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Regulator ICs
Trickle-charge IC for two-cell, lithium-ion batteries
BA3170
The BA3170 is a trickle-charge IC developed for two-cell, lithium-ion batteries.The IC includes a charge control circuit, a charge output transistor, and an LED driver for showing the charging status. FApplications Lithium-ion (two cell) battery chargers, and charging circuits FFeatures 1) Output voltage can be varied using an external resistor. 2) The output pin is PNP output with low saturation voltage. 3) Built-in output current limiting circuit protects batteries from excessive current, and prevents destruction of the IC due to output shorts. The initial charge current is set to a low value (the current limit pin voltage can be used to vary the current limit value). 4) Pulse charging at over 99% of the final voltage. FAbsolute maximum ratings (Ta = 25_C)
Built-in over-discharge battery return circuit. Built-in charge fault protection circuit. Built-in over-voltage battery operation circuit. Built-in LED output for charge display (two outputs). 12-pin power package provides large power dissipation in a compact package. 10) Temperature protection circuit prevents thermal destruction of the IC.
5) 6) 7) 8) 9)
FRecommended operating conditions (Ta = 25_C)
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Regulator ICs
FBlock diagram
BA3170
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FPin descriptions
BA3170
FElectrical characteristics (unless otherwise noted, Ta = 25_C, VCC = 12V, R1 = 58.7k, R2 = 10k)
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Regulator ICs
BA3170
FOperation notes (1) Do not use values other than CT = 0.022F for the timing capacitor, and C1 = 10F for the output capacitor. (2) For the output capacitor C1, use a tantalum capacitor with low capacitance variation with temperature, and a static capacitance tolerance of 10% or less. (3) For the timing capacitor CT, use a film capacitor with low capacitance variation with temperature, a static capacitance tolerance of 10% or less, and a temperature variation rate of 2% or less. FMeasurement circuit
Fig.1
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FTiming chart
BA3170
Fig.2
FExternal components Setting the "end point voltage"
Set the "end point voltage" Vbuf using resistors R1 and R2. Example: To set Vbuf to 8.4V: 1.22 = R2 / (R1 ) R2) 8.4 R1 = 5.88 . . . R2 If R2 = 10k, then R1 = 58.7k
For measurement of the electrical characteristics, Vref and Vbuf are shorted.
Fig.3
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Regulator ICs
FReference data S Output current limit value
BA3170
Set the value for the OCP voltage using R3 and R4(Ta = 25_C, VCC = 12V, Vbuf = 8.4V, and Vo = 7.4V (Typ.))
Fig.4
S Charging current and charge complete current for when the "end point voltage" is set to 8.4V 50mV (Ta = 25_C and VCC = 12V)
S Charge "end point voltage" temperature characteristic (VCC = 12V, R1 = 58.7k, R2 = 10k, and CT = 2.2V)
FOperation notes (1) Application circuit (in the block diagram) We guarantee the application circuit design, but recommend that you thoroughly check its characteristics in actual use. If you change any of the external component values, check both the static and transient characteristics of the circuit, and allow sufficient margin in your selections to take into account variations in the components and ICs. Note that Rohm has not fully investigated patent rights regarding this product.
(2) Operating voltage range Provided that the IC is operated within the recommended operating voltage range, the operation of the circuit is guaranteed within the allowed operating temperature range. With regard to the values for the characteristics, the rating values for electrical characteristics cannot be guaranteed, but within these ranges there will not be a dramatic change in the values for the characteristics. (3) Notes regarding power dissipation (Pd) A derating characteristic is provided for power dissipation. Your design should not require the component to dissipate more than its maximum allowed power dissipation over the operating temperature range.
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(4) Over-voltage protection circuit When the voltage between VCC (pin 6) and GND (pin 12) exceeds about 27V (at normal temperature), the overvoltage protection circuit switches all outputs off. Make sure to use the IC within this voltage limit. (5) Capacitors to prevent oscillation of the outputs Be certain to connect capacitors between OUT (pin 5) and ground, and CP (pin 2) and ground to prevent oscillation. We recommend tantalum capacitors that have low capacitance variation with temperature (particularly for the OUT pin). (6) Thermal shutdown circuit A thermal shutdown circuit is provided on the IC to prevent it from being destroyed by high temperatures. When this circuit operates, all outputs go off, and when the temperature drops to a certain level, operation resumes. (7) Output circuit construction The outputs use PNP power transistors. When the VCC (pin 6) voltage drops, even if the external capacitor on the output side causes the output-side voltage to exceed the VCC-side voltage, the IC will not be destroyed.
BA3170
(8) Grounding With regard to the ground connections shown in the application example circuit, make the PCB connections from each earth to the GND pin (pin 12) reasonably short, and design your pattern layout to avoid electrical interference between the pattern lines. (9) ASO This IC includes a variety of protection circuits, but depending on the operation conditions, it may be possible to exceed the ASO. Exceeding the ASO will result in destruction of the IC, so take due care to ensure that the ASO conditions are never exceeded. (10) Great care has been paid to the quality of this component. However, due to the nature of lithium-ion batteries, if there is a risk of danger due to failure of this component (e.g. fire or explosion), be certain to take appropriate measures in your design (fuses etc.).
FElectrical characteristics curves
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Regulator ICs
BA3170
FExternal dimensions (Units: mm)
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