SSL3250A_3

© NXP B.V. 2009. All rights reserved.

Product data sheet

Rev. 03 — 30 June 2009

17 of 26

NXP Semiconductors

SSL3250A

Photo flash dual LED driver

9.

Application design-in information

9.1 Input capacitor

For good input voltage decoupling a low ESR ceramic capacitor is highly recommended. A

4.7

µF (X5R/X7R) 6.3 V is the minimum recommended value. Since the input capacitor is

supplying the input ripple current, a larger capacitor will improve transient behavior of the

regulator and EMI behavior of the power supply. Taking the capacitor DC bias and the

temperature derating specifications into account, a 10

µF (X5R/X7R) is preferred.

Although it is increasing the component count, a smaller capacitor of 100 nF (X5R/X7R)

placed in parallel to the input capacitor will also improve EMI behavior.

When the circuit is used in other than battery powered applications and the input capacitor

is located relatively far from the DC buffer capacitors, it is recommended to add a 150

µF

tantalum or a 470

µF electrolytic capacitor in parallel near the input capacitor.

9.2 Output capacitor

The output capacitor supplies the current to the main LED, while the inductor is being

charged, and it also ensures loop stability. The minimum capacitance for stable loop

operation would be 2.2

µF, but taking the capacitor DC bias and the temperature derating

specifications into account, a low ESR ceramic capacitor of 4.7

µF (X5R/X7R) is highly

recommended. A higher value of capacitance will improve output current ripple, while

01h

Timer control

7 to 5

Reserved

-

-

4

TO_DEF

R/W

0

*

Select time-out limit (default)

1

Select timed operation

3 to 0

TO

R/W

0000

*

820 ms (default)

0001

765 ms

.....

.....

1110

56 ms

1111

1 ms

02h

Flash strobe

7 to 1

Reserved

-

-

-

0

FLASH_STRB

R/W

0

*

-

1

Enable flash

03h

Status

7 to 4

Reserved

-

-

3

OStrig

R

0

*

LED not shorted to GND

1

LED shorted to GND

2

OTPtrig

R

0*

Temperature < maximum temperature

1

Temperature > maximum temperature;

Protection triggered

1

TOtrig

R

0

*

Flash time < Time-out

1

Flash time > Time-out, Protection triggered

0

OVPtrig

R

0

*

Table 6.

Legend: * default register value

Address

Register

Bit

Symbol

Access

Value

Description