Datasheet

MAX1758
Stand-Alone, Switch-Mode
Li+ Battery Charger with Internal 28V Switch
13
Maxim Integrated
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 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.
An internal clamp limits the noncontrolling signals to
within 200mV of the controlling signal to prevent delay
when switching between regulation loops.
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 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
SHUTDOWN
FASTCHG = HIGH
FULLCHG = HIGH
FAULT = HIGH
RESET
FASTCHG = HIGH
FULLCHG = HIGH
FAULT = HIGH
PREQUAL
FASTCHG = LOW
FULLCHG = HIGH
FAULT = HIGH
FAULT
FASTCHG = HIGH
FULLCHG = HIGH
FAULT = LOW
FAST CHARGE
FASTCHG = LOW
FULLCHG = HIGH
FAULT = HIGH
FULL CHARGE
FASTCHG = HIGH
FULLCHG = LOW
FAULT = HIGH
DONE
FASTCHG = HIGH
FULLCHG = HIGH
FAULT = HIGH
TOP-OFF
FASTCHG = HIGH
FULLCHG = HIGH
FAULT = HIGH
TEMP
OK
TEMP
OK
TEMP
OK
TEMP
OK
TEMP
NOT OK
TOP-OFF
TIMEOUT
I
CHARGE
< I
MIN
OR
FULL-CHARGE
TIMEOUT
ONCE PER
SECOND
ONCE PER
SECOND
TEMP
QUAL
V
BATT
> 2.5V
V
BATT
< 0.95 × V
BATTR
V
BATT
< 0.95 × V
BATTR
V
DCIN
< BATT
V
BATT
< UNDERVOLTAGE
THRESHOLD
V
BATT
= BATTERY
REGULATION VOLTAGE (V
BATTR
)
FAST-CHARGE
TIMEOUT
PREQUAL
TIMEOUT
TEMP
NOT OK
TEMP
NOT OK
SHUTDOWN IS
ENTERED FROM ALL STATES
WHEN SHDN IS LOW.
SHDN HIGH
V
DCIN
> V
BATT
Figure 4. State Diagram