lt3651-4.2 Linear Technology Corporation, lt3651-4.2 Datasheet - Page 7

• Manufacturer Part Number: lt3651-4.2
• Description: Monolithic 4a High Voltage Li-ion Battery Charger Features
• Manufacturer: Linear Technology Corporation

pin FuncTions
CHRG (Pin 26): Open-Collector Charger Status Output.
This pin indicates the battery charging status. Typically
a resistor pull-up is used on this pin. This status pin can
be pulled up to voltages as high as V
and can sink currents up to 10mA when enabled. CHRG
is pulled low during a battery charging cycle. When the
charge cycle is terminated, the CHRG pin becomes high
impedance. If the internal timer is used for termination,
the pin stays low during the charging cycle until the charge
current drops below a C/10 rate, or approximately 10%
of the maximum charge current. A temperature fault also
causes this pin to be pulled low.
SHDN (Pin 27): Shutdown Pin. This pin can be used for
precision UVLO functions. When this pin rises above the
1.20V threshold, the part is enabled. The pin has 95mV of
voltage hysteresis. When in shutdown mode, all charging
functions are disabled. When the SHDN pin is pulled below
0.4V, the IC enters a low current shutdown mode where
the V
input bias current is 10nA. Connect the pin to V
shutdown function is not desired.
I
allows for setting and dynamic adjustment of the system
input current limit, and can be used to employ a soft-start
function. The voltage on this pin sets the maximum input
current by setting the maximum voltage across the input
current sense resistor, placed between CLP and CLN.
The effective range on the pin is 0V to 1V. 50µA is sourced
from this pin usually to a resistor (R
represents approximately 11 times the maximum voltage
across the input current sense resistor. If no R
the part will default to maximum input current.
Soft-start functionality for input current can be imple-
mented with a capacitor (C
soft-start capacitor and the programming resistor can be
implemented in parallel.
LIM
(Pin 28): Input Current Limit Programming This pin
IN
pin current is reduced to 17µA. Typical SHDN pin
ILIM
) from I
ILIM
LIM
IN
) to ground. V
when disabled,
to ground. The
ILIM
IN
is used
if the
IILIM
CLP/CLN (Pin 29/Pin 30): System Current Limit Positive
and Negative Input. System current levels are monitored
by connecting a sense resistor from the input power supply
to the CLP pin, connecting a sense resistor from the CLP
pin to the CLN pin and then connecting CLN to V
system load is then delivered from the CLN pin. The LT3651
servos the maximum charge current required to maintain
programmed maximum system current. The system cur-
rent limit is set as a function of the voltage on the I
pin and the input current sense resistor. This function is
disabled by shorting CLP , CLN and V
V
power for the LT3651. Charge current for the battery flows
into this pin. I
tion. Connect both pins together.
RNG/SS (Pin 35): Charge Current Range and Soft-Start
Pin. This pin allows for setting and dynamic adjustment
of the maximum charge current, and can be used to em-
ploy a soft-start function. The voltage on this pin sets the
maximum charge current by setting the maximum voltage
across the charge current sense resistor, R
between SENSE and BAT.
The effective range on the pin is 0V to 1V. 50µA is sourced
from this pin usually to a resistor (R
V
voltage across the charge current sense resistor. If no
R
current.
Soft-start functionality for charge current can be imple-
mented by connecting a capacitor (C
to ground. The soft-start capacitor and the programming
resistor can be implemented in parallel. The RNG/SS pin
is pulled low during fault conditions, allowing graceful
recovery from faults if C
RT (Pin 36): Switcher Oscillator Timer Set Pin. A resis-
tor from this pin to ground sets the switcher oscillator
frequency. Typically this is 54.9k for f
IN
RNG/SS
RNG/SS
(Pins 32, 33): Charger Input Supply. This pin provides
represents approximately 10 times the maximum
is used the part will default to maximum charge
VIN
is less than 100µA after charge termina-
RNG/SS
is used.
LT3651-4.2
RNG/SS
IN
OSC
RNG/SS
together.
= 1MHz.
) from RNG/SS
SENSE
) to ground.
, placed
IN
. The
365142f

LIM