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PDF LT1308 Data sheet ( Hoja de datos )
| Número de pieza | LT1308 | |
| Descripción | Single Cell High Current Micropower 600kHz Boost DC/DC Converter | |
| Fabricantes | Linear Technology | |
| Logotipo |  |
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Hay una vista previa y un enlace de descarga de LT1308 (archivo pdf) en la parte inferior de esta página. Total 8 Páginas | ||
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FEATURES
s 5V at 1A from a Single Li-Ion Cell
s 3.3V at 300mA from a Single NiCd Cell
s Low Quiescent Current: 100µA
s Operates with VIN as Low as 1V
s Fixed Frequency Operation: 600kHz
s Current Mode PWM Delivers Low Output Ripple
s Guaranteed Start-Up into Full Load
s Low Shutdown Current: 3µA
s Low-Battery Comparator
s Automatic Burst ModeTM Operation at Light Load
s Low VCESAT Switch: 300mV at 2A
U
APPLICATIONS
s GSM Terminals
s Digital Cameras
s Answer-Back Pagers
s Cordless Telephones
s DECT Phones
s GPS Receivers
s Battery Backup Supplies
Final Electrical Specifications
LT1308
Single Cell High Current
Micropower 600kHz
Boost DC/DC Converter
January 1998
DESCRIPTION
The LT®1308 is a micropower, fixed frequency boost
DC/DC converter that operates from an input voltage as
low as 1V. Capable of delivering 5V at load current of 1A
from a single Li-Ion cell, the LT1308 also features power
saving Burst Mode operation at light loads. High efficiency
is maintained over a broad 1mA to 1A load range.
The device contains a low-battery detector with a 200mV
reference and shuts down to less than 5µA quiescent
current. No-load quiescent current is 100µA and the
internal NPN power switch handles a 2A current with a
voltage drop of just 300mV.
High frequency 600kHz switching allows the use of small,
surface mount components. The LT1308’s current mode
architecture provides fast response to load and line varia-
tions. The device is available in an 8-lead SO package.
, LTC and LT are registered trademarks of Linear Technology Corporation.
Burst Mode is a trademark of Linear Technology Corporation.
TYPICAL APPLICATION
4.2V TO 3V
Li-Ion
CELL
C1
10µF
SHDN
LBI
LT1308
VIN
SW
LBO FB
VC GND
RC
47k
CC
22nF
L1
4.7µH
R1
301k
D1
5V
1A
+
R2
100k
C2
100µF
C1: CERAMIC
C2: AVX TPS SERIES
D1: INTERNATIONAL RECTIFIER 10BQ015
L1: COILTRONICS CTX5-1
COILCRAFT DO3316-472
1308F01
Figure 1. Single Li-Ion Cell to 5V/1A DC/DC Converter
Converter Efficiency
95
VIN = 3.6V
90
VIN = 4.2V
85
80
VIN = 3V
75
70
65
1
10 100
LOAD CURRENT (mA)
1000
1308 F01a
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.
1
1 page  
LT1308
PIN FUNCTIONS
SW (Pin 5): Switch Pin. Connect inductor/diode here.
Minimize trace area at this pin to keep EMI down.
VIN (Pin 6): Supply Pin. Must have local bypass capacitor
right at the pin, connected directly to ground.
LBI (Pin 7): Low-Battery Detector Input. 200mV refer-
ence. Voltage on LBI must stay between ground and
700mV. Low-battery detector does not function with
SHDN pin grounded. If not used, float LBI pin.
LBO (Pin 8): Low-Battery Detector Output. Open collec-
tor, can sink 10µA. A 1MΩ pullup is recommended. LBO
is high impedance when SHDN is grounded.
BLOCK DIAGRAM
VIN
6
R5
40k
VOUT
R1
(EXTERNAL)
FB
R2
(EXTERNAL)
FB
2
Q1
VIN
R6
40k
+
gm
–
ERROR
AMPLIFIER
Q2
×10
R3
30k
R4
140k
RAMP
GENERATOR
600kHz
OSCILLATOR
VC
1
BIAS
+
Σ
+
SHUTDOWN
LBI
+ 7+
–
A1
ENABLE
200mV
–
COMPARATOR
–
FF
+
A2
RQ
S
A4
DRIVER
+
A=3
–
SHDN
3
LBO
8
SW
5
Q3
0.03Ω
4
GND
1308 BD
APPLICATIONS INFORMATION
LAYOUT HINTS
The LT1308 switches current at high speed, mandating
careful attention to layout for proper performance. You will
not get advertised performance with careless layouts.
Figure 2 shows recommended component placement.
Follow this closely in your PC layout. Note the direct path
of the switching loops. Input capacitor CIN must be placed
close (< 5mm) to the IC package. As little as 10mm of wire
or PC trace from CIN to VIN will cause problems such as
inability to regulate or oscillation. A 10µF ceramic bypass
capacitor is the only input capacitance required provided
the battery has a low inductance path to the circuit. The
battery itself provides the bulk capacitance the device
requires for proper operation. If the battery is located some
GROUND PLANE
1
2 LT1308
3
4
8
7
6
5
L
VIN
MULTIPLE
VIAs
CIN
GND
COUT
D
VOUT
1308 F02
Figure 2. Recommended Component Placement. Traces
Carrying High Current Are Direct. Trace Area at FB Pin and VC
Pin is Kept Low. Lead Length to Battery Should Be Kept Short.
Ground Plane Should Be Placed Under All Components
5
5 Page | ||
| Páginas | Total 8 Páginas | |
| PDF Descargar | [ Datasheet LT1308.PDF ] | |
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