LTM4686B datasheet(21/132 Pages) AD

21 / 132 page

LTM4683

Rev. 0

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eliminate this power loss through these linear regulators,

the VBIAS powers both at very high efficiency.

VBIAS (N10): 5.5V step-down output that powers both

internal controllers to reduce power loss. Provide a 22µF

ceramic bypass capacitor on this pin to GND. SVIN_01

and SVIN_23 must be higher than 7V for this VBIAS to

supply the controllers. When the input voltage is between

4.5V to 5.75V, pull the RUNP pin to GND, and connect

SVIN_01 and SVIN_23 to INTVCC_01 and INTVCC_23, respec-

tively. Powering up the VBIAS regulator with the SVIN_01

and SVIN_23 greater than 7V will power the INTVCC_01,

INTVCC_02, the VDD33_01, VDD33_23, VDD25_01, and

VDD25_23 from VBIAS. Otherwise, these sources will get

their power from SVIN_01 and SVIN_23. This will allow pro-

gramming each internal controller’s EEPROM with the

power regulator channels in the off position.

RUNP (N11): This pin enables the Internal 5.5V VBIAS

Step-Down Regulator. Pulling this pin above 0.85V will

enable the Internal regulator. The pin is rated to VIN, so

connect to VIN to enable, and connect to GND to disable.

When the input voltage is between 4.5V to 5.75V, pull the

RUNP pin to GND, and connect SVIN_01 and SVIN_23 to

INTVCC_01 and INTVCC_23, respectively.

VOUT2 (N13-N15, P13-P15, R13-R15, T13-T15, U13-

U15): Channel 2 Output Voltage. Place recommended

output capacitors from this shape to GND. See the Layout

Checklist/Example section.

SW2 (P1-P2, R1-R2, T1-T2): Switching Node of Channel 2

Step-Down Converter Stage. Used for test purposes or

EMI-snubbing. It may be routed a short distance to a local

test point to monitor the switching action of Channel 2,

if desired, but do not route near any sensitive signals.

Otherwise, leave it open.

VOSNS2+ (P8): Channel 2 Positive Differential Voltage

Sense Input. Together, VOSNS2+ and VOSNS2– serve to

Kelvin-sense the VOUT2 output voltage at VOUT2’s point-

of-load (POL) and provide the differential feedback signal

directly to Channel 2’s feedback loop. Command VOUT2’s

target regulation voltage by serial bus. Its initial command

value at SVIN_23 power-up is dictated by NVM (nonvolatile

memory) contents (factory default: 0.5V)—or, optionally,

may be set by configuration resistors; see VOUT2_CFG,

VTRIM2_CFG and the Applications Information section.

IIN_23– (P9): Negative Current Sense Amplifier Input. If

the input current sense amplifier is not used, this pin

must be shorted to the IIN_23+ and SVIN_23 pins. See the

Applications Information section for more details about

the input current sensing.

INTVCC_23 (P10): Internal Regulator, 5.5V Output. When

operating the LTM4683 from 5.75V ≤ SVIN_23 ≤ 14V, an

internal LDO generates INTVCC_23 from SVIN_23 to bias

internal control circuits and the MOSFET drivers of the

LTM4683’s Channel 2 and Channel 3. An external 4.7µF

ceramic decoupling capacitor is required. INTVCC_23 is

regulated regardless of the RUNn pin state. When operat-

ing the LTM4683 with 4.5V ≤ SVIN_23 < 5.75V, INTVCC_23

must be electrically shorted to SVIN_23, and the RUNP pin

must be pulled to GND. VBIAS takes over after start-up

when the input voltage is greater than 7V.

SVIN_23 (P11): Input Supply for LTM4683’s Internal

Control IC for Channel 2 and Channel 3. In most applica-

tions, SVIN_23 connects to VIN_23. SVIN_23 can be operated

from an auxiliary supply separate from VIN23 for powering

the VIN23 from a lower supply like 6V. The SVIN_23 pin

requires 1Ω and 1µF decoupling capacitor to measure the

actual control chip current. See MFR_READ_ICHIP and

MFR_ADC_CONTROL command section. When operating

from 4.5V to 5.75V with no auxiliary bias supply, then

the main device input supply should connect to SVIN_23

and INTVCC_23. See Test Circuit 2 for an example. In this

configuration, the ICHIP current will not be relevant since

INTVCC_23 is connected to SVIN_23. See Input Voltage and

Limits to update low VIN operation parameters.

VOSNS2– (R8): Channel 2 Negative Differential Voltage

Sense Input. See VOSNS2+.

IIN_23+ (R9): Positive Current Sense Amplifier Input. If

the input current sense amplifier is not used, this pin

must be shorted to the IIN_23– and SVIN_23 pins. See the

Applications Information section for more details about

the input current sensing.

PIN FUNCTIONS

LTM4686B Datasheet(PDF) 21 Page - Analog Devices

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