Datasheet

ManualsBrandsTEXAS INSTRUMENTS ManualsPMICsPMIC - battery management Charge management, Surge/undervoltage protection Li-Ion VQFN 20

Not Recommended for New Designs

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SLUS702A –JULY 2010–REVISED NOVEMBER 2010

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To limit the adapter inrush current when ACFET is turned on to power system from adapter, the Cgs and Cgd

external capacitor of ACFET must be carefully selected. The larger the Cgs and Cgd capacitance, the slower turn

on of ACFET will be and less inrush current of adapter. However, if Cgs or Cgd is too large, the ACDRV-CMSRC

voltage may still go low after the 20ms turn on time window is expired. To make sure ACFET will not be turned

on when adapter is hot plugged in, the Cgs value should be 20 times or higher than Cgd. The most cost effective

way to reduce adapter in-rush current is to minimize system total capacitance.

Battery LEARN Cycle

A battery LEARN cycle can be activated via SMBus command (ChargeOption() bit[6]=1 enable LEARN cycle,

bit[6]=0 disable LEARN cycle). When LEARN is enabled with ACFET/RBFET connected, the system power

selector logic is over-driven to switch to battery by turning off ACFET/RBFET and turning on BATFET. LEARN

function allows the battery to discharge in order to calibrate the battery gas gauge over a complete

discharge/charge cycle. The controller automatically exits LEARN cycle when the battery voltage is below battery

depletion threshold, and the system switches back to adapter input by turning off BATFET and turning on

ACFET/RBFET. After LEARN cycle, the LEARN bit is automatically reset to 0. The battery depletion threshold

can be set to 59.19%, 62.65%, 66.55%, and 70.97% of voltage regulation level via SMBus command

(ChargeOption() bit[12:11]).

Enable and Disable Charging

In Charge mode, the following conditions have to be valid to start charge:

• Charge is enabled via SMBus (ChargeOption() bit [0]=0, default is 0, charge enabled);

• ILIM pin voltage higher than 105mV;

• All three regulation limit DACs have valid value programmed;

• ACOK is valid (See the Adapter Detect and ACOK Output section for details);

• ACFET and RBFET turns on and gate voltage is high enough (See the System Power Selection section for

details);

• V

SRN

does not exceed BATOVP threshold;

• IC Temperature doesn’t exceed TSHUT threshold;

• Not in ACOC condition (See the Input Over Current Protection (ACOC) section for details);

One of the following conditions will stop on-going charging:

• Charge is inhibited via SMBus (ChargeOption() bit[0]=1);

• ILIM pin voltage lower than 75mV;

• One of three regulation limit DACs is set to 0 or out of range;

• ACOK is pulled low (See the Adapter Detect and ACOK Output section for details);

• ACFET turns off;

• V

SRN

exceeds BATOVP threshold;

• TSHUT IC temperature threshold is reached;

• ACOC is detected (See the Input Over Current Protection (ACOC) section for details);

• Short circuit is detected (See the Inductor Short, MOSFET Short Protection section for details);

• Watchdog timer expires if watchdog timer is enabled (See the Charger Timeout section for details);

Automatic Internal Soft-Start Charger Current

Every time the charge is enabled, the charger automatically applies soft-start on charge current to avoid any

overshoot or stress on the output capacitors or the power converter. The charge current starts at 128mA, and the

step size is 64mA in CCM mode for a 10mΩ current sensing resistor. Each step lasts around 240µs in CCM

mode, till it reaches the programmed charge current limit. No external components are needed for this function.

During DCM mode, the soft start up current step size is larger and each step lasts for longer time period due to

the intrinsic slow response of DCM mode.

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