LTC3835 datasheet(9/40 Pages) LINER

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LTC3890-3

38903f

For more information www.linear.com/3890-3

BG1, BG2 (Pin 23, Pin 18): High Current Gate Drives

for Bottom (Synchronous) N-Channel MOSFETs. Voltage

swing at these pins is from ground to INTVCC.

BOOST1,BOOST2(Pin24,Pin17):BootstrappedSupplies

to the Topside Floating Drivers. Capacitors are connected

between the BOOST and SW pins and Schottky diodes are

tied between the BOOST and INTVCC pins. Voltage swing

at the BOOST pins is from INTVCC to (VIN + INTVCC).

SW1, SW2 (Pin 25, Pin 16): Switch Node Connections

to Inductors.

TG1, TG2 (Pin 26, Pin 15): High Current Gate Drives for

Top N-Channel MOSFETs. These are the outputs of float-

ing drivers with a voltage swing equal to INTVCC – 0.5V

superimposed on the switch node voltage SW.

pin FuncTions

PGOOD1 (Pin 27): Open-Drain Logic Output. PGOOD1 is

pulled to ground when the voltage on the VFB1 pin is not

within ±10% of its set point.

TRACK/SS1, TRACK/SS2 (Pin 28, Pin 14): External Track-

ing and Soft-Start Input. The LTC3890-3 regulates the

VFB1,2 voltage to the smaller of 0.8V or the voltage on the

TRACK/SS1,2 pin. An internal 1µA pull-up current source

is connected to this pin. A capacitor to ground at this

pin sets the ramp time to final regulated output voltage.

Alternatively, a resistor divider on another voltage supply

connected to this pin allows the LTC3890-3 output to track

the other supply during start-up.

Table 1. Summary of the Differences Between the Parts in the LTC3890 Family

LTC3890

LTC3890-1

LTC3890-2

LTC3890-3

ILIM Pin for Adjustable

Current Sense Voltage?

Yes

CLKOUT and PHASMD Pins

for PolyPhase® Operation?

Yes

Independent PGOOD Pins for

Each Channel

Yes; PGOOD1 and PGOOD2

No; PGOOD1 Only

Yes; PGOOD1 and PGOOD2

No; PGOOD1 Only

Overvoltage Protection

Bottom Gate “Crowbar?”

Yes

No; BG Not Forced On

Current Foldback During

Overcurrent Events

Yes

Light Load Operation When

Synchronized to External

Clock Using PLLIN/MODE Pin

Forced Continuous

Pulse-Skipping

SENSE Pins Common Mode

Range

Operation with SENSE

Common Mode < 0.5V

Requires VFB < 0.65V

Operation with SENSE

Common Mode < 0.5V

Requires VFB < 0.65V

Not Dependent on VFB

Voltage. Makes It Easy to

Make a Non-synchronous

Boost or SEPIC Converter

with Ground-Referenced

Current Sensing

Not Dependent on VFB

Voltage. Makes It Easy to

Make a Non-synchronous

Boost or SEPIC Converter

with Ground-Referenced

Current Sensing

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