SSL3250A_3

© NXP B.V. 2009. All rights reserved.

Product data sheet

Rev. 03 — 30 June 2009

11 of 26

NXP Semiconductors

SSL3250A

Photo flash dual LED driver

8.3.7 Indicator LED

input pin. Internally a linear current sink controls the indicator LED current to reach the

required current level.

internal 3-bit register sets the actual indicator LED according to the formula in Equation 6.

The external resistor R_IND is ignored.

(6)

When using the Direct enable mode, the indicator current can be determined by an

external resistor R_IND. The indicator current is defined using Equation 7. It can be set

between 2.5 mA and 20 mA. When not using the resistor, the indicator current will be set

to a default level of 10 mA. This current is similar to connecting an external resistor of

50 k

Ω. Entering Flash mode in Direct enable mode can be done using the EN1 and EN2

pins. The LED will stay on in Flash mode for as long as the enable pins are set.

(7)

If there is no resistor connected to the R_IND pin, it can either be left unconnected or

connected to VIN. Never connect the R_IND pin to GND since it will cause unnecessary

reference currents to flow to GND.

illustrates the Indicator mode current setting equation for the Direct enable mode.

Fig 9.

The inductor current during TxMask

Flash

Average

inductor

current

T

×Mask

t < 50

µs

014aaa296

I

I _IND

Register

2.5 mA

×

=

I

I _IND

50 k

Ω

R

R_IND

------------------

10 mA

×

=