LT8614
1
8614fc
For more information www.linear.com/LT8614
TYPICAL APPLICATION
FEATURES DESCRIPTION
42V, 4A Synchronous
Step-Down Silent Switcher
with 2.5µA Quiescent Current
The LT
®
8614 step-down regulator features Silent Switcher
architecture designed to minimize EMI/EMC emissions
while delivering high efficiency at frequencies up to 3MHz.
Assembled in a 3mm × 4mm QFN, the monolithic construc
-
tion with integrated power switches and inclusion of all
necessar
y circuitry yields a solution with a minimal PCB
footprint. An ultralow 2.5µA quiescent current—with the
output in full regulation— enables applications requiring
highest efficiency at very small load currents. Transient
response remains excellent and output voltage ripple is
below 10mV
P-P
at any load, from zero to full current.
The LT8614 allows high V
IN
to low V
OUT
conversion at
high frequency with a fast minimum top switch on-time of
30ns. Operation is safe in overload even with a saturated
inductor.
Essential features are included and easy to use: An open-
drain PG pin signals when the output is in regulation. The
SYNC pin allows clock synchronization and choice of Burst
Mode operation or pulse-skipping mode. Soft-start and
tracking functionality is accessed via the TR/SS pin. An
accurate enable threshold can be set using the
EN/UV pin
and a resistor at the RT pin programs switch frequency.
5V 4A Step-Down Converter
12V
IN
to 5V
OUT
Efficiency
APPLICATIONS
n
Silent Switcher™ Architecture:
Ultralow EMI/EMC Emissions
n
High Efficiency at High Frequency
Up to 96% Efficiency at 1MHz
Up to 94% Efficiency at 2MHz
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
Fast Minimum Switch-On Time: 30ns
n
Low Dropout Under All Conditions: 200mV at 1A
n
Safely Tolerates Inductor Saturation in Overload
n
Adjustable and Synchronizable: 200kHz to 3MHz
n
Peak Current Mode Operation
n
Accurate 1V Enable Pin Threshold
n
Internal Compensation
n
Output Soft-Start and Tracking
n
Small 18-Lead 3mm × 4mm QFN
n
Automotive and Industrial Supplies
n
General Purpose Step-Down
n
GSM Power Supplies
L, LT , LT C , LT M , Linear Technology, the Linear logo and Burst Mode are registered trademarks
and Silent Switcher is a trademark of Linear Technology Corporation. All other trademarks are
the property of their respective owners.
V
IN2
V
IN1
EN/UV
PG
LT8614
8614 TA01a
BST
SYNC/MODE SW
TR/SS BIAS
INTV
CC
FB
RT GND
1µF
0.1µF
4.7pF
47µF
1M
V
OUT
5V
4A
1µF
4.7µF
V
IN
5.8V TO 42V
10nF
41.2k
1µF
4.7µH
243k
GND2GND1
f
SW
= 1MHz
LOAD CURRENT (A)
0
EFFICIENCY (%)
80
90
4.0
8614 TA01b
70
60
1.0
2.0
3.0
0.5
1.5
2.5
3.5
100
1MHz
2MHz
75
85
65
95