Datasheet LTC1760 (Analog Devices) - 10

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