Datasheet

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MAX16977

36V, 2A, 2.2MHz Step-Down Converter

with Low Operating Current

General Description

The MAX16977 is a 2A, current-mode, step-down con-

verter with an integrated high-side switch. The device is

designed to operate with input voltages from 3.5V to 36V

while using only 30FA quiescent current at no load. The

switching frequency is adjustable from 1MHz to 2.2MHz

by an external resistor and can be synchronized to an

external clock. The output voltage is pin selectable to

be 5V fixed or adjustable from 1V to 10V. The wide input

voltage range along with its ability to operate at high duty

cycle during undervoltage transients make the device

ideal for automotive and industrial applications.

The device operates in skip mode for reduced current

consumption in light-load applications. Protection features

include overcurrent limit, overvoltage, and thermal shut-

down with automatic recovery. The device also features

a power-good monitor to ease power-supply sequencing.

The device operates over the -40NC to +125NC automo-

tive temperature range, and is available in 16-pin TSSOP

and TQFN (5mm x 5mm) packages with exposed pads.

Applications

Automotive

Industrial/Military

High-Voltage Input DC-DC Converters

Point-of-Load Applications

Features

S Wide 3.5V to 36V Input Voltage Range

S 42V Input Transients Tolerance

S High Duty Cycle During Undervoltage Transients

S 5V Fixed or 1V to 10V Adjustable Output Voltage

S Integrated 2A Internal High-Side (70mI typ)

Switch

S Fast Load-Transient Response and Current-Mode

Architecture

S Adjustable Switching Frequency (1MHz to 2.2MHz)

S Frequency Synchronization Input

S 30µA Standby Mode Operating Current

S 5µA Typical Shutdown Current

S Spread Spectrum (Optional)

S Overvoltage, Undervoltage, Overtemperature, and

Short-Circuit Protections

Typical Application Circuit

19-5844; Rev 2; 8/13

Ordering Information appears at end of data sheet.

For related parts and recommended products to use with this part,

refer to: www.maximintegrated.com/MAX16977.related

EVALUATION KIT AVAILABLE

OUT

22µF

IN2

4.7µF

COMP

20kI

PGOOD

10kI

FOSC

12kI

2.2µH

OUT

5V AT 2A

BST

0.1µF

BST

OUT

BIAS

OUT

BAT

BIAS

PGOOD

FOSC

BIAS

1µF

COMP2

12pF

BIAS

COMP1

2.2nF

COMP

FSYNC

SUPSWSUP

GND

IN1

47µF

POWER GOOD

MAX16977

For pricing, delivery, and ordering information, please contact Maxim Direct

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

Summary of content (18 pages)

PAGE 1
EVALUATION KIT AVAILABLE MAX16977 36V, 2A, 2.2MHz Step-Down Converter with Low Operating Current General Description Features The MAX16977 is a 2A, current-mode, step-down converter with an integrated high-side switch. The device is designed to operate with input voltages from 3.5V to 36V while using only 30FA quiescent current at no load. The switching frequency is adjustable from 1MHz to 2.2MHz by an external resistor and can be synchronized to an external clock.
PAGE 2
MAX16977 36V, 2A, 2.2MHz Step-Down Converter with Low Operating Current ABSOLUTE MAXIMUM RATINGS SUP, SUPSW, LX, EN to GND................................-0.3V to +42V SUP to SUPSW......................................................-0.3V to +0.3V BST to GND............................................................-0.3V to +47V BST to LX ................................................................-0.3V to +6V OUT to GND...........................................................-0.
PAGE 3
MAX16977 36V, 2A, 2.2MHz Step-Down Converter with Low Operating Current ELECTRICAL CHARACTERISTICS (continued) (VSUP = VSUPSW = 14V, VEN = 14V, CBIAS = 1FF, RFOSC = 12kI, TA = TJ = -40NC to +125NC, unless otherwise noted. Typical values are at TA = +25NC.) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS VFB = VBIAS, normal operation 4.925 5 5.075 V 4.925 5 5.
PAGE 4
MAX16977 36V, 2A, 2.2MHz Step-Down Converter with Low Operating Current ELECTRICAL CHARACTERISTICS (continued) (VSUP = VSUPSW = 14V, VEN = 14V, CBIAS = 1FF, RFOSC = 12kI, TA = TJ = -40NC to +125NC, unless otherwise noted. Typical values are at TA = +25NC.) PARAMETER External Input Clock Low Threshold Soft-Start Time SYMBOL VFSYNC_LO CONDITIONS MIN TYP VFSYNC falling tSS MAX UNITS 0.4 V 8.
PAGE 5
MAX16977 36V, 2A, 2.2MHz Step-Down Converter with Low Operating Current Typical Operating Characteristics (VSUP = VSUPSW = 14V, VEN = 14V, VOUT = 5V, VFSYNC = 0V, RFOSC = 12.1kHz, TA = +25NC, unless otherwise noted.) NO-LOAD STARTUP BEHAVIOR (5V/2.2MHz) FULL-LOAD STARTUP BEHAVIOR MAX16977 toc01 MAX16977 toc02 5V/2.2MHz RESISTIVE LOAD = 2.
PAGE 6
MAX16977 36V, 2A, 2.2MHz Step-Down Converter with Low Operating Current Typical Operating Characteristics (continued) (VSUP = VSUPSW = 14V, VEN = 14V, VOUT = 5V, VFSYNC = 0V, RFOSC = 12.1kHz, TA = +25NC, unless otherwise noted.) LOAD-TRANSIENT RESPONSE (SKIP MODE) LINE-TRANSIENT RESPONSE (5V/2.2MHz) MAX16977 toc08 MAX16977 toc09 5V/2.
PAGE 7
MAX16977 36V, 2A, 2.2MHz Step-Down Converter with Low Operating Current Typical Operating Characteristics (continued) (VSUP = VSUPSW = 14V, VEN = 14V, VOUT = 5V, VFSYNC = 0V, RFOSC = 12.1kHz, TA = +25NC, unless otherwise noted.) SHORT CIRCUIT TO GROUND TEST (5V/2.2MHz) 5.10 VIN = 14V 5.08 2V/div VOUT 5.06 5.04 5V/div 0V VOUT (V) 0V VPGOOD MAX16977 toc15 VOUT LOAD REGULATION (5V/2.2MHz) MAX16977 toc14 5.02 5.00 4.98 4.96 ILX 10A/div 4.94 0A 4.92 4.90 10ms/div 0 0.4 0.8 1.2 1.6 2.
PAGE 8
MAX16977 36V, 2A, 2.2MHz Step-Down Converter with Low Operating Current Typical Operating Characteristics (continued) (VSUP = VSUPSW = 14V, VEN = 14V, VOUT = 5V, VFSYNC = 0V, RFOSC = 12.1kHz, TA = +25NC, unless otherwise noted.) ISHDN vs. SUPPLY VOLTAGE 16 TA = +125°C 12 8 6 5.6 5.4 TA = +25°C 10 5.2 5.0 4.8 4.6 TA = -40°C 4 4.4 2 4.2 0 VEN = 0V VIN = 14V 5.8 ISHDN (µA) 14 MAX16977 toc21 VEN = 0V 18 ISHDN (µA) ISHDN vs. TEMPERATURE 6.0 MAX16977 toc20 20 4.
PAGE 9
MAX16977 36V, 2A, 2.2MHz Step-Down Converter with Low Operating Current SUPSW SUPSW LX LX 16 15 14 13 12 11 10 TOP VIEW BST SUP LX LX SUPSW EN I.C. TOP VIEW SUPSW Pin Configurations 12 11 10 9 9 EN 13 I.C. 14 FSYNC 15 7 BST 6 GND 5 BIAS 8 1 GND PGOOD TSSOP 2 3 4 TQFN (5mm × 5mm) COMP 7 BIAS PGOOD 6 COMP FOSC 5 FB FSYNC 4 OUT 3 EP + FB FOSC 16 OUT EP + 2 SUP MAX16977 MAX16977 1 8 Pin Descriptions PIN NAME FUNCTION 15 FSYNC Synchronization Input.
PAGE 10
MAX16977 36V, 2A, 2.2MHz Step-Down Converter with Low Operating Current Pin Descriptions (continued) PIN NAME FUNCTION TSSOP TQFN 10 8 SUP 11, 12 9, 10 LX 13, 14 11, 12 SUPSW 15 13 EN 16 14 I.C. Internally Connected. Connect to ground for proper operation. EP Exposed Pad. Connect EP to a large-area contiguous copper ground plane for effective power dissipation. Do not use as the only IC ground connection. EP must be connected to GND. — — Voltage Supply Input.
PAGE 11
MAX16977 36V, 2A, 2.2MHz Step-Down Converter with Low Operating Current Detailed Description The MAX16977 is a constant-frequency, current-mode, automotive buck converter with an integrated high-side switch. The device operates with input voltages from 3.5V to 36V and tolerates input transients up to 42V. During undervoltage events, such as cold-crank conditions, the internal pass device maintains 98% duty cycle. The switching frequency is resistor programmable from 1MHz to 2.
PAGE 12
MAX16977 36V, 2A, 2.2MHz Step-Down Converter with Low Operating Current Skip Mode/Standby Mode During light-load operation, IINDUCTOR P 185mA, the device enters skip mode operation. Skip mode turns off the majority of circuitry and allows the output to drop below regulation voltage before the switch is turned on again. The lower the load current, the longer it takes for the regulator to initiate a new cycle.
PAGE 13
MAX16977 36V, 2A, 2.2MHz Step-Down Converter with Low Operating Current ratio (LIR = 0.3). The switching frequency, input voltage, output voltage, and selected LIR then determine the inductor value as follows: Table 1. Inductor Size Comparison INDUCTOR SIZE V (V − VOUT ) L = OUT SUP VSUP fSWI OUTLIR where VSUP, VOUT, and IOUT are typical values (so that efficiency is optimum for typical conditions). The switching frequency is set by RFOSC (see the Internal Oscillator section).
PAGE 14
MAX16977 36V, 2A, 2.2MHz Step-Down Converter with Low Operating Current The output capacitance must be high enough to absorb the inductor energy while transitioning from full-load to no-load conditions without tripping the overvoltage fault protection. When using high-capacitance, low-ESR capacitors, the filter capacitor’s ESR dominates the output-voltage ripple.
PAGE 15
MAX16977 36V, 2A, 2.2MHz Step-Down Converter with Low Operating Current In a current-mode step-down converter, the output capacitor, its ESR, and the load resistance introduce a pole at the following frequency: fpMOD = 1 2π × C OUT × R LOAD The output capacitor and its ESR also introduce a zero at: fzMOD = 1 2π × ESR × C OUT When COUT is composed of “n” identical capacitors in parallel, the resulting COUT = n x COUT(EACH) and ESR = ESR(EACH)/n.
PAGE 16
MAX16977 36V, 2A, 2.2MHz Step-Down Converter with Low Operating Current Therefore: GAINMOD(fC) × f VFB × g m,EA × R C × zMOD = 1 VOUT fC Solving for RC: RC = VOUT × fC g m,EA × VFB × GAINMOD(fC) × fzMOD Set the error-amplifier compensation zero formed by RC and CC at the fpMOD (fzEA = fpMOD) CC = 1 2π × fpMOD × R C If fzMOD is less than 5 x fC, add a second capacitor CF from COMP to GND.
PAGE 17
MAX16977 36V, 2A, 2.
PAGE 18
MAX16977 36V, 2A, 2.2MHz Step-Down Converter with Low Operating Current Revision History REVISION NUMBER REVISION DATE DESCRIPTION PAGES CHANGED 0 5/11 Initial release 1 4/13 Added Spread Spectrum section, updated part numbers 12, 16 — 2 8/13 Updated the pole frequency and gain calculation equations in the Compensation Network section 14, 15 Maxim Integrated cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim Integrated product.