Low-Profile, 5V/12V or Adjustable, Step-Up

DC-DC Converters for Flash Memory/PCMCIA Cards

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11

Diode Selection

The MAX606/MAX607’s high switching frequency

demands a high-speed rectifier. Use a Schottky diode

with at least a 0.5A average current rating and a 1.2A

peak current rating, such as an MBR0520L. See Table

3 for a list of component suppliers.

Capacitor Selection

Output Filter Capacitor

The output voltage ripple is a function of the output

capacitor’s equivalent series resistance (ESR) and

capacitance. For best performance, use ceramic

capacitors. Higher-ESR capacitors, such as tantalums,

will cause excessive ripple. See Table 3 for a list of

component suppliers.

The output voltage ripple is approximately 100mVp-p

for the 12V Standard Application Circuit (Figure 1) and

50mV for the 5V circuit (Figure 2). To further reduce this

ripple, or to reduce the ripple on a different application

circuit, increase the value of the output filter capacitor.

If this capacitor is low ESR (e.g., ceramic), the output

voltage ripple will be dominated by this capacitance.

Input Bypass Capacitors

For applications where the MAX606/MAX607 are physi-

cally close to the input supply’s filter capacitor (e.g., in

PCMCIA drivers from the host computer), the input

bypass capacitor may not be necessary.

In other applications where the MAX606/MAX607 are

more than a few inches away from the supply (such as

memory cards), the input bypass capacitor is needed

to reduce reflected current ripple to the supply and

improve efficiency by creating a low-impedance path

for the ripple current. Under these circumstances, the

associated high Q and low ESR of ceramic capacitors

do not diminish the problem. Therefore, include some

low-Q, moderate-ESR capacitance (e.g., tantalum) at

the input in order to reduce ringing.

Layout

The MAX606/MAX607’s high-frequency operation and

high peak currents make PC board layout critical to

minimize ground bounce and noise. Locate input

bypass and output filter capacitors as close to the

device pins as possible. All connections to OUT (and to

FB when operating in adjustable-output mode) should

also be kept as short as possible. A ground plane is

recommended. Solder GND and PGND directly to the

ground plane. Refer to the MAX606/MAX607 evaluation

kit manual for a suggested surface-mount layout.

___________________Chip Topography

LX

0.084"

(2.134mm)

0.058"

(1.473mm)

LX

LX

OUT

SS

GND

PGND

PGND

PGND

SEL

SHDN

V+

TRANSISTOR COUNT: 613

SUBSTRATE CONNECTED TO GND