Datasheet LT3651-4.1, LT3651-4.2 (Analog Devices) - 8

LT3651-4.1/LT3651-4.2
PIN FUNCTIONS CHRG (Pin 26):
Open-Collector Charger Status Output.
CLP/CLN (Pin 29/Pin 30):
System Current Limit Positive This pin indicates the battery charging status. Typically and Negative Input. System current levels are monitored a resistor pull-up is used on this pin. This status pin can by connecting a sense resistor from the input power sup- be pulled up to voltages as high as VIN when disabled, ply to the CLP pin, connecting a sense resistor from the and can sink currents up to 10mA when enabled. CHRG CLP pin to the CLN pin and then connecting CLN to VIN. is pulled low during a battery charging cycle. When the The system load is then delivered from the CLN pin. The charge cycle is terminated, the CHRG pin becomes high LT3651 servos the maximum charge current required to impedance. If the internal timer is used for termination, maintain programmed maximum system current. The the pin stays low during the charging cycle until the charge system current limit is set as a function of the voltage current drops below a C/10 rate, or approximately 10% on the ILIM pin and the input current sense resistor. This of the maximum charge current. A temperature fault also function is disabled by shorting CLP, CLN and VIN together. causes this pin to be pulled low.
VIN (Pins 32, 33, 34):
Charger Input Supply. These pins
SHDN (Pin 27):
Shutdown Pin. This pin can be used for provide power for the LT3651. Charge current for the precision UVLO functions. When this pin rises above the battery flows into this pin. IVIN is less than 100µA after 1.20V threshold, the part is enabled. The pin has 95mV of charge termination. Connect the pins together. voltage hysteresis. When in shutdown mode, all charging
RNG/SS (Pin 35):
Charge Current Range and Soft-Start functions are disabled. When the SHDN pin is pulled below Pin. This pin allows for setting and dynamic adjustment 0.4V, the IC enters a low current shutdown mode where of the maximum charge current, and can be used to em- the VIN pin current is reduced to 17µA. Typical SHDN pin ploy a soft-start function. The voltage on this pin sets the input bias current is 10nA. Connect the pin to VIN if the maximum charge current by setting the maximum voltage shutdown function is not desired. across the charge current sense resistor, RSENSE , placed
ILIM (Pin 28):
Input Current Limit Programming. This pin between SENSE and BAT. allows for setting and dynamic adjustment of the system The effective range on the pin is 0V to 1V. 50µA is sourced input current limit, and can be used to employ a soft-start from this pin usually to a resistor (R function. The voltage on this pin sets the maximum input RNG/SS) to ground. V current by setting the maximum voltage across the input RNG/SS represents approximately 10 times the maximum voltage across the charge current sense resistor. If no R current sense resistor, placed between CLP and CLN. RNG/ SS is used the part will default to maximum charge current. The effective range on the pin is 0V to 1V. 50µA is sourced Soft-start functionality for charge current can be imple- from this pin usually to a resistor (RILIM) to ground. VIILIM mented by connecting a capacitor (C represents approximately 11 times the maximum voltage RNG/SS) from RNG/SS to ground. The soft-start capacitor and the programming across the input current sense resistor. If no RILIM is used resistor can be implemented in parallel. The RNG/SS pin the part will default to maximum input current. is pulled low during fault conditions, allowing graceful Soft-start functionality for input current can be imple- recovery from faults if CRNG/SS is used. mented with a capacitor (CILIM) from ILIM to ground. The
RT (Pin 36):
Switcher Oscillator Timer Set Pin. A resis- soft-start capacitor and the programming resistor can be tor from this pin to ground sets the switcher oscillator implemented in parallel. frequency. Typically this is 54.9k for fOSC = 1MHz. 365142ff 8 For more information www.linear.com/LT3651-4.1 Document Outline Features Description Applications Typical Application Absolute Maximum Ratings Pin Configuration Order Information Pin Functions Block Diagram Operation Applications Information Typical Applications Revision History Typical Application Related Parts