Electronic Components Datasheet Search |
|
LTC4065LEDC Datasheet(PDF) 11 Page - Linear Integrated Systems |
|
LTC4065LEDC Datasheet(HTML) 11 Page - Linear Integrated Systems |
11 / 16 page 11 LTC4065/LTC4065A 4065fb Once the charge cycle terminates, the LTC4065 continu- ously monitors the BAT pin voltage using a comparator with a 2ms filter time. When the average battery voltage falls below 4.1V (which corresponds to 80% to 90% battery capacity), a new charge cycle is initiated and a 2.25 hour timer begins. 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 assumes a strong pull-down state during recharge cycles until C/10 is reached when it transitions to a high impendance state. Trickle Charge and Defective Battery Detection At the beginning of a charge cycle, if the battery voltage is low (below 2.9V), the charger goes into trickle charge, reducing the charge current to 10% of the full-scale current. If the low-battery voltage persists for one quarter of the total time (1.125 hour), the battery is assumed to be defective, the charge cycle is terminated and the CHRG pin output pulses at a frequency of 2Hz with a 75% duty cycle. If for any reason the battery voltage rises above 2.9V, the charge cycle will be restarted. To restart the charge cycle (i.e., when the defective battery is replaced with a dis- charged battery), simply remove the input voltage and reapply it, temporarily pull the EN pin above the shutdown threshold (LTC4065), or momentarily float the PROG pin and reconnect it (LTC4065A). CHRG Status Output Pin The charge status indicator pin has three states: pull- down, pulse at 2Hz (see Trickle Charge and Defective Battery Detection) and high impedance. The pull-down state indicates that the LTC4065 is in a charge cycle. A high impedance state indicates that the charge current has dropped below 10% of the full-scale current or the LTC4065 is disabled. Figure 2 shows the CHRG status under various conditions. Power Supply Status Indicator (ACPR, LTC4065A Only) The power supply status output has two states: pull-down and high impedance. The pull-down state indicates that VCC is above the undervoltage lockout threshold (see Undervoltage Lockout). When this condition is not met, the ACPR pin is high impedance indicating that the LTC4065A is unable to charge the battery. Charge Current Soft-Start and Soft-Stop The LTC4065 includes a soft-start circuit to minimize the inrush current at the start of a charge cycle. When a charge cycle is initiated, the charge current ramps from zero to the full-scale current over a period of approximately 180 µs. Likewise, internal circuitry slowly ramps the charge cur- rent from full-scale to zero when the charger is shut off or self terminates. This has the effect of minimizing the transient current load on the power supply during start-up and charge termination. Constant-Current/Constant-Voltage/ Constant-Temperature The LTC4065/LTC4065A use a unique architecture to charge a battery in a constant-current, constant-voltage and constant-temperature fashion. Figures 1a and 1b show simplified block diagrams of the LTC4065 and LTC4065A, respectively. Three of the amplifier feedback loops shown control the constant-current, CA, constant- voltage, VA, and constant-temperature, TA modes. A fourth amplifier feedback loop, MA, is used to increase the output impedance of the current source pair; M1 and M2 (note that M1 is the internal P-channel power MOSFET). It ensures that the drain current of M1 is exactly 1000 times greater than the drain current of M2. Amplifiers CA and VA are used in separate feedback loops to force the charger into constant-current or constant- voltage mode, respectively. Diodes D1 and D2 provide priority to either the constant-current or constant-voltage loop; whichever is trying to reduce the charge current the most. The output of the other amplifier saturates low which effectively removes its loop from the system. When in constant-current mode, CA servos the voltage at the PROG pin to be precisely 1V. VA servos its inverting input to an internal reference voltage when in constant-voltage mode and the internal resistor divider, made up of R1 and R2, ensures that the battery voltage is maintained at 4.2V. The PROG pin voltage gives an indication of the charge current during constant-voltage mode as discussed in “Programming Charge Current”. OPERATIO |
Similar Part No. - LTC4065LEDC |
|
Similar Description - LTC4065LEDC |
|
|
Link URL |
Privacy Policy |
ALLDATASHEET.COM |
Does ALLDATASHEET help your business so far? [ DONATE ] |
About Alldatasheet | Advertisement | Datasheet Upload | Contact us | Privacy Policy | Link Exchange | Manufacturer List All Rights Reserved©Alldatasheet.com |
Russian : Alldatasheetru.com | Korean : Alldatasheet.co.kr | Spanish : Alldatasheet.es | French : Alldatasheet.fr | Italian : Alldatasheetit.com Portuguese : Alldatasheetpt.com | Polish : Alldatasheet.pl | Vietnamese : Alldatasheet.vn Indian : Alldatasheet.in | Mexican : Alldatasheet.com.mx | British : Alldatasheet.co.uk | New Zealand : Alldatasheet.co.nz |
Family Site : ic2ic.com |
icmetro.com |