Datasheet LTC3856 (Analog Devices) - 9

LTC3856
pin FuncTions (TSSOP/QFN) FREQ (Pin 1/Pin 29):
Frequency Setting Pin. A resistor Float or connect a 1k resistor to DIFFP pin when AVP to ground sets the operating frequency of the controller. function is not used. This pin can also be driven with a DC voltage to vary the
ITEMP (Pin 11/Pin 5):
Input to the Temperature Sensing frequency of the internal oscillator. Circuit. Connect this pin to an external NTC (negative
RUN (Pin 2/Pin 30):
Run Control Input. A voltage above temperature coefficient) resistor placed near the heat 1.22V on this pin turns on the IC. There is a 1µA pull-up source on the PCB board (e.g., inductors) changes the current for this pin. Once the RUN pin rises above 1.22V, controller’s current limit with temperature. an additional 4.5µA pull-up current is added to the pin.
PHASMD (Pin 12/Pin 6):
Connect this pin to SGND, INTVCC,
SENSE1+, SENSE2+ (Pins 3, 13/Pins 31, 7):
Current or float this pin to select the phase of CLKOUT to be 60°, Sense Comparator Inputs. The (+) inputs to the current 120° and 90°, respectively. comparators are normally connected to DCR sensing
DIFFP (Pin 15/Pin 9):
Positive Input of Remote Sensing networks or current sensing resistors. Differential Amplifier. Must connect this pin directly to
SENSE1–, SENSE2– (Pins 4, 14/Pins 32, 8):
Current the remote load voltage or local VOUT even when AVP or Sense Comparator Inputs. The (–) inputs to the current diffamp is not used. comparators are connected to the outputs.
DIFFN (Pin 16/Pin 10):
Negative Input of Remote Sens-
NC (Pins 5, 25, 34) TSSOP Package:
No Connections. ing Differential Amplifier. Connect this pin to the negative terminal of output load capacitors.
TK/SS (Pin 6/Pin 1):
Output Voltage Tracking and Soft- Start Input. When one particular IC is configured to be the
DIFFOUT (Pin 17/Pin 11):
Output of Remote Sensing master of two ICs, a capacitor to ground at this pin sets Differential Amplifier. Connect this pin to VFB through a the ramp rate for the master IC’s output voltage. When the resistive divider. IC is configured to be the slave of two ICs, the VFB voltage
ISET (Pin 18/Pin 12):
Stage Shedding Mode Comparator of the master IC is reproduced by a resistor divider and and Burst Mode Comparator Programming Pin. A resistor applied to this pin. An internal soft-start current of 1.25µA to ground programs the threshold of the Stage Shedding is charging this pin. mode comparator or Burst Mode comparator threshold
V
and current limit.
FB (Pin 7/Pin 2):
Error Amplifier Feedback Input. This pin receives the remotely sensed feedback voltage from
ILIM (Pin 19/Pin 13):
Current Comparator Sense Volt- an external resistive divider. age Range Input. This pin is to be programmed to
I
SGND, FLOAT or INTV
TH (Pin 8/Pin 3):
Current Control Threshold and Error CC to set the maximum current Amplifier Compensation Point. Each associated channels’ sense threshold to one of three different levels for both current comparator tripping threshold increases with I comparators. TH control voltage.
MODE (Pin 20/Pin 14):
Forced Continuous Mode,
SGND (Pin 9/Pin 33):
Signal Ground and Power Ground. All Burst Mode Operation or Stage Shedding Mode Selec- small-signal components and compensation components tion Pin. Connect this pin to SGND to force IC in should connect to this ground, which in turn connects to continuous mode of operation. Connect to INTVCC to PGND at one point. enable Stage Shedding mode operation. Leaving the pin floating enables Burst Mode operation.
AVP (Pin 10/Pin 4):
Active Voltage Positioning Load Slope Programming Pin. A resistor between this pin and the
PGOOD (Pin 21/Pin 15):
Power Good Indicator Output. DIFFP pin sets the load slope. The AVP function can only Open-drain logic out that is pulled to ground when the be used with the remote sensing differential amplifier. output exceeds the ±10% regulation window, after the internal 20µs power-bad mask timer expires. 3856fa For more information www.linear.com/LTC3856 9 Document Outline Features Applications Description Typical Application Absolute Maximum Ratings Pin Configuration Order Information Electrical Characteristics Typical Performance Characteristics Pin Functions FUNCTIONAL Diagram Operation Applications Information Typical Application Typical Application Related Parts