Datasheet

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General Description

The MAX1765 is a high-efficiency, low-noise, step-up

DC-DC converter intended for use in battery-powered

wireless applications. This device operates at a high

1MHz fixed frequency while maintaining an exception-

ally low quiescent supply current (200µA). Its small

external components and tiny package make this

device an excellent choice for small hand-held applica-

tions that require the longest possible battery life.

The MAX1765 uses a synchronous-rectified pulse-

width-modulation (PWM) boost topology to generate

2.5V to 5.5V outputs from a wide range of input

sources, such as one to three alkaline or NiCd/NiMH

cells or a single lithium-ion (Li+) cell. Maxim's propri-

etary architecture significantly improves efficiency at

low load currents while automatically transitioning to

fixed-frequency PWM operation at medium to high load

currents to maintain excellent full-load efficiency.

Forced-PWM mode is available for applications that

require constant-frequency operation at all load cur-

rents, and the MAX1765 may also be synchronized to

an external clock to protect sensitive frequency bands

in communications equipment.

The MAX1765’s low-dropout (LDO) linear regulator and

DC-DC converter have separate shutdown control. The

linear regulator's 250mΩ pass device maintains excel-

lent dropout voltage at currents up to 500mA. The

MAX1765 also features analog soft-start and current-

limit functions to permit optimization of efficiency, exter-

nal component size, and output voltage ripple.

The MAX1765 comes in a 16-pin QSOP package and a

thermally enhanced 16-pin TSSOP-EP.

____________________________Features

o High-Efficiency Step-Up Converter

Up to 93% Efficiency

Adjustable Output from +2.5V to +5.5V

Up to 800mA Output

PWM Synchronous-Rectified Topology

1MHz Operating Frequency (or Sync)

o LDO Linear Regulator

500mA LDO Linear Regulator

2.85V Linear Regulator Output or Adjustable

(1.25V to 5V)

Low 125mV Dropout at 500mA

o +0.7V to +5.5V Input Range

o 0.1μA Logic-Controlled Shutdown

o Adjustable Inductor Current Limit and Soft-Start

o Thermal Shutdown

o 1.5W, 16-Pin TSSOP-EP Package Available

MAX1765

800mA, Low-Noise, Step-Up DC-DC Converter

with 500mA Linear Regulator

________________________________________________________________

Maxim Integrated Products

19-1805; Rev 1; 4/11

For price, delivery, and to place orders, please contact Maxim Distribution at 1-888-629-4642,

or visit Maxim’s website at www.maxim-ic.com.

FBL ONL

TRACK

INL

POUT

PGND

OUTL

TOP VIEW

MAX1765

QSOP/TSSOP-EP

ONB

ISET

REF

OUT

GND

ONA

CLK/SEL

Pin Configuration

Wireless Handsets

PCS Phones

Palmtop Computers

Personal

Communicators

Hand-Held Instruments

Portable Audio Players

Applications

FBL

REF

ILIM

ONL

ONA

(0.7V TO 5.5V)

3.3μH

OUTL = 2.85V

(ADJ 1.25V

TO 5V)

OUT = 3.3V

OUT

OUTL

POUT

GND PGND

TRACK

CLK/SEL

ONB

INL

MAX1765

Typical Operating Circuit

Ordering Information

EP = Exposed pad.

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

PART TEMP RANGE PIN-PACKAGE

MAX1765EEE+ -40°C to +85°C 16 QSOP

MAX1765EUE+ -40°C to +85°C 16 TSSOP-EP*

Summary of content (19 pages)

PAGE 1
9-1805; Rev 1; 4/11 800mA, Low-Noise, Step-Up DC-DC Converter with 500mA Linear Regulator The MAX1765 uses a synchronous-rectified pulsewidth-modulation (PWM) boost topology to generate 2.5V to 5.5V outputs from a wide range of input sources, such as one to three alkaline or NiCd/NiMH cells or a single lithium-ion (Li+) cell.
PAGE 2
MAX1765 800mA, Low-Noise, Step-Up DC-DC Converter with 500mA Linear Regulator ABSOLUTE MAXIMUM RATINGS ONA, ONB, ONL, TRACK, OUT, INL to GND..............-0.3V, +6V PGND to GND.....................................................................±0.3V LX to GND ...............................................-0.3V to (POUT + 0.3V) OUTL to GND ..............................................-0.3V to (INL + 0.3V) CLK/SEL, REF, FB, FBL, ISET, POUT to GND...................................................-0.
PAGE 3
800mA, Low-Noise, Step-Up DC-DC Converter with 500mA Linear Regulator (VOUT = VPOUT = VINL = VONA = VONL = 3.6V, CLK/SEL = FBL = ONB = TRACK = PGND = GND, ISET = REF (bypassed with 0.22µF), LX = open, OUTL = open (bypassed with 4.7µF), TA = 0°C to +85°C, unless otherwise noted. Typical values are at TA = +25°C.) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS DC-DC SWITCHES POUT Leakage Current VLX = 0V, VOUT = 5.5V 0.1 10 µA LX Leakage Current VLX = VOUT = V ONB = 5.5V, ONA = GND N-channel 0.
PAGE 4
MAX1765 800mA, Low-Noise, Step-Up DC-DC Converter with 500mA Linear Regulator ELECTRICAL CHARACTERISTICS (continued) (VOUT = VPOUT = VINL = VONA = VONL = 3.6V, CLK/SEL = FBL = ONB = TRACK = PGND = GND, ISET = REF (bypassed with 0.22µF), LX = open, OUTL = open (bypassed with 4.7µF), TA = 0°C to +85°C, unless otherwise noted. Typical values are at TA =+25 °C.) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS CONTROL INPUTS ONA, ONB, ONL (Note 5) Input Low Level Input High Level 1.1V < VOUT < 1.8V 0.
PAGE 5
800mA, Low-Noise, Step-Up DC-DC Converter with 500mA Linear Regulator (VOUT = VPOUT = VINL = VONA = VONL = 3.6V, CLK/SEL = FBL = ONB = TRACK = PGND = GND, ISET = REF (bypassed with 0.22µF), LX = open, OUTL = open (bypassed with 4.7µF), TA = -40°C to +85°C, unless otherwise noted.) (Note 6) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS DC-DC CONVERTER FB Regulation Voltage VFB CLK/SEL = OUT, 0 < ILX < 0.55A 1.210 1.280 V OUT Voltage in Track Mode VOUTL > 2.0V, INL = POUT VOUTL + 0.
PAGE 6
MAX1765 800mA, Low-Noise, Step-Up DC-DC Converter with 500mA Linear Regulator ELECTRICAL CHARACTERISTICS (continued) (VOUT = VPOUT = VINL = VONA = VONL = 3.6V, CLK/SEL = FBL = ONB = TRACK = PGND = GND, ISET = REF (bypassed with 0.22µF), LX = open, OUTL = open (bypassed with 4.7µF), TA = -40°C to +85°C, unless otherwise noted.) (Note 6) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS CONTROL INPUTS Input Low Level Input High Level ONA, ONB, ONL (Note 5) 1.1V < VOUT < 1.8V 0.2 1.8V < VOUT < 5.
PAGE 7
800mA, Low-Noise, Step-Up DC-DC Converter with 500mA Linear Regulator 70 NORMAL MODE 60 50 40 VIN = +2.4V 20 40 VIN = +3.6V VIN = +2.4V 0.01 0.1 1 VIN = +2.4V 70 60 VIN = +1.2V PWM MODE 50 40 VIN = +1.2V 30 VIN = +2.4V 20 VIN = +1.2V 10 0 0 0.001 0.01 0.001 0.1 0.001 1 0.01 0.1 1 LOAD CURRENT (A) LOAD CURRENT (A) TRACK MODE EFFICIENCY vs. LOAD CURRENT (VOUTL = +3.3V) TRACK MODE EFFICIENCY vs. LOAD CURRENT (VOUTL = +5V) MAXIMUM OUTPUT CURRENT vs.
PAGE 8
Typical Operating Characteristics (continued) (TA = +25°C, unless otherwise noted.) LDO PSRR vs. FREQUENCY (100Hz TO 1MHz) LINE TRANSIENT RESPONSE (DC-DC) BOOST FOLLOWED BY LDO OUTPUT NOISE SPECTRUM 12 NOISE (mVRMS) -40 -50 VIN = +2.4V VOUT = +3.3V 14 -20 -30 MAX1765 toc11 -10 MAX1765 toc12 16 MAX1765 toc10 0 LDO PSRR (dB) MAX1765 800mA, Low-Noise, Step-Up DC-DC Converter with 500mA Linear Regulator 10 A 8 6 4 2 -60 0 B -70 -80 0.1 1 10 100 0.
PAGE 9
800mA, Low-Noise, Step-Up DC-DC Converter with 500mA Linear Regulator LINEAR-REGULATOR OUTPUT NOISE MAX1765 toc17 ILDO = 200mA VLDO = 2.85V A 250 150 C 50 1.0 0.8 0.6 0.4 0.2 0 500ns/div A: LX NODE, 5V/div B: INDUCTOR CURRENT, 200mA/div, AC-COUPLED C: OUTPUT RIPPLE, 20mV/div, AC-COUPLED VOUT = +3.3 1.2 SWITCH CURRENT LIMIT (A) NOISE (mVRMS) 350 B SWITCH CURRENT LIMIT vs. VISET 1.4 MAX1765 toc18 450 MAX1765 toc19 LIGHT-LOAD SWITCHING WAVEFORMS (VIN = +2.4V, VOUT = +3.3V, IOUT = 10mA) 0.
PAGE 10
800mA, Low-Noise, Step-Up DC-DC Converter with 500mA Linear Regulator MAX1765 Pin Description (continued) PIN NAME FUNCTION 9 ONB 10 PGND 11 LX 12 POUT 13 INL Linear Regulator Power Input. Source of PFET pass device connected between INL and OUTL. Connect INL to POUT. 14 OUTL Linear Regulator Output. OUTL can source up to 500mA. Bypass OUTL to GND with a 4.7µF capacitor. 15 TRACK Track-Mode Control Input for DC-DC Converter.
PAGE 11
800mA, Low-Noise, Step-Up DC-DC Converter with 500mA Linear Regulator MAX1765 MAX1765 THERMAL SENSOR SHUTDOWN LOGIC INL FBL ONL MOSFET DRIVER WITH CURRENT LIMITING ERROR AMP OUT P OUTL REF IC PWR POUT 2.15V TRACK EN GND STARTUP OSCILLATOR Q D Q P PWM CONTROLLER ONA ONB ON ONL RDY 1.250V REFERENCE REF OSC VOUT Q EN 1MHz OSCILLATOR CLK/SEL LX EN SKIP/PWM MODE N ICS IREF FB PGND IFB VOUT - 300mV TRACK ISET ISET Figure 1. Functional Diagram Table 1.
PAGE 12
MAX1765 800mA, Low-Noise, Step-Up DC-DC Converter with 500mA Linear Regulator VIN 0.7V to 3.2V 3.3μH VOUT 3.3V 33μF 100μF REF LX POUT ILIM INL OUT 0.22μF ONA LOGIC INPUTS 4.7Ω 0.68μF MAX1765 ONB TRACK ONL 165k FB 100k VOUTL = 2.85V OUTL 4.7μF FBL GND CLK/SEL PGND rising edge of the oscillator, where the N-channel is again turned on under most conditions. The P-channel zero detect circuitry is deactivated in forced PWM mode.
PAGE 13
800mA, Low-Noise, Step-Up DC-DC Converter with 500mA Linear Regulator MAX1765 Linear Regulator The MAX1765 contains an LDO with a fixed 2.85V (or adjustable) output. The MAX1765 linear regulator features a 250mΩ, P-channel MOSFET pass transistor. This provides several advantages, including longer battery life, over similar designs using a PNP pass transistor. The P-channel MOSFET requires no base-drive current.
PAGE 14
MAX1765 800mA, Low-Noise, Step-Up DC-DC Converter with 500mA Linear Regulator Table 2. Operating Mode Truth Table OPERATING MODE Shutdown TRACK ONA ONB ONL LINEAR REGULATOR DC-DC CONVERTER REF X L H L OFF OFF OFF H H X X ON ON ON H X L X L H X H ON ON ON L X L H L H X L OFF ON ON L X L L X L H H ON OFF ON Track Independent Regulation DC-DC Only LDO Only The LDO acts like a switch in this situation and disconnects the input from the load.
PAGE 15
800mA, Low-Noise, Step-Up DC-DC Converter with 500mA Linear Regulator MAX1765 INPUT 0.7V TO 5.5V INPUT 3.3μH TRACK = LOW, VOUT = 5.0V TRACK = HIGH, VOUT = 3.35V LX 33μF x 2 OFF MAX1765 LX ON ONB 4.7Ω OUTPUT POUT OUT SHDN OUT MAX1765 0.68μF TRACK 150k TRACK ON OFF OFF ON FB ONL FB ONB 50k ONA POUT 0.22μF REF INL ILIM OUTL GND CLK/SEL FBL PGND VLDO = 2.85V Figure 6. PFET Allows True Boost Shutdown 4.7μF on-chip 100kΩ resistor.
PAGE 16
MAX1765 800mA, Low-Noise, Step-Up DC-DC Converter with 500mA Linear Regulator should have a saturation current rating exceeding the N-channel switch current limit; however, it is acceptable to bias the inductor current into saturation by as much as 20% if a slight reduction in efficiency is acceptable. Lower current-rated inductors may be used if ISET is employed to reduce the peak inductor current (see Setting the Switch Current Limit and SoftStart).
PAGE 17
800mA, Low-Noise, Step-Up DC-DC Converter with 500mA Linear Regulator 0.22μF ( RSS1 ) REF 0.22μF MAX1765 ISET CSS ILIM = 1.25A tSS = RSS CSS 500kΩ < RSS < 1MΩ RSS MAX1765 MAX1765 RSS2 ILIM = 1.25A RSS1 + RSS2 tSS = (RSS1 || RSS2) CSS REF ISET CSS RSS2 Figure 9. Soft-Start, Maximum Current Limit Figure 8. Soft-Start, Reduced Current Limit Table 3. Component Selection Guide PRODUCTION 3.
PAGE 18
MAX1765 800mA, Low-Noise, Step-Up DC-DC Converter with 500mA Linear Regulator μC 270k LX CONTROL INPUTS POUT MAX1765 GND MAX1765 INL ONB ON/OFF VDD POUT I/O OUTL ONA I/O μC I/O PA RF 0.1μF 270k Figure 10. Typical Phone Application Figure 11. Momentary Pushbutton On/Off Switch Table 5. Typical Available Output Current NUMBER OF CELLS INPUT VOLTAGE (V) OUTPUT VOLTAGE (V) OUTPUT CURRENT (mA) 1 NiCd/NiMH 1.2 3.3 330 2.4 3.3 730 2.4 5.0 460 3.6 5.
PAGE 19
800mA, Low-Noise, Step-Up DC-DC Converter with 500mA Linear Regulator REVISION NUMBER REVISION DATE 0 12/00 Initial release 4/11 Added lead-free designation, updated TOCs 1 and 2, and updated Pin Description section 1 DESCRIPTION PAGES CHANGED — 1, 7, 10 Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are implied.