ACT2802 datasheet(8/21 Pages) ACTIVE-SEMI

8 / 21 page

ACT2802

Rev 0, 21-Jan-14

Innovative PowerTM

- 8 -

www.active-semi.com

Active-Semi Confidential―Do Not Copy or Distribute

ActiveSwitcher

TM is a trademark of Active-Semi.

FUNCTIONAL DESCRIPTION

ACT2802 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 ACT2802 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

ACT2802 has 3 operation modes: charge mode,

boost mode and high-impedance (HZ) mode. In

charge mode, the input current limit is enabled and

the 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.

The system operation flow chart as shown in Figure

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

ACT2802 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. A running

boost is disabled if one of the following conditions is

met:

1. After PB is released, if PB is pulled low for more

than 3 seconds.

2. Boost converter output current is below light

load threshold for 1.5 minutes.

3. Battery voltage falls below the boost cut-off

threshold.

FUNCTIONAL BLOCK DIAGRAM

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