AS3676 datasheet(19/92 Pages) AMSCO

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AS3676

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 capacitors C3 and C4 is VBAT.

8.3.1

Charge Pump Mode Switching

If automatic mode switching is enabled (cp_mode_switching (see page 20) = 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 curr30_on_cp (see page 21) …

curr33_on_cp, rgb1_on_cp … rgb3_on_cp, curr1_on_cp, curr2_on_cp, curr41_on_cp … curr43_on_cp and

curr6_on_cp) should be setup before starting the charge pump (cp_on (see page 20) = 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.

To avoid switching into 1:2 mode (battery current = 2 times output current), set cp_mode_switching = 01.

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 14. Charge Pump Characteristics

Symbol

Parameter

Condition

Min

Typ

Max

Unit

ICPOUT

Output Current

Continuous

Depending on PCB layout

0.0

400

Output Current

Pulsed

max. 200ms

VCPOUT=

VBAT * CPMODE – ILOAD * RCP

0.0

500

VCPOUTmax

Output Voltage

Internally limited, Including output ripple

5.6



Efficiency

Including current sink loss;

ICPOUT < 100mA.

ICP1_1.5

Power Consumption

without Load

fclk = 1 MHz

1:1.5 Mode

3.4

ICP1_2

1:2 Mode

3.8

Rcp1_1

Effective Charge

Pump Output

Resistance (Open

Loop, fclk = 1MHz)

1:1 Mode; VBAT

3.5V

0.57



Rcp1_1.5

1:1.5 Mode; VBAT

 3.3V

2.65

Rcp1_2

1:1.2 Mode; VBAT

 3.1V

3.25

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 -> 1:1.5 or 1:1.5 -> 1:2)

0.45

currlv_switch

CURR30-33, RGB1-

3, CURR41-3,

minimum voltage

0.2

CURR30-33

0-75.6mA range

for strobe if

curr3x_strobe_high=

0.4

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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