LTC4058X-4.2_15 Datasheet, PDF (8/12 Pages) Linear Technology – Standalone Linear Li-Ion Battery Charger with Thermal Regulation in DFN

LTC4058-4.2/LTC4058X-4.2
U
OPERATIO
POWER ON
BSENSE < 2.9V
EN DRIVEN LOW
OR
UVLO CONDITION
STOPS
SHUTDOWN MODE
I_CC DROPS TO <25µA
CHRG: Hi-Z
TRICKLE CHARGE
MODE
1/10TH FULL CURRENT
CHRG: STRONG
PULL-DOWN
BSENSE > 2.9V
CHARGE MODE
BSENSE > 2.9V
FULL CURRENT
CHRG: STRONG
PULL-DOWN
PROG < 100mV
EN DRIVEN HIGH
OR
UVLO CONDITION
STANDBY MODE
NO CHARGE CURRENT
CHRG: Hi-Z
405842 F01
2.9V < BSENSE < 4.1V
Figure 1. State Diagram of a Typical Charge Cycle
Power Supply Status Indicator (ACPR)
The power supply status output has two states: pull-down
and high impedance. The pull-down state indicates that
V_CC is above the UVLO threshold (3.8V) and is also 100mV
above the battery voltage. When these conditions are not
met, the ACPR pin is high impedance indicating that the
LTC4058 is unable to charge the battery.
charger will automatically reduce the current in worst-case
conditions. DFN power considerations are discussed fur-
ther in the Applications Information section.
Undervoltage Lockout (UVLO)
An internal undervoltage lockout circuit monitors the input
voltage and keeps the charger in shutdown mode until V_CC
rises above the undervoltage lockout threshold. The UVLO
circuit has a built-in hysteresis of 200mV. Furthermore, to
protect against reverse current in the power MOSFET, the
UVLO circuit keeps the charger in shutdown mode if V_CC
falls to within 30mV of the BSENSE voltage. If the UVLO
comparator is tripped, the charger will not come out of
shutdown mode until V_CC rises 100mV above the BSENSE
voltage.
Manual Shutdown
At any point in the charge cycle, the LTC4058 can be put
into shutdown mode by driving the EN pin high. This
reduces the battery drain current to less than 2µA and the
supply current to less than 50µA. When in shutdown
mode, the CHRG pin is in the high impedance state. A new
charge cycle can be initiated by driving the EN pin low. A
resistor pull-down on this pin forces the LTC4058 to be
enabled if the pin is allowed to float.
Thermal Limiting
An internal thermal feedback loop reduces the programmed
charge current if the die temperature attempts to rise above
a preset value of approximately 120°C. This feature protects
the LTC4058 from excessive temperature and allows the
user to push the limits of the power handling capability of
a given circuit board without risk of damaging the LTC4058.
The charge current can be set according to typical (not worst
case) ambient temperature with the assurance that the
Automatic Recharge
Once the charge cycle is terminated, the LTC4058 continu-
ously monitors the voltage on the BSENSE pin using a
comparator with a 2ms filter time (t_RECHARGE). A charge
cycle restarts when the battery voltage falls below 4.10V
(which corresponds to approximately 80% to 90% battery
capacity). This ensures that the battery is kept at, or near,
a fully charged condition and eliminates the need for
periodic charge cycle initiations. The CHRG output enters
a pull-down state during recharge cycles.
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