Datasheet

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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, synchronous

topology enables operation with efficiency as high as 93%.

High-frequency operation allows the use of small induc-

tors and capacitors, resulting in a compact solution. The

MAX1530 includes three linear regulator 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 stepdown

converter current-limit function and a versatile overcurrent

shutdown protect the power supplies against fault condi-

tions. The MAX1530/MAX1531 use a currentmode 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

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

Pin Configuration appears at end of data sheet.

+Denotes a lead(Pb)-free/RoHS-compliant package.

T = Tape and reel.

*EP = Exposed pad.

PART TEMP RANGE PIN-PACKAGE

MAX1530ETJ+ -40°C to +125°C 32 TQFN-EP*

MAX1530ETJ+T -40°C to +125°C 32 TQFN-EP*

MAX1531ETJ+ -40°C to +125°C 32 TQFN-EP*

MAX1531ETJ+T -40°C to +125°C 32 TQFN-EP*

RESET

GOFF

-9V

= 12V

ONL2

ONL5

ONL4

ONL3

SEQ

RSTIN

OUT

3.3V/1.5A

DRV3

FBL3

FBL1

DRV1

BST

PGND

COMP

FBL2

DRV2

FBL5

DRV5

DRV4

FBL4

CSH

CSL

FREQ

ILIM

AGND

MAX1530

GON

25V

LOGIC

25V/500mA

OUT

SOURCE

10V/500mA

GAMMA

-9.7V

MAX1530/MAX1531 Multiple-Output Power-Supply

Controllers for LCD Monitors

19-2866; Rev 3; 3/14

Minimal Operating Circuit

Ordering Information

EVALUATION KIT AVAILABLE

Summary of content (33 pages)

PAGE 1
EVALUATION KIT AVAILABLE MAX1530/MAX1531 Multiple-Output Power-Supply Controllers for LCD Monitors 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, stepdown regulator. The low-cost, all N-channel, synchronous topology enables operation with efficiency as high as 93%.
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
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 Comparator Bandwidth For EN, FB, FBL_ Duration to Trigger Fault Latch For FB, FBL_ 51 64 Overcurrent Protection Threshold (VCSH - VCSL) 270 300 Overcurrent Sense Common-Mode Range VCSH, VCSL 2.7 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 MAX TYP UNITS SOFT-START Step Size Period Measured at FB 1.
PAGE 5
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 Soft-Start Period MIN MAX TYP FREQ = GND 1024 / fOSC FREQ = VL 2048 / fOSC 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
MAX1530/MAX1531 Multiple-Output Power-Supply Controllers for LCD Monitors Typical Operating Characteristics (Circuit of Figure 1; including R5, R6, and D2; TA = +25°C, unless otherwise noted.) VIN = 12V VIN = 20V 70 60 SWITCHING FREQUENCY vs. LOAD CURRENT MAX1530 toc03 MAX1530 toc02 520 515 -0.04 FREQUENCY (kHz) EFFICIENCY (%) 90 OUTPUT-VOLTAGE ERROR (%) fSW = 500kHz 80 0 MAX1530 toc01 100 50 STEP-DOWN LOAD REGULATION STEP-DOWN EFFICIENCY vs. LOAD CURRENT -0.
PAGE 8
MAX1530/MAX1531 Multiple-Output Power-Supply Controllers for LCD Monitors Typical Operating Characteristics (continued) (Circuit of Figure 1; including R5, R6, and D2; TA = +25°C, unless otherwise noted.) -0.5 -1.0 -1.5 LR1 NORMALIZED LINE REGULATION 0.2 LR1 LOAD TRANSIENT MAX1530 toc12 MAX1530 toc11 MAX1530 toc10 LR1 NORMALIZED LOAD REGULATION OUTPUT-VOLTAGE ERROR (%) VOLTAGE ERROR (%) 0 0 A 2.5V -0.2 -0.4 -0.6 B -0.8 0mA 200mA LOAD CURRENT 100 200 300 400 -1.
PAGE 9
MAX1530/MAX1531 Multiple-Output Power-Supply Controllers for LCD Monitors Typical Operating Characteristics (continued) (Circuit of Figure 1; including R5, R6, and D2; TA = +25°C, unless otherwise noted.) LR4 NORMALIZED LOAD REGULATION -0.2 -0.3 -0.4 -0.5 MAX1530 toc20 OUTPUT-VOLTAGE ERROR (%) VOLTAGE ERROR (%) -0.1 LR4 NORMALIZED LINE REGULATION 0.2 MAX1530 toc19 0 0 -0.2 -0.4 -0.6 -0.8 200mA LOAD CURRENT -0.6 0 100 200 300 400 -1.
PAGE 10
MAX1530/MAX1531 Multiple-Output Power-Supply Controllers for LCD Monitors Typical Operating Characteristics (continued) (Circuit of Figure 1; including R5, R6, and D2; TA = +25°C, unless otherwise noted.) MAX1530 toc25 -0.4 -0.6 -0.8 -1.0 0 10 20 30 40 50 LR5 NORMALIZED LINE REGULATION 20mA LOAD CURRENT OUTPUT-VOLTAGE ERROR (%) VOLTAGE ERROR (%) -0.2 1.0 MAX1530 toc26 LR5 NORMALIZED LOAD REGULATION 0 0.8 0.6 0.4 0.2 0 -0.
PAGE 11
MAX1530/MAX1531 Multiple-Output Power-Supply Controllers for LCD Monitors Pin Description (continued) 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
MAX1530/MAX1531 Multiple-Output Power-Supply Controllers for LCD Monitors Pin Description (continued) PIN NAME FUNCTION 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% R5* 10Ω R4 20.0kΩ 1% IN 24 30 VL 5V/30mA 28 C4 1µF 26 25 R7 100kΩ 12 16 R14 121kΩ 1% 17 18 R16 43.2kΩ 1% 19 C11 0.1µF VIN EN BST IN DH VL FREQ LX SEQ DL 27 23 N1-A ONL4 ONL5 PGND MAX1531 DRV1 22 R6* 10Ω 21 C7 22µF 6.3V N1-B 20 R8 6.8kΩ 29 32 RSTIN COMP R2 10.7kΩ 1% C22 2.2µF Q1 VLOGIC 2.5V/500mA C9 10µF 6.
PAGE 15
MAX1530/MAX1531 Multiple-Output Power-Supply Controllers for LCD Monitors VIN = 12V C3 4.7µF 25V R3 124kΩ 1% R4 20.0kΩ 1% R5* 10Ω 30 28 C4 1µF 26 25 R7 100kΩ R14 121kΩ 1% 12 17 5 6 7 8 VGAMMA 9.7V/50mA EN IN VL DH FREQ LX SEQ ONL2 MAX1530 C12 0.47µF PGND ONL3 N.C. N.C. DRV1 C1 1µF 23 22 21 VOUT 3.3V/1.5A L1 10µH C7 22µF 6.3V N1-B 20 32 N.C. DRV2 FBL2 10 N.C. Q1 VLOGIC 2.5V/500mA C9 10µF 6.
PAGE 16
MAX1530/MAX1531 Multiple-Output Power-Supply Controllers for LCD Monitors Table 1. Selected Component List DESIGNATION DESCRIPTION DESIGNATION DESCRIPTION C3 4.7µF, 25V X7R ceramic capacitor (1210) TDK C3225X7R1E475K D3*, D4*, D5* C7 22µF, 6.3V X7R ceramic capacitor TDK C3216X7R0J226M L1 10µH, 2.3A (DC) inductor Sumida CDR7D28MN-100 C9 10µF, 6.3V X5R ceramic capacitor TDK C2012X5R0J106M N1 2.
PAGE 17
MAX1530/MAX1531 Multiple-Output Power-Supply Controllers for LCD Monitors FREQ EN RSTIN RESET OSC VREF REF THERMAL MAX1531 IN VLOK VL VL TIMER GND COMP COMP FB FB ILIM ILIM CLOCK SLOPE LX DL DL FLT3 LDO3EN SOFTSTART PGND SOFTSTART FLTM SEQ VREF FBL3 LR3 0.9VREF DRV4 EN FAULT LOGIC LR1 0.
PAGE 18
MAX1530/MAX1531 Multiple-Output Power-Supply Controllers for LCD Monitors CURRENT SENSE AND CURRENT LIMIT SLOPE SS DONE DC-DC EN VREF FB SOFTSTART GM IN R Q DH S Q DL PWM COMP COMP CLOCK CURRENT LIMIT ILIM FAULT COMPARATOR 0.9VREF LX PGND FLTM Figure 4. Step-Down Controller Block Diagram extra windings coupled to the step-down converter inductor.
PAGE 19
MAX1530/MAX1531 The ILIM pin is a dual-mode input. When ILIM is connected to VL, a default low-side current limit of 250mV typ) is used. If ILIM is connected to a voltage between 250mV and 3V, the low-side current limit is typically 1/5th the ILIM voltage. The MAX1530/MAX1531s’ current limits are comparatively inaccurate, since the maximum load current is a function of the MOSFETs’ on-resistances and the inductor value, as well as the accuracy of the two thresholds.
PAGE 20
MAX1530/MAX1531 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. (See the Soft-Start section).
PAGE 21
MAX1530/MAX1531 Multiple-Output Power-Supply Controllers for LCD Monitors switched at 500kHz, large MOSFETs with a total of 40nC total gate charge would require 40nC × 500kHz, which is approximately 20mA. EN > 1.24V AND VL > 3.5V 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 the desired delay for the controller that starts last (ONLd). Using 0.1μF for C1 provides about 16ms 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
MAX1530/MAX1531 A good compromise between size and losses is typically found at a 30% ripple current to load current ratio (LIR = 0.3), which corresponds to a peak inductor current 1.15 times the DC load current: L= VOUT × (VIN − VOUT ) VIN × f SW × 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.
PAGE 24
MAX1530/MAX1531 Multiple-Output Power-Supply Controllers for LCD Monitors AGND at ILIM. The threshold is approximately 1/5th the voltage on ILIM over a range of 0.25V to 3V: I VALLEY × R DS(ON)_HOT < 0.2 × VILIM × (1 − K) K is the accuracy of the current-limit threshold, which is 20% when the threshold is 250mV. For example, Figure 1’s N1 MOSFET has a maximum RDS(ON) at room temperature of 145mΩ and an estimate of its maximum at our chosen maximum temperature of +85°C is 188mΩ.
PAGE 25
MAX1530/MAX1531 pensation resistor RCOMP, the FB regulation VFB, and the output voltage set point VOUT:  A VCS × R DS(ON) × ∆ILOAD  VOUT ×    +∆SC UNDER   VUNDER_AC = VFB × R COMP × g m Use the following to calculate the slope compensation change during the sag:   V ∆SC UNDER =437.5mV × D UNDER - OUT  V IN   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 lowfrequency pole and a single high-frequency pole.
PAGE 27
MAX1530/MAX1531 Multiple-Output Power-Supply Controllers for LCD Monitors pole, which also results in lower crossover frequency. The following formula gives the crossover frequency as a function the MOSFET RDS(ON) and the output capacitance: f CROSSOVER = g m × VFB × R11 2µ × A VCS × VOUT(SET) × C OUT × R DS(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.
PAGE 28
MAX1530/MAX1531 Because R11 is less than 100kΩ, use 100kΩ for R11 and recalculate C10 as (step 3): C10 ≈ Multiple-Output Power-Supply Controllers for LCD Monitors Charge Pumps Selecting the Number of Charge-Pump Stages For highest efficiency, always choose the lowest number 1 of charge-pump stages that meet the output requirement. 370pF = 2µ × 4.
PAGE 29
MAX1530/MAX1531 Multiple-Output Power-Supply Controllers for LCD Monitors Flying Capacitors Increasing the flying capacitor 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 30
MAX1530/MAX1531 coupling. If there is still an unacceptable 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
MAX1530/MAX1531 4) Next, calculate the pole set by each linear regulator’s feedback resistance and the capacitance (CFBL_) between FBL_ and AGND (approximately 5pF including stray capacitance): f POLE(FBL1) = f POLE(FBL2) = f POLE(FBL3) = f POLE(FBL4) = f POLE(FBL5) = 1 2µC FBL1(R9 || R10) 1 2µC FBL2 (R18 || R19) 1 2µC FBL3 (R25 || R26) 1 and 2µC FBL4 (R22 || R23) 1 2µC FBL5 (R28 || R29) 5) Next, calculate the zero caused by the output capacitor’s ESR: 1 f ESR_ZERO = 2µC LRR ESR where RESR is the equ
PAGE 32
MAX1530/MAX1531 Multiple-Output Power-Supply Controllers for LCD Monitors Pin Configuration DRV1 FBL1 EN AGND VL IN FREQ SEQ 31 30 29 28 27 26 25 + PROCESS: BiCMOS 32 TOP VIEW Chip Information Package Information DRV2 1 24 BST FBL2 2 23 DH For the latest package outline information and land patterns (footprints), go to www.maximintegrated.com/packages. Note that a “+”, “#”, or “-” in the package code indicates RoHS status only.
PAGE 33
MAX1530/MAX1531 Multiple-Output Power-Supply Controllers for LCD Monitors Revision History REVISION NUMBER REVISION DATE PAGES CHANGED 0 0 1 11/09 Changing an existing part to an automotive-qualified part (/V) 2 12/10 Removed the /V part from Ordering Information and minor edits 3 3/14 Removed automotive reference from the Applications section DESCRIPTION Initial release — 1, 13, 32, 33, 34 3, 4 1 For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-464