Datasheet LT3650-4.1, LT3650-4.2 (Analog Devices) - 6

LT3650-4.1/LT3650-4.2
pin FuncTions VIN (Pin 1):
Charger Input Supply. VIN pin operating range be pulled low. If no fault conditions exist, the FAULT pin is 4.75V to 32V. VIN ≥ 7.5V or (VBOOST – VSW) > 2V is remains high impedance (see the Applications Informa- required for start-up. IVIN = 85µA after charge termination. tion section).
CLP (Pin 2):
System Current Limit Input. System current
TIMER (Pin 6):
End-Of-Cycle Timer Programming Pin. levels can be monitored by connecting the input power If a timer-based charge termination is desired, connect supply to the CLP pin and connecting a sense resistor a capacitor from this pin to ground. Full charge end-of- from the CLP pin to the VIN pin. Additional system load is cycle time (in hours) is programmed with this capacitor drawn from the VIN pin connection, and maximum system following the equation: load is achieved when VCLP – VVIN = 50mV. The LT3650 t servos the maximum charge current required to maintain EOC = CTIMER • 4.4 • 106 programmed maximum system current. If this function is A bad-battery fault is generated if the battery does not not desired, connect the CLP pin to the VIN pin (see the reach the precondition threshold voltage within one-eighth Applications Information section). of tEOC, or:
SHDN (Pin 3):
Precision Threshold Shutdown Pin. The tPRE = CTIMER • 5.5 • 105 enable threshold is 1.225V (rising), with 120mV of input A 0.68µF capacitor is typically used, which generates a hysteresis. When in shutdown mode, all charging functions timer EOC at three hours, and a precondition limit time of are disabled. The precision threshold allows use of the 22.5 minutes. If a timer-based termination is not desired, SHDN pin to incorporate UVLO functions. If the SHDN pin the timer function is disabled by connecting the TIMER is pulled below 0.4V, the IC enters a low current shutdown pin to ground. With the timer function disabled, charging mode where the VIN pin current is reduced to 15µA. Typi- terminates when the charge current drops below a C/10 cal SHDN pin input bias current is 10nA. If the shutdown rate, or I function is not desired, connect the pin to the V CHG(MAX)/10. IN pin.
RNG/SS (Pin 7):
Charge Current Programming Pin. This
CHRG (Pin 4):
Open-Collector Charger Status Output; pin allows a dynamic adjustment of the maximum charge typically pulled up through a resistor to a reference volt- current, and can be used to employ a soft-start function. age. This status pin can be pulled up to voltages as high Maximum charge current is adjusted by setting the volt- as VIN when disabled, and can sink currents up to 10mA age on this pin, such that the maximum desired voltage when enabled. During a battery charging cycle, CHRG is across the inductor current sense resistor (V pulled low. When the charge cycle is terminated, the CHRG SENSE – VBAT) is 0.1 • V pin becomes high impedance. If the internal timer is used RNG/SS, so the maximum charge current reduces to: for termination, the pin stays low during the charging VRNG/SS • ICHG(MAX) cycle until the charge current drops below a C/10 rate, or This pin has an effective range from 0V to 1V. 50µA is ICHG(MAX)/10. A temperature fault also causes this pin to sourced from this pin, so the maximum charge current be pulled low (see the Applications Information section). can be programmed by connecting a resistor (RRNG/SS)
FAULT (Pin 5):
Open-Collector Fault Status Output; typi- from RNG/SS to ground, such that the voltage dropped cally pulled up through a resistor to a reference voltage. across the resistor is equivalent to the desired program- This status pin can be pulled up to voltages as high as V ming voltage, or: IN when disabled, and can sink currents up to 10mA when VRNG/SS = 50µA • RRNG/SS enabled. This pin indicates charge cycle fault conditions during a battery charging cycle. A temperature fault causes Soft-start functionality can be implemented by con- this pin to be pulled low. If the internal timer is used for necting a capacitor (CRNG/SS) from RNG/SS to ground, termination, a bad-battery fault also causes this pin to such that the time required to charge the capacitor to 1V 36504142fc 6 Document Outline Features Applications Description Typical Application Absolute Maximum Ratings Pin Configuration Order Information Electrical Characteristics Typical Performance Characteristics Pin Functions Block Diagram Operation Applications Information Typical Applications Package Description Revision History Typical Application Related Parts