Stand-Alone, Switch-Mode
Li+ Battery Charger with Internal 28V Switch
SHUTDOWN
SHUTDOWN IS
FASTCHG = HIGH
ENTERED FROM ALL STATES
FULLCHG = HIGH
FAULT = HIGH
WHEN SHDN IS LOW.
V
DCIN
< BATT
SHDN HIGH
RESET
V
BATT
< UNDERVOLTAGE
THRESHOLD
FASTCHG = HIGH
FULLCHG = HIGH
FAULT = HIGH
V
DCIN
> V
BATT
PREQUAL
FAULT
PREQUAL
TIMEOUT
FASTCHG = LOW
FULLCHG = HIGH
FAULT = HIGH
FASTCHG = HIGH
FULLCHG = HIGH
FAULT = LOW
V
BATT
> 2.5V
FAST-CHARGE
TIMEOUT
TEMP
NOT OK
TEMP
OK
FAST CHARGE
FASTCHG = LOW
FULLCHG = HIGH
FAULT = HIGH
ONCE PER
SECOND
V
< 0.95 × V
BATTR
BATT
V
= BATTERY
TEMP
OK
BATT
REGULATION VOLTAGE (V
)
BATTR
ONCE PER
SECOND
FULL CHARGE
FASTCHG = HIGH
FULLCHG = LOW
FAULT = HIGH
TEMP
QUAL
V
< 0.95 × V
BATTR
BATT
TEMP
OK
TEMP
NOT OK
I
< I OR
CHARGE MIN
FULL-CHARGE
TIMEOUT
TEMP
NOT OK
TEMP
OK
DONE
TOP-OFF
FASTCHG = HIGH
FULLCHG = HIGH
FAULT = HIGH
FASTCHG = HIGH
FULLCHG = HIGH
FAULT = HIGH
TOP-OFF
TIMEOUT
Figure 4. State Diagram
An internal clamp limits the noncontrolling signals to
within 200mV of the controlling signal to prevent delay
when switching between regulation loops.
When the current-sense resistor is chosen, note that the
voltage drop across this resistor adds to the power
loss, reducing efficiency. Reducing the voltage across
the current-sense resistor may degrade input current
limit accuracy due to the input offset of the input cur-
rent-sense amplifier.
The current mode PWM controller measures the induc-
tor current to regulate the output voltage or current,
simplifying stabilization of the regulation loops.
Separate compensation of the regulation circuits allows
each to be optimally stabilized. Internal slope compen-
sation is included, ensuring stable operation over a
wide range of duty cycles.
The input current error amplifier (GMS) is compensated
at CCS. A 0.1µF capacitor at CCS provides suitable
performance for most applications.
PWM Controller
The PWM controller drives the internal high-side MOS-
FET to control charging current or voltage. The input to
the PWM controller is the lowest of CCI, CCV, or CCS.
The controller drives an internal N-channel MOSFET
switch to step the input voltage down to the battery
voltage. The high-side MOSFET gate is driven to a volt-
age higher than the input source voltage by a bootstrap
______________________________________________________________________________________ 13
MAXIM [ MAXIM INTEGRATED PRODUCTS ]
