MAX746CSE データシートの表示（PDF） - Maxim Integrated

部品番号

コンポーネント説明

メーカー

MAX746CSE

High-Efficiency, PWM, Step-Down, N-Channel DC-DC Controller

Maxim Integrated 

High-Efficiency, PWM, Step-Down,

N-Channel DC-DC Controller

or equal to the N-FET’s VGS threshold voltage. Once

the switch is off, the voltage at EXT is pulled to GND

and the N-FET source voltage is a Schottky diode

drop below GND. However, this is not always the case

in the “in-between” mode, due to the changing duty

cycle inherent with DCM. When the device is at maxi-

mum duty cycle, EXT turns off at VGS, but the switch

sometimes turns on again after the minimum off-time

before EXT can be pulled to GND. This results in short

spikes, which can be seen on the EXT waveform in the

Typical Operating Characteristics.

AC Stability with Low Input/Output Differentials

At low input/output differentials, the inductor current

cannot slew quickly enough to respond to load

changes, so the output filter capacitor must hold up the

voltage as the load transient is applied. In Figure 1a’s

circuit, for V+ = 6V, increase the output filter capacitor

to 900µF (Sprague 595D low-ESR capacitors) to obtain

a transient response less than 250mV with a load step

from 0.1A to 3A. As V+ increases, the inductor current

slews faster, so the size of the output filter capacitor can

be reduced (see Table 1).

Table 3. Component Suppliers

SUPPLIER

PHONE

FAX

INDUCTORS

Coiltronics

(305) 781-8900 (305) 782-4163

Gowanda

(716) 532-2234 (716) 532-2702

Sumida USA

(708) 956-0666 (708) 956-0702

Sumida Japan

81-3-3607-511 81-3-3607-5428

CAPACITORS

Kemet

(803) 963-6300 (803) 963-6322

Matsuo

(714) 969-2491 (714) 960-6492

Nichicon

(708) 843-7500 (708) 843-2798

Sprague

(603) 224-1961 (603) 224-1430

Sanyo USA

(619) 661-6322

Sanyo Japan

81-3-3837-6242

United Chemi-Con

(714) 255-9500 (714) 255-9400

DIODES

Motorola

(800) 521-6274

Nihon USA

(805) 867-2555 (805) 867-2698

Nihon Japan

81-3-3494-7411 81-3-3494-7414

POWER TRANSISTORS

Harris

(407) 724-3739 (407) 724-3937

International Rectifier (213) 772-2000 (213) 772-9028

Siliconix

(408) 988-8000 (408) 727-5414

RESISTORS

IRC

(512) 992-7900 (512) 992-3377

___________________Chip Topography

LBI LBO GND V+

SS

CP

REF

SHDN

HIGH

EXT

0.130"

(3.30mm)

FB CC AV+ OUT CS

0.080"

(2.03mm)

TRANSISTOR COUNT: 508;

SUBSTRATE CONNECTED TO HIGH.

AGND

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.

16 __________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 (408) 737-7600

© 1993 Maxim Integrated Products

Printed USA

is a registered trademark of Maxim Integrated Products.

Share Link: