Datasheet LTM4638 (Analog Devices) - 7

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PIN FUNCTIONS PACKAGE ROW AND COLUMN LABELING MAY VARY TRACK/SS (E2):
Output Tracking and Soft-Start Pin of the
AMONG µModule PRODUCTS. REVIEW EACH PACKAGE
Switching Mode Regulator. Allows the user to control the
LAYOUT CAREFULLY.
rise time of the output voltage. Putting a voltage below
VOUT (A1-A5, F3, G1-G3):
Power Output Pins of the 0.6V on this pin bypasses the internal reference input to the Switching Mode Regulator. Apply output load between error amplifier, instead it servos the FB pin to the TRACK these pins and GND pins. Recommend placing output voltage. Above 0.6V, the tracking function stops and the decoupling capacitance directly between these pins and internal reference resumes control of the error amplifier. GND pins. See the Applications Information section for There’s an internal 6µA pul -up current from INTVCC on this paralleling outputs. pin, so putting a capacitor here provides soft-start func-
COMPb (F1):
Internal Loop Compensation Network. tion. See the Applications Information section for details. Connect to COMPa to use the internal compensation in
MODE/CLKIN (D2):
Discontinuous Mode Select Pin and majority of applications. External Synchronization Input to Phase Detector. Tie
FREQ (E1):
Switching Frequency Program Pin. Frequency is MODE/CLKIN to GND for discontinuous mode of operation. set internally to 600kHz. An external resistor can be placed Floating MODE/CLKIN or tying it to a voltage above 1V will from this pin to GND to increase frequency, or from this select forced continuous mode. Furthermore, connecting pin to INTV MODE/CLKIN to an external clock will synchronize the CC to reduce frequency. See the Applications Information section for frequency adjustment. system clock to the external clock and puts the part in forced continuous mode. See Applications Information
COMPa (D1):
Current control threshold and error ampli- section for details. fier compensation point of the switching mode regulator
–
channel. The internal current comparator threshold is
VOSNS (C2):
Negative Input to the Differential Remote linearly proportional to this voltage. Tie the COMPa pins Sense Amplifier. Connect an external resistor between FB – from different channels together for parallel operation. and VOSNS pin to set the output voltage of the specific The device is internal compensated. Connect to COMPb channel. See the Applications Information section for to use the internal compensation. Or connect to a Type-II details. C-R-C network to use customized compensation.
CLKOUT (F2):
Output Clock Signal for PolyPhase Op-
FB (C1):
The Negative Input of the Error Amplifier for the eration. The phase of CLKOUT with respect to CLKIN is switching mode regulator. This pin is internally connected determined by the state of the respective PHMODE pin. to V + CLKOUT’s peak-to-peak amplitude is INTVCC to GND. See OSNS with a 60.4kΩ precision resistor. Output voltages can be programmed with an additional resistor between Application Information section for details. FB and V – OSNS pins. In PolyPhase® operation, tying the
VIN (D3-D4, E3-E4, F4, G4):
Power input pins connect to FB pins together allows for parallel operation. See the the drain of the internal top MOSFET and signal VIN to the Applications Information section for details. internal 3.3V regulator for the control circuitry for each
V +
switching mode regulator channel. Apply input voltages
OSNS (B1):
Positive Input to the Differential Remote Sense Amplifier. Internally, this pin is connected to FB between these pins and GND pins. Recommend placing with a 60.4k 0.5% precision resistor. See the Applications input decoupling capacitance directly between each of VIN Information section for details. pins and GND pins.
PHMODE (G5):
Control Input to the Phase Selector of the
INTVCC (B3):
Internal 3.3V Regulator Output of the Switch- Switching Mode Regulator. Determines the phase rela- ing Mode Regulator Channel. The internal power drivers tionship between internal oscillator and CLKOUT. Tie it to and control circuits are powered from this voltage. The INTV LTM4638 has an internal 2.2µF decoupling capacitor. No CC for 2-phase operation, tie it to SGND for 3-phase operation, and tie it to INTV external decoupling capacitor is required. CC/2 for 4-phase operation. See Application Information section for details. Rev. B For more information www.analog.com 7 Document Outline Features Applications Typical Application Description Absolute Maximum Ratings Order Information Pin Configuration Electrical Characteristics Typical Performance Characteristics Pin Functions Block Diagram Decoupling Requirements Operation Applications Information Package Description Revision History Package Photo Related Parts