AS3689 datasheet(43/72 Pages) AMSOSRAM

43 / 72 page

AS3689

austriami crosyst ems

Datasheet, Confidential

www.austriamicrosystems.com (mlg, ptr)

Revision 1.0.2 / 20070115

41 - 70

Figure 23 – Charge Pump for Generation of positive voltages

O-LED Charge

Pump

RGB2

BAS40

AS3689

RGB1

RGB3

1.375MΩ

220pF

2.2µF

15V,

5mA

10µA

Pulse

Skip

VBAT

125kΩ

1.25V

7.4.7.1 External chargepump Registers

Addr: 00h

Reg. Control

This register enables/disables the LDOs, Charge Pumps, Charge Pump LEDs, current

sinks, the Step Up DC/DC Converter.

Bit

Bit Name

Default

Access

Description

cp_ext_on

R/W

Enable the external chargepump

0b = Disable the external chargepump.

1b = Enable the external chargepump

Addr: 1Dh

Ext. chargepump mode

This register selects the modes of the external chargepump

Bit

Bit Name

Default

Access

Description

1:0

cp_ext_mode

R/W

Selects the mode of the Ext. charge pump

00b = regulate to negative voltage (e.g.: -6V)

01b = regulate to positive voltage (e.g.:+15V)

10b = unregulated (free running)

11b = reserved Select the mode of the current sink CURR41

3:2

cp_ext_clk<1:0>

R/W

Selects the switching frequency

00b = 250kHz

01b = 500kHz

10b = 1MHz

11b = NA

cp_ext_lowcurr

R/W

Driving capability of ext. charge pump

0b = normal current = Iout

1b = reduced current = Iout / 4

Output noise and ripple will be reduced

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