Feed-Forward Capacitor

When adjusting the output voltage, it may be necessary

to parallel a 47pF to 220pF capacitor across R2, as

shown in Figures 2 and 3. Choose the lowest capacitor

value that insures stability; high capacitance values

may degrade line regulation.

__________Applications Information

Starting Up Under Load

The

Typical Operating Characteristics show the Start-Up

Voltage vs. Load Current graphs for 5V and 12V output

voltages. These graphs depend on the type of power

switch used. The MAX608 is not designed to start up

under full load with low input voltages.

Layout Considerations

Due to high current levels and fast switching wave-

forms, which radiate noise, proper PC board layout is

essential. Protect sensitive analog grounds by using a

star ground configuration. Minimize ground noise by

connecting GND, the input bypass capacitor ground

lead, and the output filter capacitor ground lead to a

single point (star ground configuration). Also, minimize

lead lengths to reduce stray capacitance, trace resis-

tance, and radiated noise. Place input bypass capaci-

tor C2 as close as possible to OUT and GND.

If an external resistor divider is used (Figures 2 and

3), the trace from FB to the resistors must be

extremely short.

5V or Adjustable, Low-Voltage,

Step-Up DC-DC Controller

______________________________________________________________________________________

11

PRODUCTION

INDUCTORS

CAPACITORS

TRANSISTORS

Surface Mount

Sumida

CD54 series

CDR125 series

Coiltronics

CTX20 series

Coilcraft

DO3316 series

DO3340 series

Matsuo

267 series

Sprague

595D series

AVX

TPS series

Sanyo

OS-CON series

Siliconix

Si9410DY

Si4410DY

Si6426DQ

Si6946DQ

Motorola

MTP3055EL

MTD20N03HDL

MMFT3055ELT1

Through Hole

Sumida

RCH855 series

RCH110 series

Sanyo

OS-CON series

Nichicon

PL series

Motorola

1N5817–1N5822

MUR105 (high-speed

silicon)

Central Semiconductor

CMPSH-3

CMPZ5240

Nihon

EC11 FS1 series (high-

speed silicon)

Motorola

MBRS1100T3

MMBZ5240BL

DIODES

USA: (603) 224-1961

(603) 224-1430

Sprague

USA: (800) 554-5565

(408) 970-3950

Siliconix

USA: (619) 661-6835

(619) 661-1055

Japan: 81-7-2070-1005

81-7-2070-1174

Sanyo

USA: (708) 843-7500

(708) 843-2798

USA: (805) 867-2555

(805) 867-2556

Nihon

USA: (708) 956-0666

(708) 956-0702

Japan: 81-3-3607-5111

81-3-3607-5144

Sumida

USA: (516) 435-1110

(516) 435-1824

Central

Semiconductor

USA: (800) 521-6274

(602) 952-4190

Motorola

USA: (708) 639-6400

(708) 639-1469

Coilcraft

USA: (714) 969-2491

(714) 960-6492

Japan: 81-6-337-6450

81-6-337-6456

USA: (407) 241-7876

(407) 241-9339

Coiltronics

PHONE

FAX

SUPPLIER

USA: (803) 448-9411

(803) 448-1943

AVX

Matsuo

Nichicon