LTC4009 LTC4009-1/LTC4009-2 pin FuncTions FVS0 (Pin 9, LTC4009-1/LTC4009-2): Battery Voltage CSP (Pin 15): Charge Current Sense Positive Input. Select Input (LSB). This pin is one of two pins used on the Place an external input resistor (RIN, Figure 1) be- LTC4009-1 or LTC4009-2 to select one of four preset battery tween this pin and the positive side of the charge voltages. Selection is done by connecting to either GND or current sense resistor. Operating voltage ranges from INTVDD. Operating voltage range is GND to INTVDD. (BAT – 50mV) to (BAT + 200mV). VFB (Pin 10, LTC4009): Battery Voltage Feedback Input. An BGATE (Pin 16): External Synchronous NFET Gate Control external resistor divider between FBDIV and GND with the Output. This output provides gate drive to an external NMOS center tap connected to VFB programs the charger output power transistor switch used for synchronous rectification voltage. In constant voltage mode, this pin is nominally to increase efficiency in the step-down DC/DC converter. at 1.2085V. Refer to the Applications Information section Operating voltage is GND to INTVDD. BGATE should be for complete details on programming battery float voltage. left floating if not used. Operating voltage range is GND to 1.25V. INTVDD (Pin 17): Internal 5V Regulator Output. This pin FVS1 (Pin 10, LTC4009-1/LTC4009-2): Battery Voltage provides a means of bypassing the internal 5V regulator Select Input (MSB). This pin is one of two pins used on used to power the LTC4009 PWM FET drivers. This supply the LTC4009-1 or LTC4009-2 to select one of four preset shuts down when the LTC4009 shuts down. Refer to the battery voltages. Selection is done by connecting to Application Information section for details if additional either GND or INTVDD. Operating voltage range is GND power is drawn from this pin by the application circuit. to INTVDD. SW (Pin 18): PWM Switch Node. The LTC4009 uses the BAT (Pin 11): Battery Pack Connection. The LTC4009 uses voltage on this pin as the source reference for its topside the voltage on this pin to control PWM operation when NFET (PWM switch) driver. Refer to the Applications In- charging. Operating voltage range is GND to CLN. formation section for additional PCB layout suggestions ITH (Pin 12): PWM Control Voltage and Compensation related to this critical circuit node. Operating voltage range Node. The LTC4009 develops a voltage on this pin to is GND to CLN. control cycle-by-cycle peak inductor current. An external TGATE (Pin 19): External NFET Switch Gate Control Output. R-C network connected to ITH provides PWM loop com- This output provides gate drive to an external NMOS power pensation. Refer to the Applications Information section transistor switch used in the DC/DC converter. Operating for further details on establishing loop stability. Operating voltage range is GND to (CLN + 5V). voltage range is GND to INTVDD. BOOST (Pin 20): TGATE Driver Supply Input. A bootstrap PROG (Pin 13): Charge Current Programming and Monitor- capacitor is returned to this pin from a charge network ing Pin. An external resistance connected between PROG connected to SW and INTVDD. Refer to the Applications and GND, along with the current sense and PWM input Information section for complete details on circuit topol- resistors, programs the maximum charge current. The ogy and component values. Operating voltage ranges from voltage on this pin can also provide a linearized indicator (INTVDD – 1V) to (CLN + 5V). of charge current. Refer to the Applications Information GND (Exposed Pad Pin 21): Ground. The package paddle section for complete details on current programming and provides a single-point ground for the internal voltage monitoring. Operating voltage range is GND to INTVDD. reference and other critical LTC4009 circuits. It must be CSN (Pin 14): Charge Current Sense Negative In- soldered to a suitable PCB copper ground pad for proper put. Place an external input resistor (RIN, Figure 1) electrical operation and to obtain the specified package between this pin and the negative side of the charge thermal resistance. current sense resistor. Operating voltage ranges from (BAT – 50mV) to (BAT + 200mV). 4009fd Document Outline Features Applications Description Typical Application Absolute Maximum Ratings Pin Configuration Order Information Electrical Characteristics Test Circuits Typical Performance Characteristics Pin Functions Block Diagram Operation Applications Information Package Description Revision History Typical Application Related Parts