AS3687 datasheet(16/55 Pages) AMSCO

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AS3687/87XM

Datasheet

www.austriamicrosystems.com/AS3687

1v3-4

15 - 54

Table

6 – Charge Pump Characteristics

Symbol

Parameter

Min

Typ

Max

Unit

Note

Rcp1_2

(Open Loop, fclk =

1MHz)

3.25

Ω

1:1.2 Mode; VBAT >= 3.1V

fclk Accuracy

Accuracy of Clock

Frequency

-10

currhv_switch

CURR1, 2, 6

minumum voltage

0.45

Vcurr3x_switch

CURR30-33

minumum voltage

0.2

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)

240

μsec cp_start_debounce=0

tdeb

CP automatic up-

switching debounce

time

2000

μsec

After switching on CP (cp_on set to

1), if cp_start_debounce=1

7.2.1 Charge Pump Mode Switching

If automatic mode switching is enabled (cp_mode_switching = 00 or cp_mode_switching = 01) the charge pump

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

sources (sinks), the registers cp_mode_switch1 and cp_mode_switch2 (register bits curr30_on_cp …

curr33_on_cp, curr1_on_cp, curr2_on_cp, curr6_on_cp) should be setup before starting the charge pump

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

currhv_switch, curr3x_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 = 10.

If the currX_on_cp=0 and the according current sink is connected to the chargepump, the current sink will be

functional, but there is no up switching of the chargepump, if the voltage compliance is too low for the current sink

to supply the specified current.

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