LTC4009
LTC4009-1/LTC4009-2
8
4009fd
pin FuncTions
FVS0 (Pin 9, LTC4009-1/LTC4009-2): Battery Voltage
Select Input (LSB). This pin is one of two pins used on the
LTC4009-1 or LTC4009-2 to select one of four preset battery
voltages. Selection is done by connecting to either GND or
INTV
DD
. Operating voltage range is GND to INTV
DD
.
V
FB
(Pin 10, LTC4009): Battery Voltage Feedback Input. An
external resistor divider between FBDIV and GND with the
center tap connected to V
FB
programs the charger output
voltage. In constant voltage mode, this pin is nominally
at 1.2085V. Refer to the Applications Information section
for complete details on programming battery float voltage.
Operating voltage range is GND to 1.25V.
FVS1 (Pin 10, LTC4009-1/LTC4009-2): Battery Voltage
Select Input (MSB). This pin is one of two pins used on
the LTC4009-1 or LTC4009-2 to select one of four preset
battery voltages. Selection is done by connecting to
either GND or INTV
DD
. Operating voltage range is GND
to INTV
DD
.
BAT (Pin 11): Battery Pack Connection. The LTC4009 uses
the voltage on this pin to control PWM operation when
charging. Operating voltage range is GND to CLN.
ITH (Pin 12): PWM Control Voltage and Compensation
Node. The LTC4009 develops a voltage on this pin to
control cycle-by-cycle peak inductor current. An external
R-C network connected to ITH provides PWM loop com-
pensation. Refer to the Applications Information section
for further details on establishing loop stability. Operating
voltage range is GND to INTV
DD
.
PROG (Pin 13): Charge Current Programming and Monitor-
ing Pin. An external resistance connected between PROG
and GND, along with the current sense and PWM input
resistors, programs the maximum charge current. The
voltage on this pin can also provide a linearized indicator
of charge current. Refer to the Applications Information
section for complete details on current programming and
monitoring. Operating voltage range is GND to INTV
DD
.
CSN (Pin 14): Charge Current Sense Negative In-
put. Place an external input resistor (R
IN
, Figure 1)
between this pin and the negative side of the charge
current sense resistor. Operating voltage ranges from
(BAT – 50mV) to (BAT + 200mV).
CSP (Pin 15): Charge Current Sense Positive Input.
Place an external input resistor (R
IN
, Figure 1) be-
tween this pin and the positive side of the charge
current sense resistor. Operating voltage ranges from
(BAT – 50mV) to (BAT + 200mV).
BGATE (Pin 16): External Synchronous NFET Gate Control
Output. This output provides gate drive to an external NMOS
power transistor switch used for synchronous rectification
to increase efficiency in the step-down DC/DC converter.
Operating voltage is GND to INTV
DD
. BGATE should be
left floating if not used.
INTV
DD
(Pin 17): Internal 5V Regulator Output. This pin
provides a means of bypassing the internal 5V regulator
used to power the LTC4009 PWM FET drivers. This supply
shuts down when the LTC4009 shuts down. Refer to the
Application Information section for details if additional
power is drawn from this pin by the application circuit.
SW (Pin 18): PWM Switch Node. The LTC4009 uses the
voltage on this pin as the source reference for its topside
NFET (PWM switch) driver. Refer to the Applications In-
formation section for additional PCB layout suggestions
related to this critical circuit node. Operating voltage range
is GND to CLN.
TGATE (Pin 19): External NFET Switch Gate Control Output.
This output provides gate drive to an external NMOS power
transistor switch used in the DC/DC converter. Operating
voltage range is GND to (CLN + 5V).
BOOST (Pin 20): TGATE Driver Supply Input. A bootstrap
capacitor is returned to this pin from a charge network
connected to SW and INTV
DD
. Refer to the Applications
Information section for complete details on circuit topol-
ogy and component values. Operating voltage ranges from
(INTV
DD
– 1V) to (CLN + 5V).
GND (Exposed Pad Pin 21): Ground. The package paddle
provides a single-point ground for the internal voltage
reference and other critical LTC4009 circuits. It must be
soldered to a suitable PCB copper ground pad for proper
electrical operation and to obtain the specified package
thermal resistance.
