LTC7130 datasheet(8/36 Pages) LINER

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LTC7130

7130fb

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PIN FUNCTIONS

FREQ (B7): Oscillator Frequency Control Input. A 10µA

current source flows out of this pin. Connecting a resistor

between this pin and ground sets a DC voltage which in

turn programs the oscillator frequency. Alternatively, this

pin can be driven with a DC voltage to vary the frequency

of the internal oscillator.

RUN (B6): Run Control Input. A voltage above 1.22V

turns on the IC. Pulling this pin below 1.1V causes the IC

to shut down. There is a 1μA pull-up current for the pin.

Once the RUN pin rises above 1.22V, an additional 4.5μA

pull-up current is added to the pin.

TK/SS (B5): Output Voltage Tracking and Soft-Start Input.

Aninternalsoft-startcurrentof1.25μAchargestheexternal

soft-start capacitor connected to this pin.

ITH (A5): Current Control Threshold and Error Ampli-

fier Compensation Pin. The current comparator tripping

threshold is proportional with this voltage.

VFB(A6):ErrorAmplifierFeedbackInput.Thispinreceives

the remotely sensed feedback voltage to set the output

voltage through an external resistive divider connected to

the DIFFOUT pin or the output.

DIFFOUT (A4): Output of Remote Sensing Differential

Amplifier. Connect this pin to VFB through a resistive

divider to set the desired output voltage.

DIFFN (A2): Negative Input of Remote Sensing Differen-

tial Amplifier. Connect this pin close to the ground of the

output load.

DIFFP (A3): Positive Input of Remote Sensing Differential

Amplifier. Connect this pin close to the output load.

SNSD+ (B1): DC Current Sense Comparator Input. The (+)

outputtotheDCcurrent.Comparatorisnormallyconnected

to a DC current sensing network with a time constant that

matches the bandwidth, L/DCR, of the inductor.

SNS– (B2): Negative Current Sense Input. This negative

input of the current comparator is to be connected to the

output.

SNSA+ (C1): AC Current Sense Comparator Input. The (+)

outputtotheACcurrentcomparatorisnormallyconnected

toaDCRsensingnetwork.WhencombinedwiththeSNSD+

pin, the DCR sensing network can be skewed to increase

the AC ripple voltage by a factor of 5.

ILIM(C2):CurrentComparatorSenseVoltageLimit.Apply

a DC voltage to set the maximum current sense threshold

for the current comparator.

CLKOUT (C3): Clock Output Pin. The CLKOUT signal is

180° out of phase to the rising edge of the IC internal clock.

GND (D2, D3, D4, E1, E2, E3, F2, F3, G4, G5, G6, H4,

H5, H6, H7, J4, J5, J6, J7): Power Ground. Connect

this pin closely to the (–) terminal of CVCC and the (–)

terminal of CIN.

SW (G1, G2, G3, H1, H2, H3, J1, J2, J3): Switch Node

Connection. Connect this pin to the output filter induc-

tor, bottom N-channel MOSFET drain and top N-channel

MOSFET source. Voltage swing at these pins is from a

Schottkydiode(external)voltagedropbelowgroundtoVIN.

BOOST (F1): Boosted Top Gate Driver Supply. The (+)

terminal of the bootstrap capacitor connects to this pin.

This pin swings from a diode voltage drop below INTVCC

up to VIN + INTVCC.

INTVCC (D1): Internal 5.5V Regulator Output. The internal

control circuits are powered from this voltage. Decouple

this pin to PGND with a 4.7μF low ESR tantalum or ce-

ramic capacitor.

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