Datasheet LTC3875 (Analog Devices) - 10

LTC3875
PIN FUNCTIONS PHASMD (Pin 32):
Phase Programmable Pin. This pin can
TCOMP1/ITEMP1, TCOMP2/ITEMP2 (Pin 37, Pin 12):
be tied to SGND, INTVCC or left floating. It determines the Input of the Temperature Balancing Circuitries. Connect relative phases between the internal controllers as well these pins to external NTC resistors or temperature sensing as the phasing of the CLKOUT signal. See Table 1 in the ICs placed near inductors. These pins are used to sense Operation section for details. temperature of each channel and balance the temperature
MODE/PLLIN (Pin 33):
Forced Continuous Mode, Burst of the whole system accordingly. When thermal balancing Mode or Pulse-Skipping Mode Selection Pin and External function is disabled, these pins can be programmed to Synchronization Input to Phase Detector Pin. Connect compensate the temperature coefficient of the DCR. Con- this pin to SGND to force the IC into continuous mode of nect to an NTC (negative tempco) resistor placed near the operation. Connect to INTV output inductor to compensate for its DCR change over CC to enable pulse-skipping mode of operation. Leave the pin floating to enable Burst temperature. Floating this pin disables the DCR temperature Mode operation. A clock on the pin will force the IC into compensation function. continuous mode of operation and synchronize the internal
SNSD1+, SNSD2+ (Pin 38, Pin 11):
DC Current Sense Com- oscillator with the clock on this pin. The PLL compensation parator Inputs. The (+) input to the DC current comparator network is integrated into the IC. is normally connected to a DC current sensing network.
RUN1, RUN2 (Pin 34, Pin 16):
Run Control Inputs. A volt- Ground these pins to disable the novel DCR sensing and age above 1.22V on either pin turns on the IC. However, enable normal DCR sensing with five times current limit. forcing both pins below 1.14V causes the IC to shut down.
SNS1–, SNS2– (Pin 39, Pin 10):
AC and DC Current There is a 1.0µA pull-up current for both pins. Once the Sense Comparator Inputs. The (–) inputs to the current RUN pin rises above 1.22V, an additional 4.5µA pull-up comparators are connected to the output. current is added to the pin.
SNSA1+, SNSA2+ (Pin 40, Pin 9):
AC Current Sense
ILIM (Pin 35):
Current Comparators’ Sense Voltage Range Comparator Inputs. The (+) input to the AC current com- Input. A resistor divider sets the maximum current sense parator is normally connected to a DCR sensing network. threshold to five different levels for the current comparators. When combined with the SNSD+ pin, the DCR sensing
TRSET1, TRSET2 (Pin 36, Pin 14):
Input of the Tempera- network can be skewed to increase the AC ripple voltage ture Balancing Circuitries. Connect these pins through by a factor of 5. resistors to ground to convert the TCOMP pin voltages
SGND/PGND (Exposed Pad Pin 41):
Signal/Power Ground to currents. These currents are then mirrored to pin TAVG Pin. Connect this pin closely to the sources of the bot- and are added together for all channels. Float this pin if tom N-channel MOSFETs, the (–) terminal of CVCC and thermal balancing is not used. the (–) terminal of CIN. All small-signal components and compensation components should connect to this ground. 3875fb 10 For more information www.linear.com/LTC3875 Document Outline Features Applications Description Typical Application Absolute Maximum Ratings Pin Configuration Order Information Electrical Characteristics Typical Performance Characteristics Pin Functions Block Diagram Operation Applications Information Typical Applications Related Parts