LTC1772_15 Datasheet, PDF (1/12 Pages) Linear Technology – Constant Frequency Current Mode Step-Down DC/DC Controller in SOT-23

LTC1772
Constant Frequency
Current Mode Step-Down
DC/DC Controller in SOT-23
FEATURES
■ _{High Efficiency: Up to 94%}
■ _{High Output Currents Easily Achieved}
■ _{Wide VIN Range: 2.5V to 9.8V}
■ _{Constant Frequency 550kHz Operation}
■ _{Burst Mode}^® _{Operation at Light Load}
■ _{Low Dropout: 100% Duty Cycle}
■ _{Tiny 6-Lead SOT-23 Package}
■ _{0.8V Reference Allows Low Output Voltages}
■ _{Current Mode Operation for Excellent Line and Load}
Transient Response
■ _{Low Quiescent Current: 270µA}
■ _{Shutdown Mode Draws Only 8µA Supply Current}
■ _{±2.5% Reference Accuracy}
U
APPLICATIO S
■ _{One or Two Lithium-Ion-Powered Applications}
■ _{Cellular Telephones}
■ _{Wireless Modems}
■ _{Portable Computers}
■ _{Distributed 3.3V, 2.5V or 1.8V Power Systems}
■ _Scanners
DESCRIPTIO
The LTC^®1772 is a constant frequency current mode step-
down DC/DC controller providing excellent AC and DC load
and line regulation. The device incorporates an accurate
undervoltage lockout feature that shuts down the LTC1772
when the input voltage falls below 2.0V.
The LTC1772 provides a ±2.5% output voltage accuracy
and consumes only 270µA of quiescent current. For
applications where efficiency is a prime consideration, the
LTC1772 is configured for Burst Mode operation, which
enhances efficiency at low output current.
To further maximize the life of a battery source, the
external P-channel MOSFET is turned on continuously in
dropout (100%dutycycle).In shutdown, the device draws
a mere 8µA. High constant operating frequency of 550kHz
allows the use of a small external inductor.
The LTC1772 is available in a small footprint 6-lead
SOT-23.
, LTC and LT are registered trademarks of Linear Technology Corporation.
Burst Mode is a registered trademark of Linear Technology Corporation.
All other trademarks are the property of their respective owners.
TYPICAL APPLICATIO
10k
220pF
1
6
I_TH/RUN PGATE
LTC1772
2
GND
3
V_FB
5
V_IN
SENSE^{– 4}
R1
0.03Ω
L1
M1 _4.7µH
+
D1
C1
10µF
10V
C2A
47µF
6V
V_IN
2.5V
TO 9.8V
V_OUT
2.5V
C2B
2A
1µF
10V 174k
C1: TAIYO YUDEN LMK325BJ106K-T
C2A: SANYO 6TPA47M
C2B: AVX 0805ZC105KAT1A
D1: MOTOROLA MBRM120T3
L1: MURATA LQN6C-4R7
M1: FAIRCHILD FDC638P
R1: IRC LRC-LR1206-01-R030F
80.6k
1772 F01a
Figure 1. High Efficiency, High Output Current 2.5V/2A Regulator
Efficiency vs Load Current
100
V_IN = 3.3V ^{VIN = 4.2V}
90
80
V_IN = 6V
70
V_IN = 9.8V ^{VIN = 8.4V}
60
50
40
1
V_OUT = 2.5V
10
100
1000
LOAD CURRENT (mA)
10000
1772 F01b
1772fb
1