C11 datasheet(43/72 Pages) AMSOSRAM

43 / 72 page

AS3688

austriami crosyst ems

Datasheet, Confidential

www.austriamicrosystems.com (ptr,tje)

Revision 1.1.1 / 20060707

41 - 70

7.4.7.1 External chargepump Registers

Reg. Control

Addr: 00h

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

Ext. chargepump mode

Addr: 1Dh

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

7.4.8 PWM Generator

The PWM generator can be used for any current sink (CURR1, CURR2, CURR3x, CURR4x, RGB).. It can be

programmed to use the pin GPIO0 (pwm_mode=0) or an internal PWM generator (pwm_mode=1). The setting

applies for all current sinks, which are controlled by the pwm generator (e.g. CURR1 is pwm controlled if

curr1_mode = 10, RGB1 is pwm controlled if rgb1_mode = 10). The pwm modulated signal (internal / external)

can switch on/off the current sinks and therefore depending on its duty cycle change the brightness of an

attached LED.

7.4.8.1 Internal PWM Generator

The internal PWM generator uses the 2MHz internal clock as input frequency and its dimming range is 6 bits

digital (2MHz / 2^6 = 31.3kHz pwm frequency) and 2 bits analog. Depending on the actual code in the register

‘pwm_code’ the following algorithm is used:

If pwm_code bit 7 = 1

Then the upper 6 bits (Bits 7:2) of pwm_code are used for the 6 bits PWM generation, which controls the

selected currents sinks directly

If pwm_code bit 7 =0 and bit 6 = 1

Then bits 6:1 of pwm_code are used for the 6 bits PWM generation. This signal controls the selected current

sinks, but the analog current of these sinks is divided by 2

If pwm_code bit 7 and bit 6 = 0

Then bits 5:0 of pwm_code are used for the 6 bits PWM generation. This signal controls the selected current

sinks, but the analog current of these sinks is divided by 4

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