bq24700, bq24701

NOTEBOOK PC BATTERY CHARGE CONTROLLER

AND SELECTOR WITH DPM

SLUS452B – APRIL 2001 – REVISED NOVEMBER 2002

13

POST OFFICE BOX 655303

APPLICATION INFORMATION

dynamic power management

The dynamic power management (DPM) feature allows a cost effective choice of an ac wall-adapter that

accommodates 90% of the system’s operating-current requirements. It minimizes battery charge time by

current exceeds the adapter current limit, as shown in Figure 2, the DPM feature reduces the battery charge

current to maintain an overall input current consumption within user defined power capability of the wall-adapter.

As the system’s current requirements decrease, additional current can be directed to the battery, thereby

increasing battery charge current and minimizing battery charge time.

The DPM feature is inherently designed into the PWM controller by inclusion of the three control loops,

battery-charge regulation voltage, battery-charge current, and adapter-charge current, refer to Figure 3. If any

of the three user programmed limits are reached, the corresponding control loop commands the PWM controller

to reduce duty cycle, thereby reducing the battery charge current.

UDG–00113

NO

CHARGE

MAXIMUM

CHARGE CURRENT

DYNAMIC POWER

MANAGEMENT

MAXIMUM

CHARGE CURRENT

ADAPTER CURRENT

SYSTEM CURRENT

BATTERY CHARGE CURRENT

ADAPTER CURRENT LIMIT

Figure 2. Dynamic Power Management

ACDET operation

The ACDET function senses the loss of adequate adapter power. If the voltage on ACDET drops below the

internal 1.2 V reference voltage, a loss of ADAPTER power is declared and the bq24700/bq24701 switches to

battery power as the main system power. In addition, the bq24700/bq24701 shuts down its 5-V VREF and enters

a low power sleep mode. Under normal operation with a battery present, the low impedance battery node

system voltage down to the battery voltage level. However, in conditions where the battery has been removed

or appears high impedance due to battery protector operation, the residual system energy stored in the load

rating of the SRN and SRP pins.