LT1938_15 Datasheet, PDF (1/24 Pages) Linear Technology – 25V, 2.2A, 2.8MHz Step-Down Switching Regulator

FEATURES
■ _{Wide Input Voltage Range: 3.6V to 25V}
■ _{2.2A Maximum Output Current}
■ _{Adjustable Switching Frequency: 300kHz to 2.8MHz}
■ _{Low Shutdown Current: IQ < 1µA}
■ _{Integrated Boost Diode}
■ _{Power Good Flag}
■ _{Saturating Switch Design: 0.18Ω On-Resistance}
■ _{1.265V Feedback Reference Voltage}
■ _{Output Voltage: 1.265V to 20V}
■ _{Soft-Start Capability}
■ _{Small 10-Pin Thermally Enhanced (3mm × 3mm)}
DFN Package
APPLICATIONS
■ _{Automotive Battery Regulation}
■ _{Power for Portable Products}
■ _{Distributed Supply Regulation}
■ _{Industrial Supplies}
■ _{Wall Transformer Regulation}
LT1938
25V, 2.2A, 2.8MHz
Step-Down
Switching Regulator
DESCRIPTION
The LT^®1938 is an adjustable frequency (300kHz to
2.8MHz) monolithic buck switching regulator that accepts
input voltages up to 25V. A high efficiency 0.18Ω switch
is included on the die along with a boost Schottky diode
and the necessary oscillator, control and logic circuitry.
Current mode topology is used for fast transient response
and good loop stability. The LT1938’s high operating fre-
quency allows the use of small, low cost inductors and
ceramic capacitors resulting in low output ripple while
keeping total solution size to a minimum. The low current
shutdown mode reduces input supply current to less than
1µA while a resistor and capacitor on the RUN/SS pin
provide a controlled output voltage ramp (soft-start). A
power good flag signals when V_OUT reaches 90% of the
programmed output voltage. The LT1938 is available in
a 3mm × 3mm DFN package with Exposed Pad for low
thermal resistance.
, LT, LTC and LTM are registered trademarks of Linear Technology Corporation.
All other trademarks are the property of their respective owners.
TYPICAL APPLICATION
3.3V Step-Down Converter
V_IN
4.5V TO
25V
4.7µF
OFF ON
16.2k
680pF
V_IN
RUN/SS
BD
BOOST
V_C
SW
LT1938
RT
PG
BIAS
60.4k
GND
FB
V_OUT
3.3V
2.2A
0.47µF 4.7µH
324k
200k
22µF
1938 TA01
Efficiency (V_OUT = 3.3V)
90
V_IN = 7V
85
80
V_IN = 24V V_IN = 12V
75
70
65
60
55
L: NEC PLC-0745-4R7
f = 800kHz
50
0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0 2.2
LOAD CURRENT (A)
1938 G02
1938fa
1