LTC1760
10
1760fc
For more information
www.linear.com/LTC1760
GB1O (Pin 8):
BAT1 Output Switch Gate Drive. Together
with GB1I, this pin drives the gate of the P-channel switch
in series with the BAT1 input switch.
GB1I (Pin 9):
BAT1 Input Switch Gate Drive. Together with
GB1O, this pin drives the gate of the P-channel switch
connected to the BAT1 input.
GB2O (Pin 10):
BAT2 Output Switch Gate Drive. Together
with GB2I, this pin drives the gate of the P-channel switch
in series with the BAT2 input switch.
GB2I (Pin 11):
BAT2 Input Switch Gate Drive. Together
with GB2O, this pin drives the gate of the P-channel switch
connected to the BAT2 input.
CLP (Pin 36):
The Positive Input to the Supply Current
Limiting Amplifier CL1. The threshold is set at 100mV above
the voltage at the DCIN pin. When used to limit supply
current, a filter is needed to filter out the switching noise.
Battery Charging Related
V
SET
(Pin 13):
The Tap Point of a Programmable Resistor
Divider which Provides Battery Voltage Feedback to the
Charger. A capacitor from CSN to V
SET
and from V
SET
to
GND provide necessary compensation and filtering for
the voltage loop.
I
TH
(Pin 14):
The Control Signal of the Inner Loop of the
Current Mode PWM. Higher I
TH
voltage corresponds to
higher charging current in normal operation. A capacitor
of at least 0.1µF to GND filters out PWM ripple. Typical
full-scale output current is 30µA. Nominal voltage range
for this pin is 0V to 2.4V.
I
SET
(Pin 15):
A capacitor from I
SET
to GND is required to
filter higher frequency components from the delta-sigma I
DAC
.
I
LIMIT
(Pin 32):
An external resistor (R
ILIMIT
) is connected
between this pin and GND. The value of the external resis-
tor programs the range and resolution of the programmed
charger current.
V
LIMIT
(Pin 33):
An external resistor (R
VLIMIT
)is connected
between this pin and GND. The value of the external resis-
tor programs the range and resolution of the voltage DAC.
CSN (Pin 34):
Current Amplifier CA1 Input. Connect this
to the common output of the charger MUX switches.
CSP (Pin 35):
Current Amplifier CA1 Input. This pin and
the CSN pin measure the voltage across the charge cur-
rent sense resistor, R
SENSE
, to provide the instantaneous
current signals required for both peak and average current
mode operation.
COMP1 (Pin 37):
The Compensation Node for the Am-
plifier CL1. A capacitor is required from this pin to GND
if input current amplifier CL1 is used. At input adapter
current limit, this node rises to 1V. By forcing COMP1 to
GND, amplifier CL1 will be defeated (no adapter current
limit). COMP1 can source 10µA.
BGATE (Pin 39):
Drives the gate of the bottom external
MOSFET of the battery charger buck converter.
SW (Pin 42):
PWM Switch Node. Connected to the source
of the top external MOSFET. Used as reference for top
gate driver.
BOOST (Pin 43):
Supply to Topside Floating Driver. The
bootstrap capacitor is returned to this pin. Voltage swing
at this pin is from a diode drop below V
CC
to (DCIN + V
CC
).
TGATE (Pin 44):
Drives the gate of the top external MOSFET
of the battery charger buck converter.
SCH1 (Pin 45), SCH2 (Pin 48):
Charger MUX N-Channel
Switch Source Returns. These two pins are connected to
the sources of the back-to-back switch pairs Q3/Q4 and
Q9/Q10 (see Typical Applications). A small pull-down cur-
rent source returns these nodes to 0V when the switches
are turned off.
GCH1 (Pin 46), GCH2 (Pin 47):
Charger MUX N-Channel
Switch Gate Drives. These two pins drive the gates of the
back-to-back switch pairs, Q3/Q4 and Q9/Q10, between
the charger output and the two batteries (see Typical
Applications).
External Power Supply Pins
V
PLUS
(Pin 1):
Supply. The V
PLUS
pin is connected via
four internal diodes to the DCIN, SCN, BAT1, and BAT2
pins. Bypass this pin with a 0.1µF capacitor and a 1µF
capacitor (see Typical Applications for complete circuit).
BAT1 (Pin 3), BAT2 (Pin 2):
These two pins are the inputs
from the two batteries for power to the LTC1760.
PIN FUNCTIONS
