LTC4012-2 Linear Technology Corporation, LTC4012-2 Datasheet - Page 9

• Manufacturer Part Number: LTC4012-2
• Description: Multi-Chemistry Battery Charger
• Manufacturer: Linear Technology Corporation

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PIN FUNCTIONS
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
CSN (Pin 14): Charge Current Sense Negative Input.
Place an external input resistor (R
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
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 rectifi cation
to increase effi ciency in the step-down DC/DC converter.
Operating voltage is GND to INTV
left fl oating if not used.
INTV
provides a means of bypassing the internal 5V regulator
used to power the LTC4012 PWM FET drivers. This supply
shuts down when the LTC4012 shuts down. Refer to the
Application Information section for details if additional
power is drawn from this pin by the application circuit.
DD
(Pin 17): Internal 5V Regulator Output. This pin
DD
. BGATE should be
IN
, Figure 1) be-
IN
, Figure 1)
DD
.
SW (Pin 18): PWM Switch Node. The LTC4012 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
Information section for complete details on circuit topol-
ogy and component values. Operating voltage ranges from
(INTV
Exposed Pad (Pin 21): Ground. The package paddle
provides a single-point ground for the internal voltage
reference and other critical LTC4012 circuits. It must be
soldered to a suitable PCB copper ground pad for proper
electrical operation and to obtain the specifi ed package
thermal resistance.
DD
– 1V) to (CLN + 5V).
LTC4012-1/LTC4012-2
DD
. Refer to the Applications
LTC4012/
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