LTC1703 datasheet(6/36 Pages) LINER

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LTC1703

1703fa

VID

n pin includes an on-chip 40k

Ω pull-up resistor in

series with a diode (see Block Diagram).

VCC (Pin 18): Power Supply Input. All internal circuits

except the output drivers are powered from this pin. VCC

should be connected to a low noise power supply voltage

between 3V and 7V and should be bypassed to SGND with

at least a 1

µF capacitor in close proximity to the LTC1703.

FB2 (Pin 19): Controller 2 Feedback Input. FB2 should be

connected through a resistor divider network to VOUT2 to

set the ouput voltage. The loop compensation network for

controller 2 also connects to FB2.

COMP2 (Pin 20): Controller 2 Loop Compensation. See

COMP1.

RUN/SS2 (Pin 21): Controller 2 Run/Soft-Start. See RUN/

SS1.

FAULT (Pin 22): Output Overvoltage Fault (Latched). The

FAULT pin is an open-drain output with an internal 10

µA

pull-up. If either regulated output voltage rises more than

15% above its programmed value for more than 25

µs, the

FAULT output will go high and the entire LTC1703 will be

disabled. When FAULT is high, both BG pins will go high,

turning on the bottom MOSFET switches and pulling down

the high output voltage. The LTC1703 will remain latched

in this state until the power is cycled. When FAULT mode

is active, the FAULT pin will be pulled up with an internal

µA current source. Tying FAULT directly to SGND will

disable latched FAULT mode and will allow the LTC1703 to

resume normal operation when the overvoltage fault is

removed.

PGND (Pin 23): Power Ground. The BG

n drivers return to

this pin. Connect PGND to a high current ground node in

close proximity to the sources of external MOSFETs, QB1

and QB2, and the VIN and VOUT bypass capacitors.

SW2 (Pin 24): Controller 2 Switching Node. See SW1.

TG2 (Pin 25): Controller 2 Top Gate Drive. See TG1.

BG2 (Pin 26): Controller 2 Bottom Gate Drive. See BG1.

BOOST2 (Pin 27): Controller 2 Top Gate Driver Supply.

See BOOST1.

IMAX2 (Pin 28): Controller 2 Current Limit Set. See IMAX1.

VCC

2000pF

BOOST1

TG1

BG1

SW1

IMAX1

FCB

VID0:4

RUN/SS1

COMP1

FB1

SENSE

LTC1703

BOOST2

TG2

BG2

SW2

IMAX2

FAULT

RUN/SS2

COMP2

FB2

0.1

µF

100

µF

VFB1

VFB2

VFAULT

IBOOST1

ICC

IPVCC

IBOOST2

fOSC

MEASURED

1703 TC

PVCC

GND

PGND

Test Circuit 1

PI FU CTIO S

TEST CIRCUIT

LTC1703 Datasheet(PDF) 6 Page - Linear Technology

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