LTC1701_15 Datasheet, PDF (1/12 Pages) Linear Technology – 1MHz Step-Down DC/DC Converters in SOT-23

LTC1701/LTC1701B
1MHz Step-Down
DC/DC Converters in SOT-23
FEATURES
s _{Tiny 5-Lead SOT-23 Package}
s _{Uses Tiny Capacitors and Inductor}
s _{High Frequency Operation: 1MHz}
s _{High Output Current: 500mA}
s _{Low RDS(ON) Internal Switch: 0.28Ω}
s _{High Efficiency: Up to 94%}
s _{Current Mode Operation for Excellent Line}
and Load Transient Response
s _{Short-Circuit Protected}
s _{Low Quiescent Current: 135µA (LTC1701)}
s _{Low Dropout Operation: 100% Duty Cycle}
s _{Ultralow Shutdown Current: IQ < 1µA}
s _{Peak Inductor Current Independent of Inductor Value}
s _{Output Voltages from 5V Down to 1.25V}
U
APPLICATIO S
s _{PDAs/Palmtop PCs}
s _{Digital Cameras}
s _{Cellular Phones}
s _{Portable Media Players}
s _{PC Cards}
s _{Handheld Equipment}
DESCRIPTIO
The LTC^®1701/LTC1701B are the industry’s first SOT-23
step-down, current mode, DC/DC converters. Intended for
low to medium power applications, they operate from 2.5V
to 5.5V input voltage range and switch at 1MHz, allowing
the use of tiny, low cost capacitors and inductors 2mm or
less in height. The output voltage is adjustable from 1.25V
to 5V. A built-in 0.28Ω switch allows up to 0.5A of output
current at high efficiency. OPTI-LOOP^TM compensation
allows the transient response to be optimized over a wide
range of loads and output capacitors.
The LTC1701 incorporates automatic power saving Burst
Mode^TM operation to reduce gate charge losses when the
load current drops below the level required for continuous
operation. The LTC1701B operates continuously to very
low load currents to provide low ripple at the expense of
light load efficiency. With no load, the LTC1701 draws only
135µA. In shutdown, both devices draw less than 1µA,
making them ideal for current sensitive applications.
Their small size and switching frequency enables a
complete DC/DC converter function to consume less than
0.3 square inches of PC board area.
, LTC and LT are registered trademarks of Linear Technology Corporation.
Burst Mode and OPTI-LOOP are trademarks of Linear Technology Corporation.
TYPICAL APPLICATION
V_IN
2.5V TO
5.5V
C1 ⁺
10µF
V_IN
SW
R4
1M
LTC1701
I_TH/RUN
V_FB
R3
GND
5.1k
C3
330pF
L1
4.7µH
D1
R2
121k
+
R1
121k
V_OUT
(2.5V/
500mA)
C2
47µF
C1: TAIYO YUDEN JMK316BJ106ML
C2: SANYO POSCAP 6TPA47M
D1: MBRM120L
L1: SUMIDA CD43-4R7
1701 F01a
Figure 1. 2.5V/500mA Step-Down Regulator
Efficiency Curve
100
95
V_IN = 3.3V
V_OUT = 2.5V
90
85 ^LTC1701
80
75
LTC1701B
70
65
60
55
50
1
10
100
LOAD CURRENT (mA)
1000
1701 F01b
1