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Linear Technology Electronic Components Datasheet

LT1949-1 Datasheet

1A Switch PWM DC/DC Converter

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FEATURES
s 1A, 0.5, 30V Internal Switch
s 1.1MHz Fixed Frequency Operation
s Operates with VIN as Low as 1.5V
s Low-Battery Detector Stays Active in Shutdown
s Low VCESAT Switch: 410mV at 800mA
s Pin-for-Pin Compatible with the LT1317B
s Uses Ceramic Capacitors
s Small 8-Lead MSOP Package
U
APPLICATIO S
s LCD Bias Supplies
s GPS Receivers
s Battery Backup
s Portable Electronic Equipment
s Diagnostic Medical Instrumentation
Final Electrical Specifications
LT1949-1
1.1MHz, 1A Switch
PWM DC/DC Converter
June 2000
DESCRIPTIO
The LT®1949-1 is a fixed frequency step-up DC/DC con-
verter with a 1A, 0.5internal switch. Capable of gener-
ating 10V at 175mA from a 3.3V input, the LT1949-1 is
ideal for generating bias voltages for large screen LCD
panels. Constant frequency 1.1MHz operation results in a
low noise output that is easy to filter and the 30V switch
rating allows output voltage up to 28V using a single
inductor. The high switching frequency allows the use of
ceramic output capacitors. An external compensation pin
gives the user flexibility in optimizing loop compensation,
allowing small, low ESR ceramic capacitors to be used at
the output. The 8-lead MSOP package ensures a low
profile overall solution.
The LT1949-1 includes a low-battery detector that stays
alive when the device goes into shutdown. Quiescent
current in shutdown is 50µA, while operating current is
8mA.
, LTC and LT are registered trademarks of Linear Technology Corporation.
TYPICAL APPLICATIO
VIN
3.3V
C1
3.3µF
CERAMIC
L1
4.7µH
VIN SW
LT1949-1
SHUTDOWN SHDN
FB
VC GND
84.5k
50pF
C1, C2: TAIYO YUDEN LMK325BJ335MD
D1: MBRM120LT3
L1: SUMIDA CLQ4D10-4R7
D1
R1
196k
1%
3pF
VOUT
10V
175mA
R2
28k
1%
C2
3.3µF
CERAMIC
1949-1 F01
Figure 1. 3.3V to 10V/175mA DC/DC Converter
90
VOUT = 10V
80
70
3.6VIN 4.2VIN 3VIN
60
50
40
30
20
5
10 50 100
LOAD CURRENT (mA)
300
1949-1 F02
Figure 2. 3.3V to 10V Converter Efficiency
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


Linear Technology Electronic Components Datasheet

LT1949-1 Datasheet

1A Switch PWM DC/DC Converter

No Preview Available !

LT1949-1
ABSOLUTE AXI U RATI GS
(Note 1)
VIN, LBO Voltage ..................................................... 12V
SW Voltage ............................................... – 0.4V to 30V
FB Voltage .................................................... VIN + 0.3V
VC Voltage ................................................................ 2V
LBI Voltage ............................................ 0V VLBI 1V
SHDN Voltage ........................................................... 6V
Junction Temperature .......................................... 125°C
Operating Temperature Range (Note 2) ...–40°C to 85°C
Storage Temperature ........................... – 65°C to 150°C
Lead Temperature (Soldering, 10sec).................. 300°C
UW U
PACKAGE/ORDER I FOR ATIO
TOP VIEW
VC 1
FB 2
SHDN 3
GND 4
8 LBO
7 LBI
6 VIN
5 SW
MS8 PACKAGE
8-LEAD PLASTIC MSOP
TJMAX = 125°C, θJA = 120°C/W
ORDER PART
NUMBER
LT1949-1EMS8
MS8 PART MARKING
LTQX
Consult factory for Industrial and Military grade parts.
ELECTRICAL CHARACTERISTICS The q denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C. VIN = 2V, VSHDN = 2V unless otherwise noted.
SYMBOL PARAMETER
CONDITIONS
MIN TYP MAX UNITS
IQ Quiescent Current
VFB Feedback Voltage
VSHDN = 0V
q
q
1.22
q 1.20
8 14
50 80
1.24 1.26
1.24 1.26
mA
µA
V
V
IB FB Pin Bias Current (Note 3)
Input Voltage Range
q
q 1.7
24 150
12
nA
V
gm Error Amp Transconductance
AV Error Amp Voltage Gain
Maximum Duty Cycle
I = 5µA
q 140 280 480 µmhos
700 V/V
q 80
85
%
Switch Current Limit (Note 4)
fOSC Switching Frequency
Shutdown Pin Current
LBI Threshold Voltage
VIN = 2.5V, Duty Cycle = 30%
VSHDN = VIN
VSHDN = 0V
1 1.1 1.5
A
q 0.85 1.1 1.35 MHz
q
0.015
0.1
µA
q
– 5 – 14
µA
190 200 210 mV
q 180 200 220 mV
LBO Output Low
LBO Leakage Current
LBI Input Bias Current (Note 5)
Low-Battery Detector Gain
ISINK = 10µA
VLBI = 250mV, VLBO = 5V
VLBI = 150mV
1MPull-Up
q
q
q
0.15 0.25
20 100
30 120
2000
V
nA
nA
V/V
Switch Leakage Current
Switch VCESAT
Reference Line Regulation
SHDN Input Voltage High
VSW = 5V
ISW = 800mA
ISW = 500mA
1.8V VIN 12V
q
q
q 1.4
0.01 3
µA
410 mV
270 400 mV
0.08 %/V
6V
SHDN Input Voltage Low
q 0.4 V
Note 1: Absolute Maximum Ratings are those values beyond which the life
of a device may be impaired.
Note 2: The LT1949-1E is guaranteed to meet performance specifications
from 0°C to 70°C. Specifications over the – 40°C to 85°C operating
temperature range are assured by design, characterization and correlation
with statistical process controls.
Note 3: Bias current flows into FB pin.
Note 4: Switch current limit guaranteed by design and/or correlation to
static tests. Duty cycle affects current limit due to ramp generator.
Note 5: Bias current flows out of LBI pin.
2


Part Number LT1949-1
Description 1A Switch PWM DC/DC Converter
Maker Linear Technology
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