LTM4677 datasheet(52/110 Pages) AD

52 / 110 page

LTC3888-1

Rev. 0

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OUTPUT VOLTAGE SENSING

Accurate Kelvin sensing techniques should be used

to connect the output voltage differentially back to the

LTC3888-1 VSENSE± pins of the master channel for best

output voltage regulation at the point of load. These pins

also provide the ADC inputs for output voltage telemetry.

These connections are not strictly required for disabled

master channels (i.e. forced to be slave phases using bit

4 of MFR_PWM_MODE_LTC3888-1, with an external

ITH connection). However, because the LTC3888-1 error

amplifier is an OTA, it is sometimes advantageous to

wire-OR ITH pins and use multiple VOUT sense points to

provide improved power plane voltage averaging. Post-

manufacture selection of the most ideal load sense point

via final EEPROM programming is also possible. So in

general, sound Kelvin VOUT sensing techniques for all

LTC3888-1 master channels is recommended. Refer to

Figure 28.

APPLICATIONS INFORMATION

CLASSICAL ANALOG OUTPUT VOLTAGE CONTROL

The LTC3888-1 employs a classical analog approach for

setting output voltage when using default factory EEPROM

values. This control uses the circuit of Figure 28, where

external resistors R1 and R2 are used to set VOUT accord-

ing to the following equation.

VOUT=(R1+R2)/R2x400mV

In this mode, output margining is still possible using the

OPERATION command. The margining levels, along with

undervoltage and overvoltage supervisor fault thresholds,

are preset according to the following table. These values

are relative to the nominal output voltage created by R1

and R2.

Figure 29. High Frequency Paths and Branch Current Waveforms

RL1

SW1

VOUT1

COUT1

VIN

CIN

RIN

RL0

BOLD LINES INDICATE

HIGH SWITCHING

CURRENT. KEEP LINES

TO A MINIMUM LENGTH.

SW0

388812 F29

VOUT0

COUT0

LTM4677 Datasheet(PDF) 52 Page - Analog Devices

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