Datasheet

ManualsBrandsMAXIM INTEGRATED ManualsPMICsPMIC - DC/DC voltage regulator Holder SOIC 8

General Description

The MAX1951/MAX1952 high-efficiency, DC-to-DC

step-down switching regulators deliver up to 2A of out-

put current. The devices operate from an input voltage

range of 2.6V to 5.5V and provide an output voltage

from 0.8V to V

, making the MAX1951/MAX1952 ideal

for on-board postregulation applications. The MAX1951

total output error is less than 1% over load, line, and

temperature.

The MAX1951/MAX1952 operate at a fixed frequency of

1MHz with an efficiency of up to 94%. The high operating

frequency minimizes the size of external components.

Internal soft-start control circuitry reduces inrush current.

Short-circuit and thermal-overload protection improve

design reliability.

The MAX1951 provides an adjustable output from 0.8V

to V

, whereas the MAX1952 has a preset output of

1.8V. Both devices are available in a space-saving 8-pin

SO package.

Applications

ASIC/DSP/µP/FPGA Core and I/O Voltages

Set-Top Boxes

Cellular Base Stations

Networking and Telecommunications

Features

♦ Compact 0.385in

Circuit Footprint

♦ 10µF Ceramic Input and Output Capacitors, 2µH

Inductor for 1.5A Output

♦ Efficiency Up to 94%

♦ 1% Output Accuracy Over Load, Line, and

Temperature (MAX1951, Up to 1.5A)

♦ Guaranteed 2A Output Current

♦ Operate from 2.6V to 5.5V Supply

♦ Adjustable Output from 0.8V to V

(MAX1951)

♦ Preset Output of 1.8V (1.5% Accuracy) (MAX1952)

♦ Internal Digital Soft-Soft

♦ Short-Circuit and Thermal-Overload Protection

MAX1951/MAX1952

1MHz, All-Ceramic, 2.6V to 5.5V Input,

2A PWM Step-Down DC-to-DC Regulators

________________________________________________________________ Maxim Integrated Products 1

Ordering Information/

Selector Guide

19-2622; Rev 2; 6/09

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

OUTPUT

MAX1951ESA+ -40°C to +85°C 8 SO Adj 0.8V to V

MAX1952ESA+ -40°C to +85°C 8 SO Fixed 1.8V

MAX1951

OFF

COMP

OUTPUT

0.8V TO V

, UP TO 2A

INPUT

2.6V TO 5.5V

REF

PGND GND

OPTIONAL

Typical Operating Circuit

Pin Configuration

PGND

COMPFB

LXREF

GND

TOP VIEW

MAX1951

MAX1952

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

Summary of content (15 pages)

PAGE 1
9-2622; Rev 2; 6/09 1MHz, All-Ceramic, 2.6V to 5.5V Input, 2A PWM Step-Down DC-to-DC Regulators The MAX1951/MAX1952 high-efficiency, DC-to-DC step-down switching regulators deliver up to 2A of output current. The devices operate from an input voltage range of 2.6V to 5.5V and provide an output voltage from 0.8V to VIN, making the MAX1951/MAX1952 ideal for on-board postregulation applications. The MAX1951 total output error is less than 1% over load, line, and temperature.
PAGE 2
MAX1951/MAX1952 1MHz, All-Ceramic, 2.6V to 5.5V Input, 2A PWM Step-Down DC-to-DC Regulators ABSOLUTE MAXIMUM RATINGS IN, VCC to GND ........................................................-0.3V to +6V COMP, FB, REF to GND .............................-0.3V to (VCC + 0.3V) LX to Current (Note 1).........................................................±4.5A PGND to GND .............................................Internally Connected Continuous Power Dissipation (TA = +85°C) 8-Pin SO (derate 12.
PAGE 3
1MHz, All-Ceramic, 2.6V to 5.5V Input, 2A PWM Step-Down DC-to-DC Regulators (VIN = VCC = 3.3V, PGND = GND, FB in regulation, CREF = 0.1µF, TA = 0°C to +85°C, unless otherwise noted. Typical values are at TA = +25°C.) PARAMETER CONDITIONS MIN TYP MAX UNITS 266 mΩ 206 mΩ 0.24 0.35 Ω 3.1 4.5 LX LX On-Resistance, PMOS LX On-Resistance, NMOS VIN = 5V 116 VIN = 3.3V 140 VIN = 2.6V 163 VIN = 5V 93 VIN = 3.3V 106 VIN = 2.6V 116 LX Current-Sense Transimpedance From LX to COMP, VIN = 2.
PAGE 4
MAX1951/MAX1952 1MHz, All-Ceramic, 2.6V to 5.5V Input, 2A PWM Step-Down DC-to-DC Regulators ELECTRICAL CHARACTERISTICS (continued) (VIN = VCC = 3.3V, PGND = GND, FB in regulation, CREF = 0.1µF, TA = -40°C to +85°C, unless otherwise noted.) (Note 3) PARAMETER CONDITIONS MIN TYP MAX UNITS COMP MAX1951 40 80 MAX1952 26.7 53.3 COMP Transconductance From FB to COMP, VCOMP = 1.25V COMP Clamp Voltage, Low VIN = 2.6V to 5.5V, VFB = 1.3V 0.6 1.2 V COMP Clamp Voltage, High VIN = 2.6V to 5.
PAGE 5
1MHz, All-Ceramic, 2.6V to 5.5V Input, 2A PWM Step-Down DC-to-DC Regulators 70 VOUT = 1.5V 50 40 30 20 1.994 VOUT = 1.8V 70 60 VOUT = 1.5V 50 40 30 VOUT = 0.8V 1.995 VOUT = 0.8V 20 10 MAX1951 toc03 80 EFFICIENCY (%) VOUT = 2.5V 60 TA = +85°C 1.993 TA = +25°C 1.992 1.991 TA = -40°C 1.990 10 0 0 10 100 10,000 1000 1.989 10 100 LOAD CURRENT (mA) 10,000 1000 1.05 1.00 TA = +25°C 0.95 TA = -40°C 0.85 0.80 2.6 3.1 3.6 10 4.1 4.6 5.1 VOUT = 2.
PAGE 6
Typical Operating Characteristics (continued) (Typical values are at VIN = VCC = 5V, VOUT = 1.5V, IOUT = 1.5A, and TA = +25°C, unless otherwise noted. See Figure 2.) SWITCHING WAVEFORMS SOFT-START WAVEFORMS MAX1951 toc08 MAX1951 toc09 INDUCTOR CURRENT 1A/div VCOMP 2V/div 0A VLX 5V/div 0V OUTPUT VOLTAGE 1V/div OUTPUT VOLTAGE 10mV/div, AC-COUPLED VIN = 3.3V VOUT = 1.8V ILOAD = 1.5A VIN = VCC = 3.3V VOUT = 2.5V ILOAD = 1.
PAGE 7
1MHz, All-Ceramic, 2.6V to 5.5V Input, 2A PWM Step-Down DC-to-DC Regulators PIN NAME FUNCTION 1 VCC Supply Voltage. Bypass VCC with 0.1µF capacitor to ground and 10Ω resistor to IN. 2 REF Reference Bypass. Bypass REF with 0.1µF capacitor to ground. 3 GND Ground 4 FB Feedback Input. Connect FB to the output to regulate using the internal feedback resistor string (MAX1952). Connect an external resistordivider from the output to FB and GND to set the output to a voltage between 0.
PAGE 8
MAX1951/MAX1952 1MHz, All-Ceramic, 2.6V to 5.5V Input, 2A PWM Step-Down DC-to-DC Regulators POSITIVE AND NEGATIVE CURRENT LIMITS VCC OSC IN CLOCK CURRENT SENSE PWM CONTROL LX RAMP GEN SLOPE COMP CLAMP ERROR SIGNAL THERMAL SHUTDOWN gm COMP SOFT-START/ UVLO PGND FB DAC REF 2V REF BANDGAP REF 1.25V MAX1951 GND Figure 1. Functional Diagram through the high-side MOSFET body diode, back to the input, until the beginning of the next cycle or until the inductor current drops to zero.
PAGE 9
1MHz, All-Ceramic, 2.6V to 5.5V Input, 2A PWM Step-Down DC-to-DC Regulators Output Voltage Selection: Adjustable (MAX1951) or Preset (MAX1952) The MAX1951 provides an adjustable output voltage between 0.8V and VIN. Connect FB to output for 0.8V output. To set the output voltage of the MAX1951 to a voltage greater than VFB (0.8V typ), connect the output to FB and GND using a resistive divider, as shown in Figure 2a.
PAGE 10
MAX1951/MAX1952 1MHz, All-Ceramic, 2.6V to 5.5V Input, 2A PWM Step-Down DC-to-DC Regulators Typical Operating Characteristics), the controller responds by regulating the output voltage back to its nominal state. The controller response time depends on the closed-loop bandwidth. A higher bandwidth yields a faster response time, thus preventing the output from deviating further from its regulating value.
PAGE 11
1MHz, All-Ceramic, 2.6V to 5.5V Input, 2A PWM Step-Down DC-to-DC Regulators RLOAD = VOUT/IOUT(MAX) = 1.5V/1.5 A = 1Ω fpMOD = [1/(2π x COUT x (RLOAD + RESR)] = [1/(2 x π ×10 ×10-6 x (1 + 0.01)] = 15.76kHz. fzESR = [1/(2π xCOUT RESR)] = [1/(2 x π × 10 ×10-6 × 0.01)] = 1.59MHz. For 2µH output inductor, pick the closed-loop unity-gain crossover frequency (f C ) at 200kHz. Determine the power modulator gain at fC: GMOD(fc) = gmc × RLOAD × fpMOD/fC = 4.2 × 1 × 15.76kHz/200kHz = 0.
PAGE 12
MAX1951/MAX1952 1MHz, All-Ceramic, 2.6V to 5.5V Input, 2A PWM Step-Down DC-to-DC Regulators L1 2μH 2.6V TO 5.5V IN R4 10Ω C5 0.1μF MAX1951ESA REF COMP C1 10μF R3 14.7kΩ 1% FB VCC R1 51.1kΩ GND PGND R2 16.9kΩ 1% OFF C2 220pF ON 1.5V AT 1.5A LX C3 0.1μF Q1 R5 10kΩ C4 10μF GND OUTPUT COMPONENT VALUES VOLTAGE (V) R1 (kΩ) R2 (kΩ) R3 (kΩ) C2 (pF) 220 SHORT OPEN 0.8 33.2 220 14.7 16.9 1.5 51.1 220 30 14 2.5 82.5 220 75 24 3.3 110 OPTIONAL SHUTDOWN CONTROL Figure 2a.
PAGE 13
1MHz, All-Ceramic, 2.6V to 5.5V Input, 2A PWM Step-Down DC-to-DC Regulators IN R4 10Ω C5 0.1μF MAX1951ESA GND REF PGND OFF C2 100pF ON Q1 R5 10kΩ R3 12.7kΩ 1% FB COMP C1 10μF 1.8V, 2A LX VCC R1 100kΩ MAX1951/MAX1952 L1 1.1μH 3.3V ±5% C3 0.1μF R2 10kΩ 1% C4 22μF GND L1: TOKO A915AY-1R1M C1: TAIYO YUDEN JMK316BJ106ML C4: TAIYO YUDEN JMK325BJ226MM OPTIONAL SHUTDOWN CONTROL Figure 2c.
PAGE 14
MAX1951/MAX1952 1MHz, All-Ceramic, 2.6V to 5.5V Input, 2A PWM Step-Down DC-to-DC Regulators Table 2. External Components List COMPONENT (FIGURE 2) FUNCTION DESCRIPTION L1 Output inductor C1 Input filtering capacitor 10µF ±20%, 6.3V X5R capacitor Taiyo Yuden JMK316BJ106ML or TDK C3216X5R0J106MT C2 Compensation capacitor 220pF ±10%, 50V capacitor Murata GRM39X7R221K050AD or Taiyo Yuden UMK107CH221KZ 2µH ±20% inductor Sumida CDRH4D28-1R8 or Toko A915AY-2R0M C3 Reference bypass capacitor 0.
PAGE 15
1MHz, All-Ceramic, 2.6V to 5.5V Input, 2A PWM Step-Down DC-to-DC Regulators REVISION NUMBER REVISION DATE 0 10/02 Initial release 1 8/03 Updated data sheet title, Features, Typical Operating Circuit, Detailed Description and added Thermal Considerations section. 2 6/09 Revised Ordering Information, Electrical Characteristics, Typical Operating Characteristics, Pin Description, and the Compensation Design section.