Max 1674

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For free samples & the latest literature: http://www.maxim-ic.com, or phone 1-800-998-8800.For small orders, phone 408-737-7600 ext. 3468.

General DescriptionThe M A X1674/M A X1675/M A X1676 com pact, high-effi-ciency, step -up D C -D C converters fit in sm all M A Xpackages. They feature a built-in synchronous rectifier,w hich im proves efficiency and red uces size and costby elim inating the need for an external Schottky diode.Q uiescent supply current is only 16A .

The inp ut voltag e ranges from 0.7V to V O U T, w he reVO U T can b e set from 2V to 5.5V . Start-up is guaran-teed from 1.1V inp uts. The M A X1 674/M A X 1675 /M A X1676 have a preset, pin-selectab le output for 5V or3.3V. The outputs can also be adjusted to other volt-ages using tw o external resistors.

A ll three device s have a 0.3 N -channel M O SFETpow er sw itch. The M A X1674 has a 1A current lim it. The

M A X1675 has a 0.5A current lim it, w hich perm its theuse of a sm aller ind uctor. The M A X1676 com es in a10-pin M A X package and features an adjustable cur-rent lim it and circuitry to reduce inductor ringing.

________________________ApplicationsPagers

W ireless P hones

M edical D evices

H and-H eld C om puters

P D A s

R F Tags

1 to 3-C ell H and-H eld D evices

____________________________Features

94% Efficient at 200mA Output Current 16A Quiescent Supply Current

Internal Synchronous Rectifier (no external diode)

0.1A Logic-Controlled Shutdown

LBI/LBO Low-Battery Detector

Selectable Current Limit for Reduced Ripple

Low-Noise, Anti-Ringing Feature (MAX1676)

8-Pin and 10-Pin MAX Packages

Preassembled Evaluation Kit (MAX1676EVKIT)

MAX1674/MAX1

675/MAX1676

High-Efficiency, Low-Supply-Current,Compact, Step-Up DC-DC Converters

________________________________________________________________Maxim Integrated Products 1

GNDLBO

SHDNREF

1

2

8

7

OUT

LXLBI

FB

MAX1674

MAX1675

MAX

TOP VIEW

3

4

6

5

1

2

3

4

5

10

9

8

7

6

OUT

LX

GND

BATTCLSEL

LBO

LBI

FB

MAX1676

MAX

SHDNREF

MAX1674

MAX1675

INPUT0.7V TO VOUT

SHDN LX

LBO

OUT

LBI

0.1F

LOW-BATTERYDETECT OUT

OFFON

REF GNDFB

OUTPUT3.3V, 5V, OR

ADJ (2V TO 5.5V)UP TO 300mA

LOW-BATTERYDETECT IN

PART

MAX1674EU A -40C to +85C

TEMP. RANGE PIN-PACKAGE

8 M AX

_______________Ordering Information

MAX1675EU A -40C to +85C 8 M AX

MAX1676EU B -40C to +85C 10 M A X

EVALUATIO

NKIT

AVAILABLE

Typical Operating Circuit

Pin Configurations

19-1360; R ev 0; 7/98

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MAX1674/MA

X1675/MAX167

6


2 _______________________________________________________________________________________

ABSOLUTE MAXIMUM RATINGS

ELECTRICAL CHARACTERISTICS(VBATT = 2V, FB = O U T (VO U T = 3.3V ), R L = ,TA= 0C to +85C, unless otherw ise noted. Typical values are at TA = + 25C .)

Stresses beyond those listed under Absolute M axim um R ating sm ay cause p erm anent dam age to the device. These are stress ratings only, and functional

op eration of the device at these or any other cond itions beyond those ind icated in the operational sections of the specifications is not im plied . Exposure to

ab solute m axim um rating cond itions for extended period s m ay affect device reliab ility.

Supply V oltage (O U T to G N D )..............................-0.3V to + 6.0VSw itch Voltage (LX to G N D ).....................-0.3V to (VO U T + 0.3V)B attery V oltage (BA TT to G N D ).............................-0.3V to + 6.0VSHDN,LBOto G N D ..............................................-0.3V to + 6.0VLB I, R EF, FB , C LSEL to G N D ...................-0.3V to (VO U T + 0.3V)Sw itch C urrent (LX)...............................................-1.5A to +1.5AO utput C urrent (O U T)...........................................-1.5A to +1.5A

C ontinuous Pow er D issipation (TA = + 70C )8-Pin M A X (derate 4.1m W /C ab ove + 70C ) .............330m W10-Pin M A X (derate 5.6m W /C ab ove + 70C ) ...........444m W

O perating Tem perature R ange ...........................-40C to + 85CJunction Tem perature......................................................+ 150CStorag e Tem perature Range .............................-65C to + 165CLead Tem perature (soldering, 10sec).............................+ 300C

TA = + 25C , R L = 3k (N ote 1)

VLX = 0, 5.5V ; VO U T = 5.5V

TA = + 25C

M AX1675, M AX1676 (C LSEL = G N D )

M AX1674, M AX1676 (C LSEL = O U T)

ILX = 100m A

FB = O U T(VO U T = 3.3V)

VO U T = 2V to 5.5V

IR EF = 0 to 100A

90 130M A X1675,

M AX1676 (C LSEL = G N D )

FB = O U T

FB = G N D

IREF = 0

CONDITIONS

A0.05 1ILEAKLX Leakage C urrent

A0.4 0.5 0.65

ILIM0.80 1 1.20LX Sw itch C urrent

Lim it (N FE T)

0.3 0.6R DS(O N)Internal N FE T, PFE TO n-R esistance

V1.274 1.30 1.326FB , LB I Input Threshold

m V/V0.08 2.5VR EF_LIN ER eference V oltag e LineR eg ulation

m V3 15VREF_LOA DR eference V oltage LoadR eg ulation

m V/C0.024TE M P C OR eference Voltage Tem pco

V1.274 1.30 1.326VR EFR eference Voltag e

V0.9 1.1Start-U p Voltag e

V1.1 5.5VIN

V0.7M inim um Inp ut Voltag e

O perating Voltag e

150 220

FB = G N D(VO U T = 5V)

M A X1675,

M AX1676 (C LSEL = G N D )

180 285

IO U TM A X1674,M AX1676 (C LSEL = O U T)

m A

300 420

Steady-State O utput C urrent(N ote 2)

m V/C-2Start-U p Voltage Tem pco

V3.17 3.30 3.43

VO U TO utput Voltag e4.80 5 5.20

M A X1674,M AX1676 (C LSEL = O U T)

V2 5.5O utput Voltage R ang e

UNITSMIN TYP MAXSYMBOLPARAMETER

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MAX1674/MAX1

675/MAX1676


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ELECTRICAL CHARACTERISTICS(VBATT = 2V, FB = O U T, R L = ,TA= -40C to +85C, unless otherw ise noted .) (N ote 4)

Note 1: Start-up voltag e operation is guaranteed w ith the ad dition of a S chottky M B R 0520 external diod e betw een the inp ut andoutput.

Note 2: Steady-state output current indicates that the d evice m aintains output voltag e regulation under load. See Figures 5 and 6.Note 3: D evice is bootstrap ped (pow er to the IC com es from O U T). This correlates d irectly w ith the actual battery supply.

VO U T = 2V, IL O A D = 1m A

VO U T = 3.3V , IL O A D = 200m A

SHDN= G N D

CONDITIONS

%85

Efficiency90

A0.1 1Shutdow n C urrent into O U T

UNITSMIN TYP MAXSYMBOLPARAMETER

M A X1676, VBATT = 2V

V LBO = 5.5V , VLB I= 5.5V

VLB I= 0, ISIN K = 1m A

V SHDN= 0 or VO U T

VFB = 1V, VO U T = 3.3V

M AX1676, C LSEL = O U T

VLB I= 1.4V

VFB = 1.4V

VFB = 1V, VO U T = 3.3V

0.8VO U TVIH

0.2VO U TVILC LSEL Input Voltage

V0.8VO U TVIH

0.2VO U TVILSHDNInp ut Voltag e

88 150D am ping Sw itch R esistance

A0.07 1ILBOLBOO ff Leakage C urrent

V0.2 0.4LBOLow O utput Voltage

nA0.07 50ISHDNSHDNInp ut C urrent

A1.4 3ICLSELC LSEL Input C urrent

nA1 50ILB ILB I Inp ut C urrent

nA0.03 50IFBFB Inp ut C urrent

s0.8 1 1.2tO FFLX Sw itch O ff-Tim e

s3 4 7tO NLX S w itch O n-Tim e

V

ELECTRICAL CHARACTERISTICS (continued)(VBATT = 2V, FB = O U T (VO U T = 3.3V ), R L = ,TA= 0C to +85C, unless otherw ise noted. Typical values are at TA = + 25C .)

FB = G N D

FB = O U T

VFB = 1V, VO U T = 3.3V

VFB = 1V, VO U T = 3.3V

SHDN= G N D

VFB = 1.4V , VO U T = 3.3V

IR EF = 0

M AX1675, M AX1676 (C LSEL = G N D )

M AX1674, M AX1676 (C LSEL = O U T)

CONDITIONS

0.36 0.69A

0.75 1.25ILIM

LX Sw itch C urrentLim it (N FE T)

V2.20 5.5O utput Voltage R ang e

V4.75 5.25

3.13 3.47VO U TO utput Voltag e

s0.75 1.25tO FFLX Sw itch O ff-Tim e

s2.7 7.0tO NLX S w itch O n-Tim e

A1Shutdow n C urrent into O U T

A40O perating C urrent into O U T(N ote 3)

V1.2675 1.3325VR EFR eference Voltag e

V1.2675 1.3325FB , LB I Thresholds

0.6R DS(O N)Internal N FE T, PFE TO n-R esistance

UNITSMIN MAXSYMBOLPARAMETER

VFB = 1.4V , VO U T = 3.3V A16 35O perating C urrent into O U T(N ote 3)

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MAX1674/MA

X1675/MAX167

6


4 _______________________________________________________________________________________

Typical Operating Characteristics(L = 22H , C IN = 47F, C O U T = 47F0.1F, C R EF = 0.1F, TA = + 25C , unless otherw ise noted .)

VLBO= 5.5V , VLB I= 5.5V

VS H D N = 0 or VO U T

M AX1676, C LSEL = O U T

CONDITIONS

A1ILBOLBOO ff Leakage C urrent

nA75ISHDNSHDNInp ut C urrent

A3ICLSELC LSEL Input C urrent

UNITSMIN MAXSYMBOLPARAMETER

ELECTRICAL CHARACTERISTICS (continued)(VBATT = 2V, FB = O U T, R L = ,TA= -40C to +85C, unless otherw ise noted .) (N ote 4)

Note 4: Specifications to -40C are guaranteed by design, not prod uction tested .

100

00.01 0.1 1 10 100 1000

EFFICIENCY vs. LOAD CURRENT

20

30

10

M

AX1674toc01

LOAD CURRENT (mA)

EFFICIENCY(%)

40

50

60

70

90

80

VIN= 1.2V

VOUT= 5 VILIMIT= 500mA

VIN = 2.4VVIN = 3.6V

100

00.01 0.1 1 10 100 1000


20

30

10

M

AX1674toc02

LOAD CURRENT (mA)

EFFICIENCY(%)

40

50

60

70

90

80

VIN= 1.2V

VOUT= 5VILIMIT= 1A

VIN= 2.4VVIN = 3.6V

100

00.01 0.1 1 10 100 1000

EFFICI ENCY vs. LOAD CURRENT

20

30

10

M

AX1674toc03

LOAD CURRENT (mA)

EFFICIENCY(%)

40

50

60

70

90

80

VIN= 1.2V

VOUT= 3.3VILIMIT= 500mA

VIN= 2.4V

100

0

0.01 0.1 1 10 100 1000


20

30

10

M

AX1674toc04

LOAD CURRENT (mA)

EFFICIENCY(%)

40

50

60

70

90

80

VIN= 1.2V

VOUT= 3.3VILIMIT= 1A

VIN = 2.4V

1.290

1.292

1.296

1.294

1.298

1.300

-40 0-20 20 40 60 80 100

REFERENCE OUTPUT VOLTAGE

vs. TEMPERATURE

M

AX1674toc05

TEMPERATURE (C)

REFE

RENCEOUTPUTVOLTAGE(V)

IREF= 0

IREF= 100A

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MAX1674/MAX1

675/MAX1676


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0

40

20

100

80

60

140

120

160

0 1.5 2.00.5 1.0 2.5 3.0 3.5 4.0 4.5

NO-LOAD BATTERY CURRENT

vs. INPUT BATTERY VOLTAGE

M

AX1674toc07

INPUT BATTERY VOLTAGE (V)

INPUTBATTERYCURRENT(A)

ILIMIT= 1A, 5.0V

ILIMIT= 0.5A, 5.0V

ILIMIT= 0.5A, 3.3V

ILIMIT= 1A, 3.3V

1.8

0

0.01 1 100.1 100

START-UP VOLTAGE

vs. LOAD CURRENT

0.2

0.4

M

AX1674toc08

LOAD CURRENT (mA)

START-UPVOLTAGE(V)

0.8

0.6

1.0

1.2

1.4

1.6

WITHOUT DIODE

WITH 1N5817

-1.0

-0.6

-0.8

-0.2

-0.4

0.2

0

0.4

0.8

0.6

1.0

1 2.0 2.5 3.01.5 3.5 4.0 4.5 5.0 5.5

SHUTDOWN CURRENT

vs. SUPPLY VOLTAGE

M

AX167toc09

SUPPLY VOLTAGE (V)

SHUTDOWNCURRENT(A)

0

0.4

0.2

0.8

0.6

1.2

1.0

1.4

0 1.0 1.50.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0

SHUTDOWN THRESHOLD

vs. SUPPLY VOLTAGE

M

AX1674TOC10

SUPPLY VOLTAGE (V)

SHUTDOWNTHRESHOLD(V)

0

200

100

500

300

400

800

700

600

900

1.0 2.01.5 2.5 3.0 3.5 4.0 4.5

MAXIMUM OUTPUT CURRENT

vs. INPUT VOLTAGE (VOUT= 5V)

M

AX1674toc11

INPUT VOLTAGE (V)

MAXIMUM

OUTPUTCURRENT(mA)

1A CURRENT LIMIT

0.5A CURRENT LIMIT

0

200

100

400

300

600

500

800

700

1.0 1.4 1.61.2 1.8 2.0 2.2 2.4 2.6 2.8 3.0

MAXIMUM OUTPUT CURRENT

vs. INPUT VOLTAGE (VOUT= 3.3V)

M

AX1674toc12

INPUT VOLTAGE (V)

MAXIMUM

OUTPUTCURRENT(mA)

0.5A CURRENT LIMIT

1A CURRENT LIMIT

Typical Operating Characteristics (continued)(L = 22H , C IN = 47F, C O U T = 47F0.1F, C R EF = 0.1F, TA = +25C, unless otherw ise noted .)

1s/div

HEAVY-LOAD SWITCHING WAVEFORMSMAX1674 TOC13

VLX5V/div

ILX

0.5A/div

VOUTAC COUPLED

100mV/divVIN = 2.4V

VOUT = 5.0V0

0.4

0.2

0.8

0.6

1.0

1.2

2.0 3.0 3.52.5 4.0 4.5 5.0

LX CURRENT LIMIT

vs. OUTPUT VOLTAGE

M

AX1674toc14

OUTPUT VOLTAGE (V)

ILIM(A

)

MAX1674, M AX1676 (CLSEL = OUT)

MAX1675, M AX1676 (CLSEL = GND)

0

0.15

0.10

0.05

0.25

0.20

0.35

0.30

0.45

0.40

-60 -20-4 0 0 20 40 60 80 100

SWITCH RESISTANCE vs. TEMPERATURE

M

AX1674toc13.5

TEMPERATURE (C)

RESISTANCE()

P-CHANNEL

N-CHANNEL

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10s/div

LINE-TRANSIENT RESPONSEMAX1674 TOC15

VIN2V TO 3V

1V/div

VOUTAC COUPLED

100mV/divILOAD

100mA

5s/div

LOAD-TRANSIENT RESPONSEMAX1674 TOC16

IOUT200mA/div

VOUT50mV/div

AC

COUPLED

VIN = 2.4V

VOUT = 3.3V

500 s/div

EXITING SHUTDOWNMAX1674 TOC17

VSHDN2V/div

VOUT2V/div

MAX1674/MA

X1675/MAX167

6


6 _______________________________________________________________________________________

Typical Operating Characteristics (continued)(L = 22H , C IN = 47F, C O U T = 47F0.1F, C R EF = 0.1F, TA = +25C, unless otherw ise noted .)

Pin Description

PIN

NAME FUNCTIONMAX1674MAX1675

MAX1676

1 1 FBD ual-M ode Feedback Input. C onnect to G N D for +5.0V output.C onnect to O U T for +3.3V output. U se a resistor netw ork to set theoutput voltag e from +2.0V to + 5.5V .

2 2 LB I Low -B attery C om parator Input. Internally set to trip at +1.30V.

3 3 LBOO pen-D rain Low -B attery C om parator O utput. O utput is low w hen

VLB Iis

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Detailed DescriptionThe M A X1674/M A X1675/M A X1676 com pact, step-upD C -D C converters start up w ith voltag es as low as 0.9Van d op erate w ith a n inp ut voltag e d ow n to 0 .7V .C on sum ing on ly 16A of quiesc en t cu rren t, the sed evices offer a b uilt-in synchronous rectifier thatred uces cost by elim inating the need for an externaldiod e and im proves overall efficiency b y m inim izinglosses in the circuit (see Synchronous R ectificationsec-tion for details). The internal M O SFET resistance is typi-cally 0.3, w hich m inim izes losses. The current lim it ofthe M AX1674 and M A X1675 are 1A and 0.5A , respec-tively. The M A X1675s low er current lim it allow s the useof a physically sm aller inductor in sp ace-sensitiveapplications. The M A X1676 features a circuit that elim i-nates noise due to inductor ringing. In addition, the

M A X1676 offers a selectab le current lim it (0.5A or 1A )for design flexibility.

PFM Control SchemeA unique m inim um -off-tim e, current-lim ited, pulse-fre-quency-m od ulation (PFM ) control schem e is a key fea-ture of the M A X1674/M AX1675/M A X1676. This schem e

com bines the high output pow er and efficiency of apulse-w idth-m odulation (PW M ) device w ith the ultra-low

quiescent current of a traditional PFM (Figure 1). Thereis no oscillator; a constant-peak-current lim it in thesw itch allow s the inductor current to vary b etw een thispeak lim it and som e lesser value. A t light loads, thesw itching freq uency is governed by a p air of one-shotsthat set a typical m inim um off-tim e (1s) and a typicalm axim um on -tim e (4 s). Th e sw itch ing freq ue nc ydepends up on the load and the input voltage, and canrange up to 500kH z. The peak current of the internal N -cha nn el M O S FE T p ow er sw itch is fixed at 1A(M A X 16 74 ), at 0.5A (M A X 16 75 ), or is selec tab le(M A X1676). U nlike conventional pulse-skipping D C -D Cconverters (w here ripple am plitud e varies w ith inputvoltage), ripple in these devices d oes not exceed the

product of the sw itch current lim it and the filter-capaci-tor equivalent series resistance (ESR ).

Synchronous RectificationThe internal synchronous rectifier elim inates the needfor an external Schottky diode, thus reducing cost andboard space. D uring the cycle off-tim e, the P-channelM O SFET turns on and shunts the M O SFE T bod y diode.

MAX1674/MAX1

675/MAX1676


_______________________________________________________________________________________ 7

MAX1674

MAX1675

MAX1676

ONE-SHOTTRIGQ

F/F

RS Q

ONE-SHOT

TRIG QCURRENT-LIMITAMPLIFIER

ERRORAMPLIFIER

LOW-BATTERYCOMPARATOR

REFERENCE

REF

FB

VIN

47F

47F

R1200

R5

R6

DAMPINGSWITCH

22H

BATT

(MAX1676)

GND

LX

OUT 0.1F

0.1F

VOUT

R4LBI

LBO

R2

100k

R3

VIN VOUT

CLSEL

(MAX1676)

SHDN

MINIMUMOFF-TIMEONE-SHOT

ZEROCROSSINGAMPLIFIER

EN

MAXIMUMON-TIMEONE-SHOT

P

N

Figure 1. Sim plified Functional D iagram

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MAX1674/MA

X1675/MAX167

6 A s a resu lt, the synchronous rec tifier significantlyim proves efficiency w ithout the addition of an externalcom ponent. C onversion efficiency can be as high as94% , as show n in the Typical O perating C haracteristics.For low -voltage inputs from single cells (Alkaline, N iC d,or NiM H ), use an external Schottky diode such as the1N 5817 to ensure start-up .

Voltage ReferenceThe vo ltag e a t R E F is no m ina lly + 1.30 V. R E F c ansource up to 100A to external circuits. The referencem aintains excellent load regulation (see Typ ical O per-ating C haracteristics). A bypass cap acitor of 0.1F isrequired for proper operation.

ShutdownThe d evice e nters shutd ow n w hen V SHDN is low .

D uring shutdow n, the bod y diod e of the P-channelM O SFE T allow s current flow from the battery to the out-put. V O U T falls to approxim ately V IN - 0.6V and L Xrem ains high im pedance. The capacitance and load atO U T d eterm ine the rate a t w hich V O U T decays.Shutdow n can be p ulled as high as 6V , regardless ofthe voltag e at O U T.

Current Limit Select Pin (MAX1676)The M A X1676 allow s a selectab le ind uctor current lim itof either 0.5A or 1A . This allow s flexibility in designingfor higher current applications or for sm aller, com pactdesigns. C onnect C LSEL to O U T for 1A or to G N D for0.5A . C LSE L draw s 1.4A w hen connected to O U T.

BATT/Damping Switch (MAX1676)The M A X1676 is designed w ith an internal dam pingsw itch to m inim ize ringing at LX . The dam ping sw itchconnects an external resistor (R1) across the inductorw hen the inductors energy is d epleted (Figure 2).N orm ally, w hen the energy in the inductor is insufficientto supply current to the output, the capacitance andind uctance at LX form a resonant circuit that causesringing. The ringing continues until the energy is dissi-pated throug h the series resistance of the ind uctor. Thedam ping sw itch supplies a path to quickly dissipate thisenergy, m inim izing the ring ing at LX . D am ping LX ring-ing does not reduce VO U T ripple, but does red uce EM I.R1 = 200 w orks w ell for m ost applications w hile reduc-

ing efficiency by only 1% . Larger R1 values provide lessdam ping , but have less im pact on efficiency. G enerally,low er values of R 1 are need ed to fully dam p LX w henthe VO U T/VIN ratio is high (Figures 2, 3, and 4).


8 _______________________________________________________________________________________

MAX1676

DAMPINGSWITCH

BATT

R1200

LX

OUT

22H

VIN

0.1F 47F

VOUT

Figure 2. S im plified D iag ram of Ind uctor D am ping Sw itch

2s/div

VLX1V/div

Figure 3. LX R inging W ithout D am ping Sw itch

2s/div

VLX1V/div

Figure 4. LX W aveform w ith D am ping Sw itch (w ith 200external resistor)

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Selecting the Output VoltageVO U T can b e set to 3.3V or 5.5V by connecting the FB

pin to G N D (5V) or O U T (3.3V) (Figures 5 and 6).To adjust the output voltage, connect a resistor-dividerfrom VO U T to FB to G N D (Figure 7). C hoose a valueless than 260k for R 6. U se the follow ing equation tocalculate R5:

R 5 = R 6 [(VO U T / VR EF ) - 1]

w here VR EF = +1.3V and VO U T m ay rang e from 2V to5V. The input bias current of FB has a m axim um value

of 50nA w hich allow s large-value resistors (R 6 260k)to be used .

Low-Battery DetectionThe M A X1674/M A X1675/M A X1676 contain an on-chipcom parator for low -battery detection. If the voltage atLB I falls below the internal reference voltage (1.30V),LBO (an op en-drain output) sinks current to G N D . Thelow -battery m onitor threshold is set by tw o resistors, R 3and R 4 (Figures 5, 6, and 7). Since the LB I current isless than 50nA, large resistor values (R4 260k) canb e u sed to m inim ize loa d ing of the inp ut sup p ly.C alculate R 3 using the follow ing equation:

R 3 = R 4 [(VTR IP / VR EF) - 1]

for VTR IP 1.3V. VTR IP is the level w here the low -batterydetec tor ou tput goe s low , an d V R EF is the internal1.30V reference. C onnect a pull-up resistor of 100k orgreater from LBO to O U T w hen driving C M O S circuits.LBO is an op en-drain output, and can b e p ulled ashigh as 6V regardless of the voltage at O U T. W hen LBIis above the threshold, the LBO output is high im ped -ance. If the low -battery com parator is not used, ground

MAX1674/MAX1

675/MAX1676


_______________________________________________________________________________________ 9

MAX1674

MAX1675

MAX1676

BATT(MAX1676)

VIN

LBI

REF

GND

R3

R1200

R4

R2100k

47F10V

22H

0.1 F

LX

LBO

0.1F 47F

+3.3V200mA

VOUT

LOW-BATTERYOUTPUT

FB

SHDN

OUT

CLSEL(MAX1676)

Figure 5. Preset O utput Voltag e of + 3.3V

MAX1674

MAX1675

MAX1676

BATT(MAX1676)

VIN

LBI

REF

GND

R6

R5

R3

R1200

R4 R2100k

22H

47F

0.1F

LX

LBO

OUTPUT2V to 5.5V

FB

SHDN

OUT

CLSEL(MAX1676)

LOW-BATTERYOUTPUT

0.1 F 47F

Figure 7. S etting an A djustab le O utput

MAX1674

MAX1675

MAX1676

BATT(MAX1676)

VIN

LBI

REF

GND

R3

R1200

R4 R2100k

22H47F

0.1 F

LX

LBO

0.1 F 47F

OUTPUT5.0V,150mA

FB

SHDN

OUT

CLSEL(MAX1676)

LOW-BATTERYOUTPUT

Figure 6. P reset O utput Voltag e of +5V

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X1675/MAX167

6

LB I and LBO. For VTR IP less than 1.3V, configure thecom parator as show n in Figure 8. C alculate the value ofthe external resistors R 3 and R 4 as follow s:

R3 = R 4(VREF - VTR IP) / (VO U T - VR EF)

Since the low -battery com parator is noninverting, exter-nal hysteresis can be ad ded by connecting a resistorbetw een LBOand LB I as show n in Figure 9. W hen LBOis high, the series com bination of R 2 and R 7 sourcecurrent into the LB I sum m ing junction.

Applications Information

Inductor SelectionAn ind uctor value of 22H perform s w ell in m ost ap pli-cations. The M A X1674/M A X1675/M A X1676 w ill alsow ork w ith ind uctors in the 10H to 47H range. Sm allerinductance values typically offer a sm aller physical sizefor a given series resistance, allow ing the sm allest

overall circuit dim ensions. H ow ever, due to higher peakinductor currents, the output voltage ripple (IPEAK xoutput filter capacitor ESR ) also tends to be higher.C ircuits using larger inductance values exhibit higheroutput current capability and larger physical dim en-sions for a given series resistance. The inductors incre-m ental saturation current rating should be greater thanthe p eak sw itch-current lim it, w hich is 1 A for the

M A X1674, 500m A for the M A X1675, and 1A or 0.5A forthe M A X1676. H ow ever, it is generally accep tab le tobias the ind uctor into saturation by as m uch as 20% ,although this w ill slightly reduce efficiency. Table 1 lists

suggested com ponents.The inductors D C resistance significantly affects effi-ciency. See Table 2 for a com parison of ind uctor speci-fica tions. C alculate the m axim um ou tput current asfollow s:

w here IO UT(M AX)= m axim um output current in am ps

VBATT = input voltage

L = inductor value in H

= efficiency (typ ically 0.9)

tO FF = LX sw itchs off-tim e in s

R P = resistance of P-channel M O SFET in

ILIM = 0.5A or 1.0A

V IV V

L

tR

VO U T M A X

B A TT LIMO U T BA TT

O FFP

O U T( ) =

+

/

1 2


10 ______________________________________________________________________________________

MAX1674

MAX1675

MAX1676

BATT(MAX1676)

VIN

LBI

REFGND

R3

R1200

R4

22H47F

0.1 F

LX

LBO

VOUT

FB

R2100k

SHDN

OUT

CLSEL(MAX1676)

LOW-BATTERYOUTPUT

0.1 F 47F

Figure 8. Setting R esistor Values for the Low -Battery Indicatorw hen VIN< 1.3V

MAX1674

MAX1675

MAX1676

LBI

GND

VTRIP(VH, VL)

R3

R4

R7

VHIS THE UP PER TRIP LEVELVLIS THE L OWER TRIP LEVEL

WHERE

R2100k

LBO

OUT VOUT

0.1F 47F

V = 1.3V

V = 1 .3 V

H

L

( ) + +

( ) +

+

( . )

( . ) ( )

13

7

3

4

13

4

1 3 3

1 3 2 7

R

R

R

R

R

R

V V R

V R R

O U T

Figure 9. A dding External H ysteresis to the Low -BatteryIndicator

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Capacitor SelectionA 47F, 10V surface-m ount tantalum (SM T) output filtercapacitor provides 80m V output ripple w hen step pingup from 2V to 5V. Sm aller capacitors (dow n to 10Fw ith higher ESR s) are acceptable for light loads or inapplications that can tolerate higher output ripple.Values in the 10F to 100F rang e are recom m end ed.

The eq uivalent series resistance (ESR ) of both bypassand filter capacitors affects efficiency and output rip-ple. O utput voltage ripple is the product of the peak

ind uctor current and the output capacitor ES R . U selow -ESR capacitors for best perform ance, or connecttw o or m ore filter capacitors in parallel. Low -ESR , SM Ttantalum cap acitors are currently a va ilab le fromSprag ue (595D series) A VX (TP S series) and othersources. C eram ic surface-m ount and Sanyo O S-C O Norganic-sem iconductor throug h-hole capacitors also

exhibit very low ESR , and are especially useful for oper-ation at cold tem peratures. See Table 3 for a list of sug-gested com ponent suppliers.

MAX1674/MAX1

675/MAX1676


______________________________________________________________________________________ 11

PRODUCTIONMETHOD

INDUCTORS CAPACITORS RECTIFIERS(OPTIONAL)

Surface M ount

Sum ida C D 43 series

Sum ida C D 54 series

C oilcraft D T1608C

C oilcraft D O 1608C

C oiltronics U ni-PA C

M urata LQ H 4 series

Sp rague 593D seriesSp rague 595D seriesA VX TPS seriesceram ic

M otorola M B R 0530N ihon EC 15Q S02L

M iniature Through-H ole Sum ida R C H 654-220 Sanyo O S-C O N series

Table 1. Suggested Components

Table 2. Surface-Mount InductorSpecifications

MANUFACTURERPART NUMBER

H (max) IPEAK(A) HEIGHT

(mm)

C oilcraft D T1608C -103 10 0.095 0.7 2.92

C oilcraft D O 1608C -153 15 0.200 0.9 2.92

C oilcraft D O 1608C -223 22 0.320 0.7 2.92

C oiltronics U P1B -100 10 0.111 1.9 5.0

Table 3. Component Suppliers

COMPANY PHONE FAX

A VX U SA (803) 946-0690 U SA (803) 626-3123

C oilcraft USA (847) 639-6400 USA (847) 639-1469

C oiltronics U SA (561) 241-7876 U SA (561) 241-9339

M urataU SA (814) 237-1431

(800) 831-9172U SA (814) 238-0490

N ihonU SA (805) 867-2555

Japan 81-3-3494-7411U SA (805) 867-2556Japan 81-3-3494-7414

M otorolaU SA (303) 675-2140

(800) 521-6274U SA (303) 675-2150

SanyoU SA (619) 661-6835

Japan 81-7-2070-6306U SA (619) 661-1055

Japan 81-7-2070-1174

Sum idaU SA (647) 956-0666

Japan 81-3-3607-5111U SA (647) 956-0702

Japan 81-3-3607-5144

Taiyo Yuden U SA (408) 573-4150 U SA (408) 573-4159

S prag ue U S A (603) 224-1961 U S A (603) 224-1430

C oiltronics U P1B -150 15 0.175 1.5 5.0

C oiltronics U P1B -220 22 0.254 1.2 5.0

M urata LQ H 4N 100 10 0.560 0.4 2.6

M urata LQ H 4N 220 22 0.560 0.4 2.6

Sum ida C D 43-8R 2 8.2 0.132 1.26 3.2

Sum ida C D 43-100 10 0.182 1.15 3.2Sum ida C D 54-100 10 0.100 1.44 4.5

Sum ida C D 54-180 18 0.150 1.23 4.5

Sum ida C D 54-220 22 0.180 1.11 4.5

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12 ______________________________________________________________________________________

TRAN SISTO R C O U N T:751

Chip Information

Package Information

Optional External RectifierA lthoug h not required , a Schottky diod e (such as the

M B R 0520) connected b etw een LX and O U T allow slow er start-up voltag es (Figure 10) and is recom m end-ed for single-cell operation. N ote that adding this diodeprovides no significant efficiency im provem ent.

PC Board Layout and GroundingC areful printed circuit layout is im portant for m inim izingground bounce and noise. K eep the ICs G N D pin andthe ground leads of the input and output filter capaci-tors less than 0.2in (5m m ) apart. In addition, keep allconnections to the FB and LX pins as short as p ossi-ble. In p articular, w hen using external feedback resis-tors, locate them as close to the FB as possible. Tom axim ize output pow er and efficiency and m inim ize

output ripple voltag e, use a ground plane and solderthe ICs G N D directly to the ground plane.

MAX1674

MAX1675

MAX1676

BATT(MAX1676)

VIN SINGLE CELL

LBI

REFGND

R3

R1200

R4 R2100k

22H47F

0.1F

LX

LBO

FB

SHDN

OUT

LOW-BATTERYOUTPUT

0.1F

MBR0520

47F

CLSEL(MAX1676)

Figure 10. A dding a Schottky D iode for Sing le-C ell O peration

10LU

MA

XB

.EPS

Documents

Max 1674