LTC1874
Dual Constant Frequency
Current Mode Step-Down
DC/DC Controller
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FEATURES
DESCRIPTIO
The LTC®1874 is a dual constant frequency current mode
step-downDC/DCcontrollerwithexcellentACandDCload
and line regulation. Each controller has an accurate
undervoltage lockout that shuts down the individual con-
troller when the input voltage falls below 2.0V.
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High Efficiency: Up to 94%
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High Output Currents Easily Achieved
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Wide VIN Range: 2.5V to 9.8V
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Constant Frequency 550kHz Operation
Burst ModeTM Operation at Light Load
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Low Dropout: 100% Duty Cycle
0.8V Reference Allows Low Output Voltages
Current Mode Operation for Excellent
Line and Load Transient Response
Low Quiescent Current: 270µA (Each Controller)
Separate Shutdown Pin for Each Controller
Shutdown Mode Draws Only
8µA Supply Current (Each Controller)
±2.5% Reference Accuracy
The LTC1874 boasts ±2.5% output voltage accuracy and
consumes only 270µA of quiescent current per controller.
The LTC1874 is configured with Burst Mode operation,
which enhances efficiency at low output current for appli-
cations where efficiency is a prime consideration.
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To further maximize the life of a battery source, each
external P-channel MOSFET is turned on continuously in
dropout(100%dutycycle). Inshutdown, eachcontroller
draws a mere 8µA. High constant operating frequency of
550kHz allows the use of small external inductors.
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Available in 16-Lead Narrow SSOP
Each Controller Functions Independent of the Other
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The LTC1874 is available in a small footprint 16-lead
narrow SSOP.
, LTC and LT are registered trademarks of Linear Technology Corporation.
Burst Mode is a trademark of Linear Technology Corporation.
APPLICATIO S
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1- or 2-Cell Lithium-Ion-Powered Applications
Personal Information Appliances
Portable Computers
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Distributed 3.3V, 2.5V or 1.8V Power Systems
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TYPICAL APPLICATION
V
IN
3.5V
TO 9.5V
C
IN
R1
0.04Ω
R2
10µF
16V
×2
LTC1874
–
0.04Ω
1
2
8
V
PV
IN2
IN1
7
L2
4.7µH
SENSE1
GND1
PGATE2
PGND2
M2
V
1.8V
1A
OUT2
3
6
L1
M1
4.7µH
V
10k
OUT1
3.3V
1A
+
C2
47µF
6V
4
5
D2
V
FB1
I
/RUN2
TH
10k
+
13
14
15
16
12
11
10
9
220pF
C1
D1
I
TH
/RUN1
V
FB2
47µF
220pF
C1, C2: SANYO POSCAP 6TPA47M
6V
PGND1
GND2
–
249k
C
: TAIYO YUDEN CERAMIC
IN
EMK325BJ106MNT (×2)
100k
PGATE1 SENSE2
D1, D2: MBRM120
80.6k
PV
IN1
V
IN2
L1, L2: COILCRAFT D01608C-472
M1, M2: Si3443DV
R1, R2: DALE 0.25W
80.6k
1874 TA01
Figure 1. LTC1874 3.5V-9.5V Input to 3.3V/1A and 1.8V/1A Dual Step-Down Converter
1