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PDF LT1301C Data sheet ( Hoja de datos )
| Número de pieza | LT1301C | |
| Descripción | Micropower High Efficiency 5V/12V Step-Up DC/DC Converter for Flash Memory | |
| Fabricantes | Linear Technology | |
| Logotipo |  |
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LT1301
Micropower High Efficiency
5V/12V Step-Up DC/DC
Converter for Flash Memory
FEATURES
s 12V at 120mA from 5V or 3.3V Supply
s Supply Voltage as Low as 1.8V
s Better High Current Efficiency Than CMOS
s Up to 89% Efficiency
s 120µA Quiescent Current
s Shutdown to 10µA
s Programmable 5V or 12V Output
s Low VCESAT Switch: 170mV at 1A Typical
s ILIM Pin Programs Peak Switch Current
s Uses Inexpensive Surface Mount Inductors
s 8-Lead DIP or SOUIC Package
APPLICATIONS
s Flash Memory VPP Generator
s Palmtop Computers
s Portable Instruments
s Bar-Code Scanners
s Personal Digital Assistants
s PCMCIA Cards
DESCRIPTION
The LT1301 is a micropower step-up DC/DC converter that
utilizes Burst Mode™ operation. The device can deliver 5V
or 12V from a two-cell battery input. It features program-
mable 5V or 12V output via a logic-controlled input, no-
load quiescent current of 120µA and a shutdown pin which
reduces supply current to 10µA. The on-chip power switch
has a low 170mV saturation voltage at a switch current of
1A, a four-fold reduction over prior designs. A 155kHz
internal oscillator allows the use of extremely small sur-
face mount inductors and capacitors. Operation is guaran-
teed at 1.8V input. This allows more energy to be extracted
from the battery, increasing operating life. The ILIM pin can
be used for soft start or to program peak switch current
with a single resistor allowing the use of even smaller
inductors in lighter load applications. The LT1301 is
available in an 8-lead SOIC package, minimizing board
space requirements. For a selectable 3.3V/5V step-up
converter, please see the LT1300. For higher output
power, see the LT1302.
Burst Mode is a trademark of Linear Technology Corporation.
TYPICAL APPLICATIONS N
5V
OR
3.3V
+ C1
47µF
L1
33µH
D1
VIN
SELECT
SW
SENSE
LT1301
SHUTDOWN SHDN
PGND
ILIM N/C
GND
*REQUIRED FOR 5V OUTPUT
L1 = COILCRAFT DO3316-333
OR SUMIDA CD73-330KC
D1 = 1N5817 OR MOTOROLA
MBRS130LT3
C1 = AVX TPSD476M016R0100
OR SANYO OS-CON 165A47M
C2 = AVX TPSD336M020R0100
OR SANYO OS-CON 205A33M
12V
OUTPUT
12V
VOUT
2V/DIV
Output Voltage
+ C2
33µF
20V
0.1µF*
LT1301 F1
SHUTDOWN
10V/DIV
VIN = 5V, VOUT = 12V
LOAD = 100Ω
1ms/DIV
Figure 1. 3.3V/5V to 12V Step-Up Converter
LT1301 TAO1
Efficiency
90
88
86
84
82
80
78
76
74
72
0
1
VIN = 5V
VIN = 3.3V
10 100 300
LOAD CURRENT (mA)
LT1301 TA2
LT1300 F2
1
1 page  
TEST CIRCUITS
5V
2V
100Ω
VIN IL
SEL SW fOUT
100µF
LT1301
SENSE
GND
SHDN
PGND
LT1301
Oscillator Test Circuit
LT1301 TC
U
OPERATION
Operation of the LT1301 is best understood by referring to
the Block Diagram in Figure 2. When A1’s negative input,
related to the Sense pin voltage by the appropriate resis-
tor-divider ratio is higher that the 1.25V reference voltage,
A1’s output is low. A2, A3 and the oscillator are turned off,
drawing no current. Only the reference and A1 consume
current, typically 120µA. When A1’s negative input drops
below 1.25V, overcoming A1’s 6mV hysteresis, A1’s out-
put goes high enabling the oscillator, current comparator
A2, and driver A3. Quiescent current increases to 2mA as
the device prepares for high current switching. Q1 then
turns on in controlled saturation for (nominally) 5.3µs or
until comparator A2 trips, whichever comes first. After a
fixed off-time of (nominally) 1.2µs, Q1 turns on again. The
LT1301’s switching causes current to alternately build up
in L1 and dump into output capacitor C2 via D1, increasing
the output voltage. When the output is high enough to
cause A1’s output to go to low, switching action ceases.
C2 is left to supply current to the load until VOUT decreases
enough to force A1’s output high, and the entire cycle
repeats. Figure 4 details relevant waveforms. A1’s cycling
causes low-to-mid-frequency ripple voltage on the output.
Ripple can be reduced by making the output capacitor
large. The 33µF unit specified results in ripple of 100mV to
200mV on the 12V output. A 100µF capacitor will decrease
ripple to 50mV. If operating at 5V ouput a 0.1µF ceramic
capacitor is required at the Sense pin in addition to the
electrolytic.
If switch current reaches 1A, causing A2 to trip, switch on-
time is reduced and off-time increases slightly. This allows
continuous mode operation during bursts. A2 monitors
the voltage across 3Ω resistor R1 which is directly related
to the switch current. Q2’s collector current is set by the
emitter-area ratio to 0.6% of Q1’s collector current. When
R1’s voltage drop exceeds 18mV, corresponding to 1A
switch current, A2’s output goes high, truncating the on-
time portion of the oscillator cycle and increasing off-time
to about 2µs as shown in Figure 3, trace A. This pro-
grammed peak current can be reduced by tying the ILIM pin
to ground, causing 15µA to flow through R2 into Q3’s
collector. Q3’s current causes a 10.4mV drop in R2 so that
only an additional 7.6mV is required across R1 to turn off
the switch. This corresponds to a 400mA switch current
as shown in Figure 3, trace B. The reduced peak switch
current reduces I2R loses in Q1, L1, C1 and D1. Efficiency
can be increased by doing this provided that the accom-
panying reduction in full load current is acceptable. Lower
peak currents also extend alkaline battery life due to the
alkaline cell’s high internal impedance.
TRACE A
500mA/DIV
ILIM PIN
OPEN
TRACE B
500mA/DIV
ILIM PIN
GROUNDED
20µs/DIV
Figure 3. Switch Pin Current With ILIM Floating or Grounded
5
5 Page 
PACKAGE DESCRIPTION Dimensions in inches (millimeters) unless otherwise noted.
LT1301
0.300 – 0.320
(7.620 – 8.128)
0.009 – 0.015
(0.229 – 0.381)
+0.025
0.325 –0.015
( )8.255
+0.635
–0.381
N8 Package
8-Lead Plastic DIP
0.045 – 0.065
(1.143 – 1.651)
0.065
(1.651)
TYP
0.045 ± 0.015
(1.143 ± 0.381)
0.100 ± 0.010
(2.540 ± 0.254)
0.130 ± 0.005
(3.302 ± 0.127)
0.125
(3.175)
MIN
0.020
(0.508)
MIN
0.018 ± 0.003
(0.457 ± 0.076)
0.400
(10.160)
MAX
87 65
0.250 ± 0.010
(6.350 ± 0.254)
12
34
N8 0392
S8 Package
8-Lead Plastic S0IC
0.010
(0.254
–
–
0.020
0.508)
×
45°
0.008 – 0.010
(0.203 – 0.254)
0.053 – 0.069
(1.346 – 1.752)
0°– 8° TYP
0.004 – 0.010
(0.101 – 0.254)
0.016 – 0.050
0.406 – 1.270
0.014 – 0.019
(0.355 – 0.483)
0.050
(1.270)
BSC
*THESE DIMENSIONS DO NOT INCLUDE MOLD FLASH OR PROTRUSIONS.
MOLD FLASH OR PROTRUSIONS SHALL NOT EXCEED 0.006 INCH (0.15mm).
0.228 – 0.244
(5.791 – 6.197)
0.189 – 0.197*
(4.801 – 5.004)
8 765
1 2 34
0.150 – 0.
(3.810 – 3.
SO8 0294
Information furnished by Linear Technology Corporation is believed to be accurate and reliable.
However, no responsibility is assumed for its use. Linear Technology Corporation makes no represen-
tation that the interconnection of its circuits as described herein will not infringe on existing patent rights.
11
11 Page | ||
| Páginas | Total 12 Páginas | |
| PDF Descargar | [ Datasheet LT1301C.PDF ] | |
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