tolerate higher output ripple. Values in the 10µF to 47µF

range are recommended.

The equivalent series resistance (ESR) of both bypass

and filter capacitors affects efficiency and output ripple.

Use low-ESR capacitors for best performance, or con-

nect two or more filter capacitors in parallel. Low-ESR,

SMT tantalum capacitors are currently available from

Sprague (595D series) and AVX (TPS series). See

Table 1 for a list of suggested capacitor suppliers.

Rectifier Diode

For optimum performance, a switching Schottky diode

(such as the 1N5817 or MBR0520LTI) is recommended.

Refer to Table 1 for a list of component suppliers. For

low output power applications, a PN-junction switching

diode (such as the 1N4148) will also work well,

although its greater forward voltage drop will reduce

efficiency and raise the start-up voltage.

PC Layout and Grounding

The circuit’s high-frequency operation makes PC layout

important for minimizing ground bounce and noise.

Keep the IC’s GND pin and the ground leads of C1 and

C2 (Figure 2) less than 0.2in (5mm) apart. Also keep all

connections to the FB and LX pins as short as possible.

To maximize output power and efficiency and minimize

output ripple voltage, use a ground plane and solder

the IC’s GND (pin 7) directly to the ground plane.

3.3V/5V or Adjustable-Output,

Single-Cell DC-DC Converters

______________________________________________________________________________________

11

Table 2. Surface-Mount Inductor Information

MANUFACTURER /PART

INDUCTANCE

(

mH)

RESISTANCE

(

W)

RATED CURRENT

(A)

HEIGHT

(mm)

Sumida CD73-331

330

1.5

0.28

3.5

Sumida CD104-331

330

1.1

0.42

4

Murata-Erie LQH4N331K04M00**

330

8.2

0.095

2.6

TDK NLC565050T-331K**

330

4.9

0.14

5

Coilcraft D01608-334

330

2.9

0.16

3.2

Coilcraft DT1608-334

330*

2.9

0.16

3.2

Coilcraft D03316-334

330

0.7

0.6

5.4

Coilcraft DT3316-334

330*

0.7

0.6

5.4

J.W. Miller PM105-331K

330

1.1

0.52

5.4

* Shielded

** Low cost

___________________Chip Topography

TRANSISTOR COUNT: 357;

SUBSTRATE IS CONNECTED TO OUT.

GND

LBI

OUT

3/5

OR FB*

REF

LX

0.084"

(2.1336mm)

0.058"

(1.4732mm)

SHDN

LBO

*3/5 FOR MAX866; FB FOR MAX867.