OMO ElectronicOMO Electronic
Expand menu
Hello, Sign inMy Account
0 Cart

LT1940EFE#TRPBF

P1-P3P4-P6P7-P9P10-P12P13-P15P16-P18P19-P20
LT1940/LT1940L
1
1940fa
TYPICAL APPLICATIO
U
FEATURES
APPLICATIO S
U
DESCRIPTIO
U
■
Disk Drives
■
DSP Power Supplies
■
Wall Transformer Regulation
■
Distributed Power Regulation
■
DSL Modems
■
Cable Modems
■
Wide Input Voltage Range
LT1940: 3.6V to 25V
LT1940L: 3.6V to 7V
■
Two 1.4A Output Switching Regulators with
Internal Power Switches
■
Constant 1.1MHz Switching Frequency
■
Anti-Phase Switching Reduces Ripple
■
Independent Shutdown/Soft-Start Pins
■
Independent Power Good Indicators Ease
Supply Sequencing
■
Uses Small Inductors and Ceramic Capacitors
■
Small 16-Lead Thermally Enhanced
TSSOP Surface Mount Package
Dual Monolithic 1.4A,
1.1MHz Step-Down
Switching Regulator
The LT
®
1940 is a dual current mode PWM step-down
DC/DC converter with internal 2A power switches. Both con-
verters are synchronized to a single 1.1MHz oscillator and
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 regulator generates a power-good signal
when its output is in regulation, easing power supply se-
quencing and interfacing with microcontrollers and DSPs.
The LT1940’s 1.1MHz switching frequency allows the use
of tiny inductors and capacitors, resulting in a very small
dual 1.4A output solution. Constant frequency and ceramic
capacitors combine to produce low, predictable output
ripple voltage. With its wide input range of 3.6V to 25V, the
LT1940 regulates a wide variety of power sources, from
4-cell batteries and 5V logic rails to unregulated wall trans-
formers, lead acid batteries and distributed-power supplies.
The LT1940L is intended to operate from regulated 5V
supplies. A current mode PWM architecture provides fast
transient response with simple compensation components
and cycle-by-cycle current limiting. Frequency foldback and
thermal shutdown provide additional protection.
, LTC and LT are registered trademarks of Linear Technology Corporation.
Figure 1. 3.3V and 5V Dual Output Step-Down Converter with Output Sequencing (LT1940)
Efficiency vs Load Current
V
IN
7V TO 25V
BOOST1
SW1
FB1
V
C1
RUN/SS1
RUN/SS2
BOOST2
SW2
FB2
V
C2
PG1
PG2
LT1940
V
IN
GND
1940 F01
330pF
10µF
10µF
4.7µF
0.1µF 0.1µF
15k
330pF
15k
10.0k
16.5k
100k
30.1k
10.0k
4.7µH
3.3µH
POWER
GOOD
OUT2
5V
1.4A
OUT1
3.3V
1.4A
UPS140
UPS140
CMDSH-3
1nF
CMDSH-3
LOAD CURRENT (A)
0
EFFICIENCY (%)
100
90
80
70
60
0.5 1.0
1940 F01b
1.5
V
IN
= 12V
V
OUT
= 5V
V
OUT
= 3.3V
LT1940/LT1940L
2
1940fa
V
IN
Voltage
LT1940 .................................................... (–0.3), 25V
LT1940L ................................................... (–0.3), 7V
BOOST Pin Voltage
LT1940 ................................................................ 35V
LT1940L ............................................................. 16V
BOOST Pin Above SW Pin
LT1940 ................................................................ 25V
LT1940L ............................................................. 16V
PG Pin Voltage
LT1940 ................................................................ 25V
LT1940L ............................................................... 7V
SW Voltage ................................................................V
IN
RUN/SS, FB Pins ...................................................... 6V
Maximum Junction Temperature .......................... 125°C
Operating Temperature Range (Note 2) ...–40°C to 85°C
Storage Temperature Range ..................–65°C to 150°C
Lead Temperature (Soldering, 10 sec).................. 300°C
ORDER PART
NUMBER
T
JMAX
= 125°C, θ
JA
= 45°C/W, θ
JC
= 10°C/W
LT1940EFE
LT1940LEFE
ABSOLUTE AXI U RATI GS
W
WW
U
PACKAGE/ORDER I FOR ATIO
UUW
(Note 1)
ELECTRICAL CHARACTERISTICS
The ● denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. V
IN
= 5V, V
BOOST
= 8V unless otherwise noted. (Note 2)
PARAMETER CONDITIONS MIN TYP MAX UNITS
Minimum Operating Voltage ● 3.4 3.6 V
Quiescent Current Not Switching 3.8 4.8 mA
Shutdown Current V
RUNSS
= 0V 30 45 µA
Feedback Voltage 1.230 1.250 1.270 V
0°C to 70°C
● 1.225 1.250 1.270 V
–40°C to 85°C ● 1.215 1.250 1.270 V
FB Pin Bias Current V
FB
= 1.25V, V
C
= 0.4V ● 240 1200 nA
Reference Line Regulation LT1940: V
IN
5V to 25V 0.005 %/V
LT1940L: V
IN
4V to 7V 0.005 %/V
Error Amp GM 330 uMhos
Error Amp Voltage Gain 180
V
C
Source Current V
FB
= 1V 42 µA
V
C
Sink Current V
FB
= 1.5V 60 µA
V
C
Pin to Switch Current Gain 2.4 A/V
V
C
Switching Threshold 0.75 V
V
C
Clamp Voltage 1.8 V
Switching Frequency V
FB
= 1.1V 1 1.1 1.25 MHz
● 0.95 1.1 1.35 MHz
Switching Phase 150 180 210 Deg
Maximum Duty Cycle ● 78 88 %
Frequency Shift Threshold on FB f
SW
= 1MHz 0.5 V
Consult LTC Marketing for parts specified with wider operating temperature ranges.
FE PACKAGE
16-LEAD PLASTIC TSSOP
EXPOSED PAD (PIN 17) IS GND
MUST BE SOLDERED TO PCB
1
2
3
4
5
6
7
8
TOP VIEW
16
15
14
13
12
11
10
9
BOOST1
SW1
V
IN
V
IN
V
IN
V
IN
SW2
BOOST2
FB1
V
C1
PG1
RUN/SS1
RUN/SS2
PG2
V
C2
FB2
17
FE PART
MARKING
1940EFE
1940LEFE
LT1940/LT1940L
3
1940fa
Note 1: Absolute Maximum Ratings are those values beyond which the life
of a device may be impaired.
Note 2: The LT1940E 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.
ELECTRICAL CHARACTERISTICS
The ● denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. V
IN
= 5V, V
BOOST
= 8V unless otherwise noted. (Note 2)
PARAMETER CONDITIONS MIN TYP MAX UNITS
Foldback Frequency V
FB
= 0V 150 kHz
Switch Current Limit Note 3 1.8 2.4 3.2 A
Switch V
CESAT
I
SW
= 1A 210 320 mV
Switch Leakage Current 10 µA
Minimum Boost Voltage Above Switch (Note 4) I
SW
= 1A 1.8 2.5 V
BOOST Pin Current I
SW
= 1A 20 30 mA
RUN/SS Current 2.3 µA
RUN/SS Threshold 0.3 0.6 V
PG Threshold Offset V
FB
Rising 90 125 160 mV
PG Voltage Output Low V
FB
= 1V, I
PG
= 250µA 0.22 0.4 V
PG Pin Leakage V
PG
= 2V 0.1 1 µA
Note 3: Current limit is guaranteed by design and/or correlation to static
test. Slope compensation reduces current limit at high duty cycle.
Note 4: This is the minimum voltage across the boost capacitor needed to
guarantee full saturation of the internal power switch.
TYPICAL PERFOR A CE CHARACTERISTICS
UW
Efficiency, V
OUT
= 3.3V
Efficiency, V
OUT
= 5V
LOAD CURRENT (A)
0
EFFICIENCY (%)
90
80
70
60
50
0.5 1.0
1940 G01
1.5
V
OUT
= 1.8V
L = 2.2µH (SUMIDA CR43-2R2)
T
A
= 25°C
V
IN
= 5V
LOAD CURRENT (A)
0
EFFICIENCY (%)
100
90
80
70
60
50
0.5 1.0
1940 G02
1.5
V
OUT
= 3.3V
L = 3.3µH (SUMIDA CR43-3R3)
T
A
= 25°C
V
IN
= 5V
V
IN
= 18V
V
IN
= 12V
LOAD CURRENT (A)
0
EFFICIENCY (%)
100
90
80
70
60
0.5 1.0
1940 G03
1.5
V
OUT
= 5V
L = 4.7µH (SUMIDA CR43-4R7)
T
A
= 25°C
V
IN
= 8V
V
IN
= 18V
V
IN
= 12V
Efficiency, V
OUT
= 1.8V
P1-P3P4-P6P7-P9P10-P12P13-P15P16-P18P19-P20

LT1940EFE#TRPBF

Mfr. #:
Buy LT1940EFE#TRPBF
Manufacturer:
Analog Devices / Linear Technology
Description:
Switching Voltage Regulators Dual 1.4A Step-dn DC/DC Converter
Lifecycle:
New from this manufacturer.
Delivery:
DHL FedEx Ups TNT EMS
Payment:
T/T Paypal Visa MoneyGram Western Union

Products related to this Datasheet