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.

High-Efficiency, PWM, Step-Down,

N-Channel DC-DC Controller

SUPPLIER

PHONE

FAX

Coiltronics

(305) 781-8900

(305) 782-4163

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INDUCTORS

CAPACITORS

DIODES

POWER TRANSISTORS

RESISTORS

Table 3. Component Suppliers

___________________Chip Topography

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-

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).

HIGH

AGND

EXT

SS

REF

SHDN

LBI LBO GND

CS

OUT

CC

FB

AV+

0.130"

(3.30mm)

0.080"

(2.03mm)

TRANSISTOR COUNT: 508;

SUBSTRATE CONNECTED TO HIGH.

V+

CP