Electronic Components Datasheet Search |
|
LTC4006EGN-2 Datasheet(PDF) 11 Page - Linear Technology |
|
LTC4006EGN-2 Datasheet(HTML) 11 Page - Linear Technology |
11 / 20 page 11 LTC4006 4006fa OPERATIO This voltage is stored by C7. Then the switch is opened for a short period of time to read the voltage across the thermistor. tHOLD = 10 • RRT • 17.5pF = 54µs, for RRT = 309k When the tHOLD interval ends the result of the thermistor testing is stored in the D flip-flop (DFF). If the voltage at NTC is within the limits provided by the resistor divider feeding the comparators, then the NOR gate output will be low and the DFF will set TBAD to zero and charging will continue. If the voltage at NTC is outside of the resistor divider limits, then the DFF will set TBAD to one, the charger will be shut down, and the timer will be suspended until TBAD returns to zero (see Figure 4). be inhibited if it is not already active. If the charging current decreases below 10% to 15% of programmed current, while engaged in input current limiting, BGATE will be forced low to prevent the charger from discharging the battery. Audible noise can occur in this mode of operation. An overvoltage comparator guards against voltage tran- sient overshoots (>7% of programmed value). In this case, both MOSFETs are turned off until the overvoltage condition is cleared. This feature is useful for batteries which “load dump” themselves by opening their protec- tion switch to perform functions such as calibration or pulse mode charging. As the voltage at BAT increases to near the input voltage at DCIN, the converter will attempt to turn on the top MOSFET continuously (“dropout’’). A watchdog timer detects this condition and forces the top MOSFET to turn off for about 300ns at 40 µs intervals. This is done to prevent audible noise when using ceramic capacitors at the input and output. Charger Startup When the charger is enabled, it will not begin switching until the ITH voltage exceeds a threshold that assures initial current will be positive. This threshold is 5% to 15% of the maximum programmed current. After the charger begins switching, the various loops will control the current at a level that is higher or lower than the initial current. The duration of this transient condition depends upon the loop compensation but is typically less than 100 µs. Thermistor Detection The thermistor detection circuit is shown in Figure 3. It requires an external resistor and capacitor in order to function properly. The thermistor detector performs a sample-and-hold func- tion. An internal clock, whose frequency is determined by the timing resistor connected to RT, keeps switch S1 closed to sample the thermistor: tSAMPLE = 127.5 • 20 • RRT • 17.5pF = 13.8ms, for RRT = 309k The external RC network is driven to approximately 4.5V and settles to a final value across the thermistor of: V VR RR RTH FINAL TH TH () .• = + 45 9 6 NTC LTC4006 S1 R9 32.4k C7 0.47 µF RTH 10k NTC – + – + – + 60k ~4.5V CLK 45k 15k TBAD 4006 F03 D C Q Figure 3 CLK (NOT TO SCALE) VNTC tSAMPLE VOLTAGE ACROSS THERMISTOR tHOLD 4006 F04 COMPARATOR HIGH LIMIT COMPARATOR LOW LIMIT Figure 4 |
Similar Part No. - LTC4006EGN-2 |
|
Similar Description - LTC4006EGN-2 |
|
|
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 |