LT8609S

1

Rev. D

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TYPICAL APPLICATION

FEATURES

DESCRIPTION

42V, 2A/3A Peak

Synchronous Step-Down Regulator

with 2.5µA Quiescent Current

The LT®8609S is a compact, high efficiency, high speed

synchronous monolithic step-down switching regulator

that consumes only 1.7µA of non-switching quiescent

current. The LT8609S can deliver 2A of continuous cur-

rent with peak loads of 3A (<1sec) to support applications

such as GSM transceivers which require high transient

loads. Top and bottom power switches are included with

all necessary circuitry to minimize the need for external

components. Low ripple Burst Mode operation enables

high efficiency down to very low output currents while

keeping the output ripple below 10mVP-P. A SYNC pin

allows synchronization to an external clock, or spread

spectrum modulation of switching frequencies for low

EMI operation. Internal compensation with peak current

mode topology allows the use of small inductors and

results in fast transient response and good loop stability.

The EN/UV pin has an accurate 1V threshold and can be

used to program VIN undervoltage lockout or to shut down

the LT8609S reducing the input supply current to 1µA. A

capacitor on the TR/SS pin programs the output voltage

ramp rate during start-up while the PG flag signals when

VOUT is within ±8.5% of the programmed output voltage

as well as fault conditions. The LT8609S is available in a

small 16-lead 3mm × 3mm LQFN package.

APPLICATIONS

n

Silent Switcher® 2 Architecture

n

Ultralow EMI Emissions on Any PCB

n

Eliminates PCB Layout Sensitivity

n

Internal Bypass Capacitors Reduce Radiated EMI

n

Optional Spread Spectrum Modulation

n

Wide Input Voltage Range: 3.0V to 42V

n

Ultralow Quiescent Current Burst Mode® Operation:

n

<2.5µA IQ Regulating 12VIN to 3.3VOUT

n

Output Ripple <10mVP-P

n

High Efficiency 2MHz Synchronous Operation:

n

>93% Efficiency at 1A, 12VIN to 5VOUT

n

2A Maximum Continuous Output, 3A Peak Transient

Output

n

Fast Minimum Switch-On Time: 45ns

n

Adjustable and Synchronizable: 200kHz to 2.2MHz

n

Allows Use of Small Inductors

n

Low Dropout

n

Peak Current Mode Operation

n

Internal Compensation

n

Output Soft-Start and Tracking

n

Small 16-Lead 3mm × 3mm LQFN Package

n

AEC-Q100 Qualified for Automotive Applications

n

General Purpose Step Down

n

Low EMI Step Down

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VIN

EN/UV

ON OFF

22µF

10pF

4.7µF

VIN

5.5V TO 40V

1µF

VOUT

5V

2A

182k

8609S TA01a

2.2µH

1M

SYNC

INTVCC

TR/SS

RT

LT8609S

GND

SW

PG

FB

18.2k

5V, 2MHz Step Down

12VIN to 5VOUT Efficiency

IOUT (A)

0

100

65

90

70

55

85

80

60

95

75

50

1.50

8609S TA01b

2.50

2.00

1.00

0.50

fSW = 2MHz