LT8611
1
8611fa
For more information
TYPICAL APPLICATION
FEATURES
DESCRIPTION
42V, 2.5A Synchronous
Step-Down Regulator with
Current Sense and 2.5µA
Quiescent Current
The
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.
5V Step-Down Converter with 2.5A Output Current Limit
12V
IN
to 5V
OUT
Efficiency
APPLICATIONS
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:
n
2.5μA I
Q
Regulating 12V
IN
to 3.3V
OUT
n
Output Ripple < 10mV
P-P
n
High Efficiency Synchronous Operation:
n
96% Efficiency at 1A, 5V
OUT
from 12V
IN
n
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
n
Automotive and Industrial Supplies
n
General Purpose Step-Down
n
CCCV Power Supplies
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.
BST
V
IN
EN/UV
ON OFF
SYNC
IMON
ICTRL
INTV
CC
TR/SS
RT
SW
LT8611
GND
PGND
ISP
BIAS
ISN
PG
8611 TA01a
FB
0.1µF
V
OUT
5V
2.5A
1µF
47µF
4.7µF
V
IN
5.5V TO 42V
0.1µF
1µF
10pF
4.7µH
0.02Ω
1M
243k
60.4k
f
SW
= 700kHz
LOAD CURRENT (A)
0
EFFICIENCY (%)
80
90
100
2
8611 G01
70
60
75
85
95
65
55
50
0.5
1
1.5
2.5
V
IN
= 12V
V
IN
= 24V
f
SW
= 700kHz
