Datasheet LTC3600 (Analog Devices) - 8

LTC3600
pin FuncTions ISET (Pin 1):
Accurate 50µA Current Source. Positive input
MODE/SYNC (Pin 6):
Operation Mode Select. Tie this pin to the error amplifier. Connect an external resistor from this to INTVCC to force continuous synchronous operation at pin to signal GND to program the VOUT voltage. Connecting all output loads. Tying it to GND enables discontinuous an external capacitor from ISET to ground will soft start mode operation at light loads. Applying an external clock the output voltage and reduce current inrush when turning signal to this pin will synchronize switching frequency on. VOUT can also be programmed by driving ISET directly to the external clock. During external clock synchroniza- with an external supply from 0 to VIN, in which case the tion, RT value should be set up such that the free running external supply would be sinking the provided 50µA. Do frequency is within 30% of the external clock frequency. not drive VISET above VIN or below GND. Do not float ISET.
SW (Pin 7):
Switch Node Connection to External Inductor.
ITH (Pin 2):
Error Amplifier Output and Switching Voltage swing of SW is from a diode voltage drop below Regulator Compensation Point. The internal current ground to VIN. comparator’s trip threshold is linearly proportional to this voltage, whose normal range is from 0.3V to 2.4V.
VIN (Pin 8):
Input voltage. Must decouple to GND with a For external compensation, tie a resistor (R capacitor close to the V ITH) in series IN pin. with a capacitor (CITH) to signal GND. A separate 10pF
BOOST (Pin 9):
Boosted Floating Driver Supply for Inter- high frequency filtering capacitor can also be placed nal Top Power MOSFET. The (+) terminal of the bootstrap from ITH to signal GND. Tying ITH to INTVCC activates capacitor connects here. This pin swings from a diode internal compensation. voltage drop below INTVCC up to VIN + INTVCC.
RT (Pin 3):
Switching Frequency Programming Pin. Con-
INTVCC (Pin 10):
Internal 5V Regulator Output. The internal nect an external resistor (between 200k to 10k) from RT power drivers and control circuits are powered from this to SGND to program the frequency from 200kHz to 4MHz. voltage. Decouple this pin to GND with a minimum of 1µF Tying the RT pin to INTVCC programs 1MHz operation. low ESR ceramic capacitor. Do not float the RT pin.
V PGFB (Pin 4):
Power Good Feedback. Place a resistor
OUT (Pin 11):
Output Voltage Pin. Output of the LTC3600 voltage regulator. Also the negative input of the error divider on VOUT to detect power good level. If PGFB is amplifier which is driven to be the same voltage as ISET. more than 0.645V, or less than 0.555V, PGOOD will be pulled down. Tie PGFB to INTV
PGOOD (Pin 12):
Output Power Good with Open-Drain CC to disable the PGOOD function. Tying PGFB to a voltage greater than 0.64V and Logic. PGOOD is pulled to ground when the PGFB pin is less than 4V will force continuous synchronous operation more than 0.645V or less than 0.555V. PGOOD open-drain regardless of the MODE/SYNC state. logic will be disabled if PGFB is tied to INTVCC.
RUN (Pin 5):
Run Control Input. Enables chip operation by
GND (Exposed Pad Pin 13):
Ground. Return path of internal tying RUN above 1.55V. Tying it below 1V shuts down the power MOSFETs. Connect the exposed pad to the negative switching regulator. Tying it below 0.4V shuts off the entire terminal of the input capacitor and output capacitor. chip. When tying RUN to more than 12V, place a resistor (100k to 500k) between RUN and the voltage source. 3600fd 8 Document Outline Features Applications Typical Application Description Absolute Maximum Ratings Pin Configuration Order Information Electrical Characteristics Typical Performance Characteristics Pin Functions Functional Diagram Operation Applications Information Typical Applications Package Description Revision History Typical Application Related Parts