Datasheet LTC4000 (Analog Devices) - 10

LTC4000
pin FuncTions (QFN/SSOP) CSN (Pin 19/Pin 15):
Charge Current Sense Negative Input when the voltage at the IN pin is within its operating range and Battery Ideal Diode Cathode. Connect a sense resistor (3V to 60V). To ensure that the input PMOS is turned off between this pin and the CSP pin. The LTC4000 senses when the IN pin voltage is not within its operating range, the voltage across this sense resistor and regulates it to connect a 10M resistor from this pin to the CSP pin. a voltage equal to 1/20th (typical) of the voltage set at the
IID (Pin 23/Pin 19):
Input Ideal Diode Anode. This pin is CL pin. The maximum regulated sense voltage is 50mV. the anode of the input ideal diode driver (the cathode is The CSN pin is also the cathode input of the battery ideal the CSP pin). diode driver (the anode input is the BAT pin). Tie this pin to the CSP pin if no charge current limit is desired. Refer to
ITH (Pin 24/Pin 20):
High Impedance Control Voltage Pin. the Applications Information section for complete details. When any of the regulation loops (input current, charge current, battery float voltage or the output voltage) indicate
CSP (Pin 20/Pin 16):
Charge Current Sense Positive Input that its limit is reached, the ITH pin will sink current (up to and Input Ideal Diode Cathode. Connect a sense resis- 1mA) to regulate that particular loop at the limit. In many tor between this pin and the CSN pin for charge current applications, this ITH pin is connected to the control/ sensing and regulation. This input should be tied to CSN compensation node of a DC/DC converter. Without any to disable the charge current regulation function. This external pull-up, the operating voltage range on this pin pin is also the cathode of the input ideal diode driver (the is GND to 2.5V. With an external pull-up, the voltage on anode is the IID pin). this pin can be pulled up to 6V. Note that the impedance
OFB (Pin 21/Pin 17):
Output Feedback Voltage Pin. This connected to this pin affects the overall loop gain. For pin is a high impedance input pin used to sense the output details, refer to the Applications Information section. voltage level. In regulation, the output voltage loop sets the
CC (Pin 25/Pin 21):
Converter Compensation Pin. Connect voltage on this feedback pin to 1.193V. Connect this pin an R-C network from this pin to the ITH pin to provide a to the center node of a resistor divider between the CSP suitable loop compensation for the converter used. Refer pin and the FBG pin to set the output voltage when battery to the Applications Information section for discussion and charging is terminated and all the output load current is procedure on choosing an appropriate R-C network for a provided from the input. The output voltage can then be particular DC/DC converter. obtained as follows:
CLN (Pin 26/Pin 22):
Input Current Sense Negative Input. VOUT = ROFB2 +ROFB1 • 1.193V Connect a sense resistor between this pin and the IN pin. ROFB2 The LTC4000 senses the voltage across this sense resis- tor and regulates it to a voltage equal to 1/20th (typical) When charging a heavily discharged battery (such that VOFB of the voltage set at the IL pin. Tie this pin to the IN pin if < VOUT(INST_ON)), the battery PowerPath PMOS connected no input current limit is desired. Refer to the Applications to BGATE is regulated to set the voltage on this feedback Information section for complete details. pin to 0.974V (approximately 86% of the battery float voltage). The instant-on output voltage is then as follows:
IN (Pin 27/Pin 23):
Input Supply Voltage: 3V to 60V. Supplies power to the internal circuitry and the BIAS pin. V Connect the power source to the downstream system OUT(INST _ ON) = ROFB2 + ROFB1 • 0.974V ROFB2 and the battery charger to this pin. This pin is also the positive sense pin for the input current limit. Connect a
IGATE (Pin 22/Pin 18):
Input PMOS Gate Drive Output. The sense resistor between this pin and the CLN pin. Tie this IGATE pin drives the external PMOS to behave as an ideal pin to CLN if no input current limit is desired. A local 0.1µF diode from the IID pin (anode) to the CSP pin (cathode) bypass capacitor to ground is recommended on this pin. 4000fb 10 For more information www.linear.com/LTC4000 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