Electronic Components Datasheet Search |
|
LTC4050 Datasheet(PDF) 9 Page - Linear Technology |
|
LTC4050 Datasheet(HTML) 9 Page - Linear Technology |
9 / 12 page 9 LTC4050 4050f APPLICATIONS INFORMATION CHRG Status Output Pin (C/10) When the charge cycle starts, the CHRG pin is pulled to ground by an internal N-channel MOSFET that can drive an LED. When the charge current drops to 10% of the full- scale current (C/10), the N-channel MOSFET turns off and a weak 32 µA current source to ground is connected to the CHRG pin. After a time-out occurs, the pin goes high impedance. By using two different value pull-up resistors, a microprocessor can detect three states from this pin (charging, C/10 and stop charging). See Figure 1. When the LTC4050 is in charge mode, the CHRG pin is pulled low by an internal N-channel MOSFET. To detect this mode, force the digital output pin, OUT, high and measure the voltage at the CHRG pin. The N-channel MOSFET will pull the pin low even with a 2k pull-up resistor. Once the charge current drops to 10% of the full- scale current (C/10), the N-channel MOSFET turns off and a 32 µA current source is connected to the CHRG pin. The IN pin will then be pulled high by the 2k pull-up. By forcing the OUT pin into a high impedance state, the current source will pull the pin low through the 400k resistor. When the internal timer has expired, the CHRG pin will change to high impedance state and the 400k resistor will then pull the pin high to indicate charging has stopped. The CHRG pin open-drain device will turn on if the BAT pin falls below the trickle charge threshold and the LTC4050 has neither timed out nor been put into shutdown. For example, if the battery and NTC thermistor are both disconnected from the typical application circuit, the BAT voltage will collapse due to the thermal fault and CHRG will pull low. Entering shutdown by floating the PROG pin will prevent the CHRG pulldown from turning on. ACPR Output Pin The LTC4050 has an ACPR output pin to indicate that the input supply (wall adapter) is higher than 4V and 54mV or more above the voltage at the BAT pin. When both condi- tions are met, the ACPR pin is pulled to ground by an N-channel MOSFET that is capable of driving an LED. Otherwise, this pin is in a high impedance state. Gate Drive Typically the LTC4050 controls an external P-channel MOSFET to supply current to the battery. An external PNP transistor can also be used as the pass transistor instead of the P-channel MOSFET. Due to the low current gain of the current amplifier (CA), a high gain Darlington PNP transistor is recommended to avoid excessive charge current error. The gain of the current amplifier is around 0.6 µA/mV. For every 1µA of base current, a 1.6mV of gain error shows up at the inputs of CA. With RPROG = 19.6k (100mV across RSENSE), it represents 1.67% of error in charge current. Battery Detection The LTC4050 can detect the insertion of a new battery. When a battery with a voltage of less than 3.88V (for 4.1V cells) or 3.98V (for 4.2V cells) is inserted, the LTC4050 resets the timer and starts a new charge cycle. If the cell voltage of the new battery is above 3.88V (for 4.1V cells) or 3.98V (for 4.2V cells), a new charge cycle will not begin. If a new battery (with cell voltage above 3.88V) is inserted while in the charging process, the timer will not be reset, but will continue until the timer runs out. After a time out has occurred and the battery remains connected, a new charge cycle will begin if the battery voltage drops below the recharge threshold of 3.88V (for 4.1V cells) or 3.98V (for 4.2V cells) due to self-discharge or external loading. Stability The charger is stable without any compensation when a P-channel MOSFET is used as the pass transistor. However, a 10 µF capacitor is recommended at the BAT pin to keep the ripple voltage low when the battery is disconnected. |
Similar Part No. - LTC4050 |
|
Similar Description - LTC4050 |
|
|
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 |