MAX668EVKIT+ - Maxim Integrated

General Description

The MAX668 evaluation kit (EV kit) combines a con-

stant-frequency, pulse-width-modulation (PWM) step-

up controller with an external N-channel MOSFET and

Schottky diode to provide a regulated output voltage.

The EV kit accepts a +3V to VOUT input and converts it

to a +12V output for currents up to 1A, with greater than

90% conversion efficiency. The EV kit operates at

500kHz, allowing the use of small external components.

The MAX668 EV kit is a fully assembled and tested sur-

face-mount circuit board. This EV kit can also be con-

figured for the application circuits listed in the

EV Kit

Application Circuit Capabilities

table. For input voltages

below 3V and down to 1.8V, replace the MAX668 with a

MAX669. The MAX669 must always operate in boot-

strapped mode (JU2 shunt across pins 1 and 2).

Features

♦+3V to VOUT Input Range (as shipped)

♦+12V or Adjustable Output Voltage

♦Output Current Up to 1A

♦N-Channel External MOSFET

♦4µA IC Shutdown Current

♦500kHz Switching Frequency

♦Surface-Mount Components

♦Fully Assembled and Tested

Evaluates: MAX668/MAX669

MAX668 Evaluation Kit

________________________________________________________________

Maxim Integrated Products

19-4778; Rev 0a; 8/98

QTY DESCRIPTION

C1 1

C5 1

C2 1 0.1µF ceramic capacitor

C3 1

C4, C8 2 1µF ceramic capacitors

C7 1

C6 0

D1 1

L1 1

4.7µH power inductor

Sumida CDRH104-4R7 (shielded),

Coiltronics UP2B-4R7, or

Coilcraft DO3316P-472

0.22µF ceramic capacitor

120µF, 20V, low-ESR tantalum cap

Sprague 594D127X0020R2T

68µF, 20V, low-ESR tantalum cap

Sprague 593D686X0020E2W or

AVX TPSE686M020R0150

DESIGNATION

220pF ceramic capacitor

Not installed

3A Schottky diode

Hitachi HRF302A or

Motorola MBRS340T3

Component List

PART

MAX668EVKIT 0°C to +70°C

TEMP. RANGE IC PACKAGE

10 µMAX

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.

Ordering Information

Note: To evaluate the MAX669, request a MAX669EUB free

sample with the MAX668EVKIT.

EV Kit Application Circuit

Capabilities

VIN(MIN)

(V)

1.8

VOUT

(V)

IOUT

(A)

0.4

0.1

50.65

2.5

Note: Design information for these applications is included.

The shaded row shows EV kit configuration as shipped.

12 1

24 0.02

0.5

N1 1 N-channel MOSFET

Fairchild FDS6680 or

International Rectifier IRF7801

R1 1 0.020Ω, 1%, 1/2W resistor

Dale WSL-2010-R020F or

IRC LR2010-01-R020F

R2 1 218kΩ, 1% resistor

R3 1 24.9kΩ, 1% resistor

R4 1 100kΩ, 1% resistor

U1 1 MAX668EUB

JU1, JU2 2 3-pin headers

JU3 1 2-pin header

None 2 Shunts (JU1, JU2)

None 1 MAX668/MAX669 PC board

None 1 MAX668/MAX669 data sheet

_________________________Quick Start

The MAX668 EV kit is fully assembled and tested. Follow

these steps to verify board operation. Do not turn on

the power supply until all connections are completed.

1) Place the shunt on JU1 across pins 1 and 2. Verify

that the shunt is across JU2 pins 2 and 3 (VCC is

tied to VIN) and JU3 is open (LDO is open).

2) Connect a +5V supply to the VIN pad. Connect

ground to the GND pad.

3) Connect a voltmeter to the VOUT pad.

4) Turn on the power supply and verify that the output

voltage is 12V.

_______________Detailed Description

The MAX668 EV kit provides a regulated +12V output

voltage from an input source as low as +3V. It drives

loads up to 1A with greater than 90% conversion effi-

ciency. This EV kit is shipped configured in the non-

bootstrapped mode (VCC is tied to VIN). However, there

are several methods of connecting VCC and LDO

depending on the specific design including input and

output voltage range, quiescent power dissipation,

MOSFET selection, and load.

If the minimum input voltage is below +3.0V, use the

MAX669 with VCC bootstrapped from VOUT (Table 1). In

bootstrapped mode, if VOUT is always less than +5.5V,

then LDO may be shorted to VCC to eliminate the

dropout voltage of the LDO regulator. This increases the

gate drive to the MOSFET, which lowers the MOSFET

on-resistance but increases the MAX668 supply current

due to gate-charge loss.

If VIN is greater than +3.0V, the MAX668’s VCC can be

powered from VIN. This will decrease quiescent power

dissipation, especially when VOUT is large. If VIN is

always less than +5.5V, LDO may be shorted to VCC to

eliminate the dropout voltage of the LDO regulator. If

VIN is in the range of +3V to +4.5V, then the user may

still want to bootstrap from VOUT to increase gate drive

to the MOSFET at the expense of power dissipation. If

VIN is always greater than +4.5V, the VCC input should

always be tied to VIN, since bootstrapping from VOUT

will not increase the gate drive from LDO, but quiescent

power dissipation will rise. Jumpers JU2 and JU3 con-

trol the VCC and LDO inputs (see

MAX668/MAX669

data sheet).

Jumper Selection

The 3-pin header JU1 selects shutdown mode. Table 1

lists the selectable jumper options. The 3-pin header

JU2 selects bootstrapped mode. Table 2 lists the

selectable jumper options. For VCC less than 5.5V, use

the 2-pin header JU3 to short LDO to VCC. This elimi-

nates the internal linear regulator (LDO) dropout volt-

age. For the MAX668, this allows operation with input

voltages down to 2.7V. Table 3 lists the selectable

jumper options.

Other Output Voltages

The MAX668 EV kit can also be used to evaluate other

output voltages. Refer to the

Output Voltage Selection

section in the MAX668 data sheet for instructions on

selecting the feedback resistors R2 and R3. For output

voltages greater than 15V, replace C5 (20V) with a

capacitor that has a higher voltage rating.

In addition to the standard EV kit configuration of 3VIN

to 12VOUT at 1A, the

EV Kit Application Circuit

Capabilities

table listed several common Input/Output

combinations. Table 4 lists the components recom-

mended for these alternative circuits.

Evaluates: MAX668/MAX669

MAX668 Evaluation Kit

2 _______________________________________________________________________________________

Component Suppliers

Note: Please indicate that you are using the MAX668 when con-

tacting these component suppliers.

CoilCraft 708-639-6400 708-639-1469

SUPPLIER PHONE FAX

Dale-Vishay 402-564-3131 402-563-6418

Coiltronics 561-241-7876 561-241-9339

AVX 803-946-0690 803-626-3123

Hitachi 888-777-0384 650-244-7947

International

Rectifier 310-322-3331 310-322-3332

Fairchild 408-721-2181 408-721-1635

IRC 512-992-7900 512-992-3377

Motorola 602-303-5454 602-994-6430

Siliconix 408-988-8000 408-970-3950

Sprague 603-224-1961 603-224-1430

Sumida 708-956-0666 708-956-0702

Vishay/Vitramon 203-268-6261 203-452-5670

Evaluates: MAX668/MAX669

MAX668 Evaluation Kit

_______________________________________________________________________________________ 3

Table 1. Jumper JU1 Functions

SHUNT

LOCATION SYNC/SHDN PIN MAX668 OUTPUT

1 and 2 Connected to VCC MAX668 enabled, VOUT = 12V.

MAX668 operates at internal frequency.

2 and 3 Connected to GND Shutdown mode, VOUT = VIN - diode

Not installed Floating MAX668 can be externally synchronized when the

SYNC/SHDN pad is clocked.

Table 2. Jumper JU2 Functions

SHUNT

LOCATION VCC PIN MAX668 MODE

1 and 2 Connected to VOUT Bootstrapped mode

2 and 3 Connected to VIN Non-bootstrapped mode

Table 3. Jumper JU3 Functions

SHUNT LOCATION LDO PIN

On Connected to VCC

Off Open

Evaluates: MAX668/MAX669

MAX668 Evaluation Kit

4 _______________________________________________________________________________________

Table 4. Components for Alternate Application Circuits

VIN

(MIN)

(V)

VOUT

(V)

121.8

IOUT

(A)

1.8

0.4

0.1

MAXIM

PART

NO.

MAX669

JU2

BOOT-

STRAPPED

vs.

NON-BOOT-

STRAPPED

1 & 2

Bootstrapped

1 & 2

Bootstrapped

(µH)

4.7

Sumida

CDRH10

4-4R7

1.0

Coilcraft

D03316-

102

(mΩ)

Dale

WSL-

2010-

R020F

Dale

WSL-

2010-

R015F

122.5

0.65

MAX669

MAX668

1 & 2

Bootstrapped

1 & 2

Bootstrapped

4.7

Sumida

CDRH10

4-4R7

4.7

Sumida

CDRH12

7-4R7

Dale

WSL-

2010-

R020F

Dale

WSL-

2512-

R015F

363

2412

0.020

0.5

MAX668

2 & 3

Non-

Bootstrapped

2 & 3

Non-

Bootstrapped

4.7

Sumida

CD43-

4R7

Sumida

CD73-

220

100

Dale

WSL-

1206-

R100F

Dale

WSL-

2010-

R050F

(kΩ)

218

454

218

398

453

(kΩ)

24.9

(kΩ)

100

200

100

Hitachi

HRF302A

Hitachi

HRF302A

Hitachi

HRF302A

Hitachi

HRF502A

Central

Semi-

conductor

CMPD914

Motorola

MBRS140T3

International

Rectifier

IRF7401

International

Rectifier

IRF7401

International

Rectifier

IRF7401

Fairchild

FDS6680

Fairchild

FDS5610

Fairchild

FDS6680

68µF

20V

AVX

TPSE686M

020R0150

68µF

20V

AVX

TPSE686M

020R0150

68µF

20V

AVX

TPSE686M

020R0150

330µF

10V

Kemet

T510X337

M010

10µF

6.3V, X7R

Taiyo

Yuden

JMK325BJ1

06MN

33µF

20V

AVX

TPSD336M

020R0200

120µF

20V

Sprague

594D127X

0020R2T

22µF

35V

AVX

TPSE226M

035R0300

120µF

20V

Sprague

594D127X

0020R2T

330µF

10V

Kemet

T510X337

M010

2.2µF

50V, X7R

Kemet

C1825C22

5MR0RAC

22µF

35V

AVX

TPSE226M

035R0300

Open

22µF

35V

AVX

TPSE226M

035R0300

Open

330µF

10V

Kemet

T510X337

M010

Open

Note:

This table lists components recommended for building other application circuits using the MAX668 EV kit.

Evaluates: MAX668/MAX669

MAX668 Evaluation Kit

_______________________________________________________________________________________ 5

MAX668

4.7µH

VOUT

12V, 1A

1µF

218k

0.02Ω

100k

0.22µF

68µF

20V

24.9k

220pF

120µF

20V

MBRS340T3

OPEN

LDO

VIN

CS+

EXT 8

1VOUT

REF

FREQ

VCC

0.1µF

1µF

JU3

JU2

JU1

SYNC/

SHDN SYNC/

SHDN

PGND

REF

1.25V

GND

Figure 1. MAX668 EV Kit Schematic

Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are

implied. Maxim reserves the right to change the circuitry and specifications without notice at any time.

_____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600

Evaluates: MAX668/MAX669

MAX668 Evaluation Kit

Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are

implied. Maxim reserves the right to change the circuitry and specifications without notice at any time.

_____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600

Figure 2. MAX668 EV Kit Component Placement Guide—

Component Side

Figure 3. MAX668 EV Kit PC Board Layout—Component Side Figure 4. MAX668 EV Kit PC Board Layout—Solder Side

1.0"

1.0" 1.0"

Mouser Electronics

Authorized Distributor

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MAX668EVKIT+