AS3688 datasheet(26/72 Pages) AMSOSRAM

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AS3688

austriami crosyst ems

Datasheet, Confidential

www.austriamicrosystems.com (ptr,tje)

Revision 1.1.1 / 20060707

24 - 70

7.4

Current Sinks

The AS3688 contains general purpose current sinks intended to control backlights, buzzers, and vibrators. All

current sinks have an integrated protection against overvoltage.

CURR1 and CURR2 is also used as feedback for the Step Up DC/DC Converter (regulated to 0.5V in this

configuration).

Current sinks CURR1 and CURR2 are high-voltage compliant (15V) current sinks, used e.g., for series of

white LEDs

Current sinks CURR3x (CURR30, CURR31, CURR32 and CURR33) are parallel 5V, high-current current

sinks, used e.g., for a photocamera flash LED.

Current sinks RGB1, RGB2, and RGB3 are general purpose current sinks e.g. for a fun LED (the pins for

these current sinks are shared with the OLED charge pump)

Current sinks CURR4x (CURR41, CURR42, and CURR43) are general purpose current sinks optionally used

in place of the Step Up DC/DC Converter, e.g. for white LEDs.

As the current sinks consume current whenever enabled (currX_mode not equal ‘off’), do always disable the

current sinks by setting their currX_mode register to ‘off’ (and not by setting currX_current to 0 and not by setting

pwm_code to 0 if currX_mode = ‘PWM controlled’).

Table

11 – Current Sink Function Overview

Resolution

Current

Sink

Max.

Voltage

(V)

Max.

Current

(mA)

(Bits)

(mA)

Software

Current

Control

Hardware On/Off

Control

Alternate Function

CURR1

TBD

CURR2

TBD

15.0

38.25

0.15

Separate

LED Pattern;

PWM at GPIO0/2;

Internal PWM

CURR30 TBD

CURR31 TBD

CURR32 TBD

CURR33 TBD

153

(300 for

strobe)

(+1 for

strobe)

0.6

Combined in

Strobe/Preview

Separated

Flash LED Strobe

(GPI) & Preview

(GPIO2);

TXMask (GPIO1);

PWM at GPIO0/2;

Internal PWM;

Ext-Overtemp on

GPIO2

LED Pattern

N/A

RGB1

TBD

RGB2

TBD

RGB3

TBD

38.25

0.15

Separate

LED Pattern;

PWM at GPIO0/2;

Internal PWM

OLED Charge Pump

RGB3: LDO VANA2

CURR41 TBD

CURR42 TBD

CURR43 TBD

VBAT

(5.5V)

38.25

0.15

Separate

LED Pattern;

PWM at GPIO0/2;

Internal PWM

Step Up DC/DC

Converter (feedback at

CURR1 or CURR2)

7.4.1 High Voltage Current Sinks CURR1, CURR2

The high voltage current sinks have a resolution of 8 bits. Additionally an internal protection circuit monitors with

a voltage divider (max 3µA @ 13V) the voltage on CURR1 and CURR2 and increases the current in off state in

case of overvoltage. See section ‘Typical Operating Characteristics’ Figure ‘Current Sink CURR1 and CURR2

Protection Current’. This shows the protection current versus applied voltage depending on the register setting

currX_prot_on (X=1 or 2).

External PWM control of these current sinks is possible and can be enabled by software (Input pin GPIO0).

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