No Charger

Attach a Charge

Normal

Overcharge

Voltage Protection

Overcurrent Protection

During Charging

Shutdown

Short-Circuit

Protection

Over-Discharge

Protection

CHG: ON

DSG: OFF

VREG: ON

CHG: ON

DSG: OFF

VREG: ON

CHG: OFF

DSG: ON

VREG: ON

CHG: OFF

DSG: ON

VREG: ON

CHG: ON

DSG: ON

VREG: ON

CHG: OFF

DSG: OFF

VREG: OFF

CHG: ON

DSG: OFF

VREG: OFF

for a period of

t > 4.0 ms

VM >

– 0.9 V

for a period of t > 400 µs

VM < 0.15 V

or

No Load detected

VM > 0.15 V for a period

of 12 ms

VM < 0.15 V or

No Load detected

for a period of 4.0 ms

VM < –0.112 V

for a period of 12 ms

Charger removed and

Load detected

for a period of 4.0 ms

> 4.25 V

for a period

of 1.0 s

< 2.3 V

for a period of t > 24 ms

During Discharging

Overcurrent Protection

> 2.3 V

BAT

V

BAT

V

BAT

V

< 4.07 V

for a period of 8.0 ms

BAT

V

BAT

V

Not Recommended for New Designs

bq28550-R1

SLUSAS4A – OCTOBER 2012 – REVISED SEPTEMBER 2014

www.ti.com

7.5.6 Zero Voltage Charging

When the cell voltage is 0 V and if the charger voltage is above the minimum operating voltage for 0 V charging

(1.2-V max), the COUT output transitions to a high level and charge current can flow.

7.5.7 FET Control Protection

Figure 2 shows an overview of the FET Control Protection operation.

Figure 2. FET Control Protection

16

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