LT8350RVPBF datasheet(8/24 Pages) AD

8 / 24 page

LT8350

Rev. 0

For more information www.analog.com

PIN FUNCTIONS

VIN (Pin 2, 3): Input Voltage Pin. The VIN pin supplies

the internal circuitry and connects to the power input of

the converter. Bypass this pin to ground with a ceramic

capacitor. The bypass capacitor should be placed as

close to the chip as possible with vias directly down to

the ground plane.

EN/UVLO (Pin 5): Enable and Undervoltage Lockout

Pin. Force the pin below 0.3V to shut down the chip and

reduce VIN quiescent current below 2µA. Force the pin

above 1.235V (typical) for normal operation. The accu-

rate 1.220V falling threshold can be used to program an

undervoltage lockout (UVLO) threshold with a resistor

divider from VIN to ground. An accurate 2.5µA pull-down

current allows the programming of VIN UVLO hysteresis.

If neither function is used, tie this pin directly to VIN.

INTVCC (Pin 6): Internal 3.6V Linear Regulator Output

Pin. Powered from the VIN pin, the INTVCC supplies the

internal control circuitry and gate drivers. Do not force

any voltage on this pin. Place a 1μF bypass capacitor to

GND close to the package.

RP (Pin 7): Factory Test Pin. Always tie this pin to INTVCC.

LOADEN (Pin 8): Load Switch Enable Input. The LOADEN

pin is used to control the ON/OFF of the high side PMOS

load switch. If the load switch control is not used, tie this

pin to VREF or INTVCC. Forcing the pin low turns off all

power switches, disconnects the VC pin from all internal

loads, and turns off LOADTG.

VREF (Pin 9): Voltage Reference Output Pin. The VREF pin

provides an accurate 2V reference capable of supplying up

to 2mA current. It can be used to supply resistor networks

for setting the voltages at the CTRL pin. Place a 220nF

bypass capacitor to GND close to the package.

ISMON (Pin 10): ISP/ISN Current Monitor Output Pin. The

ISMON pin generates a buffered voltage that is equal to

ten times V(ISP-ISN) plus 0.25V offset voltage. The voltage

on the ISMON pin will be 1.25V when V(ISP-ISN) is equal

to 100mV full-scale.

ISP (Pin 11): Positive Terminal of ISP/ISN Current Sense

Resistor (RIS). Ensure accurate current sense with Kelvin

connection.

ISN (Pin 12): Negative Terminal of ISP/ISN Current

Sense Resistor (RIS). Ensure accurate current sense with

Kelvin connection.

CTRL (Pin 13): Control Input for ISP/ISN Current Sense

Threshold. The CTRL pin is used to program the ISP/ISN

regulation current:

IIS(MAX) =

– 0.25V, 1V)

10 • RIS

MIN(VCTRL

The VCTRL can be set by an external voltage reference

or a resistor divider from VREF to ground. For 0.25V ≤

VCTRL ≤ 1.15V, the current sense threshold linearly goes

up from 0mV to 90mV. For VCTRL ≥ 1.35V, the current

sense threshold is constant at 100mV full-scale value.

For 1.15V ≤ VCTRL ≤ 1.35V, the current sense threshold

smoothly transitions from the linear function of VCTRL to

the 100mV constant value. Tie CTRL pin to VREF for the

100mV full-scale threshold. Force the pin below 0.1V to

stop switching.

FB (Pin 14): Voltage Loop Feedback Input. The FB pin

is used for constant-voltage regulation and output fault

protection. The internal error amplifier with its output VC

regulates VFB to 1V through the DC/DC converter. During

the output short-circuit (VFB < 0.25V) fault condition, the

part gets into one fault mode per customer setting. During

an overvoltage (VFB > 1.1V) condition, the part turns off

all power switches and LOADTG.

VC (Pin 15): Error Amplifier Output to Set Inductor Current

Comparator Threshold. The VC pin is used to compen-

sate the control loop with an external RC network. During

LOADEN low state, the VC pin is disconnected from all

internal loads to store its voltage information.

PGOOD (Pin 16): Power Good Open Drain Output. The

PGOOD pin is pulled low when the FB pin is within ±10%

of the final regulation voltage. To function, this pin requires

an external pull-up resistor.

SS (Pin 17): Soft-Start Timer Setting. The SS pin is used

to set soft-start timer by connecting a capacitor to ground.

An internal 12.5µA pull-up current charging the external

SS capacitor gradually ramps up FB regulation voltage. A

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