LTC1874_15 Datasheet, PDF (1/12 Pages) Linear Technology – Dual Constant Frequency Current Mode Step-Down DC/DC Controller

LTC1874
Dual Constant Frequency
Current Mode Step-Down
DC/DC Controller
FEATURES
s _{High Efficiency: Up to 94%}
s _{High Output Currents Easily Achieved}
s _{Wide VIN Range: 2.5V to 9.8V}
s _{Constant Frequency 550kHz Operation}
s _{Burst Mode}^TM _{Operation at Light Load}
s _{Low Dropout: 100% Duty Cycle}
s _{0.8V Reference Allows Low Output Voltages}
s _{Current Mode Operation for Excellent}
Line and Load Transient Response
s _{Low Quiescent Current: 270µA (Each Controller)}
s _{Separate Shutdown Pin for Each Controller}
s _{Shutdown Mode Draws Only}
8µA Supply Current (Each Controller)
s _{±2.5% Reference Accuracy}
s _{Available in 16-Lead Narrow SSOP}
s _{Each Controller Functions Independent of the Other}
U
APPLICATIO S
s _{1- or 2-Cell Lithium-Ion-Powered Applications}
s _{Personal Information Appliances}
s _{Portable Computers}
s _{Distributed 3.3V, 2.5V or 1.8V Power Systems}
DESCRIPTIO
The LTC^®1874 is a dual constant frequency current mode
step-down DC/DC controller with excellent AC and DC load
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.
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.
To further maximize the life of a battery source, each
external P-channel MOSFET is turned on continuously in
dropout (100% duty cycle). In shutdown, each controller
draws a mere 8µA. High constant operating frequency of
550kHz allows the use of small external inductors.
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.
TYPICAL APPLICATION
V_IN
3.5V
TO 9.5V
C_IN
10µF
16V
×2
R1
0.04Ω
V_OUT1
3.3V
1A
L1 _M1
4.7µH
+
C1
47µF
D1
C1, C2: SANYO POSCAP 6TPA47M
C_IN: TAIYO YUDEN CERAMIC
249k
6V
EMK325BJ106MNT (× 2)
D1, D2: MBRM120
L1, L2: COILCRAFT D01608C-472
80.6k
M1, M2: Si3443DV
R1, R2: DALE 0.25W
10k
220pF
1
LTC1874
8
V_IN1
PV_IN2
2 _SENSE1–
7
PGATE2
3
GND1
6
PGND2
4
V_FB1
5
I_TH/RUN2
13
I_TH/RUN1
12
V_FB2
14
PGND1
11
GND2
15
PGATE1
SENSE2^{– 10}
16
PV_IN1
9
V_IN2
10k
220pF
R2
0.04Ω
M2 ^L2
4.7µH
+
D2
Figure 1. LTC1874 3.5V-9.5V Input to 3.3V/1A and 1.8V/1A Dual Step-Down Converter
C2
47µF
6V
V_OUT2
1.8V
1A
100k
80.6k
1874 TA01
1