Datasheet LTC4012-3 (Analog Devices) - 8

LTC4012-3 pin FuncTions
CLN (Pin 1):
Adapter Input Current Limit Negative Input.
VFB (Pin 9):
Battery Voltage Feedback Input. An external The LTC4012-3 senses voltage on this pin to determine if resistor divider between FBDIV and GND with the center less charge current should be sourced to limit total input tap connected to VFB programs the charger output voltage. current. The threshold is set 100mV below the CLP pin. An In constant voltage mode, this pin is nominally at 1.2085V. external filter should be used to remove switching noise. Refer to the Applications Information section for complete This input should be tied to CLP if not used. Operating details on programming battery voltage. Operating voltage voltage range is (CLP – 110mV) to CLP. range is GND to 1.25V.
CLP (Pin 2):
Adapter Input Current Limit Positive Input.
FBDIV (Pin 10):
Battery Voltage Feedback Resistor Divider The LTC4012-3 also draws power from this pin, including Source. The LTC4012-3 connects this pin to BAT when a small amount for some shutdown functions. Operating charging is in progress. FBDIV is an open-drain PFET output voltage range is GND to 28V. to BAT with an operating voltage range of GND to BAT.
INFET (Pin 3):
PowerPath Control Output. This output
BAT (Pin 11):
Battery Pack Connection. The LTC4012-3 drives the gate of a PMOS pass transistor connected uses the voltage on this pin to control PWM operation when between the DC input (DCIN) and the raw system supply charging. Operating voltage range is GND to CLN. rail (CLP) to maintain a forward voltage of 25mV when a
ITH (Pin 12):
PWM Control Voltage and Compensation DC input source is present. INFET is internally clamped Node. The LTC4012-3 develops a voltage on this pin to about 6V below CLP. Maximum operating voltage is CLP, control cycle-by-cycle peak inductor current. An external which is used to turn off the input PMOS transistor when R-C network connected to ITH provides PWM loop com- the DC input is removed. pensation. Refer to the Applications Information section
DCIN (Pin 4):
DC Sense Input. One of two voltage sense for further details on establishing loop stability. Operating inputs to the internal PowerPath controller (the other input voltage range is GND to INTVDD. to the controller is CLP). This input is usually supplied
PROG (Pin 13):
Charge Current Programming and Monitor- from an input DC power source. Operating voltage ranges ing Pin. An external resistance connected between PROG from GND to 28.2V. and GND, along with the current sense and PWM input
GND (Pin 5):
Ground. Internally connected to the Exposed resistors, programs the maximum charge current. The Pad (package paddle). voltage on this pin can also provide a linearized indicator
SHDN
(
Pin 6):
Active-Low Shutdown Input. Driving SHDN of charge current. Refer to the Applications Information below 300mV unconditional y forces the LTC4012-3 into the section for complete details on current programming and shutdown state. This input has a 40kΩ internal pull-down monitoring. Operating voltage range is GND to INTVDD. to GND. Operating voltage range is GND to INTVDD.
CSN (Pin 14):
Charge Current Sense Negative Input.
CHRG (Pin 7):
Active-Low Charge Indicator Output. This Place an external input resistor (RIN, Figure 1) between open-drain output provides three levels of information this pin and the negative side of the charge current sense about charge status using a strong pull-down, 25µA weak resistor. Operating voltage ranges from (BAT – 50mV) to pull-down or high impedance. Refer to the Operation and (BAT + 200mV). Applications Information sections for further details. This
CSP (Pin 15):
Charge Current Sense Positive Input. output should be left floating if not used. Place an external input resistor (RIN, Figure 1) between
ICL (Pin 8):
Active-Low Input Current Limit Indicator Out- this pin and the positive side of the charge current sense put. This open-drain output pul s to GND when the charge resistor. Operating voltage ranges from (BAT – 50mV) current is reduced because of AC adapter input current to (BAT + 200mV). limiting. This output should be left floating if not used. 40123fb Document Outline Features Applications Description Typical Application Absolute Maximum Ratings Pin Configuration Order Information Electrical Characteristics Typical Performance Characteristics Pin Functions Block Diagram Test Circuits Operation Applications Information Package Description Revision History Typical Application Related Parts