Datasheet LTC3728L-1 (Analog Devices) - 8

LTC3728L-1
PIN FUNCTIONS VOSENSE1, VOSENSE2:
Error Amplifi er Feedback Input.
TG2, TG1:
High Current Gate Drives for Top N-Channel Receives the remotely-sensed feedback voltage for each MOSFETs. These are the outputs of fl oating drivers with controller from an external resistive divider across the a voltage swing equal to INTVCC – 0.5V superimposed on output. the switch node voltage SW.
PLLFLTR:
Filter Connection for Phase-Locked Loop. Alter-
SW2, SW1:
Switch Node Connections to Inductors. Voltage natively, this pin can be driven with an AC or DC voltage swing at these pins is from a Schottky diode (external) source to vary the frequency of the internal oscillator. voltage drop below ground to VIN.
PLLIN:
External Synchronization Input to Phase Detector.
BOOST2, BOOST1:
Bootstrapped Supplies to the Top This pin is internally terminated to SGND with 50kΩ. The Side Floating Drivers. Capacitors are connected between phase-locked loop will force the rising top gate signal of the boost and switch pins and Schottky diodes are tied controller 1 to be synchronized with the rising edge of between the boost and INTVCC pins. Voltage swing at the the PLLIN signal. boost pins is from INTVCC to (VIN + INTVCC).
FCB:
Forced Continuous Control Input. This input acts
BG2, BG1:
High Current Gate Drives for Bottom (Synchro- on both controllers and is normally used to regulate a nous) N-Channel MOSFETs. Voltage swing at these pins secondary winding. Pulling this pin below 0.8V will force is from ground to INTVCC. continuous synchronous operation.
PGND:
Driver Power Ground. Connects to the sources of
ITH1, ITH2:
Error Amplifi er Output and Switching Regulator bottom (synchronous) N-channel MOSFETs, anodes of the Compensation Point. Each associated channels’ current Schottky rectifi ers and the (–) terminal(s) of CIN. comparator trip point increases with this control voltage.
INTVCC:
Output of the Internal 5V Linear Low Dropout
SGND:
Small Signal Ground. Common to both controllers, Regulator and the EXTVCC Switch. The driver and control this pin must be routed separately from high current circuits are powered from this voltage source. Must be grounds to the common (–) terminals of the COUT decoupled to power ground with a minimum of 4.7μF capacitors. tantalum or other low ESR capacitor.
3.3VOUT:
Linear Regulator Output. Capable of supplying
EXTVCC:
External Power Input to an Internal Switch Con- 10mA DC with peak currents as high as 50mA. nected to INTVCC. This switch closes and supplies VCC power, bypassing the internal
NC:
No Connect. low dropout regulator, when- ever EXTVCC is higher than 4.7V. See EXTVCC connection
SENSE2–, SENSE1–:
The (–) Input to the Differential Cur- in Applications section. Do not exceed 7V on this pin. rent Comparators.
VIN:
Main Supply Pin. A bypass capacitor should be tied
SENSE2+, SENSE1+:
The (+) Input to the Differential Current between this pin and the signal ground pin. Comparators. The ITH pin voltage and controlled offsets
PGOOD:
Open-Drain Logic Output. PGOOD is pulled to between the SENSE– and SENSE+ pins in conjunction with ground when the voltage on either V R OSENSE pin is not SENSE set the current trip threshold. within ±7.5% of its set point.
RUN/SS2, RUN/SS1:
Combination of soft-start and run
Exposed Pad (UH Package Only)
: Signal Ground. Must control inputs. A capacitor to ground at each of these pins be soldered to the PCB, providing a local ground for the sets the ramp time to full output current. Forcing either of control components of the IC, and be tied to the PGND these pins back below 1.0V causes the IC to shut down pin under the IC. the circuitry required for that particular controller. 3728l1fc 8