LTM4650 datasheet(9/38 Pages) AD

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Data Sheet

LTM4640

analog.com

Rev. 0

9 of 38

NAME

DESCRIPTION

CFG 1

INTVCC

Internal 3.3V Regulator Output of the Switching Mode Regulator Channel. The

internal power drivers and control circuits are powered by this voltage. The LTM4640

has an internal 2.2µF decoupling capacitor. No external decoupling capacitor is

required.

RUN

Run Control Input Pin. Enable regulator operation by connecting the RUN pin above

1.35V. Connecting it below 1.1V shuts down the specific regulator channel.

PGOOD

Output Power Good Pin with Open-Drain Logic. The PGOOD pin is pulled to ground

when the voltage on the FB pin is out of ±8% of the internal 0.6V reference.

Switching node of each channel that is used for testing purposes. Also, an R-C

snubber network is applied to reduce or eliminate switch node ringing. Otherwise,

leave it floating. See the Applications Information section for details.

The Negative Input of the Error Amplifier for the Switching Mode Regulator. This pin

is internally connected to VOSNS+ with a 10kΩ precision resistor. The output voltage is

programmed with an additional resistor between FB and VOSNS– pins. In a PolyPhase®

operation, connect the FB pins together to allow for a parallel operation. See the

Applications Information section for details.

VOSNS–

Negative Input to the Differential Remote Sense Amplifier. Connect an external

resistor between FB and VOSNS– pins to set the output voltage of the specific channel.

See the Applications Information section for details.

COMPa

Current control threshold and error amplifier compensation point of the switching

mode regulator channel. The internal current comparator threshold is linearly

proportional to this voltage. Connect the COMPa pins from different channels

together for a parallel operation. The device is internally compensated. Connect to

the COMPb pin to use the internal compensation. Or connect to a Type-II C-R-C

network to use customized compensation.

MODE/CLKIN

Discontinuous Mode Select Pin and External Synchronization Input to Phase

Detector. Connect MODE/CLKIN to GND for discontinuous-conduction mode (DCM)

operation. Floating MODE/CLKIN or connecting it to a voltage above 1V selects forced

continuous mode (FCM). Furthermore, connecting MODE/CLKIN to an external clock

synchronizes the system clock to the external clock and puts the part in FCM. See the

Applications Information section for details.

D3–D4, E3–

E4, F4, G4

VIN

Power input pins connect to the drain of the internal top MOSFET, and the signal VIN

to the internal 3.3V regulator for the control circuitry for each switching mode

regulator channel. Apply input voltages between these pins and GND pins.

Recommend placing input decoupling capacitance directly between each of the VIN

pins and the GND pins.

FREQ

Switching Frequency Program Pin. The frequency is set internally to 600kHz. An

external resistor is placed from this pin to GND to increase frequency, or from this pin

to INTVCC to reduce frequency. See the Applications Information section for

frequency adjustment.

TRACK/SS

Output Tracking and Soft Start Pin of the Switching Mode Regulator. The TRACK/SS

pin allows the user to control the rise time of the output voltage. Putting a voltage

below 0.6V on this pin bypasses the internal reference input to the error amplifier,

instead it servos the FB pin to the TRACK voltage. Above 0.6V, the tracking function

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