ACT2801 datasheet(9/23 Pages) ACTIVE-SEMI

9 / 23 page

Rev 2, 15-Apr-14

Innovative PowerTM

- 9 -

www.active-semi.com

ACT2801/ACT2801C

FUNCTIONAL DESCRIPTION

ACT2801/ACT2801C

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/ACT2801C

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/ACT2801C 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 ACT2801C

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/ACT2801C into charge mode. Boost

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

invalid or not present. When HZ=0, if PB is pulled

low for more than 100ms, boost converter is

enabled.

Flashlight

ACT2801C has an Flashlight function. Once PB is

pressed for more than 3 seconds, the Flashlight is

switched on. The driver will deliver up to 50mA

current to the flashlight. If another 3 seconds event

happen, the flashlight will be switched off.

Figure 1:

ACT2801 System Operation Flow Chart

Table 1: Mode Selection

HZ PIN

VIN Valid

Mode

Boost

Charge

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