LTC1871-1
Wide Input Range, No R
™
SENSE
Current Mode Boost,
Flyback and SEPIC Controller
DESCRIPTION
TheLTC®1871-1isawideinputrange,currentmode,boost,
flybackorSEPICcontrollerthatdrivesanN-channelpower
MOSFET and requires very few external components. It
eliminatestheneedforacurrentsenseresistorbyutilizing
the power MOSFET’s on-resistance, thereby maximizing
efficiency.Higheroutputvoltageapplicationsarepossible
with the LTC1871-1 by connecting the SENSE pin to a
resistor in the source of the power MOSFET.
FEATURES
n
High Efficiency (No Sense Resistor Required)
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Wide Input Voltage Range: 2.5V to 36V
n
Current Mode Control Provides Excellent
Transient Response
n
High Maximum Duty Cycle (92% Typ)
n
2% RUN Pin Threshold with 100mV Hysteresis
n
1% Internal Voltage Reference
n
Ultra Low Pulse Skip Threshold for Wide Input
Range Applications
The IC’s operating frequency can be set with an external
resistorovera50kHzto1MHzrange, andcanbesynchro-
nized to an external clock using the MODE/SYNC pin.
n
Micropower Shutdown: I = 10μA
Q
n
Programmable Operating Frequency
(50kHz to 1MHz) with One External Resistor
Synchronizable to an External Clock Up to 1.3 × f
n
n
n
n
n
The LTC1871-1 differs from the LTC1871 by having a
lower pulse skip threshold, making it ideal for applica-
tions requiring constant frequency operation at light
loads. The lower pulse skip threshold also helps maintain
constant frequency operation in applications with a wide
input voltage range. For applications requiring primary-
to-secondary side isolation, please refer to the LTC1871
datasheet.
OSC
User-Controlled Pulse Skip or Burst Mode® Operation
Internal 5.2V Low Dropout Voltage Regulator
Output Overvoltage Protection
Capable of Operating with a Sense Resistor for High
Output Voltage Applications
Small 10-Lead MSOP Package
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The LTC1871-1 is available in the 10-lead MSOP package.
L, LT, LTC, LTM and Burst Mode are registered trademarks of Linear Technology Corporation.
APPLICATIONS
n
No R
is a trademark of Linear Technology Corporation. All other trademarks are the
Telecom Power Supplies
SENSE
property of their respective owners.
n
Portable Electronic Equipment
TYPICAL APPLICATION
V
IN
3.3V
Efficiency of Figure 1
L1
100
90
80
70
60
50
40
30
1μH
D1
RUN
SENSE
Burst Mode
OPERATION
V
OUT
5V
I
V
IN
TH
7A
C
R
OUT1
C
+
(10A PEAK)
LTC1871-1
INTV
150μF
6.3V
×4
22k
PULSE-SKIP
MODE
FB
CC
C
6.8nF
C1
R1
12.1k
1%
C
OUT2
FREQ
GATE
GND
M1
22μF
6.3V
X5R
×2
C
IN
C
4.7μF
X5R
VCC
+
R2
37.4k
1%
R
T
80.6k
1%
MODE/SYNC
22μF
6.3V
×2
C
C2
47pF
GND
18711 F01a
C
C
C
:
TAIYO YUDEN JMK325BJ226MM
: PANASONIC EEFUEOJ151R
: TAIYO YUDEN JMK325BJ226MM
D1: MBRB2515L
IN
0.001
0.01
0.1
1
10
L1: SUMIDA CEP125-H 1R0MH
M1: FAIRCHILD FDS7760A
OUT1
OUT2
OUTPUT CURRENT (A)
18711 F01b
Figure 1. High Efficiency 3.3V Input, 5V Output Boost Converter (Bootstrapped)
18711fb
1
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