SP7682EB datasheet(17/19 Pages) EXAR

17 / 19 page

Sept 27-07 rev G

SP7682: Backlight and Flash Driver

Page 17

Ceramic Capacitor Materials

Capacitors with large output values are typically

composed of X7R, X5R, Z5U, or Y5V dielectric

materials,

but

Z5U

and

Y5V

are

not

recommended since they have a large change in

value

with

temperature.

X5R

and

X7R

capacitors are recommended since they are

relatively low in cost and their output value

changes with temperature are relatively small.

Capacitor Selection

Careful selection of the four external capacitors

CIN, C1, C2, and COUT is important because

they will affect turn-on time, output ripple, and

transient performance. Optimum performance

will be obtained when low equivalent series

resistance (ESR) ceramic capacitors are used.

In general, low ESR may be defined as less than

100mΩ. A value of 4.7μF for the input and 2.2μF

for the output capacitor is sufficient for most

applications. The flying capacitors C1 and C2

can be 1μF for most applications for backlight

and Flash, and for light output currents flying

capacitors of 0.47uF can be used. For

applications when the 4 backlight LED drivers

are drive 20mA or more and the Flash driver is

driven to 100mA or more, it is advisable to use a

4.7μF input capacitor in order to reduce the input

ripple as seen by the battery. If the LED current-

sinks are only programmed for low current

levels, or if the application is not very noise

sensitive, then a 2.2μF input capacitor may be

used. See table 1 for capacitor selection.

Thermal Protection

The SP7682 has a thermal protection circuit that

will shut down the internal LDO and charge

pump if the die temperature rises above the

thermal limit, and will restart when the die

temperature drops about 20

°C below the

thermal limit.

Table 1: SP7682/SP7682A Capacitor Selection

APPLICATIONS INFORMATION

Manufacturers/ Website

Part Number

Capacitance/

Voltage

Capacitor

Size/Type/Thickness

ESR at

100kHz

TDK/www.tdk.com

C1005X5R0J474K

0.47uF/6.3V

0402/X5R/0.55mm

0.05

TDK/www.tdk.com

C1005X5R0J105K

1uF/6.3V

0402/X5R/0.55mm

0.03

TDK/www.tdk.com

C1608X5R0J225K

2.2uF/6.3V

0603/X5R/0.9mm

0.03

TDK/www.tdk.com

C1608X5R0J475K

4.7uF/6.3V

0603/X5R/0.9mm

0.02

Murata/www.murata.com

GRM155R60J474KE19

0.47uF/6.3V

0402/X5R/0.55mm

0.05

Murata/www.murata.com

GRM155R60J105KE19

1uF/6.3V

0402/X5R/0.55mm

0.03

Murata/www.murata.com

GRM185R60J225KE26

2.2uF/6.3V

0603/X5R/0.55mm

0.03

Murata/www.murata.com

GRM188R60J475KE19

4.7uF/6.3V

0603/X5R/0.8mm

0.02

FOOTPRINT: 3x3mm 16 pin QFN

SP7682EB Datasheet(PDF) 17 Page - Exar Corporation

SP7682EB Datasheet(HTML) 17 Page - Exar Corporation

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19

Datasheet Download

Link URL