LT8685S

1

Rev. 0

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TYPICAL APPLICATION

FEATURES

DESCRIPTION

42V Quad, Gangable, Synchronous,

Monolithic Step-Down Regulator

The LT®8685S is a highly flexible, four channel, current

mode, monolithic regulator able to power a wide range

of automotive and industrial applications while occupying

minimal board space.

The LT8685S combines two 42V capable 2.5A buck reg-

ulators with two 8V capable 4A buck regulators. The two

42V regulators may be combined to provide up to 5A of

output current using a single inductor. Similarly, the two

8V regulators may be combined to provide up to 8A of

output current using a single inductor. Individual channel

enable, track/soft-start and power good pins provide flex-

ible power supply sequencing and control. The LT8685S

features a Silent Switcher 2 architecture, plus selectable

spread spectrum mode, to provide ultralow EMI/EMC

emissions while delivering high efficiency at high switch-

ing frequencies.

The LT8685S incorporates thermal shutdown and individ-

ual channel cycle-by-cycle current limit for short circuit

protection and robust operation.

42V Input, Quad Output 2MHz Step-Down Regulator

Efficiency and Loss

APPLICATIONS

n

n

Ultralow EMI Emissions

n

Optional Spread Spectrum Modulation

n

Two High Voltage Synchronous Buck Regulators

n

3V to 42V Input Voltage Range

n

Output Currents Up to 2.5A per Channel

n

Channels May Be Connected in Parallel Using a

Single Inductor

n

Two Low Voltage Synchronous Buck Regulators

n

3V to 8V Input Voltage Range

n

Output Currents Up to 4A per Channel

n

Channels May Be Connected in Parallel Using a

Single Inductor

n

n

Flexible Supply Sequencing and Control

n

Adjustable and Synchronizable: 350kHz to 3MHz

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Available in 36-Lead LQFN (5mm × 6mm)

n

AEC-Q100 Qualified for Automotive Applications

n

Automotive Systems

n

Industrial Controls and Power Supplies

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BST3

SW3

FB3

BST4

SW4

FB4

BIAS

BST1

SW1

FB1

BST2

SW2

FB2

EN/UVLO

EN2

EN3

EN4

6V TO 42V

PG1-4

TRK/SS1-4

RT

SYNC/MODE

OUT1

5V, 2.5A*

OUT4

1.2V, 4A

OUT3

1.8V, 4A

GND

OUT2

3.3V, 2.5A

LT8685S

OUT1

*CURRENT AVAILABLE FROM OUT1:

4

4

8685S TA01a

HV CHANNEL EFFICIENCY 12V → 5V

LV CHANNEL EFFICIENCY 5V → 1.8V

HV CHANNEL LOSS

LV CHANNEL LOSS

LOAD CURRENT (A)

0.001

0.01

0.1

1

4

0

10

20

30

40

50

60

70

80

90

100

0

0.5

1.0

1.5

2.0

2.5

3.0

8685S TA01b