MAX1723 Ver la hoja de datos (PDF) - Maxim Integrated

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componentes Descripción

Fabricante

MAX1723

1.5µA IQ, Step-Up DC-DC Converters in Thin SOT23-5

Maxim Integrated 

1.5µA IQ, Step-Up DC-DC Converters

in Thin SOT23-5

INPUT

0.8V TO VOUT

10µF

10µH

BATT

LX

OUT

MAX1722

FB

GND

OUTPUT

2V TO 5.5V

R2

10µF

R1

Figure 7. Adjustable Output Circuit

Inductor Selection

The control scheme of the MAX1722/MAX1723/

MAX1724 permits flexibility in choosing an inductor. A

10µH inductor value performs well in most applications.

Smaller inductance values typically offer smaller physi-

cal size for a given series resistance, allowing the

smallest overall circuit dimensions. Circuits using larger

inductance values may start up at lower battery volt-

ages, provide higher efficiency, and exhibit less ripple,

but they may reduce the maximum output current. This

occurs when the inductance is sufficiently large to pre-

vent the maximum current limit (ILIM) from being

reached before the maximum on-time (tON(MAX))

expires.

Table 1. Suggested Inductors and

Suppliers

MANUFACTURER

INDUCTOR

PHONE

WEBSITE

Coilcraft

DO1608 Series

847-639-2361

DO1606 Series www.coilcraft.com

Murata

LQH4C Series

770-436-1300

www.murata.com

Sumida

CDRH4D18 Series

CR32 Series

CMD4D06 Series

847-545-6700

www.sumida.com

Sumitomo/

Daidoo Electronics

CXLD140 Series

+81 (06) 6355-5733

www.daidoo.co.jp

Toko

3DF Type

D412F Type

847-297-0070

www.toko.com

For maximum output current, choose the inductor value

so that the controller reaches the current-limit before

the maximum on-time is triggered:

L < VBATT tON(MAX)

ILIM

where the maximum on-time is typically 5µs, and the

current limit (ILIM) is typically 500mA (see Electrical

Characteristics table).

For larger inductor values, determine the peak inductor

current (IPEAK) by:

IPEAK

=

VBATT

tON(MAX)

L

INPUT

0.8V TO VOUT

C1

10µF

ON

OFF

10µH

BATT

LX

OUT

MAX1724

SHDN

GND

OUTPUT

VOUT (NOM)

C2

10µF

Figure 8. MAX1724 Standard Application Circuit

The inductor’s incremental saturation current rating should

be greater than the peak switching current. However, it is

generally acceptable to bias the inductor into saturation

by as much as 20%, although this will slightly reduce effi-

ciency. Table 1 lists suggested inductors and suppliers.

Maximum Output Current

The maximum output current depends on the peak induc-

tor current, the input voltage, the output voltage, and the

overall efficiency (η):

IOUT(MAX)

=

1

2

IPEAK





VBATT

VOUT



 η

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