LTM8045 datasheet(18/54 Pages) AD

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LTM4655

Rev. 0

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COMP1a (E2): Current Control Threshold and Error

Amplifier Compensation Node for Channel 1. The trip

threshold of channel 1’s current comparator increases

with a respective rise in COMP1a voltage. A small filter

cap (10pF) internal to the LTM4655 on this pin introduces

a high frequency roll-off of the error amplifier response,

yielding good noise rejection in the control loop. Often,

COMP1a is electrically connected to COMP1b in one’s

application, thus applying default loop compensation.

Loop compensation (a series resistor capacitor) can be

applied externally from COMP1a to SVOUT1–, if desired or

needed, instead. (See COMP1b.)

COMP2a (E7): Current Control Threshold and Error

Amplifier Compensation Node for Channel 2. The trip

threshold of channel 2’s current comparator increases

with a respective rise in COMP2a voltage. A small filter

cap (10pF) internal to the LTM4655 on this pin introduces

a high frequency roll-off of the error amplifier response,

yielding good noise rejection in the control loop. Often,

COMP2a is electrically connected to COMP2b in one’s

application, thus applying default loop compensation.

Loop compensation (a series resistor capacitor) can be

applied externally from COMP2a to SVOUT2–, if desired or

needed, instead. (See COMP2b.)

COMP1b (E1): Channel 1 Internal Loop Compensation

Network. For a majority of applications, the internal,

default loop compensation of the LTM4655 is suitable to

apply “as is”, and yields very satisfactory results: apply

the default loop compensation to channel 1’s control loop

by simply connecting COMP1a to COMP1b. When more

specialized applications require a personal touch to the

optimization of control loop response, this can be easily

accomplished by connecting a series resistor-capacitor

network from COMP1a to SVOUT1– and leaving COMP1b

open circuit.

COMP2b (E6): Channel 2 Internal Loop Compensation

Network. For a majority of applications, the internal,

default loop compensation of the LTM4655 is suitable to

apply “as is”, and yields very satisfactory results: apply

the default loop compensation to channel 2’s control loop

by simply connecting COMP2a to COMP2b. When more

specialized applications require a personal touch to the

optimization of control loop response, this can be easily

accomplished by connecting a series resistor-capacitor

network from COMP2a to SVOUT2– and leaving COMP2b

open circuit.

IMON1a (C2): Channel 1 Power Inductor Current Analog

Indicator Pin and Current Limit Programming Pin. In

positive-VOUT step-down applications, only, the current

flowing out of this pin is equal to 1/40,000 of the average

channel 1 power inductor current. Optionally apply a par-

allel resistor-capacitor network to this pin and terminate

it to SVOUT1– in order to construct a voltage (VIMON1a–

SVOUT1–) that is proportional to channel 1’s power induc-

tor current.

IMON1a can be connected to IMON1b if the default resis-

tor capacitor termination network provided by IMON1b is

desired. If this analog indicator feature is not desired—

or, in negative-VOUT– buck-boost applications: connect

IMON1a to SVOUT1–.

If IMON1a–SVOUT1– exceeds a trip threshold of approxi-

mately 2V, an IMON1 control loop servos channel 1

power inductor current accordingly and thus regulates

IMON1a–SVOUT1– at 2V. In this manner, the current limit

inception threshold of channel 1 can be configured. (See

the Applications Information section.)

IMON1b (C1): Channel 1 Power Inductor Analog Indicator

Current Default Termination R-C Network. A 10k resis-

tor in parallel with a 10nF capacitor and terminating to

SVOUT1– connect to this pin. Connect IMON1b to IMON1a

to achieve default power inductor analog indicator current

characteristics: 1V (with respect to SVOUT1–) at full-scale

(4A) load current in positive-VOUT, noninverting step-

down applications. (See IMON1a.) If unused, IMON1b

can be left open circuit or connected to SVOUT1–.

PIN FUNCTIONS

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