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Linear Technology Electronic Components Datasheet

LT1941 Datasheet

Triple Monolithic Switching Regulator

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FEATURES
s Wide Input Range: 3.5V to 25V
s Three Switching Regulators with Internal Power
Switches: 3A Step-Down, 2A Step-Down,
1.5A Inverting/Boost
s Antiphase Switching Reduces Ripple
s Independent Shutdown/Soft-Start Pins
s Independent Power Good Indicators Ease Supply
Sequencing
s Input Voltage Power Good Indicators Monitor Input
Supply
s Uses Small Inductors and Ceramic Capacitors
s Constant 1.1MHz Switching Frequency
s Thermally Enhanced 28-Lead TSSOP Package
U
APPLICATIO S
s Cable Modems
s DSL Modems
s Distributed Power Regulation
s Wall Transformer Regulation
s Disk Drives
s DSP Power
, LTC and LT are registered trademarks of Linear Technology Corporation.
LT1941www.DataSheet4U.com
Triple Monolithic
Switching Regulator
DESCRIPTIO
The LT®1941 is a triple current mode DC/DC converter
with internal power switches. Two of the regulators are
step-down converters with 3A and 2A power switches.
The third regulator can be configured as a boost, inverter
or SEPIC converter and has a 1.5A power switch. All three
converters are synchronized to a 1.1MHz oscillator. The
two step-down converters run with opposite phases,
reducing input ripple current. The output voltages are set
with external resistor dividers and each regulator has
independent shutdown and soft-start circuits. Each regu-
lator generates a power good signal when its output is in
regulation, easing power supply sequencing and interfac-
ing with microcontrollers and DSPs.
The high switching frequency offers several advantages
by permitting the use of small inductors and ceramic
capacitors. Small inductors and capacitors lead to a very
small triple output solution. The constant switching fre-
quency, combined with low impedance ceramic capaci-
tors, result in low, predictable output ripple. With its wide
input voltage range of 3.5V to 25V, the LT1941 regulates
a broad array of power sources from 4-cell batteries and
5V logic rails to unregulated wall transformers, lead acid
batteries and distributed-power supplies.
TYPICAL APPLICATIO
VIN
4.7V TO 14V
5GOOD
12GOOD
VOUT1
1.8V
2.4A
VOUT3*
–12V
350mA
10µF
VOUT1
VOUT2
130k 100k
PGOOD1
5GOOD PGOOD2
12GOOD PGOOD3
3µH
33µF
0.22µF
13.7k
3300pF
7.32k 3.3k
1.5nF
BOOST1 BOOST2
LT1941
SW1 SW2
FB1 FB2
VC1 VC2
RUNSS1 RUNSS2
22µH 1µF
SW3 BIAS1
NFB BIAS2
22µH
10µF
133k 13.7k
VC3
FB3 RUNSS3
GND
100k 100k 100k
0.22µF
1000pF
10.7k
10k 2.49k
1.5nF
3.3µH
22µF
22nF
1.5nF
1.5k
*240mA AT VIN = 5V, 550mA AT VIN = 12V
1941 F01
PGOOD1
PGOOD2
PGOOD3
VOUT2
3.3V
1.4A
Figure 1. Triple Output Power Supply: 3.3V, 1.8V, –12V
RUN/SS
2V/DIV
VOUT1
2V/DIV
VOUT2
5V/DIV
VOUT3
10V/DIV
IVIN(AVE)
1A/DIV
PGOOD2
5V/DIV
Start-Up Waveforms
with Sequencing
1941 F01b
1941f
1


Linear Technology Electronic Components Datasheet

LT1941 Datasheet

Triple Monolithic Switching Regulator

No Preview Available !

LT1941
ABSOLUTE AXI U RATI GS
(Note 1)
VIN Pin ...................................................... (– 0.3V), 25V
BOOST Pin Voltage .................................................. 35V
BOOST Above SW Pin .............................................. 25V
BIAS1, BIAS2 Pins ................................................... 25V
PGOOD, 5GOOD, 12GOOD Pins ............................... 25V
RUN/SS, VC, FB, NFB Pins .......................................... 3V
SW1, SW2 Voltage .................................................... VIN
SW3 Voltage ............................................................ 40V
Maximum Junction Temperature (Note 6) ............ 125°C
Operating Ambient Temperature Range
(Note 2) .................................................. –40°C to 85°C
Storage Temperature Range .................. – 65°C to 150°C
Lead Temperature (Soldering, 10 sec)................... 300°C
www.DataSheet4U.com
UW U
PACKAGE/ORDER I FOR ATIO
VIN
VIN
SW1
1
2
3
SW1 4
BOOST1 5
PGOOD1 6
VC1 7
FB1 8
PGOOD2 9
VC2 10
FB2 11
RUN/SS1 12
RUN/SS2 13
RUN/SS3 14
TOP VIEW
29
28 BIAS2
27 SW3
26 PGND
25 VIN
24 BOOST2
23 SW2
22 VIN
21 PGOOD3
20 FB3
19 NFB
18 VC3
17 5GOOD
16 12GOOD
15 BIAS1
ORDER PART
NUMBER
LT1941EFE
FE PACKAGE
28-LEAD PLASTIC TSSOP
TJMAX = 125°C, θJA = 25°C/ W
EXPOSED PAD (PIN 29) IS GND
MUST BE SOLDERED TO PCB
Consult LTC Marketing for parts specified with wider operating temperature ranges.
ELECTRICAL CHARACTERISTICS
The q denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C.
VIN, VBIAS1, VBIAS2 = 5V, VBOOST1, VBOOST2 = 8V, unless otherwise noted. (Note 2)
PARAMETER
CONDITIONS
MIN TYP MAX UNITS
Minimum Operating Voltage
q
3.1 3.5
V
VIN Quiescent Current
BIAS1 Quiescent Current
Not Switching
Not Switching
2 3.5
5 7.5
mA
mA
BIAS2 Quiescent Current
Not Switching
1.6 2.2
mA
Shutdown Current
Reference Voltage Line Regulation
VC Source Current
VC Sink Current
VC Clamp Voltage
Switching Frequency
VRUNSS1,2,3 = 0V
5V < VIN < 25V
VC = 0.6V
VC = 0.6V
50 75
0.01
100
100
1.7
q 0.9 1.1 1.35
µA
%/V
µA
µA
V
MHz
Switching Phase
SW1 to SW2
SW1 to SW3
150 180 210
–30 0
30
Deg
Deg
Foldback Frequency
RUN/SS Current
VFB = 0V
200
123
kHz
µA
RUN/SS Threshold
0.4 0.6
V
5GOOD Threshold
5GOOD Voltage Output Low
5GOOD Leakage
VIN Rising
I5GOOD = 125µA, VIN = 4V
V5GOOD = 2V
4.5
0.2 0.4
10 400
V
V
nA
12GOOD Threshold
VIN Rising
10.8 V
1941f
2


Part Number LT1941
Description Triple Monolithic Switching Regulator
Maker Linear Technology
PDF Download

LT1941 Datasheet PDF






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