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LTC1729CS8-4.2 Datasheet(PDF) 5 Page - Linear Technology |
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LTC1729CS8-4.2 Datasheet(HTML) 5 Page - Linear Technology |
5 / 16 page 5 LTC1729 Series OVP (Pin 1): Connection to an Internal Precision Resistor Divider Used as a Voltage Feedback Monitor for Constant- Voltage Mode Charging. BAT (Pin 2): Input to Battery Monitor Circuits and OVP Resistor Divider. The battery monitor circuits activate trickle charge preconditioning, battery present detection and C/10 current detection. This pin is in a high impedance state when VCC is below the undervoltage lockout thresh- old. During trickle charge preconditioning and charging the BAT pin sources 12mA and 1.3mA respectively. The current sources are clamped from driving the BAT pin above 4.5V/cell with an internal pull-down transistor. In the No Bat, Done and Pause states or the Hold and Reset modes, the current sources are turned off, leaving only the 55k OVP divider as a load on the BAT pin. Most chargers have a 200 µA current source that will compensate for this 50 µA to 80µA load. SENSE (Pin 3): Input to C/10 Current Detection Circuit. This pin sinks 100 µAduringtheChargestatewhichisused to program the C/10 current threshold. GND (Pin 4): Ground. NTC (Pin 5): Input to the NTC Thermistor Monitoring Circuits. When the voltage on this pin is above 2.79V (cold) or below 0.405V (hot), the state machine is locked in the present state and the timer is stopped. This is called the Hold mode. While in the Hold mode, the charger is turned off via the VC pin and the current sources on BAT and SENSE pins are turned off. The STATUS pin is not affected. If the NTC pin is below 0.2V, the state machine is forced in the reset mode with all the timers cleared to zero. The current sources on the BAT pin and SENSE pin are disabled leaving the 55k OVP divider. The STATUS pin is pulled low in the Reset mode. There is a 100 µA current source on the NTC pin to bias the NTC thermistor. This current source is active when the VCC is greater than the undervoltage lockout threshold. STATUS (Pin 6): Open-Drain Output for C/10 Charge Termination Detection Circuit. When in the Charge state, this pin is pulled low. Once the charge current drops below the C/10 current threshold for three seconds, the pull- down transistor is disabled, and a 50 µA pull-down current sink remains activated until the 1- or 3-hour time-out or the battery or wall adapter is removed. VC (Pin 7): Open-Drain Output for Turning Off the Charger. When this pin is open circuit, the charger is active. Normally this pin allows the charger to be active for three hours. VCC (Pin 8): Input Supply. For 4.1V or 4.2V single cell operation, VCC should be between 8V and 28V with the IC turning off when VCC drops below 6V. For 2-cell applica- tions, the undervoltage lockout is 10.4V with a minimum VCC of 12V. Removing the wall adapter will trigger an undervoltage lockout and put the IC in a high impedance condition. When the supply is connected, the IC is initial- ized in the Reset mode with the state machine forced in the Charge state with all the timers set to zero. PI FU CTIO S |
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