SD3812-1R0-R datasheet(11/17 Pages) SKYWORKS

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AAT1274

1.5A Single Flash LED Driver IC

DATA SHEET

Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com

201981A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • May 21, 2012

Address

EN/SET

Rising

Edges

Function

Default

(No Programming)

017

Movie Mode

Current

100%

Not Used

320

Flash/Movie

Mode Cur-

rent Ratio

1/7.3

Table 1: AS2Cwire Serial Interface Addressing.

AS2Cwire Serial Interface

AS2Cwire latches data or address after the EN/SET pin

has been held high for longer than tLAT (500μs). Address

or data are differentiated by the number of EN/SET rising

edges. Since the data registers are 4 bits each, the dif-

ferentiating number of pulses is 24 or 16, so that Address

0 is signified by 17 rising edges, and Address 3 by 20

rising edges. Data is inclusively applied to any number of

rising edges between 1 and 16. A typical write protocol is

a burst of EN/SET rising edges which signify a particular

address that is followed by a pause with EN/SET held

high for the prescribed tLAT timeout period, then a burst

of rising edges signifying data, and a tLAT timeout for the

data registers. Once an address is set, then multiple

writes to the corresponding data register are allowed.

Address 0 is the default address on the first rising edge

after the AAT1274 has been disabled. When EN/SET is

transitioned from high to low and held low longer than

tOFF (500μs), the device enters a shutdown mode and

draws less than 1uA from the input supply. All data and

address are cleared (reset to 0) during shutdown.

AS2Cwire addressing allows for control of the movie mode

output current, and the ratio of movie-mode current to

flash current. If there are no programmed write instruc-

tions applied to the EN/SET pin prior to the assertion of

the FLEN pin and the device is enabled, then all registers

will be loaded with their default values shown in Table 1.

In the event that the number of rising edges applied at

the EN/SET pin is less than 17, the internal state machine

will interpret instruction to program the output currents

to the desired current level for movie-mode operation.

Movie Mode Current – Address 0

The AAT1274 movie mode current settings are controlled

using the AS2Cwire interface. The default ratio between

the flash current level and maximum movie mode cur-

rent level is 1:7.3.

For example, if an RSET value of 107kΩ is chosen, then

the flash current is set to 1500mA. For movie mode

operation, the maximum current available is then:

FL(MAX)

7.3

1500mA

7.3

MOVIE MODE =

= 206mA

Address

Data

EN/SET

Address

Data Reg 1

2 . . .

≤ 16

TLO

TLAT

LAT

Figure 1: AS2Cwire Serial Interface Timing Diagram.

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