEQ ON2 ON3 ON4 ON5 SEQUENCE SOFTSTART VREF FBL3 FLTM SEQ DRV1 FLT3 LDO3EN VREF LR3 0.
PAGE 18
MAX1530/MAX1531 Multiple-Output Power-Supply Controllers for LCD Monitors CURRENT SENSE AND CURRENT LIMIT ∑ SLOPE SS DONE IN DC-DC EN VREF SOFTSTART R Q DH S Q DL GM FB PWM COMP COMP CLOCK CURRENT LIMIT ILIM LX PGND FAULT COMPARATOR FLTM 0.9VREF During the second half of the cycle, the high-side MOSFET turns off and the low-side N-channel MOSFET turns on. Now the inductor releases the stored energy as its current ramps down, providing current to the output.
PAGE 19
Multiple-Output Power-Supply Controllers for LCD Monitors MOSFET Gate Drivers (DH, DL) The DH and DL drivers are optimized for driving moderate-size high-side and low-side MOSFETs. Adaptive dead-time circuits monitor the DL and DH drivers and prevent either FET from turning on until the other is fully off. This algorithm allows operation without shootthrough with a wide range of MOSFETs, minimizing delays and maintaining efficiency.
PAGE 20
MAX1530/MAX1531 Multiple-Output Power-Supply Controllers for LCD Monitors LR2 is typically used to generate the TFT LCD gamma reference voltage, which is usually 0.3V below the source drive supply voltage. LR2 is enabled when the step-down regulator is enabled and the voltage on ONL2 exceeds ONL2 input threshold (1.238V typ). (See the Startup Sequence (ONL_,SEQ) section.) Each time it is enabled, the controller goes through a soft-start routine that ramps up its internal reference DAC.
PAGE 21
Multiple-Output Power-Supply Controllers for LCD Monitors EN > 1.24V AND VL > 3.5V MAX1530/MAX1531 loads. For example, when switched at 500kHz, large MOSFETs with a total of 40nC total gate charge would require 40nC × 500kHz, which is approximately 20mA. SEQ = HIGH On/Off Control (EN) The EN pin has an accurate 1.238V (typ) rising threshold with 5% hysteresis. The accurate threshold allows it to be used to monitor the input voltage or other analog signals of interest.
PAGE 22
MAX1530/MAX1531 Multiple-Output Power-Supply Controllers for LCD Monitors total delay. Because of the 6µA current flowing through R1 (51kΩ), the voltage on ONLc is 0.31V greater than the voltage on ONLd and it crosses the 1.238V threshold and enables its LR_ controller about 4ms before ONLd’s controller. Similarly, the 4µA current through R2 (75kΩ) and the 2µA current through R3 (150kΩ) cause their LR_ controllers to each start about 4ms before the next one.
PAGE 23
Multiple-Output Power-Supply Controllers for LCD Monitors L= VOUT × (VIN − VOUT ) VIN × fSW × ILOAD(MAX) × LIR where ILOAD(MAX) is the maximum DC load current, and the switching frequency fSW is 500kHz when FREQ is tied to VL, and 250kHz when FREQ is tied to AGND. The exact inductor value is not critical and can be adjusted to make trade-offs among size, cost, and efficiency.
PAGE 24
MAX1530/MAX1531 Multiple-Output Power-Supply Controllers for LCD Monitors VL and AGND at ILIM. The threshold is approximately 1/5th the voltage on ILIM over a range of 0.25V to 3V: IVALLEY × RDS(ON)_ HOT < 0.2 × VILIM × (1− K) the voltage drop across the capacitor’s ESR caused by the current into and out of the capacitor: VRIPPLE = VRIPPLE(ESR) + VRIPPLE(C) VRIPPLE(ESR) = IRIPPLE × RESR K is the accuracy of the current-limit threshold, which is 20% when the threshold is 250mV.
PAGE 25
Multiple-Output Power-Supply Controllers for LCD Monitors  A VCS × RDS(ON) × ∆ILOAD  VOUT ×    + ∆SCUNDER  VUNDER _ AC = VFB × RCOMP × gm Use the following to calculate the slope compensation change during the sag:   V ∆SCUNDER = 437.5mV ×  DUNDER - OUT  VIN   where DUNDER is the duty cycle at the valley of the sag, which is usually 50%. The actual undershoot is always equal to or bigger than the worst of VESR_STEP, VSAG_LC, and VUNDER_AC.
PAGE 26
MAX1530/MAX1531 Multiple-Output Power-Supply Controllers for LCD Monitors Current-mode control has the effect of splitting the complex pole pair of the output LC filter into a single low-frequency pole and a single high-frequency pole.
PAGE 27
Multiple-Output Power-Supply Controllers for LCD Monitors fCROSSOVER = gm × VFB × R11 2π × A VCS × VOUT(SET) × COUT × RDS(ON) Change one or both of these circuit parameters to obtain the desired crossover. Recalculate ADC and repeat steps 1 to 3 after making the changes. 4) If fPOLE(HIGH) is less than the crossover frequency, cancel the pole with a feed-forward zero.
PAGE 28
MAX1530/MAX1531 Multiple-Output Power-Supply Controllers for LCD Monitors Because R11 is less than 100kΩ, use 100kΩ for R11 and recalculate C10 as (step 3): C10 ≈ 1 = 370pF 2π × 4.3kHz × 100kΩ Use the standard value of 470pF for C10 and recalculate the crossover frequency as: fCROSSOVER ≈ 100µS × 4180 = 70.8kHz 2π × 470pF × 2000 Since the crossover frequency is less than 1/5th the switching frequency, 470pF is an acceptable value for C10.
PAGE 29
Multiple-Output Power-Supply Controllers for LCD Monitors VCX > N x VIN where N is the stage number in which the flying capacitor appears, and VIN is the input voltage of the stepdown regulator. Charge-Pump Output Capacitors Increasing the output capacitance or decreasing the ESR reduces the charge pump output ripple voltage and the peak-to-peak transient voltage. With ceramic capacitors, the output voltage ripple is dominated by the capacitance value.
PAGE 30
MAX1530/MAX1531 Multiple-Output Power-Supply Controllers for LCD Monitors amount of ripple after the PC board layout has been optimized, consider increasing output capacitance. Adding more capacitance does not eliminate the ripple, but proportionally reduces the amplitude of the ripple. If increasing the output capacitance is not desirable because of space or cost concerns, then consider slowing the turn-on of the step-down DC-to-DC MOSFETs.
PAGE 31
Multiple-Output Power-Supply Controllers for LCD Monitors 1 2πCFBL1(R9 || R10) 1 fPOLE(FBL2) = 2πCFBL2 (R18 || R19) 1 fPOLE(FBL3) = 2πCFBL3 (R25 || R26) 1 fPOLE(FBL4) = and 2πCFBL4 (R22 || R23) 1 fPOLE(FBL5) = 2πCFBL5 (R28 || R29) fPOLE(FBL1) = 5) Next, calculate the zero caused by the output capacitor’s ESR: fESR _ ZERO = 1 2πCLRRESR where RESR is the equivalent series resistance of CLR.
PAGE 32
Multiple-Output Power-Supply Controllers for LCD Monitors DRV1 FBL1 EN AGND VL IN FREQ SEQ 32 31 30 29 28 27 26 25 1 24 BST FBL2 2 23 DH FBL3 3 22 LX DRV3 4 21 DL MAX1530 MAX1531 14 15 16 ILIM ONL2 ONL3 13 ONL4* 17 FB 18 8 COMP 7 12 FBL4* DRV4* 11 ONL5* RSTIN PGND 19 RESET 20 6 9 5 CSL* 10 CSH* FBL5* Chip Information TRANSISTOR COUNT: 5600 PROCESS: BiCMOS DRV2 DRV5* MAX1530/MAX1531 Pin Configuration * = N.C.
PAGE 33
Multiple-Output Power-Supply Controllers for LCD Monitors b CL 0.10 M C A B D2/2 D/2 PIN # 1 I.D. QFN THIN.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.