LTM4686B datasheet(20/132 Pages) AD

20 / 132 page

LTM4683

Rev. 0

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comparator tripping threshold increases with its compen-

sation voltage. Each channel has a 22pF to SGND.

COMP0a, COMP1a, COMP2a, COMP3a (G11, G9, T8,

V11): Loop Compensation Nodes. The internal PWM

loop compensation resistors RCOMPn of the LTM4683

can be adjusted using bit[4:0] of the MFR_PWM_COMP

command. The transconductance of the LTM4683 PWM

error amplifier can be adjusted using bit[7:5] of the MFR_

PWM_COMP command. These two loop compensation

parameters can be programmed when the device is in

operation. See the Programmable Loop Compensation

subsection in the Applications Information section for

further details. See Figure 1.

PGOOD0, PGOOD1, PGOOD2, PGOOD3 (H9, H8, R10,

T10): Power Good Indicator Outputs. The open-drain logic

output is pulled to the ground when the output exceeds

the UV and OV regulation window. The output is de-

glitched by an internal 100µs filter. A pull-up resistor to

3.3V is required in the application.

IIN_01+ (H10): Positive Current Sense Amplifier Input.

If the input current sense amplifier is not used, this pin

must be shorted to the IIN_01– and SVIN_01 pins. See the

Applications Information section for more details about

the input current sensing.

VOSNS0– (H11): Channel 0 Negative Differential Voltage

Sense Input. See VOSNS0+.

SVIN_01 (J8): Input Supply for LTM4683’s Internal Control

IC for Channel 0 and Channel 1. In most applications, it

connects to VIN01. SVIN_01 can be operated from an aux-

iliary supply separate from VIN01 for powering the VIN01

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_01

and INTVCC_01. See Test Circuit 2 for an example. In this

configuration, the ICHIP current will not be relevant since

INTVCC_01 is connected to SVIN_01. See Input Voltage and

Limits to update low VIN operation parameters.

INTVCC_01 (J9): Internal Regulator, 5.5V Output. When

operating the LTM4683 from 5.75V ≤ SVIN_01 ≤ 14V, an

internal low dropout (LDO) generates INTVCC_01 from

SVIN_01 to bias internal control circuits and the MOSFET

drivers of the LTM4683’s Channel 0 and Channel 1. An

external 4.7µF ceramic decoupling capacitor is required.

INTVCC_01 is on regulated regardless of the RUNn pin

state. When operating the LTM4683 with 4.5V ≤ SVIN_01 <

5.75V, INTVCC_01 must be electrically shorted to SVIN_01,

and the RUNP pin must be pulled to GND. VBIAS takes over

after startup when the input voltage is greater than 7V.

IIN_01– (J10): Negative Current Sense Amplifier Input. If

the input current sense amplifier is not used, this pin

must be shorted to the IIN_01+ and SVIN_01 pins. See the

Applications Information section for more details about

the input current sensing.

VOSNS0+ (J11): Channel 0 Positive Differential Voltage

Sense Input. Together, VOSNS0+ and VOSNS0– serve to

Kelvin-sense the VOUT0 output voltage at VOUT0’s point-

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

directly to Channel 0’s feedback loop. Command VOUT0’s

target regulation voltage by serial bus. Its initial command

value at SVIN_01 power-up is dictated by NVM contents

(factory default: 0.5V)—or, optionally, may be set by con-

figuration resistors; see VOUT0_CFG, VTRIM0_CFG and

the Applications Information section.

VIN23 (N5-N6, P5-P6, R5-R6, T5-T6, U5-U6, V5-V6,

W5-W6, Y5-Y6, AA5-AA6, AB5-AB6): Positive Power

Input to Channel 2 and Channel 3 Switching Stages.

Provide sufficient decoupling capacitance in the form

of MLCCs and low ESR electrolytic (or equivalent) to

handle reflected input current ripple from the step-down

switching stage. MLCCs should be placed as close to the

LTM4683 as physically possible. See the Layout Checklist/

Example section in the Applications Information section.

VIN_VBIAS (N9): Input pin to the internal step-down regula-

tor that produces 5.5V (VBIAS pin) to power both internal

controllers to reduce power dissipation after power up.

Each internal controller has an INTVCC_01 or INTVCC_23

regulator that is powered from SVIN_01 or SVIN_23. To

PIN FUNCTIONS

LTM4686B Datasheet(PDF) 20 Page - Analog Devices

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