SP6686ER-LSLASHTR datasheet(9/12 Pages) EXAR

9 / 12 page

A B

ucck

stt C

arrg

e P

p L

D D

Drriiv

err

9/12

Rev. 2.0.0

0.47μF

fly

capacitor

are

typically

recommended. For the input capacitor, a

larger value of 10μF will help reduce input

voltage ripple for applications sensitive to

ripple

the

battery

voltage.

All

the

capacitors should be ceramic to obtain low

ESR, which improves bypassing on the input

and output and improves output voltage drive

by reducing output resistance. X5R or X7R

Ceramic capacitors are recommended for most

applications. A selection of recommended

capacitors is included in Table 1. The input and

output capacitors should be located as close to

the VIN and VOUT pins as possible to obtain best

bypassing,

and

the

returns

should

connected directly to the PGND pin or to the

thermal pad ground located under the SP6686.

The fly capacitor should be located as close to

the C1 and C2 pins as possible. The sense

resistor RSENSE is determined by the value

needed in the Torch mode for the desired

output current by the equation:

Where VFB=50mV in torch mode.

Once the RSENSE resistor has been selected for

Torch mode, the VFB voltage can be selected

for Flash mode using the following equation:

Where IOUT is for Flash Mode

Next, the RSET resistor can be selected for

Flash mode using the following equation:

1.26

11.2Ω

For an example of 150mA Torch mode and

400mA Flash mode, the values RSENSE=0.33Ω,

VFB=135mV (Flash Mode), and RSET=106kΩ are

calculated. The power obtained in the Flash

mode would be:

133

400

The typical 0603 surface mount resistor is

rated at 1/10 Watt continuous power and 1/5

Watt pulsed power, more than enough for this

application. For other applications, the PFLASH

can be calculated from the resistor size

selected. The RSENSE resistor is recommended

to be size 0603 for most applications.

EVALUATION BOARD LAYOUT

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