Rainbow-electronics MAX1765 Instrukcja Użytkownika Pobierz pdf (Strona 17)

where I

LIM

is the peak inductor current limit, f

is the

operating frequency (typically 1.2MHz), L is the induc-

tance of the chosen inductor, L

RESR

is the resistance of

the chosen inductor, R

NCH

and R

PCH

are the resis-

tances of the internal N-channel and P-channel,

respectively.

Table 5 lists the typical available output current when oper-

ating with one or more NiCd/NiMH cells or one Li+ cell.

Adding a Manual Power Reset

A momentary pushbutton switch can be used to turn

the MAX1765 on and off (Figure 11). ONA is pulled low

and ONB is pulled high to turn the device off. When the

momentary switch is pressed, ONB is pulled low and

VI R L

VVI RL

VIRR

OUT MAX LIM

RIPPLE

IN LIM NCH ESR

OUT IN LIM NCH ESR

OUT LIM PCH NCH

=−













−

()

=××−× +

()

[]

−+ × +

()

+−

()

MAX1765

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

with 500mA Linear Regulator

______________________________________________________________________________________ 17

Figure 9. Soft-Start, Maximum Current Limit

LIM

= 1.25A

= R

500k

Ω

< R

< 1M

Ω

MAX1765

REF

ISET

0.22

Figure 8. Soft-Start, Reduced Current Limit

MAX1765

REF

ISET

0.22

SS1

SS2

LIM

= 1.25A

= (R

SS1

|| R

SS2

) C

( )

SS2

SS1

SS2

Table 3. Component Selection Guide

PRODUCTION 3.3µH INDUCTORS CAPACITORS SCHOTTKY DIODES

Surface Mount

Coilcraft DS3316P

Coilcraft LPT3305

AVX TPS series

Kemet T510 series

Sanyo POSCAP series

Motorola MBR0520L

Nihon EP10QY03

Table 4. Component Suppliers

SUPPLIER COUNTRY PHONE

AVX

USA

843-448-9411

Coilcraft

USA

847-639-6400

Kemet

USA

810-287-2536

USA 408-629-4789

Motorola

Japan 81-45-474-7030

USA 847-956-0666

Sumida

Japan 81-3-3607-3302

Note: Please indicate that you are using the MAX1765 when

contacting these component suppliers.

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