9/13

L6920

Table 7. Capacitors distributors main list

5.3 Inductor selection

Usually, inductors ranging between 5

µH to 40µH satisfy most of the applications.

Small value inductors have smaller physical size and guarantee a faster response to load transient but in steady

state condition a bigger ripple on output voltage is generated. In fact the output ripple voltage is given by Ipeak

multiplied by ESR. Furthermore, as shown in equation (1), inductor size affects also the maximum current de-

liverable to the load. Lastly, a low series resistance is suggested if very high efficiency values are needed. Any-

way, the saturation current of the choke should be higher than the peak current limit of the device (1A).

Good surface mounting inductors are available from COILCRAFTS, COILTRONICS, MURATA and other souc-

es. In the following table are listed some suggested components.

Table 8. Inductors distributors main list

5.4 Layout Guidelines

The board layout is very important in order to minimize noise, high frequency resonance problems and electro-

magnetic interference.

It is essential to keep as small as possible the high switching current circulating paths to reduce radiation and

resonance problems. So, the output and input cap should be very close to the device.

The external resistor dividers, if used, should be as close as possible to the pins of the device (FB and LBI) and

as far as possible from the high current circulating paths, to avoid pick up noise.

Large traces for high current paths and an extended groundplane, help to reduce the noise and increase the

efficiency.

For an example of recommended layout see the following evaluation board.

Manufacturer

Series

Cap Value (

µF)

Rated Voltage (V)

ESR (m

Ω)

AVX

TPS

15 to 470

6.3

50 to 1500

KEMET

T510/T494/

T495

10 to 470

6

30 to 1000

PANASONIC

EEFCD

22 to 47

6.3

50 to 700

SANYO POSCAP

TPA/B/C

22 to 230

6.3

40 to 80

SPRAGUE

595D

100 to 390

6.3

160 to 700

Manufacturer

Series

Inductor Value (uH)

Saturation Current (A)

Coilcraft

DO1813HC

22 to 33

1 to 1.2

DO1608

4.7 to 15

0.9 to 1.5

Coiltronics

UP1B

22 to 33

1 to 1.2

TP3

4.7 to 15

0.97 to 1.6

BI

HM76-2

22 to 33

1 to 1.2

HM76-1

4.7 to 10

1 to 1.5

Murata

LQN6C

10 to 22

1.2 to 1.7

Panasonic

ELL6SH

10 to 22

0.9 to 1.5

ELL6RH

5.1 to10

11 to 1.55

Sumida

CR43

4.7 to 10

0.84 to 1.15