LT3790 datasheet(10/30 Pages) LINER

10 / 30 page

LT8390A

8390afa

For more information www.linear.com/LT8390A

CTRL: Control Input for ISP/ISN Current Sense Threshold.

The CTRL pin is used to program the ISP/ISN current limit:

IIS(MAX) =

Min VCTRL −0.25V,1V

(

)

10 •RIS

The VCTRL can be set by an external voltage reference or

a resistor divider from VREF to ground. For 0.3V ≤ VCTRL

≤ 1.15V, the current sense threshold linearly goes up

from 5mV 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 to VREF for the 100mV full scale

threshold. Force the pin below 0.3V to stop switching.

ISP: Positive Terminal of the ISP/ISN Current Sense Re-

sistor (RIS). Ensure accurate current sense with Kelvin

connection.

ISN: Negative Terminal of the ISP/ISN Current Sense

Resistor (RIS). Ensure accurate current sense with Kelvin

connection.

ISMON:ISP/ISNCurrentSenseMonitorOutput.TheISMON

pin generates a voltage that is equal to ten times V(ISP-ISN)

plus 0.25V offset voltage. For parallel applications, tie the

masterLT8390AISMONpintotheslaveLT8390ACTRLpin.

PGOOD: 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, the pin requires an

external pull-up resistor.

SS: 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

22nF capacitor is recommended on this pin. Any UVLO or

thermal shutdown immediately pulls SS pin to ground and

stops switching. Using a single resistor from SS to VREF,

the LT8390A can be set in three different fault protection

modes during output short-circuit condition: hiccup (no

resistor), latch-off (499kΩ), and keep-running (100kΩ).

See more details in the Application Information section.

FB: 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 1.00V through the DC/DC converter. During output

PIN FUNCTIONS

short-circuit(VFB<0.25V)condition,thepartgetsintoone

fault mode per customer setting. During an overvoltage

(VFB > 1.1V) condition, the part turns off all TG1, BG1,

TG2, BG2, and LOADTG.

VC: Error Amplifier Output to Set Inductor Current Com-

parator Threshold. The VC pin is used to compensate the

control loop with an external RC network. During LOADEN

low state, the VCpinisdisconnectedfromallinternalloads

to store its voltage information.

RT: Switching Frequency Setting. Connect a resistor from

this pin to ground to set the internal oscillator frequency

from 600kHz to 2MHz.

SYNC/SPRD: Switching Frequency Synchronization or

Spread Spectrum. Ground this pin for switching at inter-

nal oscillator frequency. Apply a clock signal for external

frequency synchronization. Tie to INTVCC for 25% triangle

spread spectrum above internal oscillator frequency.

LOADTG: High Side PMOS Load Switch Top Gate Drive. A

bufferedandinvertedversionoftheLOADENinputsignal,the

LOADTG pin drives an external high side PMOS load switch

with a voltage swing from the higher voltage of (VOUT-5V)

and 1.2V to VOUT. Leave this pin unconnected if not used.

VOUT: Output Supply. The VOUT pin must be tied to the

power output to determine the buck, buck-boost, or boost

operation regions. The VOUTpinalsoservesaspositiverail

for the LOADTG drive. Locally bypass this pin to ground

with a minimum 1µF ceramic capacitor.

TG2: Boost Side Top Gate Drive. Drives the gate of boost

side top N-Channel MOSFET with a voltage swing from

SW2 to BST2.

SW2: Boost Side Switch Node. The SW2 pin swings from

a Schottky diode voltage drop below ground to VOUT.

BST2: Boost Side Bootstrap Floating Driver Supply. The

BST2 pin has an integrated bootstrap Schottky diode from

theINTVCCpinandrequiresanexternalbootstrapcapacitor

to the SW2 pin. The BST2 pin swings from a diode voltage

drop below INTVCC to (VOUT + INTVCC).

BG2: Boost Side Bottom Gate Drive. Drives the gate of

boost side bottom N-channel MOSFET with a voltage

swing from ground to INTVCC.

GND (Exposed Pad): Ground. Solder the exposed pad

directly to the ground plane.

LT3790 датащи(PDF) 10 Page - Linear Technology

LT3790 датащи(HTML) 10 Page - Linear Technology

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30

датащи скачать

ссылки URL