LT8636/LT8637

1

Rev. C

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TYPICAL APPLICATION

FEATURES

42V, 5A/7A Peak Synchronous Step-Down

Silent Switcher with 2.5µA Quiescent Current

DESCRIPTION

The LT®8636/LT8637 synchronous step-down regulator

features Silent Switcher architecture designed to minimize

EMI emissions while delivering high efficiency at high

switching frequencies. Peak current mode control with

a 30ns minimum on-time allows high step-down ratios

even at high switching frequencies.

The LT8636’s ultralow 2.5µA quiescent current—with the

output in full regulation—enables applications requiring

highest efficiency at very small load currents. The LT8637

has external compensation to enable current sharing and

fast transient response at high switching frequencies. A

CLKOUT pin enables synchronizing other regulators to

the LT8636/LT8637.

Burst Mode operation enables ultralow standby current

consumption, forced continuous mode can control fre-

quency harmonics across the entire output load range, or

spread spectrum operation can further reduce EMI emis-

sions. Soft-start and tracking functionality is accessed

via the TR/SS pin, and an accurate input voltage UVLO

threshold can be set using the EN/UV pin.

5V, 5A Step-Down Converter

APPLICATIONS

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Ultralow EMI Emissions

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Optional Spread Spectrum Modulation

n

High Efficiency at High Frequency

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Wide Input Voltage Range: 3.4V to 42V

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5A Maximum Continuous, 7A Peak Transient Output

n

n

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External Compensation: Fast Transient Response

and Current Sharing (LT8637)

n

Fast Minimum Switch On-Time: 30ns

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Low Dropout Under All Conditions: 100mV at 1A

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Forced Continuous Mode

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Adjustable and Synchronizable: 200kHz to 3MHz

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Output Soft-Start and Power Good

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Small 20-Lead 4mm

× 3mm LQFN Package

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AEC-Q100 Qualified for Automotive Applications

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Automotive and Industrial Supplies

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General Purpose Step-Down

All registered trademarks and trademarks are the property of their respective owners. Protected

by U.S. patents, including 8823345.

EFFICIENCY

POWER LOSS

1MHz, L = 2.7µH

2MHz, L = 1.5µH

3MHz, L = 1µH

LOAD CURRENT (A)

0.5 1 1.5 2 2.5 3 3.5 4 4.5 5

60

65

70

75

80

85

90

95

100

0

0.4

0.8

1.2

1.6

2.0

2.4

2.8

3.2

8636 TA01b

LT8636

8636 TA01a

SW

BST

GND

GND

EN/UV

BIAS

RT

FB

GND

100µF

1µF

1M

5V

5A

4.7µF

1µF

1µF

0.1µF

10pF

3.3µH

5.7V TO 42V

41.2k

243k