AS3677 datasheet(15/68 Pages) AMSCO

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AS3677

Datasheet - D e ta i l e d D e s c r i p t i o n

The maximum voltage on the flying capacitor C4 is VBAT.

8.3.1

Charge Pump Mode Switching

If automatic mode switching is enabled (cp_mode_switching (see page 16) = 00 or cp_mode_switching = 01) the

charge pump monitors the current sinks, which are connected via a led to the output CPOUT. To identify these current

sources (sinks), the registers CP mode Switch1 and CP mode Switch2 (register bits rgb1_on_cp … rgb3_on_cp,

curr1_on_cp, curr2_on_cp and curr6_on_cp) should be setup before starting the charge pump (cp_on (see page 16) =

1). If any of the voltage on these current sources drops below the threshold (currlv_switch, currhv_switch), the next

higher mode is selected after the debounce time.

If the currX_on_cp=0 and the according current sink is connected to the charge pump, the current sink will be func-

tional, but there is no up switching of the charge pump, if the voltage compliance is too low for the current sink to sup-

ply the specified current.

Table 12. Charge Pump Characteristics

Symbol

Parameter

Condition

Min

Typ

Max

Unit

ICPOUT

Output Current

Continuous

Depending on PCB layout

0.0

VCPOUTmax

Output Voltage

Internally limited, Including output ripple

5.6

Efficiency

Including current sink loss;

ICPOUT < 50mA.

ICP1_2

Power Consumption

without Load,

fclk = 1 MHz

1:2 Mode

2.15

Rcp1_1

Effective Charge

Pump Output

Resistance (Open

Loop, fclk = 1MHz)

1:1 Mode; VBAT

= 3V

8.8

Rcp1_2

1:1.2 Mode; VBAT

= 3V

fclk Accuracy

Accuracy of Clock

Frequency

-10

currhv_switch

CURR1, 2, 6

minimum voltage

If the voltage drops below this threshold, the

charge pump will use the next available

mode

(1:1 -> 1:2)

0.45

currlv_switch

RGB1-3 minimum

voltage

0.2

tdeb

CP automatic up-

switching debounce

time

cp_start_debounce=0

240

µsec

After switching on CP (cp_on set to 1), if

cp_start_debounce=1

2000

µsec

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