Datasheet LT8641 (Analog Devices)

LT8641 65V, 3.5A Synchronous Step-Down Silent Switcher with 2.5µA Quiescent Current
FEATURES DESCRIPTION
n
Silent Switcher
®
Architecture
The LT®8641 step-down regulator features Silent Switcher n
Ultralow EMI Emissions
architecture designed to minimize EMI emissions while n
Spread Spectrum Frequency Modulation
delivering high efficiency at frequencies up to 3MHz. As- n
High Efficiency at High Frequency
sembled in a 3mm × 4mm QFN, the monolithic construc- n
Up to 95% Efficiency at 1MHz, 12V
tion with integrated power switches and inclusion of all
IN to 5VOUT
n
Up to 94% Efficiency at 2MHz, 12V
necessary circuitry yields a solution with a minimal PCB
IN to 5VOUT
n
Wide Input Voltage Range: 3V to 65V
footprint. An ultralow 2.5µA quiescent current—with the n
3.5A Maximum Continuous Output,
output in full regulation—enables applications requiring highest efficiency at very small load currents. Transient
5A Peak Transient Output
n response remains excellent and output voltage ripple is
Ultralow Quiescent Current Burst Mode
®
Operation
n below 10mV
2.5μA I
P-P at any load, from zero to full current.
Q Regulating 12VIN to 3.3VOUT
n
Output Ripple < 10mVP-P
The LT8641 allows high VIN to low VOUT conversion at n
Fast Minimum Switch On-Time: 35ns
high frequency with a fast minimum top switch on-time of n
Low Dropout Under All Conditions: 130mV at 1A
35ns. Operation is safe in overload even with a saturated n Safely Tolerates Inductor Saturation in Overload inductor. n Adjustable and Synchronizable: 200kHz to 3MHz Essential features are included and easy to use: An n Peak Current Mode Operation open-drain PG pin signals when the output is in regula- n Output Soft-Start and Tracking tion. The SYNC/MODE pin selects between Burst Mode, n Small 18-Lead 3mm × 4mm QFN pulse-skipping, or spread spectrum mode, and also al- lows synchronization to an external clock. Soft-start and
APPLICATIONS
tracking functionality is accessed via the TR/SS pin. An accurate enable threshold can be set using the EN/UV pin n Automotive and Industrial Supplies and a resistor at the RT pin programs switch frequency. n General Purpose Step-Down n GSM Power Supplies All registered trademarks and trademarks are the property of their respective owners. Protected by U.S. patents, including 8823345.
TYPICAL APPLICATION 12VIN to 5VOUT Efficiency
100 2.600
5V 3.5A Step-Down Converter
V 95 2.275 IN 5.5V TO 65V 4.7µF 90 1.950 EN/UV EFFICIENCY POWER LOSS (W) VIN1 VIN2 1µF 1µF 85 1.625 GND1 GND2 LT8641 80 1.300 PG BST 0.1µF 4.7µH VOUT 10nF 75 0.975 SYNC/MODE SW 5V EFFICIENCY (%) TR/SS BIAS 3.5A POWER LOSS 70 0.650 1µF 4.7pF 1M 1MHz, L = 3.3μH 65 0.325 INTVCC FB 47µF 2MHz, L = 2.2μH 41.2k 3MHz, L = 1.5μH RT GND 191k 60 0 0.5 1 1.5 2 2.5 3 3.5 LOAD CURRENT (A) fSW = 1MHz 8641 TA01a 8641 TA01b Rev A Document Feedback For more information www.analog.com 1 Document Outline Features Applications Description Typical Application Absolute Maximum Ratings Pin Configuration Order Information Electrical Characteristics Typical Performance Characteristics Pin Functions Block Diagram Operation Applications Information Typical Applications Package Description Typical Applications Related Parts