LT8611 Datasheet, PDF (1/24 Pages) Linear Technology – 42V, 2.5A Synchronous Step-Down Regulator

FEATURES
n _{Rail-to-Rail Current Sense Amplifier with Monitor}
n _{Wide Input Voltage Range: 3.4V to 42V}
n _{Ultralow Quiescent Current Burst Mode}^® _Operation:
2.5μA I_Q Regulating 12V_IN to 3.3V_OUT
Output Ripple < 10mV_P-P
n _{High Efficiency Synchronous Operation:}
96% Efficiency at 1A, 5V_OUT from 12V_IN
94% Efficiency at 1A, 3.3V_OUT from 12V_IN
n _{Fast Minimum Switch-On Time: 50ns}
n _{Low Dropout Under All Conditions: 200mV at 1A}
n _{Allows Use Of Small Inductors}
n _{Low EMI}
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 × 5mm 24-Lead}
QFN Package
APPLICATIONS
n _{Automotive and Industrial Supplies}
n _{General Purpose Step-Down}
n _{CCCV Power Supplies}
Electrical Specifications Subject to Change
LT8611
42V, 2.5A Synchronous
Step-Down Regulator with
Current Sense and 2.5µA
Quiescent Current
DESCRIPTION
The LT^®8611 is a compact, high efficiency, high speed
synchronous monolithic step-down switching regulator
that consumes only 2.5μA of quiescent current. Top and
bottom power switches are included with all necessary
circuitry to minimize the need for external components.
The built-in current sense amplifier with monitor and
control pins allows accurate input or output current
regulation and limiting. Low ripple Burst Mode operation
enables high efficiency down to very low output currents
while keeping the output ripple below 10mV_P-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 V_IN
undervoltage lockout or to shut down the LT8611 reduc-
ing 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 V_OUT is within ±9% of
the programmed output voltage as well as fault conditions.
The LT8611 is available in a small 24-lead 3mm × 5mm
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 Linear Technology Corporation. All other trademarks are the property of their respective
owners.
TYPICAL APPLICATION
5V Step-Down Converter with 2.5A Output Current Limit
V_IN
5.5V TO 42V
V_IN
BST
4.7μF _{ON OFF EN/UV}
SYNC
LT8611
SW
IMON
ICTRL
ISP
ISN
BIAS
INTV_CC
PG
TR/SS
0.1μF
RT
FB
PGND GND
1μF
52.3k
0.1μF
4.7μH
0.02Ω
1μF
V_OUT
5V
2.5A
10pF
1M
243k
47μF
f_SW = 800kHz
8611 TA01a
12V_IN to 5V_OUT Efficiency
100
95
90
85
80
75
70
65
60
55
50
0
f_SW = 700kHz
V_IN = 12V
V_IN = 24V
0.5
1
1.5
2
2.5
LOAD CURRENT (A)
8611 TA01b
8611p
1