LT3668_15 Datasheet, PDF (1/28 Pages) Linear Technology – 40V 400mA Step-Down Switching Regulator with Dual Fault Protected Tracking LDOs

LT3668
40V 400mA Step-Down
Switching Regulator with Dual
Fault Protected Tracking LDOs
FEATURES
DESCRIPTION
nn _{Dual Low Dropout Linear Tracking Regulators}
nn _{200mA Outputs with Programmable Current Limits}
nn _{1.6V to 45V Input Range}
nn _{Fault Protected to ±45V}
nn _{Triple Output Supply from a Single Input Requires}
Only One Inductor
nn _{IQ = 50μA at 12VIN to 6V and 5V with No Load}
nn _{Buck Regulator:}
nn _{Low Ripple (<15mVP-P) Burst Mode}^® _Operation
nn _{400mA Output with Internal Power Switch}
nn _{4.3V to 40V Input Operation Range (60V Max)}
nn _{Adjustable 250kHz to 2.2MHz Switching Frequency}
nn _{Power Good Indicator}
nn _{Available in a Thermally-Enhanced 16-Lead}
MSOP Package
APPLICATIONS
nn _{Fault-Protected Sensor Supply}
nn _{Automotive and Industrial Supplies}
nn _{Power for Portable Instrumentation}
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.
The LT^®3668 is a monolithic triple power supply composed
of a 400mA buck switching regulator and two 200mA low
dropout linear tracking regulators (LDOs).This provides a
complete and robust power solution for applications that
require the power supply of a sensor to tightly track the
power supply of a measurement ASIC.
Each tracking LDO supplies 200mA of output current with
a typical dropout voltage of 340mV, and each LDO has an
accurate resistor programmable current limit.
Internal protection circuitry includes reverse-battery
protection, current limiting, thermal limiting and reverse
current protection.
The buck regulator includes a high efficiency switch, a
boost diode, and the necessary oscillator, control and
logic circuitry. Current mode topology is used for fast
transient response and good loop stability. Low ripple
Burst Mode operation maintains high efficiency at low
output currents while keeping output ripple below 15mV
in a typical application.
The LT3668 is available in a thermally-enhanced 16-lead
MSOP package with exposed pad for low thermal resistance.
TYPICAL APPLICATION
V_IN
7V TO 40V
TRANSIENT
TO 60V
4.7µF _IN1
BOOST
SW
ON OFF EN
PG
RT
f = 600kHz 174k
LT3668
DA
IN3/BD
IN2
FB1
5V
150mA
(FOLLOWS
OUT3)
ADJ2
ADJ3
OUT2
OUT3
10µF EN2/ILIM2 GND EN3/ILIM3
0.22µF _27µH
232k
22pF
931k
294k
5V
150mA
10µF
3668 TA01a
6V
100mA
22µF
For more information www.linear.com/LT3668
100
90
80
70
60
50
40
30
20
10
0
5
No-Load Supply Current
10 15 20 25 30 35
INPUT VOLTAGE (V)
3668 TA01b
3668fa
1