Document
LT8612 42V, 6A Synchronous Step-Down Regulator with 3µA Quiescent Current
FEATURES
n Wide Input Voltage Range: 3.4V to 42V n Ultralow Quiescent Current Burst Mode® Operation:
nn 3μA IQ Regulating 12VIN to 3.3VOUT nn Output Ripple < 10mVP-P n High Efficiency Synchronous Operation: nn 95% Efficiency at 3A, 5VOUT from 12VIN nn 94% Efficiency at 3A, 3.3VOUT from 12VIN n Fast Minimum Switch-On-Time: 40ns n Low Dropout Under All Conditions: 250mV at 3A n Allows Use of Small Inductors n Safely Tolerates Inductor Saturation in Overload Conditions n Adjustable and Synchronizable: 200kHz to 2.2MHz n Current Mode Operation n Accurate 1V Enable Pin Threshold n Internal Compensation n Output Soft-Start and Tracking n Small Thermally Enhanced 3mm × 6mm 28-Lead QFN Package
APPLICATIONS
n Automotive and Industrial Supplies n General Purpose Step-Down n GSM Power Supplies
DESCRIPTION
The LT®8612 is a compact, high efficiency, high speed synchronous monolithic step-down switching regulator that consumes only 3µA of quiescent current. 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. 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 LT8612 reducing the input supply current to 1µA. A capacitor on the TR/SS pin programs the output voltage ramp rate during start-up. The PG flag signals when VOUT is within ±9% of the programmed output voltage as well as fault conditions. The LT8612 is available in a small 3mm × 6mm 28-lead QFN package with exposed pad for low thermal resistance.
L, LT, LTC, LTM, Burst Mode, Linear Technology and the Linear logo are registered trademarks of Analog Devices, Inc. All other trademarks are the property of their respective owners.
TYPICAL APPLICATION
5V 6A Step-Down Converter
VIN 5.6V TO 42V
10µF
10nF 1µF
VIN EN/UV PG
LT8612 SYNC
BST
SW BIAS
TR/SS
FB
INTVCC RT PGND GND
60.4k
0.1µF 3.9µH
1M 10pF
243k
fSW = 700kHz L: EPCOS B82559
8612 TA01a
VOUT 5V 100µF 6A 1210
EFFICIENCY (%)
Efficiency at 5VOUT
100 VIN = 12V 95 90 VIN = 24V
85
80
75
70
65 fSW = 700kHz L = 3.9µH
60 01 2 3 4 LOAD CURRENT (A)
56
8612 TA01b
For more information www.linear.com/LT8612
8612fa
1
GND NC GND NC GND NC GND NC
LT8612
ABSOLUTE MAXIMUM RATINGS
(Note 1)
VIN, EN/UV, PG...........................................................42V BIAS...........................................................................25V FB, TR/SS ...................................................................4V SYNC Voltage .............................................................