LT3757 datasheet(13/48 Pages) AD

13 / 48 page

LTC7841

Rev. 0

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SW1, SW2 (Pins 28, 17): Switch Node. Connect to the

source of the synchronous N-channel MOSFET, the drain

main N-channel MOSFET and the inductor.

TG1, TG2 (Pins 27, 18): Top Gate. Connect to the gate of

the synchronous N-channel MOSFET.

PGOOD (Pin 16): Power Good Indicator. Open-drain logic

output that is pulled to ground when the output voltage is

more than ±10 % away from the regulated output voltage.

To avoid false trips the output voltage must be outside the

range for 25μs before this output is activated.

SS (Pin 10): Output Soft-Start Input. A capacitor to

ground at this pin sets the ramp rate of the output volt-

age during start-up.

ITH (Pins 14): Error Amplifier Outputs and Switching

Regulator Compensation Points. Each associated chan-

nel’s current comparator trip point increases with this

control voltage.

VOUT (Pin 1): Output Voltage Sense Input. This pin

receives the remotely sensed output voltage and is input

to the internal ADC. The converted value is readable by

the READ_VOUT PMBus command.

SENSE1+, SENSE2+ (Pins 2, 12): Positive Current Sense

Comparator Input. The (+) input to the current comparator

is normally connected to the positive terminal of a cur-

rent sense resistor. The current sense resistor is normally

placed at the input of the boost controller in series with

the inductor. This pin also supplies power to the current

comparator.

CSLEW (Pin 34): Slew Rate Control. Add a capacitor to pro-

gram VOUT transition slew rate during changing the output

voltage. The slew rate is equal to 1.7% per ms per nF

of slew rate capacitance. With a 1nF capacitor, the slew

rate is 1.7%/ms. Two default slew rates are also available

when this pin is open or connected to INTVCC. The slew

rate can also be increased 2x or decreased 0.125x using

the MFR_CONFIG command.

ASEL (Pin 35): Serial Bus Address Configuration Input.

Connect a ±1% resistor from this pin to ground in order

to select the 3 LSBs of the serial bus interface address.

(see Table 4).

ALERT (Pin 31): Open Drain Digital Output. Connect the

system SMBALERT interrupt signal to this pin. A pull-up

resistor is required in the application.

SDA (Pin 29): Serial Bus Data Input and Output. A pull-up

resistor is required in the application.

SCL (Pin 30): Serial Bus Clock Input. A pull-up resistor

is required in the application.

VFB (Pin 13): Error Amplifier Feedback Input. This pin

receives the remotely sensed feedback voltage from an

external resistive divider connected across the output.

VOUT_CFG (Pin 32): Internal Reference Power-On Voltage.

This pin function is disabled in the LTC7841.

TSNS (Pin 33): External Temperature Sensor Input. A NTC

resistor from this pin to ground is used to monitor the

external temperature. The temperature can be read via

the PMBus.

VCCF (Pin 36): Leave this pin unconnected or use 0.1µF

capacitor for internal supply decoupling. For input or

output voltages greater than 55V, connect a small signal

Schottky diode from INTVCC to this pin to achieve best

ADC readback accuracy.

PIN FUNCTIONS

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