LT3500_15 Datasheet, PDF (1/28 Pages) Linear Technology – Monolithic 2A Step-Down Regulator Plus Linear Regulator/Controller

FEATURES
n _{Wide Input Range: 3V to 36V Operating,}
40V Maximum
n _{Short-Circuit Protected Over Full Input Range}
n _{2A Output Current Capability}
n _{Adjustable/Synchronizable Fixed Frequency}
Operation from 250kHz to 2.2MHz
n _{Soft-Start/Tracking Capability}
n _{Output Adjustable Down to 0.8V}
n _{Adjustable Linear Regulator/Driver with 13mA}
Output Capability
n _{Power Good Comparator with Complimentary}
Outputs
n _{Low Shutdown Current: 12μA}
n _{Thermally Enhanced 3mm × 3mm DFN or 16-Pin}
MSOP Package
APPLICATIONS
n _{Automotive Battery Regulation}
n _{Industrial Control}
n _{Wall Transformer Regulation}
n _{Distributed Power Regulation}
LT3500
Monolithic 2A Step-Down
Regulator Plus Linear
Regulator/Controller
DESCRIPTION
The LT^®3500 is a current mode PWM step-down DC/DC
converter with an internal 2.3A switch. The wide input range
of 3V to 40V makes the LT3500 suitable for regulating
power from a wide variety of sources, including automo-
tive batteries, 24V industrial supplies and unregulated
wall adapters.
Resistor-programmable 250kHz to 2.2MHz frequency
range and synchronization capability enable optimization
between efficiency and external component size. Cycle-
by-cycle current limit, frequency foldback and thermal
shutdown provide protection against a shorted output.
The soft-start feature controls the ramp rate of the output
voltage, eliminating input current surge during start-up,
and also provides output tracking.
The LT3500 contains an internal NPN transistor with feed-
back control which can be configured as a linear regulator
or as a linear regulator controller.
The LT3500’s low current shutdown mode (<12μA) enables
easy power management in battery-powered systems.
L, LT, LTC, LTM, 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
Dual Step-Down Converters
V_IN
6V TO 36V
2.2μF
0.47μF
53.6k
330pF
40.2k
V_IN
BST
LT3500
SW
SHDN
SS
FB
PG
PG
R_T/SYNC LDRV
V_C
LFB
0.47μF
6.8μH
B240A
42.2k
8.06k
V_OUT1
5V
1A
22μF
1k
24.9k
8.06k
V_OUT2
3.3V
22μF ^1A
3500 TA01a
Switching Converter Efficiency
90
85
80
V_OUT1 = 5V AT 1A
AC COUPLED
75
2mV/DIV
70
65
60
55
V_IN = 12V
I_OUT2 = 0A
FREQUENCY = 800kHz
50
0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0
LOAD CURRENT (A)
3500 TA01b
V_OUT2 = 3.3V AT 1A
AC COUPLED
2mV/DIV
Output Voltage Ripple
500ns/DIV
3500 TA01c
3500fc
1