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PDF LT1309 Data sheet ( Hoja de datos )
| Número de pieza | LT1309 | |
| Descripción | 500kHz Micropower DC/DC Converter for Flash Memory | |
| Fabricantes | Linear Technology | |
| Logotipo |  |
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LT1309
500kHz Micropower
DC/DC Converter
for Flash Memory
FEATURES
s 60mA Output Current at 12V from 3V or 5V Supply
s Shutdown to 9µA
s VPP VALID Comparator
s Up to 85% Efficiency
s Switching Frequency: 500kHz (Typical)
s Quiescent Current: 650µA
s Low VCESAT Switch: 300mV at 0.5A (Typical)
s Soft Start Reduces Supply Current Transients
s Uses Low Value, Small Size,
Surface Mount Inductors
s Available in 8-Lead SO Package
APPLICATI S
s Flash Memory VPP Generators
s Type II and III PCMCIA Card DC/DC Converters
s 3V to 12V, 5V to 12V Converters
s Portable Computers and Instruments
s Cellular Telephones
s DC/DC Converter Module Replacements
DESCRIPTIO
The LT ®1309 is a 500kHz micropower DC/DC converter
for Flash Memory. The regulator features Burst ModeTM
operation with a 0.5A, 300mV switch, enabling 85%
efficiency at the fixed 12V output. High frequency opera-
tion permits the use of small value, and therefore small
size, surface mount inductors and capacitors. The LT1309
comes in an 8-lead SO package allowing extremely
compact PC board layouts. These features make the
device attractive for PCMCIA cards, cellular phones and
other applications where PC board space is limited.
Quiescent current is 650µA decreasing to 9µA when the
part shuts down. The device includes a soft start feature
which limits supply current transients during turn-on.
The LT1309 contains a VPP VALID comparator with a
logic output that goes low when the output voltage is
ready to program 12V Flash Memory. This comparator
simplifies the interface to external control logic.
, LTC and LT are registered trademarks of Linear Technology Corporation.
Burst Mode is a trademark of Linear Technology Corporation.
TYPICAL APPLICATI
12V, 60mA Flash Memory Programming Supply
VIN
3.3V TO 5V
L1*
10µH
D1† VPP 12V, 60mA
VPP VALID
ON/OFF
+ C1
4.7µF
VIN VSW
VPP VALID SENSE
LT1309
ON/OFF
SOFT
START
PGND
GND
R1
1M
C3
0.1µF
C2
1µF**
*MURATA ERIE LQH3C100K0YM00
** CERAMIC
†
MOTOROLA MBR0530
LT1309 • TA01
12V Output Efficiency
86
VIN = 5V
84
82
80
VIN = 3.3V
78
76
74
72
70
1
10
LOAD CURRENT (mA)
100
LT1309 • TA02
1
1 page  
W
BLOCK DIAGRA
LT1309
SENSE ON/OFF
78
POWER ON
864k
–
C2
+
4k
–
C1
100k +
VREF 1.24V
VCC
200k
6 VPP VALID
OFF
500kHz
OSCILLATOR
+
C3
–
36mV
–+
VCC
2
R2
700Ω
R1
3Ω
Q3 BIAS
1
SOFT START
SW
4
Q2
× 1 Q1
× 50
5
GND
3
PGND
1309 BD
U
OPERATIO
The LT1309 is a current limited, Burst Mode (gated
oscillator) type switching regulator that produces a 12V
output from a 3.3V or 5V input. Operation can best be
understood by referring to the Block Diagram. When the
voltage at the Sense pin (Pin 7) is less than 12V, compara-
tor C1 enables the oscillator, turning switches Q1 and Q2
on. The switch turns off when current limit is reached or
when the oscillator maximum on-time is reached. When
Q2 turns off, current built up in the inductor flows into the
output capacitor and load. This action occurs until the
output voltage reaches 12V. During start-up, the Sense pin
voltage is either 3.3V or 5V, depending on the input. The
VPP VALID signal remains high until the output voltage
reaches 12V, signaling correct voltage level to program
flash memory. Connecting a 1µF/0.1µF parallel RC to the
Soft Start pin limits inrush current during start-up.
5
5 Page | ||
| Páginas | Total 8 Páginas | |
| PDF Descargar | [ Datasheet LT1309.PDF ] | |
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