ACT2801_16 datasheet(10/25 Pages) ACTIVE-SEMI

10 / 25 page

Rev 8, 01-Nov-16

Innovative PowerTM

- 10 -

www.active-semi.com

ACT2801/ACT2801B

FUNCTIONAL DESCRIPTION

ACT2801/ACT2801B is a complete battery charging

and discharging power management solution for

applications of single-cell lithium-based backup

battery pack or power bank. There is a power path

from input to output with programmable input

current limit. When output is over loaded, the input

switch Q1 starts going into linear mode and thus

output voltage starts to drop. If output voltage drops

below 4.25V, the input switch Q1 turns off and

restart in 2 seconds.

With

the

advanced

ACT2801/ACT2801B

architecture, a synchronous buck/boost converter is

connected from VOUT to switching node (SW). With

the bidirectional architecture, the converter could be

configured as either buck to charge battery or boost

to discharge battery. With switching charger and

discharger, the higher charge current and higher

conversion efficiency are achieved.

Modes of Operation

ACT2801/ACT2801B has 3 operation modes:

charge mode, boost mode and high-impedance

(HZ) mode. In charge mode, the input current limit

Q1 is enabled and Q2 and Q3 operate as a buck

converter to charge battery. In boost mode, Q2 and

Q3 operate as boost converter to step battery

voltage up to +5V at VOUT, and the current limit

switch Q1 is turned off, and the reverse current from

VOUT to VIN is blocked. In HZ mode, all the

switches are turned off and the drainage current

from battery is very low. ACT2801 system operation

flow chart as shown in Figure 1, and ACT2801B

system operation flow chart as shown in Figure 2.

Any transitions between boost mode and charge

mode go through HZ mode by turning off all the

switches Q1-Q3 into HZ mode for 2 seconds before

enabling the other mode.

The modes are determined by HZ pin and VIN pin

as shown in the table 1. A valid VIN voltage forces

ACT2801/ACT2801B into charge mode. Boost

mode is enabled if HZ pin is pulled low and VIN is

invalid or not present. For ACT2801/ACT2801B,

when HZ=0, if PB is pulled low for more than 30ms,

boost converter is enabled. For ACT2801, during

boost on, if PB is pressed more than 1.5s, boost

converter will be off.

Table 1: Mode Selection

Flashlight

ACT2801B has an flashlight function. Once PB is

pressed for 3 seconds, the flashlight is switched on.

The driver will deliver up to 50mA current to the

flashlight. During flashlight on, if PB is pressed for 3

seconds, flashlight will be switched off.

Figure 1:

ACT2801 System Operation Flow Chart

HZ PIN

VIN Valid

Mode

Boost

Charge

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