LTC1266
LTC1266-3.3/LTC1266-5
Synchronous Regulator
Controller for
N- or P-Channel MOSFETs
FEATURES
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DESCRIPTIO
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Ultrahigh Efficiency: Over 95% Possible
Drives N-Channel MOSFET for High Current or
P-Channel MOSFET for Low Dropout
Pin Selectable Burst Mode Operation
1% Output Accuracy (LTC1266A)
Pin Selectable Phase of Topside Driver for Boost
or Step-Down Operation
Wide V
IN
Range: 3.5V to 20V
On-Chip Low-Battery Detector
High Efficiency Maintained Over Large Current Range
Low 170µA Standby Current at Light Loads
Current Mode Operation for Excellent Line and Load
Transient Response
Logic Controlled Micropower Shutdown: I
Q
< 40µA
Short-Circuit Protection
Synchronous Switching with Nonoverlaping Gate Drives
Available in 16-Pin Narrow SO Package
The LTC
®
1266 series is a family of synchronous switching
regulator controllers featuring automatic Burst Mode
TM
operation to maintain high efficiencies at low output
currents. These devices drive external power MOSFETs at
switching frequencies up to 400kHz using a constant off-
time current mode architecture providing constant ripple
current in the inductor. They can drive either an N-channel
or a P-channel topside MOSFET.
The operating current level is user-programmable via an
external current sense resistor. Wide input supply range
allows operation from 3.5V to 18V (20V maximum).
Constant off-time architecture provides low dropout regu-
lation limited only by the R
DS(ON)
of the topside MOSFET
(when using the P-channel) and the resistance of the
inductor and current sense resistor.
The LTC1266 series combines synchronous switching for
maximum efficiency at high currents with an automatic
low current operating mode, called Burst Mode operation,
which reduces switching losses. Standby power is re-
duced to only 1mW at V
IN
= 5V (at I
OUT
= 0). Load currents
in Burst Mode operation are typically 0mA to 500mA.
, 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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Notebook and Palmtop Computers
Portable Instruments
Cellular Telephones
DC Power Distribution Systems
GPS Systems
TYPICAL APPLICATIO
V
IN
4V TO 9V
D2
MBR0530T1
+
C
IN
100µF
×2
LOW BAT OUT
V
IN
LB
IN
PINV
PWR V
IN
LB
OUT
TDRIVE
SENSE
+
SENSE
–
BDRIVE
PGND
1000pF
N-CHANNEL
Si9410
D1
MBRS130LT3
1266 TA01
C
B
0.1µF
N-CHANNEL
Si9410
L*
5µH
100k
LOW BAT IN
LTC1266-3.3
0V = NORMAL
>1.5V = SHUTDOWN
R
C
470Ω
C
C
3300pF
SHDN
I
TH
C
T
BINH
SGND
V
OUT
3.3V
5A
EFFICIENCY (%)
R
SENSE
0.02Ω
+
C
T
180pF
C
OUT
330µF
×
2
*TOKO 919AS-4R7M
Figure 1. High Efficiency Step-Down Converter
U
LTC1266-3.3 Efficiency
100
V
IN
= 5V
95
90
85
80
0.01
0.1
1
LOAD CURRENT (A)
5
1266 TA02
U
U
1
LINER [ LINEAR TECHNOLOGY ]
