Datasheet

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General Description

The MAX15038 high-efficiency switching regulator

delivers up to 4A load current at output voltages from

0.6V to 90% of V

. The IC operates from 2.9V to 5.5V,

making it ideal for on-board point-of-load and postregu-

lation applications. Total output error is less than ±1%

over load, line, and temperature ranges.

The MAX15038 features fixed-frequency PWM mode

operation with a switching frequency range of 500kHz

to 2MHz set by an external resistor. The MAX15038

provides the option of operating in a skip mode to

improve light-load efficiency. High-frequency operation

allows for an all-ceramic capacitor design. The high

operating frequency also allows for small-size external

components.

The low-resistance on-chip nMOS switches ensure high

efficiency at heavy loads while minimizing critical induc-

tances, making the layout a much simpler task with

respect to discrete solutions. Following a simple layout

and footprint ensures first-pass success in new designs.

The MAX15038 comes with a high bandwidth (28MHz)

voltage-error amplifier. The voltage-mode control archi-

tecture and the voltage-error amplifier permit a type III

compensation scheme to be utilized to achieve maxi-

mum loop bandwidth, up to 20% of the switching fre-

quency. High loop bandwidth provides fast transient

response, resulting in less required output capacitance

and allowing for all-ceramic-capacitor designs.

The MAX15038 provides two three-state logic inputs to

select one of nine preset output voltages. The preset

output voltages allow customers to achieve ±1% out-

put-voltage accuracy without using expensive 0.1%

resistors. In addition, the output voltage can be set to

any customer value by either using two external resis-

tors at the feedback with a 0.6V internal reference or

applying an external reference voltage to the REFIN

input. The MAX15038 offers programmable soft-start

time using one capacitor to reduce input inrush current.

Applications

Server Power Supplies

POLs

ASIC/CPU/DSP Core and I/O Voltages

DDR Power Supplies

Base-Station Power Supplies

Telecom and Networking Power Supplies

RAID Control Power Supplies

Features

♦ Internal 31mΩ R

DS(ON)

High-Side and 24mΩ

DS(ON)

Low-Side MOSFETs

♦ Continuous 4A Output Current Over Temperature

♦ ±1% Output Accuracy Over Load, Line, and

Temperature

♦ Operates from 2.9V to 5.5V V

Supply

♦ Adjustable Output from 0.6V to (0.9 x V

)

♦ Soft-Start Reduces Inrush Supply Current

♦ 500kHz to 2MHz Adjustable Switching Frequency

♦ Compatible with Ceramic, Polymer, and

Electrolytic Output Capacitors

♦ Nine Preset and Adjustable Output Voltages

0.6V, 0.7V, 0.8V, 1.0V, 1.2V, 1.5V, 1.8V, 2.0V,

2.5V, and Adjustable

♦ Monotonic Startup for Safe-Start into Prebiased

Outputs

♦ Selectable Forced PWM or Skip Mode for Light

Load Efficiency

♦ Overcurrent and Overtemperature Protection

♦ Output Current Sink/Source Capable with Cycle-

by-Cycle Protection

♦ Open-Drain Power-Good Output

♦ Lead-Free, 4mm x 4mm, 24-Pin Thin QFN Package

MAX15038

4A, 2MHz Step-Down Regulator

with Integrated Switches

________________________________________________________________

Maxim Integrated Products

OUTPUT

1.8V, 4A

INPUT

2.9V TO 5.5V

BST

OUT

CTL2

CTL1

PGND

COMP

PWRGD

FREQ

REFIN

GND

MODE

MAX15038

Typical Operating Circuit

Ordering Information

19-4320; Rev 3; 12/10

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.

PART TEMP RANGE PIN-PACKAGE

MAX15038ETG+ -40°C to +85°C 24 Thin QFN-EP*

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

EP = Exposed pad.

Pin Configuration appears at end of data sheet.

EVALUATION KIT

AVAILABLE

Summary of content (19 pages)

PAGE 1
9-4320; Rev 3; 12/10 KIT ATION EVALU E L B AVAILA 4A, 2MHz Step-Down Regulator with Integrated Switches Features The MAX15038 high-efficiency switching regulator delivers up to 4A load current at output voltages from 0.6V to 90% of VIN. The IC operates from 2.9V to 5.5V, making it ideal for on-board point-of-load and postregulation applications. Total output error is less than ±1% over load, line, and temperature ranges.
PAGE 2
MAX15038 4A, 2MHz Step-Down Regulator with Integrated Switches ABSOLUTE MAXIMUM RATINGS IN, PWRGD to GND..................................................-0.3V to +6V VDD to GND ..................-0.3V to the lower of +4V or (VIN + 0.3V) COMP, FB, MODE, REFIN, CTL1, CTL2, SS, FREQ to GND ..........................................-0.3V to (VDD + 0.3V) OUT, EN to GND ......................................................-0.3V to +6V BST to LX..................................................................
PAGE 3
4A, 2MHz Step-Down Regulator with Integrated Switches (VIN = VEN = 5V, CVDD = 2.2μF, TA = TJ = -40°C to +85°C, typical values are at TA = +25°C, circuit of Figure 1, unless otherwise noted.) (Note 3) PARAMETER CONDITIONS MIN TYP MAX UNITS ERROR AMPLIFIER COMP Clamp Voltage, High VIN = 2.9V to 5V, VFB = 0.5V, VREFIN = 0.6V 2 COMP Clamp Voltage, Low VIN = 2.9V to 5V, VFB = 0.7V, VREFIN = 0.6V 0.7 V COMP Slew Rate VFB step from 0.5V to 0.7V in 10ns 1.
PAGE 4
MAX15038 4A, 2MHz Step-Down Regulator with Integrated Switches ELECTRICAL CHARACTERISTICS (continued) (VIN = VEN = 5V, CVDD = 2.2μF, TA = TJ = -40°C to +85°C, typical values are at TA = +25°C, circuit of Figure 1, unless otherwise noted.) (Note 3) PARAMETER LX Switching Frequency CONDITIONS VIN = 2.9V to 5V MIN TYP MAX RFREQ = 49.9kΩ 0.9 1 1.1 RFREQ = 23.6kΩ 1.8 2 2.2 Switching Frequency Range 500 LX Minimum Off-Time LX Maximum Duty Cycle RFREQ = 49.9kΩ LX Minimum Duty Cycle RFREQ = 49.
PAGE 5
4A, 2MHz Step-Down Regulator with Integrated Switches (VIN = VEN = 5V, CVDD = 2.2μF, TA = TJ = -40°C to +85°C, typical values are at TA = +25°C, circuit of Figure 1, unless otherwise noted.) (Note 3) PARAMETER CONDITIONS MIN TYP MAX UNITS FB Hiccup Threshold VFB falling 70 % VREFIN Hiccup Threshold Blanking Time VFB falling 28 μs Note 3: Specifications are 100% production tested at TA = +25°C. Limits over the operating temperature range are guaranteed by design.
PAGE 6
Typical Operating Characteristics (continued) (Typical values are VIN = VEN = 5V, VOUT = 1.8V, RFREQ = 49.9kΩ, IOUT = 4A, TA = +25°C, circuit of Figure 1, unless otherwise noted.
PAGE 7
4A, 2MHz Step-Down Regulator with Integrated Switches EXPOSED PAD TEMPERATURE vs. AMBIENT TEMPERATURE RMS INPUT CURRENT DURING SHORT CIRCUIT vs. INPUT VOLTAGE MAX15038 toc14 0.5 RMS INPUT CURRENT (A) 1V/div VOUT 0V 5A/div IOUT 0A IIN 1A/div 0.4 0.3 0.2 0.1 0A 90 80 70 60 50 40 4A LOAD 30 20 10 VOUT = 0V 0 MEASURED ON A MAX15038EVKIT 0 2.5 400μs/div 3.0 3.5 4.0 4.5 5.0 5.5 INPUT VOLTAGE (V) 0 20 40 60 80 100 AMBIENT TEMPERATURE (°C) FEEDBACK VOLTAGE vs.
PAGE 8
MAX15038 4A, 2MHz Step-Down Regulator with Integrated Switches Typical Operating Characteristics (continued) (Typical values are VIN = VEN = 5V, VOUT = 1.8V, RFREQ = 49.9kΩ, IOUT = 4A, TA = +25°C, circuit of Figure 1, unless otherwise noted.) STARTING INTO PREBIASED OUTPUT (MODE = VDD/2, VOUT = 2.5V, NO LOAD) STARTING INTO PREBIASED OUTPUT (MODE = VDD, VOUT = 2.
PAGE 9
4A, 2MHz Step-Down Regulator with Integrated Switches PIN NAME 1 MODE FUNCTION Functional MODE Selection Input. See the MODE Selection section for more information. 3.3V LDO Output. Supply input for the internal analog core. Connect a low-ESR, ceramic capacitor with a minimum value of 2.2μF from VDD to GND. 2 VDD 3 CTL1 4 CTL2 5 REFIN 6 SS 7 GND 8 COMP Voltage Error-Amplifier Output. Connect the necessary compensation network from COMP to FB and OUT.
PAGE 10
4A, 2MHz Step-Down Regulator with Integrated Switches MAX15038 Block Diagram VDD MAX15038 3.3V LDO UVLO CIRCUITRY SHUTDOWN CONTROL EN BST CURRENT-LIMIT COMPARATOR BST SWITCH IN BIAS GENERATOR VOLTAGE REFERENCE THERMAL SHUTDOWN CONTROL LOGIC LX IN SS SOFT-START PGND CURRENT-LIMIT COMPARATOR REFIN OUT ERROR AMPLIFIER 8kΩ PWM COMPARATOR MODE FB CTL1 CTL2 VID VOLTAGECONTROL CIRCUITRY FREQ 1VP-P OSCILLATOR COMP PWRGD SHDN FB COMP CLAMPS 0.
PAGE 11
4A, 2MHz Step-Down Regulator with Integrated Switches 2.2Ω INPUT 2.9V TO 5.5V OPTIONAL IN C6 22μF C7 0.1μF BST C15 1000pF C10 0.1μF L1 0.47μH MAX15038 OUTPUT 1.8V, 4A LX VDD C5 2.2μF OUT C8 22μF C3 560pF CTL2 C9 0.01μF R3 158Ω CTL1 PGND EN FB FREQ C2 1500pF R2 2.67kΩ REFIN R4 49.9kΩ SS C1 33pF C4 0.022μF COMP MODE GND VDD R1 20kΩ PWRGD Figure 1. 1MHz, All-Ceramic-Capacitor Design with VIN = 2.9V to 5.5V and VOUT = 1.
PAGE 12
MAX15038 4A, 2MHz Step-Down Regulator with Integrated Switches Controller Function The controller logic block is the central processor that determines the duty cycle of the high-side MOSFET under different line, load, and temperature conditions. Under normal operation, where the current-limit and temperature protection are not triggered, the controller logic block takes the output from the PWM comparator and generates the driver signals for both high-side and low-side MOSFETs.
PAGE 13
4A, 2MHz Step-Down Regulator with Integrated Switches Programming the Output Voltage (CTL1, CTL2) As shown in Table 1, the output voltage is pin programmable by the logic states of CTL1 and CTL2. CTL1 and CTL2 are trilevel inputs: VDD, unconnected, and GND. An 8.06kΩ resistor must be connected between VOUT and FB when CTL1 and CTL2 are connected to GND. The logic states of CTL1 and CTL2 should be programmed only before power-up. Once the part is enabled, CTL1 and CTL2 should not be changed.
PAGE 14
MAX15038 4A, 2MHz Step-Down Regulator with Integrated Switches where the output ripple due to output capacitance, ESR, and ESL is: VRIPPLE(C) = IP −P 8 x COUT x fS VRIPPLE(ESR) = IP −P x ESR I VRIPPLE(ESL) = P −P x ESL tON or: I VRIPPLE(ESL) = P −P x ESL tOFF or whichever is larger. The peak-to-peak inductor current (IP-P) is: IP −P = VIN − VOUT V x OUT fS × L VIN Use these equations for initial output capacitor selection. Determine final values by testing a prototype or an evaluation circuit.
PAGE 15
4A, 2MHz Step-Down Regulator with Integrated Switches f Z1_ EA = 1 2π × R1 × C1 f Z2 _ EA = 1 2π × R3 × C3 fP3 _ EA = 1 2π × R1 × C2 fP2 _ EA = 1 2π × R2 × C3 The above equations are based on the assumptions that C1 >> C2 and R3 >> R2 are true in most applications. Placements of these poles and zeros are determined by the frequencies of the double pole and ESR zero of the power transfer function. It is also a function of the desired close-loop bandwidth.
PAGE 16
MAX15038 4A, 2MHz Step-Down Regulator with Integrated Switches R2 = C O x ESR C3 Set the third compensation pole at 1/2 of the switching frequency. Calculate C2 as follows: 1 C2 = π × R1 × fS The above equations provide application compensation when the zero-cross frequency is significantly higher than the double-pole frequency. When the zero-cross frequency is near the double-pole frequency, the actual zero-cross frequency is higher than the calculated frequency.
PAGE 17
4A, 2MHz Step-Down Regulator with Integrated Switches Changing from skip mode to forced-PWM mode and vice-versa can be done at any time. The output capacitor should be large enough to limit the output-voltage overshoot/undershoot due to the settling times to reach different duty-cycle set points corresponding to forcedPWM mode and skip mode at light loads. Skip Mode Careful PCB layout is critical to achieve clean and stable operation.
PAGE 18
Pin Configuration Chip Information PGND PGND LX LX LX BST PROCESS: BiCMOS TOP VIEW 18 17 16 15 14 13 Package Information PGND 19 12 PWRGD PGND 20 11 FREQ IN 21 10 OUT MAX15038 IN 22 IN 23 3 4 5 6 REFIN SS 2 CTL2 1 CTL1 + VDD EN 24 EP MODE MAX15038 4A, 2MHz Step-Down Regulator with Integrated Switches 9 FB 8 COMP 7 GND For the latest package outline information and land patterns, go to www.maxim-ic.com/packages.
PAGE 19
4A, 2MHz Step-Down Regulator with Integrated Switches REVISION NUMBER REVISION DATE 0 10/08 1 12/09 2 5/10 3 12/10 DESCRIPTION PAGES CHANGED Initial release — Updated the Typical Operating Characteristics 5 Updated the Electrical Characteristics table, Table 1, and updated the Compensation Design section Corrected the C1 equation in the Compensation Design section (changed 2.5 to 1.