AS3665 datasheet(32/78 Pages) AMSCO

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AS3665

Datasheet, Confidential - D e ta i l e d D e s c r i p t i o n C h a r g e P u m p

The charge pump starts operation always in 1:1 mode and returns back to 1:1 mode if all current sources are switched

off

7. If the voltage across a enabled current source is no longer sufficient to operate the current source, the charge

pump automatically select the next operating mode (which modes are allowed is controlled by cp_mode_switching.

cp_auto_on or cp_on should be set for enabling this logic). In 1:1.5 mode and if cp_mode_switching=00, the charge

pump also can automatically switch back into 1:1 mode if the voltage across all current sources is sufficiently high to

use the more efficient 1:1 mode (a fine adjustment of this hysteresis is possible with cp_down_hyst).

Application Hint

Its usually safe to keep the default values of the charge pump registers. Only if a red LED is used (on LED7...LED9),

reset the register bits LED7_on_cp=0, LED8_on_cp=0 and/or LED9_on_cp=0 to improve efficiency.

7. Exception: The manual mode switching mode (cp_mode_switching=11) can override this behavior.

Table 38. CP_Mode_Switch Register

Addr: 06h

CP_Mode_Switch Register

Bit

Bit Name

Default Access

Description

LED7_on_cp

R/W

Configure if LED7 is powered by charge pump

LED7 is powered by VBAT (e.g. red LED)

LED7 is powered from VOUT

LED8_on_cp

R/W

Configure if LED8 is powered by charge pump

LED8 is powered by VBAT (e.g. red LED)

LED8 is powered from VOUT

LED9_on_cp

R/W

Configure if LED9 is powered by charge pump

LED9 is powered by VBAT (e.g. red LED)

LED9 is powered from VOUT

cp_max_5V4

R/W

Adjusts the maximum output voltage of the charge pump

charge pump VOUT regulates to 4.5V

charge pump VOUT regulates to maximum 5.4V

cp_skip_on

R/W

Allows pulse skip mode of charge pump

Pulse skip of charge pump is disabled

Enable pulse skip of charge pump in low load

conditions (reduce quiescent current in 1:1.5 mode)

cp_auto_reset

R/W

If all current sources are off, reset the charge pump back to

1:1 mode

charge pump keeps last mode

Reset charge pump to 1:1 if all current sources are off

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