AAT3170 datasheet(9/15 Pages) AAT

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AAT3170

High Current LED Flash Driver Charge Pump IC

3170.2006.11.1.1

matching. Also, F1 and F2 can be connected

together for single output configuration.

Modes of Operation

In addition to the data registers that set the current

levels for the two current sinks, the AAT3170 has

three mode registers.

mode register. It sets the maximum per channel

current level to either 300mA or 50mA. Each chan-

nel can be set independently so one channel can

be for flash while the other can be in a low constant

current mode.

Data = 1, both current sources are enabled (default);

when set with Data = 2, both current sources are dis-

abled. When Register 4 is set to OFF, the device is

in standby mode with significantly reduced quiescent

current.

The AAT3170 has a software programmable timer

function to automatically adjust the flash on-time

duration. This feature can be used directly to set

the flash on-time, or it can be used indirectly for

fault tolerant flash protection. When used for flash

protection, the user can be sure that the flash will

still turn off in the event of any system software or

hardware malfunction.

Write to Address 5 to enable the flash timer and

flash channels. When the timer register is

addressed and data is latched, the ON/OFF regis-

ter is automatically switched to ON, enabling the

current sinks for the duration of the programmed

time. When the timer expires, the ON/OFF register

is switched to OFF, disabling the current sinks.

The on-time T depends on the combination of the

setting of the timer register and the value of the tim-

ing capacitor, which are listed in the “Timer

according to the following formula:

where CT is in micro-farads.

For example, using a 0.1µF timer capacitor value

results in an on-time duration of one second.

The AAT3170 also includes a regulated output

voltage mode setting. By setting Register 6 with

Data = 2 for voltage mode, the charge pump deliv-

ers a regulated 4.5V output that continuously oper-

ates in 1.5X mode. It is suitable for driving loads

of up to 200mA. The voltage mode may be used

to drive LEDs with ballast resistors. Driving either

F1 or F2 in current mode will override the voltage

mode state until F1 and F2 are set back to zero

current by either data or mode register. Setting

to current mode and the charge pump output volt-

age will regulate appropriately.

AS2Cwire Serial Interface

The AAT3170 utilizes the AS2Cwire serial interface

to enable/disable the charge pump, set the operat-

ing mode, and adjust the output current level of

each constant current sink. Each current sink can

be independently programmed with sixteen current

levels (see table below). AS2Cwire incorporates

addressing to program the operating modes and

current level settings.

Constant Current Sink

Nominal Programming Levels

AS2Cwire relies on the number of rising edges of

the EN/SET pin to address and load the registers.

300mA HI Scale

50mA LO Scale

Data

ISINK (mA/chnl)

300

267

238

214

190

167

152

133

119

105

T (seconds) = 10 · C

T (µF)

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