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LTC4006EGN-2 Datasheet(PDF) 10 Page - Linear Technology |
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LTC4006EGN-2 Datasheet(HTML) 10 Page - Linear Technology |
10 / 16 page 10 LTC4006 sn4006 4006is APPLICATIO S I FOR ATIO Charger Current Programming The basic formula for charging current is: I mV R CHARGE MAX SENSE () = 100 Table 2. Recommended RSENSE Resistor Values IMAX (A) RSENSE (Ω) 1% RSENSE (W) 1.0 0.100 0.25 2.0 0.050 0.25 3.0 0.033 0.5 4.0 0.025 0.5 Setting the Timer Resistor The charger termination timer is designed for a range of 1hour to 3 hour with a ±15% uncertainty. The timer is programmed by the resistor RRT using the following equation: tTIMER = 227 • RRT • 175pF (Refer to Figure 5) It is important to keep the parasitic capacitance on the RT pin to a minimum. The trace connecting RT to RRT should be as short as possible. CHG Status Output Pin When the charge cycle starts, the CHG pin is pulled down to ground by an internal N-channel MOSFET that can drive more than 100 µA. When the charge current drops to 10% of the full-scale current (C/10), the N-channel MOSFET is turned off and a weak 25 µA current source to ground is connected to the CHG pin. After a time out occurs, the pin will go into a high impedance state. 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 6. Battery Detection It is generally not good practice to connect a battery while the charger is running. The timer is in an unknown state and the charger could provide a large surge current into the battery for a brief time. The circuit shown in Figure 7 keeps the charger shut down and the timer reset while a battery is not connected. Alternatively, a normally closed switch can be used to detect when the battery is present (see Figure 8). Figure 5. tTIMER vs RRT RRT (kΩ) 100 0 20 60 80 100 200 140 200 300 350 4006 F05 40 160 180 120 150 250 400 450 500 LTC4006 CHG 33k 200k 4006 F06 VDD 3.3V µP IN OUT Figure 6. Microprocessor Interface DCIN ACP/SHDN 470k LTC4006 ADAPTER POWER SWITCH CLOSED IF BATTERY CONNECTED 4006 F07 Figure 7 DCIN ACP/SHDN LTC4006 ADAPTER POWER SWITCH OPEN WHEN BATTERY CONNECTED 4006 F08 Figure 8 |
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Similar Description - LTC4006EGN-2 |
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