LTC4070EDDB#TRMPBF Integrated Circuits (ICs)

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1. Describe

LTC®4070 Allows Simple Charging of Li-Ion/Polymer Batteries from very low current, intermittent or continuous charging sources. 450nA to 50mA operating current enables previously unusable charging source. plus an external pass device, The shunt current can be boosted to 500mA. Stacking unit height Voltage battery packs are inherently balanced with shunts TOLL. With its low operating current, the LTC4070 is Ideal for charging thin-film batteries in energy harvesting applications where the charging source may be intermittent or very low power. unique architectural style The LTC4070 allows an extremely simple battery charger Solution; just need an external resistor. The LTC4070 offers a pin-selectable float voltage with 1% Accuracy over the entire operating temperature range and shunt current. Integrated thermal battery qualifier extends battery life and improves reliability by Automatically reduce battery float voltage at NTC Thermistor temperature is above 40°C. The LTC4070 also Provides low and high battery status outputs. for For applications requiring battery pack protection, see the LTC4071. The device is available in two thermally enhanced packages, Compact low profile (0.75mm) 8 leads (2mm × 3mm) DFN and 8-pin MSOP packages.

2. Feature

    1. Low operating current (450nA)

    2. 1% floating voltage accuracy over temperature and shunt current range

    3. 50mA maximum internal shunt current (500mA with external PFET)

    4. Pin selectable floating voltage options: 4.0V, 4.1V, 4.2V

    5. Ultra-low power pulsed NTC float regulation for Li-ion/polymer protection

    6. Suitable for intermittent, continuous and very low power charging sources

    7. Low and high battery status outputs

    8. Simple low voltage load disconnect application

    9. Thermally Enhanced, Low Profile (0.75mm) 8-Lead (2mm × 3mm) DFN and MSOP Packages

3. Application

    1. Low power Li-ion/polymer battery backup

    2. Solar power system with backup

    3. memory backup

    4. Embedded car

    5. thin film battery

    6. Energy scavenging/harvesting

4. Pin configuration

5. Pin Description

    1. NTCBIAS : NTC Bias Pin. 

    2. NTC : Input to the Negative Temperature Coefficient Thermistor Monitoring Circuit.

    3. ADJ : Float Voltage Adjust Pin. 

    4. HBO : High Battery Monitor Output (Active High).

    5. GND : Ground.  The exposed package pad must be connected to PCB ground for rated thermal performance.

    6. LBO : Low Battery Monitor Output (Active High).

    7. DRV : External Drive Output.

    8. VCC : Input Supply Pin.

6. Typical application

The LTC4070 status pins have sufficient drive strength to be used with LEDs to visually indicate charging status. Note that LED D1 will discharge the battery until VCC falls below VLBTH. The green LED D2 connected to the HBO pin lights up when the battery is charging. When the battery voltage rises to within the VHBTH range of the float voltage, including NTC qualification, VFLOAT_EFF, D2 turns off to indicate that the battery is no longer charging. Optionally, a low leakage diode D3 is placed between the cathode of D2 and the battery. This diode prevents D2 from discharging the battery when input power is not present. This simple application eliminates the need to replace NiMH charging solutions for charge termination or cell balancing scenarios. NiMH can be charged without termination, but the algorithm limits the charging rate to C/10. LTC4070 applications allow Li-Ion batteries to be charged faster without overcharging concerns. If the battery voltage is 3.6V the battery receives about 205mA of full charge current. If the battery temperature is below 40°C, the float voltage rises to 4.1V (ADJ = float), then the Q1 LTC4070 shunts 192mA from the battery. If the battery temperature increases, the shunt current increases to regulate the float voltage to reduce the battery temperature by 75mV for every 10°C increase, as described in Table 1. At a maximum shunt current of 200mA, the minimum float voltage is maintained at 3.8V when the battery temperature is above 70°C.