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LTC4058-4.2 Datasheet(PDF) 8 Page - Linear Technology |
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LTC4058-4.2 Datasheet(HTML) 8 Page - Linear Technology |
8 / 12 page 8 LTC4058-4.2/LTC4058X-4.2 sn405842 405842fs OPERATIO Power Supply Status Indicator (ACPR) The power supply status output has two states: pull-down and high impedance. The pull-down state indicates that VCC 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. 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.Thisfeatureprotects 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 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 VCC 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 VCC falls to within 30mV of the BSENSE voltage. If the UVLO comparator is tripped, the charger will not come out of shutdown mode until VCC 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 2 µA and the supply current to less than 50 µA. 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. 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 (tRECHARGE). 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. Figure 1. State Diagram of a Typical Charge Cycle TRICKLE CHARGE MODE 1/10TH FULL CURRENT BSENSE > 2.9V BSENSE < 2.9V BSENSE > 2.9V CHRG: STRONG PULL-DOWN CHARGE MODE FULL CURRENT CHRG: STRONG PULL-DOWN SHUTDOWN MODE CHRG: Hi-Z EN DRIVEN LOW OR UVLO CONDITION STOPS EN DRIVEN HIGH OR UVLO CONDITION ICC DROPS TO <25µA POWER ON PROG < 100mV STANDBY MODE NO CHARGE CURRENT CHRG: Hi-Z 2.9V < BSENSE < 4.1V 405842 F01 |
Similar Part No. - LTC4058-4.2 |
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Similar Description - LTC4058-4.2 |
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