Datasheet LTC3868 (Analog Devices) - 9

LTC3868
PIN FUNCTIONS RUN1, RUN2 (Pin 7, Pin 8):
Digital Run Control Inputs
SW1, SW2 (Pin 25, Pin 16):
Switch Node Connections for Each Controller. Forcing either of these pins below to Inductors. 1.26V shuts down that controller. Forcing both of these pins below 0.7V shuts down the entire LTC3868, reduc-
TG1, TG2 (Pin 26, Pin 15):
High Current Gate Drives for ing quiescent current to approximately 8µA. Do not float Top N-Channel MOSFETs. These are the outputs of float- these pins. ing drivers with a voltage swing equal to INTVCC – 0.5V superimposed on the switch node voltage SW.
ILIM (Pin 28):
Current Comparator Sense Voltage Range Inputs. Tying this pin to SGND, FLOAT or INTV
PGOOD1, PGOOD2 (Pin 27, Pin 14):
Open-Drain Logic CC sets the maximum current sense threshold to one of three different Output. PGOOD1,2 is pulled to ground when the voltage levels for both comparators. on the VFB1,2 pin is not within ±10% of its set point.
INTV SS1, SS2 (Pin 29, Pin 13):
External Soft-Start Input.
CC (Pin 19):
Output of the Internal Linear Low Dropout Regulator. The driver and control circuits are powered from The LTC3868 regulates the VFB1,2 voltage to the smaller this voltage source. Must be decoupled to power ground of 0.8V or the voltage on the SS1,2 pin. An internal 1µA with a minimum of 4.7µF ceramic or other low ESR ca- pull-up current source is connected to this pin. A capacitor pacitor. Do not use the INTV to ground at this pin sets the ramp time to final regulated CC pin for any other purpose. output voltage. This pin is also used as the short-circuit
EXTVCC (Pin 20):
External Power Input to an Internal LDO latchoff timer. Connected to INTVCC. This LDO supplies INTVCC power, bypassing the internal LDO powered from V
ITH1, ITH2 (Pin 30, Pin 12):
Error Amplifier Outputs and IN whenever EXTV Switching Regulator Compensation Points. Each associ- CC is higher than 4.7V. See EXTVCC Connection in the Applications Information section. Do not exceed 14V ated channel’s current comparator trip point increases on this pin. with this control voltage.
PGND (Pin 21):
Driver Power Ground. Connects to the
VFB1, VFB2 (Pin 31, Pin 11):
Receives the remotely sensed sources of bottom (synchronous) N-channel MOSFETs feedback voltage for each controller from an external and the (–) terminal(s) of C resistive divider across the output. IN.
V SENSE1+, SENSE2+ (Pin 32, Pin 10):
The (+) Input to the
IN (Pin 22):
Main Supply Pin. A bypass capacitor should be tied between this pin and the signal ground pin. differential current comparators are normally connected to DCR sensing networks or current sensing resistors.
BG1, BG2 (Pin 23, Pin 18):
High Current Gate Drives The ITH pin voltage and controlled offsets between the for Bottom (Synchronous) N-Channel MOSFETs. Voltage SENSE– and SENSE+ pins in conjunction with RSENSE set swing at these pins is from ground to INTVCC. the current trip threshold.
BOOST1, BOOST2 (Pin 24, Pin 17):
Bootstrapped Supplies to the Topside Floating Drivers. Capacitors are connected between the BOOST and SW pins and Schottky diodes are tied between the BOOST and INTVCC pins. Voltage swing at the BOOST pins is from INTVCC to (VIN + INTVCC). 3868fe For more information www.linear.com/LTC3868 9 Document Outline Features Description Applications Typical Application Absolute Maximum Ratings Pin Configuration Typical Performance Characteristics Pin Functions Operation Package Description Typical Application Related Parts