FeaTures
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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.
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Rail-to-Rail Current Sense Amplifier with Monitor
Wide Input Voltage Range: 3.4V to 42V
Ultralow Quiescent Current Burst Mode
®
Operation:
2.5μA I
Q
Regulating 12V
IN
to 3.3V
OUT
Output Ripple < 10mV
P-P
High Efficiency Synchronous Operation:
96% Efficiency at 1A, 5V
OUT
from 12V
IN
94% Efficiency at 1A, 3.3V
OUT
from 12V
IN
Fast Minimum Switch-On Time: 50ns
Low Dropout Under All Conditions: 200mV at 1A
Allows Use Of Small Inductors
Low EMI
Adjustable and Synchronizable: 200kHz to 2.2MHz
Current Mode Operation
Accurate 1V Enable Pin Threshold
Internal Compensation
Output Soft-Start and Tracking
Small Thermally Enhanced 3mm
×
5mm 24-Lead
QFN Package
applicaTions
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Automotive and Industrial Supplies
General Purpose Step-Down
CCCV Power Supplies
Typical applicaTion
5V Step-Down Converter with 2.5A Output Current Limit
V
IN
5.5V TO 42V
4.7µF ON OFF
V
IN
EN/UV
SYNC
IMON
ICTRL
LT8611
SW
ISP
ISN
BIAS
INTV
CC
0.1µF
1µF
f
SW
= 700kHz
60.4k
TR/SS
RT
PGND
GND
FB
PG
10pF
BST
0.1µF
4.7µH
0.02
1µF
EFFICIENCY (%)
100
95
90
12V
IN
to 5V
OUT
Efficiency
V
OUT
5V
2.5A
85
80
75
70
65
60
f
SW
= 700kHz
V
IN
= 12V
V
IN
= 24V
0
0.5
1.5
1
LOAD CURRENT (A)
2
2.5
8611 G01
1M
243k
8611 TA01a
55
47µF
50
8611f
1
LINEAR_DIMENSIONS [ LINEAR DIMENSIONS SEMICONDUCTOR ]
