LT1936HMS8E#PBF [Linear]
LT1936 - 1.4A, 500kHz Step-Down Switching Regulator; Package: MSOP; Pins: 8; Temperature Range: -40°C to 125°C;
| 型号： | LT1936HMS8E#PBF |
| 厂家： | 
Linear |
| 描述： | LT1936 - 1.4A, 500kHz Step-Down Switching Regulator; Package: MSOP; Pins: 8; Temperature Range: -40°C to 125°C 稳压器 开关式稳压器或控制器 电源电路 开关式控制器 光电二极管 |
| 文件： | 总20页 (文件大小：293K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
LT1936
1.4A, 500kHz Step-Down
Switching Regulator
FEATURES
DESCRIPTION
The LT®1936 is a current mode PWM step-down DC/DC
converter with an internal 1.9A power switch, packaged
in a tiny, thermally enhanced 8-lead MSOP. The wide in-
put range of 3.6V to 36V makes the LT1936 suitable for
regulating power from a wide variety of sources, including
automotive batteries, 24V industrial supplies and unregu-
latedwalladapters.Itshighoperatingfrequencyallowsthe
use of small, low cost inductors and ceramic capacitors,
resulting in low, predictable output ripple.
■
Wide Input Range: 3.6V to 36V
■
Short-Circuit Protected Over Full Input Range
■
1.9A Guaranteed Minimum Switch Current
■
5V at 1.4A from 10V to 36V Input
■
3.3V at 1.4A from 7V to 36V Input
■
5V at 1.2A from 6.3V to 36V Input
■
3.3V at 1.2A from 4.5V to 36V Input
■
Output Adjustable Down to 1.20V
■
500kHz Fixed Frequency Operation
■
Soft-Start
Cycle-by-cycle current limit, frequency foldback and
thermal shutdown provide protection against shorted
outputs, and soft-start eliminates input current surge
during start-up. Transient response can be optimized by
usingexternalcompensationcomponents,orboardspace
can be minimized by using internal compensation. The
low current (<2μA) shutdown mode enables easy power
management in battery-powered systems.
■
Uses Small Ceramic Capacitors
■
Internal or External Compensation
■
Low Shutdown Current: <2μA
■
Thermally Enhanced 8-Lead MSOP Package
APPLICATIONS
■
Automotive Battery Regulation
L, LT, LTC and LTM are registered trademarks of Linear Technology Corporation. All other
trademarks are the property of their respective owners.
■
Industrial Control Supplies
■
Unregulated Wall Adapters
TYPICAL APPLICATION
3.3V Step-Down Converter
Efficiency
95
V
= 12V
IN
V
IN
4.5V TO 36V
V
= 5V
OUT
90
85
80
75
70
65
0.22μF
V
BOOST
SW
IN
10μH
17.4k
V
3.3V
1.2A
OUT
SHDN
ON OFF
V
= 3.3V
OUT
LT1936
4.7μF
COMP
FB
GND
V
C
10k
22μF
1936 TA01a
0
0.5
1
1.5
LOAD CURRENT (A)
1936 TA01b
1936fd
1
LT1936
ABSOLUTE MAXIMUM RATINGS
PIN CONFIGURATION
(Note 1)
V Voltage................................................. –0.4V to 36V
IN
TOP VIEW
BOOST Voltage .........................................................43V
BOOST Above SW Voltage ........................................20V
SHDN Voltage ............................................ –0.4V to 36V
BOOST
1
2
3
4
8 COMP
7 V
6 FB
V
SW
IN
C
9
5 SHDN
GND
FB, V , COMP Voltage.................................................6V
C
MS8E PACKAGE
8-LEAD PLASTIC MSOP
Operating Temperature Range (Note 2)
θ
= 40°C/W, θ = 10°C/W
JA
JC
LT1936E............................................... –40°C to 85°C
LT1936I.............................................. –40°C to 125°C
LT1936H ............................................ –40°C to 150°C
Maximum Junction Temperature
EXPOSED PAD (PIN 9) IS GND, MUST BE SOLDERED TO PCB
LT1936E, LT1936I ............................................. 125°C
LT1936H ........................................................... 150°C
Storage Temperature Range................... –65°C to 150°C
Lead Temperature (Soldering, 10 sec) .................. 300°C
ORDER INFORMATION
LEAD FREE FINISH
LT1936EMS8E#PBF
LT1936IMS8E#PBF
LT1936HMS8E#PBF
LEAD BASED FINISH
LT1936EMS8E
TAPE AND REEL
PART MARKING
LTBMT
PACKAGE DESCRIPTION
TEMPERATURE RANGE
LT1936EMS8E#TRPBF
LT1936IMS8E#TRPBF
LT1936HMS8E#TRPBF
TAPE AND REEL
8-Lead Plastic MSOP
8-Lead Plastic MSOP
8-Lead Plastic MSOP
PACKAGE DESCRIPTION
8-Lead Plastic MSOP
8-Lead Plastic MSOP
8-Lead Plastic MSOP
–40°C to 85°C
LTBRV
–40°C to 125°C
–40°C to 150°C
TEMPERATURE RANGE
–40°C to 85°C
LTBWB
PART MARKING
LTBMT
LT1936EMS8E#TR
LT1936IMS8E#TR
LT1936HMS8E#TR
LT1936IMS8E
LTBRV
–40°C to 125°C
–40°C to 150°C
LT1936HMS8E
LTBWB
Consult LTC Marketing for parts specified with wider operating temperature ranges.
For more information on lead free part marking, go to: http://www.linear.com/leadfree/
For more information on tape and reel specifications, go to: http://www.linear.com/tapeandreel/
ELECTRICAL CHARACTERISTICS The ● denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C. VIN = 12V, VBOOST = 17V, unless otherwise noted. (Note 2)
PARAMETER
CONDITIONS
MIN
TYP
3.45
1.8
MAX
3.6
UNITS
V
Undervoltage Lockout
Quiescent Current
V
V
= 1.5V
2.5
mA
μA
FB
Quiescent Current in Shutdown
FB Voltage
= 0V
0.1
2
SHDN
●
1.175
1.200
1.215
V
●
●
FB Pin Bias Current (Note 4)
V
= 1.20V, E and I Grades
50
50
200
300
nA
nA
FB
H Grade
FB Voltage Line Regulation
Error Amp gm
V
= 5V to 36V
0.01
250
150
%/V
μS
IN
V = 0.5V, I
C
= 5μA
VC
Error Amp Voltage Gain
V = 0.8V, 1.2V
C
1936fd
2
LT1936
ELECTRICAL CHARACTERISTICS The ● denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C. VIN = 12V, VBOOST = 17V, unless otherwise noted. (Note 2)
V Clamp
1.8
0.7
50
V
V
C
V Switch Threshold
C
Internal Compensation R
Internal Compensation C
COMP Pin Leakage
kΩ
pF
V
V
= 1V
150
COMP
●
●
= 1.8V, E and I Grades
H Grade
1
2
μA
μA
COMP
Switching Frequency
V
FB
V
FB
= 1.1V
= 0V
400
500
40
600
kHz
kHz
●
Maximum Duty Cycle
Switch Current Limit
87
92
2.2
410
%
A
(Note 3)
1.9
2.6
520
2
Switch V
I
= 1.2A
mV
μA
V
CESAT
SW
Switch Leakage Current
Minimum BOOST Voltage Above SW
BOOST Pin Current
I
I
= 1.2A
= 1.2A
= 0V
2
2.2
50
1
SW
28
0.1
mA
μA
V
SW
BOOST Pin Leakage
V
SW
SHDN Input Voltage High
SHDN Input Voltage Low
SHDN Pin Current
2.3
0.3
V
V
SHDN
V
SHDN
V
SHDN
= 2.3V (Note 5)
= 12V (Note 5)
= 0V
34
140
0.01
50
240
0.1
μA
μA
μA
Note 1: Stresses beyond those listed under Absolute Maximum Ratings
may cause permanent damage to the device. Exposure to any Absolute
Maximum Rating condition for extended periods may affect device
reliability and lifetime.
with statistical process controls. The LT1936I specifications are
guaranteed over the –40°C to 125°C temperature range. The LT1936H
specifications are guaranteed over the –40°C to 150°C temperature range.
Note 3: Current limit guaranteed by design and/or correlation to static test.
Note 2: The LT1936E 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
Slope compensation reduces current limit at higher duty cycle.
Note 4: Current flows out of pin.
Note 5: Current flows into pin.
TYPICAL PERFORMANCE CHARACTERISTICS
Efficiency, VOUT = 5V
Efficiency, VOUT = 3.3V
Switch Current Limit
3.0
2.5
100
90
100
90
V
IN
= 12V
= 24V
V
= 5V
IN
TYP
2.0
1.5
V
IN
V
= 12V
= 24V
IN
MIN
80
80
V
IN
1.0
0.5
0
70
70
V
A
= 5V
V
= 3.3V
OUT
OUT
T
= 25°C
T = 25°C
A
D1 = DFLS140L
D1 = DFLS140L
L1 = 10μH, TOKO D63CB
L1 = 15μH, TOKO D63CB
60
60
0
0.5
1.0
1.5
0
0.5
1.0
1.5
0
20
40
60
80
100
LOAD CURRENT (A)
LOAD CURRENT (A)
DUTY CYCLE (%)
1936 G01
1936 G02
1936 G03
1936fd
3
LT1936
TYPICAL PERFORMANCE CHARACTERISTICS
Maximum Load Current
Maximum Load Current
Switch Voltage Drop
1.8
1.6
1.4
1.2
1.8
1.6
1.4
1.2
600
500
400
300
200
100
0
V
= 5V
V
OUT
= 3.3V
OUT
T
= 85°C
A
L = 10μH
T
= 25°C
A
L = 15μH
T
= –45°C
A
L = 10μH
L = 6.8μH
1.0
1.0
0
5
10
15
20
25
30
0
5
10
15
20
25
30
0
0.5
1.0
1.5
INPUT VOLTAGE (V)
INPUT VOLTAGE (V)
SWITCH CURRENT (A)
1936 G04
1936 G05
1936 G06
Feedback Voltage
Undervoltage Lockout
Switching Frequency
1.210
1.205
1.200
1.195
1.190
1.185
3.8
3.6
3.4
3.2
600
550
500
450
3.0
400
–50 –25
0
25 50 75 100 125 150
–50 –25
0
25 50 75 100 125 150
–50 –25
0
25 50 75 100 125 150
TEMPERATURE (°C)
TEMPERATURE (°C)
TEMPERATURE (°C)
1936 G08
1936 G09
1936 G07
Frequency Foldback
Soft-Start
SHDN Pin Current
700
600
500
400
300
200
100
0
3.0
2.5
200
150
100
50
T
= 25°C
T = 25°C
A
DC = 30%
T
= 25°C
A
A
2.0
1.5
1.0
0.5
0
0
0
0.5
1.0
1.5
0
1
2
3
4
0
4
8
12
16
SHDN PIN VOLTAGE (V)
FB PIN VOLTAGE (V)
SHDN PIN VOLTAGE (V)
1936 G10
1936 G12
1936 G11
1936fd
4
LT1936
TYPICAL PERFORMANCE CHARACTERISTICS
Minimum Input Voltage
Minimum Input Voltage
Switch Current Limit
3.0
2.5
2.0
1.5
7.0
6.5
5.0
4.5
4.0
3.5
3.0
V
A
L = 15μH
= 5V
V
= 3.3V
OUT
OUT
T
= 25°C
T = 25°C
A
L = 10μH
6.0
5.5
5.0
4.5
4.0
1.0
0.5
0
1
10
100
1000
1
10
100
1000
–50 –25
0
25 50 75 100 125 150
LOAD CURRENT (mA)
LOAD CURRENT (mA)
TEMPERATURE (°C)
1936 G13
1936 G15
1936 G14
Switching Waveforms,
Discontinuous Mode
Switching Waveforms
V
V
SW
10V/DIV
SW
10V/DIV
I
I
L
L
500mA/DIV
500mA/DIV
V
V
OUT
20mV/DIV
OUT
20mV/DIV
1936 G16
1936 G17
V
V
= 12V
1μs/DIV
V
V
= 12V
IN
1μs/DIV
IN
= 3.3V
OUT
= 1A
OUT
= 3.3V
OUT
OUT
I
I
= 50mA
L = 10μH
C
L = 10μH
C
= 22μF
= 22μF
OUT
OUT
VC Voltages
Error Amp Output Current
2.5
2.0
1.5
1.0
0.5
0
60
40
T
= 25°C
= 0.5V
A
C
V
CURRENT LIMIT CLAMP
SWITCHING THRESHOLD
20
0
–20
–40
–60
–50 –25
0
25 50 75 100 125 150
0
1
2
TEMPERATURE (°C)
FB PIN VOLTAGE (V)
1936 G18
1936 G19
1936fd
5
LT1936
PIN FUNCTIONS
BOOST (Pin 1): The BOOST pin is used to provide a drive
voltage,higherthantheinputvoltage,totheinternalbipolar
NPN power switch.
FB (Pin 6): The LT1936 regulates its feedback pin to
1.200V. Connect the feedback resistor divider tap to this
pin. Set the output voltage according to V
(1 + R1/R2). A good value for R2 is 10k.
= 1.200V
OUT
V (Pin 2): The V pin supplies current to the LT1936’s
IN
IN
internal regulator and to the internal power switch. This
V (Pin 7): The V pin is used to compensate the LT1936
C C
pin must be locally bypassed.
control loop by tying an external RC network from this pin
to ground. The COMP pin provides access to an internal
RC network that can be used instead of the external
components.
SW (Pin 3): The SW pin is the output of the internal power
switch. Connect this pin to the inductor, catch diode and
boost capacitor.
COMP (Pin 8): To use the internal compensation network,
GND (Pin 4): Tie the GND pin to a local ground plane
below the LT1936 and the circuit components. Return the
feedback divider to this pin.
tie the COMP pin to the V pin. Otherwise, tie COMP to
C
ground or leave it floating.
Exposed Pad (Pin 9): The Exposed Pad must be soldered
to the PCB and electrically connected to ground. Use a
large ground plane and thermal vias to optimize thermal
performance.
SHDN (Pin 5): The SHDN pin is used to put the LT1936 in
shutdown mode. Tie to ground to shut down the LT1936.
Tie to 2.3V or more for normal operation. If the shutdown
feature is not used, tie this pin to the V pin. SHDN also
IN
provides a soft-start function; see the Applications Infor-
mation. Do not drive SHDN more than 5V above V .
IN
BLOCK DIAGRAM
V
IN
V
2
IN
C2
INT REG
AND
UVLO
D2
BOOST
1
∑
ON OFF
SLOPE
COMP
R
S
Q
R3
SHDN
C3
5
Q
DRIVER
Q1
C4
L1
SW
FB
OSC
V
OUT
3
6
C1
D1
FREQUENCY
FOLDBACK
R1
R2
V
C
g
m
C
C
R
1.200V
GND
C
150pF
50k
V
C
COMP
1936 BD
7
8
4
R4
C5
1936fd
6
LT1936
OPERATION (Refer to Block Diagram)
The LT1936 is a constant frequency, current mode step-
downregulator.A500kHzoscillatorenablesanRSflip-flop,
turning on the internal 1.9A power switch Q1. An ampli-
fier and comparator monitor the current flowing between
Aninternalregulatorprovidespowertothecontrolcircuitry.
Thisregulatorincludesanundervoltagelockouttoprevent
switching when V is less than ~3.45V. The SHDN pin is
IN
used to place the LT1936 in shutdown, disconnecting the
output and reducing the input current to less than 2μA.
the V and SW pins, turning the switch off when this
IN
current reaches a level determined by the voltage at V .
C
The switch driver operates from either the input or from
the BOOST pin. An external capacitor and diode are used
to generate a voltage at the BOOST pin that is higher than
the input supply. This allows the driver to fully saturate
the internal bipolar NPN power switch for efficient opera-
tion.
An error amplifier measures the output voltage through
an external resistor divider tied to the FB pin and servos
the V pin. If the error amplifier’s output increases, more
C
current is delivered to the output; if it decreases, less
current is delivered. An active clamp (not shown) on the
V pin provides current limit. The V pin is also clamped
C
C
The oscillator reduces the LT1936’s operating frequency
when the voltage at the FB pin is low. This frequency
foldbackhelpstocontroltheoutputcurrentduringstartup
and overload.
to the voltage on the SHDN pin; soft-start is implemented
by generating a voltage ramp at the SHDN pin using an
external resistor and capacitor.
1936fd
7
LT1936
APPLICATIONS INFORMATION
FB Resistor Network
Inductor Selection and Maximum Output Current
The output voltage is programmed with a resistor divider
between the output and the FB pin. Choose the 1% resis-
tors according to:
A good first choice for the inductor value is
L = 2.2 (V
+ V )
D
OUT
where V is the voltage drop of the catch diode (~0.4V)
D
ꢀ
ꢃ
VOUT
1.200
and L is in μH. With this value the maximum output cur-
R1=R2
–1
ꢅ
ꢂ
ꢁ
ꢄ
rent will be above 1.2A at all duty cycles and greater than
1.4A for duty cycles less than 50% (V > 2 V ). The
IN
OUT
R2 should be 20k or less to avoid bias current errors.
Reference designators refer to the Block Diagram.
inductor’s RMS current rating must be greater than the
maximumloadcurrentanditssaturationcurrentshouldbe
about 30% higher. For robust operation in fault conditions
(start-up or short circuit) and high input voltage (>30V),
the saturation current should be above 2.6A. To keep the
efficiency high, the series resistance (DCR) should be less
than 0.1Ω, and the core material should be intended for
high frequency applications. Table 1 lists several vendors
and suitable types.
Input Voltage Range
The input voltage range for LT1936 applications depends
on the output voltage and the Absolute Maximum Ratings
of the V and BOOST pins.
IN
The minimum input voltage is determined by either the
LT1936’s minimum operating voltage of ~3.45V or by its
maximum duty cycle. The duty cycle is the fraction of
time that the internal switch is on and is determined by
the input and output voltages:
Table 1. Inductor Vendors
VENDOR
Murata
TDK
URL
PART SERIES
TYPE
www.murata.com
www.component.tdk.com
LQH55D
Open
SLF7045
SLF10145
Shielded
Shielded
V
OUT + VD
DC =
V – VSW + VD
IN
Toko
www.toko.com
D62CB
D63CB
D75C
Shielded
Shielded
Shielded
Open
where V is the forward voltage drop of the catch diode
D
D75F
(~0.5V) and V is the voltage drop of the internal switch
SW
Sumida
www.sumida.com
CR54
Open
(~0.5V at maximum load). This leads to a minimum input
CDRH74
CDRH6D38
CR75
Shielded
Shielded
Open
voltage of:
V
OUT + V
V
=
D – VD + VSW
IN(MIN)
DCMAX
Of course, such a simple design guide will not always
result in the optimum inductor for your application. A
larger value provides a slightly higher maximum load
current and will reduce the output voltage ripple. If your
load is lower than 1.2A, then you can decrease the value
oftheinductorandoperatewithhigherripplecurrent. This
allows you to use a physically smaller inductor, or one
with a lower DCR resulting in higher efficiency. Be aware
that if the inductance differs from the simple rule above,
then the maximum load current will depend on input volt-
age. There are several graphs in the Typical Performance
Characteristics section of this data sheet that show the
maximum load current as a function of input voltage and
inductor value for several popular output voltages. Low
with DC
= 0.87.
MAX
The maximum input voltage is determined by the absolute
maximum ratings of the V and BOOST pins and by the
IN
MIN
minimum duty cycle DC
= 0.08:
V
OUT + V
DCMIN
V
=
D – VD + VSW
IN(MAX)
Notethatthisisarestrictionontheoperatinginputvoltage;
the circuit will tolerate transient inputs up to the absolute
maximum ratings of the V and BOOST pins.
IN
1936fd
8
LT1936
APPLICATIONS INFORMATION
inductance may result in discontinuous mode operation,
which is okay but further reduces maximum load current.
For details of maximum output current and discontinuous
mode operation, see Linear Technology Application Note
combined with trace or cable inductance forms a high
quality (under damped) tank circuit. If the LT1936 circuit
is plugged into a live supply, the input voltage can ring to
twice its nominal value, possibly exceeding the LT1936’s
voltage rating. This situation is easily avoided; see the Hot
Plugging Safety section.
44. Finally, for duty cycles greater than 50% (V /V
OUT IN
> 0.5), there is a minimum inductance required to avoid
subharmonic oscillations. Choosing L greater than 1.6
For space sensitive applications, a 2.2μF ceramic capaci-
tor can be used for local bypassing of the LT1936 input.
However, the lower input capacitance will result in in-
creased input current ripple and input voltage ripple, and
may couple noise into other circuitry. Also, the increased
voltage ripple will raise the minimum operating voltage
of the LT1936 to ~3.7V.
(V
+ V ) μH prevents subharmonic oscillations at all
D
OUT
duty cycles.
Catch Diode
A 1A Schottky diode is recommended for the catch diode,
D1. The diode must have a reverse voltage rating equal
to or greater than the maximum input voltage. The ON
Semiconductor MBRM140 is a good choice. It is rated
for 1A DC at a case temperature of 110°C and 1.5A at a
casetemperatureof95°C.DiodeIncorporated’sDFLS140L
is rated for 1.1A average current; the DFLS240L is rated
for 2A average current. The average diode current in an
Output Capacitor
The output capacitor has two essential functions. Along
with the inductor, it filters the square wave generated
by the LT1936 to produce the DC output. In this role it
determines the output ripple, and low impedance at the
switching frequency is important. The second function
is to store energy in order to satisfy transient loads and
stabilize the LT1936’s control loop.
LT1936 application is approximately I
(1 – DC).
OUT
Input Capacitor
Bypass the input of the LT1936 circuit with a 4.7μF or
higher value ceramic capacitor of X7R or X5R type. Y5V
types have poor performance over temperature and ap-
plied voltage, and should not be used. A 4.7μF ceramic
is adequate to bypass the LT1936 and will easily handle
the ripple current. However, if the input power source has
high impedance, or there is significant inductance due to
long wires or cables, additional bulk capacitance may be
necessary. This can be provided with a low performance
electrolytic capacitor.
Ceramic capacitors have very low equivalent series re-
sistance (ESR) and provide the best ripple performance.
A good value is:
150
VOUT
COUT
=
where C
is in μF. Use X5R or X7R types. This choice
OUT
willprovidelowoutputrippleandgoodtransientresponse.
Transient performance can be improved with a high value
capacitor if the compensation network is also adjusted to
maintain the loop bandwidth.
Step-down regulators draw current from the input sup-
ply in pulses with very fast rise and fall times. The input
capacitor is required to reduce the resulting voltage
ripple at the LT1936 and to force this very high frequency
switching current into a tight local loop, minimizing EMI.
A 4.7μF capacitor is capable of this task, but only if it is
placed close to the LT1936 and the catch diode; see the
PCB Layout section. A second precaution regarding the
ceramic input capacitor concerns the maximum input
voltage rating of the LT1936. A ceramic input capacitor
Alowervalueofoutputcapacitorcanbeused,buttransient
performance will suffer. With an external compensation
network,theloopgaincanbeloweredtocompensateforthe
lowercapacitorvalue. Whenusingtheinternalcompensa-
tion network, the lowest value for stable operation is:
66
VOUT
COUT
>
1936fd
9
LT1936
APPLICATIONS INFORMATION
Table 2. Capacitor Vendors
VENDOR
PHONE
URL
PART SERIES
COMMENTS
Panasonic
(714) 373-7366
www.panasonic.com
Ceramic,
Polymer,
Tantalum
EEF Series
Kemet
Sanyo
(864) 963-6300
(408) 749-9714
www.kemet.com
Ceramic,
Tantalum
T494, T495
POSCAP
www.sanyovideo.com
Ceramic,
Polymer,
Tantalum
Murata
AVX
(404) 436-1300
(864) 963-6300
www.murata.com
www.avxcorp.com
Ceramic
Ceramic,
Tantalum
TPS Series
Taiyo Yuden
www.taiyo-yuden.com
Ceramic
This is the minimum output capacitance required, not
the nominal capacitor value. For example, a 3.3V output
requires 20μF of output capacitance. If a small 22μF, 6.3V
ceramic capacitor is used, the circuit may be unstable be-
cause the effective capacitance is lower than the nominal
capacitance when biased at 3.3V. Look carefully at the
capacitor’s data sheet to find out what the actual capaci-
tance is under operating conditions (applied voltage and
temperature). A physically larger capacitor, or one with a
higher voltage rating, may be required.
This capacitor (C ) is not part of the loop compensation
F
but is used to filter noise at the switching frequency, and
is required only if a phase-lead capacitor is used or if the
output capacitor has high ESR. An alternative to using
external compensation components is to use the internal
RC network by tying the COMP pin to the V pin. This re-
C
ducescomponentcountbutdoesnotprovidetheoptimum
transientresponsewhentheoutputcapacitorvalueishigh,
andthecircuitmaynotbestablewhentheoutputcapacitor
value is low. If the internal compensation network is not
used, tie COMP to ground or leave it floating.
High performance electrolytic capacitors can be used for
theoutputcapacitor. LowESRisimportant, sochooseone
that is intended for use in switching regulators. The ESR
should be specified by the supplier, and should be 0.05Ω
or less. Such a capacitor will be larger than a ceramic
capacitor and will have a larger capacitance, because the
capacitor must be large to achieve low ESR. Table 2 lists
several capacitor vendors.
Loop compensation determines the stability and transient
performance.Designingthecompensationnetworkisabit
LT1936
CURRENT MODE
POWER STAGE
SW
OUTPUT
ERROR
AMPLIFIER
g
= 2mho
m
C
PL
R1
FB
–
Frequency Compensation
g
=
m
250μmho
ESR
+
1.2V
The LT1936 uses current mode control to regulate the
output.Thissimplifiesloopcompensation.Inparticular,the
LT1936 does not require the ESR of the output capacitor
for stability, so you are free to use ceramic capacitors to
achieve low output ripple and small circuit size.
C1
+
600k
C1
150pF
50k
POLYMER
OR
TANTALUM
CERAMIC
V
COMP
GND
C
R
C
F
R2
C
Frequency compensation is provided by the components
C
C
tied to the V pin, as shown in Figure 1. Generally a capaci-
C
tor (C ) and a resistor (R ) in series to ground are used.
C
C
1936 F01
In addition, there may be lower value capacitor in parallel.
Figure 1. Model for Loop Response
1936fd
10
LT1936
APPLICATIONS INFORMATION
complicatedandthebestvaluesdependontheapplication
and in particular the type of output capacitor. A practical
approach is to start with one of the circuits in this data
sheet that is similar to your application and tune the com-
pensation network to optimize the performance. Stability
should then be checked across all operating conditions,
includingloadcurrent, inputvoltageandtemperature. The
LT1375datasheetcontainsamorethoroughdiscussionof
loop compensation and describes how to test the stability
using a transient load.
current proportional to the voltage at the V pin. Note that
C
the output capacitor integrates this current, and that the
capacitor on the V pin (C ) integrates the error amplifier
C
C
output current, resulting in two poles in the loop. In most
cases a zero is required and comes from either the output
capacitor ESR or from a resistor R in series with C .
C
C
This simple model works well as long as the value of the
inductor is not too high and the loop crossover frequency
is much lower than the switching frequency. A phase lead
capacitor (C ) across the feedback divider may improve
PL
the transient response.
Figure1showsanequivalentcircuitfortheLT1936control
loop. The error amplifier is a transconductance amplifier
withfiniteoutputimpedance.Thepowersection,consisting
of the modulator, power switch and inductor, is modeled
as a transconductance amplifier generating an output
Figure 2 compares the transient response across several
output capacitor choices and compensation schemes.
In each case the load current is stepped from 200mA to
800mA and back to 200mA.
C
= 22μF
OUT
(AVX 1210ZD226MAT)
V
OUT
(2a)
(2b)
(2c)
COMP
100mV/DIV
V
C
C
= 22μF ×2
OUT
V
OUT
COMP
100mV/DIV
V
C
C
= 150μF
OUT
(4TPC150M)
V
OUT
100mV/DIV
COMP
V
C
C
= 150μF
OUT
(4TPC150M)
V
OUT
100mV/DIV
(2d)
COMP
V
C
800mA
OUT
I
220k
100pF
500mA/DIV
200mA
1936 F02
50μs/DIV
Figure 2. Transient Load Response of the LT1936 with Different Output
Capacitors as the Load Current is Stepped from 200mA to 800mA. VOUT = 3.3V
1936fd
11
LT1936
APPLICATIONS INFORMATION
BOOST Pin Considerations
circuitbyusinga1μFboostcapacitorandagood, lowdrop
Schottkydiode(suchastheONSemiMBR0540). Because
the required boost voltage increases at low temperatures,
the circuit will supply only 1A of output current when the
ambient temperature is –45°C, increasing to 1.2A at 0°C.
Also, the minimum input voltage to start the boost circuit
is higher at low temperature. See the Typical Applications
section for a 2.5V schematic and performance curves.
Capacitor C3 and diode D2 are used to generate a boost
voltage that is higher than the input voltage. In most cases
a 0.22μF capacitor and fast switching diode (such as the
1N4148 or 1N914) will work well. Figure 3 shows two
ways to arrange the boost circuit. The BOOST pin must
be at least 2.3V above the SW pin for best efficiency. For
outputs of 3V and above, the standard circuit (Figure 3a)
is best. For outputs between 2.8V and 3V, use a 0.47μF
capacitor and a Schottky diode. For lower output voltages
the boost diode can be tied to the input (Figure 3b), or to
anothersupplygreaterthan2.8V. ThecircuitinFigure3ais
moreefficientbecausetheBOOSTpincurrentcomesfrom
a lower voltage. You must also be sure that the maximum
voltage rating of the BOOST pin is not exceeded.
The minimum operating voltage of an LT1936 application
is limited by the undervoltage lockout (~3.45V) and by
the maximum duty cycle as outlined above. For proper
start-up, the minimum input voltage is also limited by the
boost circuit. If the input voltage is ramped slowly, or the
LT1936 is turned on with its SHDN pin when the output
is already in regulation, then the boost capacitor may not
be fully charged. Because the boost capacitor is charged
with the energy stored in the inductor, the circuit will rely
on some minimum load current to get the boost circuit
running properly. This minimum load will depend on input
and output voltages, and on the arrangement of the boost
circuit. The minimum load generally goes to zero once the
circuit has started. Figure 4 shows a plot of minimum load
to start and to run as a function of input voltage. In many
cases the discharged output capacitor will present a load
to the switcher, which will allow it to start. The plots show
A 2.5V output presents a special case. This is a popular
output voltage, and the advantage of connecting the
boost circuit to the output is that the circuit will accept a
36V maximum input voltage rather than 20V (due to the
BOOST pin rating). However, 2.5V is marginally adequate
to support the boosted drive stage at low ambient tem-
peratures. Therefore, special care and some restrictions
onoperationarenecessarywhenpoweringtheBOOSTpin
from a 2.5V output. Minimize the voltage loss in the boost
theworst-casesituationwhereV isrampingveryslowly.
IN
D2
For lower start-up voltage, the boost diode can be tied to
V ; however, this restricts the input range to one-half of
IN
C3
BOOST
LT1936
the absolute maximum rating of the BOOST pin.
V
V
OUT
V
SW
IN
IN
At light loads, the inductor current becomes discontinu-
ous and the effective duty cycle can be very high. This
reduces the minimum input voltage to approximately
GND
V
– V ≅ V
SW OUT
BOOST
300mV above V . At higher load currents, the inductor
OUT
MAX V
≅ V + V
IN OUT
BOOST
current is continuous and the duty cycle is limited by the
maximum duty cycle of the LT1936, requiring a higher
input voltage to maintain regulation.
(3a)
D2
C3
BOOST
LT1936
Soft-Start
V
V
OUT
V
SW
IN
IN
TheSHDNpincanbeusedtosoft-starttheLT1936,reducing
themaximuminputcurrentduringstart-up. TheSHDNpin
is driven through an external RC filter to create a voltage
ramp at this pin. Figure 5 shows the start-up waveforms
with and without the soft-start circuit. By choosing a large
GND
1933 F03
V
– V ≅ V
BOOST
SW IN
≅ 2V
IN
MAX V
BOOST
(3b)
Figure 3. Two Circuits for Generating the Boost Voltage
1936fd
12
LT1936
APPLICATIONS INFORMATION
Minimum Input Voltage VOUT = 5V
Minimum Input Voltage VOUT = 3.3V
8
7
6
5
4
6.0
V
T
= 5V
V
T
= 3.3V
OUT
A
OUT
A
= 25°C
= 25°C
L = 15μH
L = 10μH
5.5
TO START
TO START
5.0
4.5
4.0
3.5
3.0
TO RUN
TO RUN
0
10
100
1000
1
10
100
1000
LOAD CURRENT (mA)
LOAD CURRENT (mA)
1936 F04a
1936 F04b
Figure 4. The Minimum Input Voltage Depends on Output Voltage, Load Current and Boost Circuit
RUN
5V/DIV
I
RUN
SHDN
GND
IN
500mA/DIV
V
OUT
5V/DIV
1936 F05a
50μs/DIV
RUN
15k
RUN
5V/DIV
I
SHDN
GND
IN
500mA/DIV
0.22μF
V
OUT
5V/DIV
1936 F05b
0.5ms/DIV
Figure 5. To Soft-Start the LT1936, Add a Resistor and Capacitor to the SHDN Pin.
VIN = 12V, VOUT = 3.3V, COUT = 2 × 22μF, RLOAD = 3.3Ω
RCtimeconstant,thepeakstart-upcurrentcanbereduced
to the current that is required to regulate the output, with
no overshoot. Choose the value of the resistor so that it
can supply 60μA when the SHDN pin reaches 2.3V.
where the output will be held high when the input to the
LT1936 is absent. This may occur in battery charging ap-
plications or in battery backup systems where a battery
or some other supply is diode OR-ed with the LT1936’s
output. If the V pin is allowed to float and the SHDN pin
IN
Shorted and Reversed Input Protection
is held high (either by a logic signal or because it is tied
to V ), then the LT1936’s internal circuitry will pull its
IN
If the inductor is chosen so that it won’t saturate exces-
sively, an LT1936 buck regulator will tolerate a shorted
output. There is another situation to consider in systems
quiescent current through its SW pin. This is fine if your
system can tolerate a few mA in this state. If you ground
1936fd
13
LT1936
APPLICATIONS INFORMATION
the SHDN pin, the SW pin current will drop to essentially
IN
C2
GND
MINIMIZE
LT1936
zero. However, if the V pin is grounded while the output
IN
C2, D1 LOOP
is held high, then parasitic diodes inside the LT1936 can
R4
pull large currents from the output through the SW pin
D2
C3
and the V pin. Figure 6 shows a circuit that will run only
IN
whentheinputvoltageispresentandthatprotectsagainst
a shorted or reversed input.
R2
R1
D1
D4
MBRS140
L1
C1
V
V
BOOST
LT1936
SHDN
IN
IN
GND
V
SW
OUT
OUT
VIAS
V
C
1936 F07
COMP GND FB
Figure 7. A Good PCB Layout Ensures Low EMI Operation
BACKUP
High Temperature Considerations
1936 F06
The die temperature of the LT1936 must be lower than the
maximum rating of 125°C (150°C for the H grade). This is
generally not a concern unless the ambient temperature
is above 85°C. For higher temperatures, care should be
taken in the layout of the circuit to ensure good heat sink-
ing of the LT1936. The maximum load current should be
derated as the ambient temperature approaches 125°C
(150°C for the H grade).
Figure 6. Diode D4 Prevents a Shorted Input from Discharging
a Backup Battery Tied to the Output; It Also Protects the Circuit
from a Reversed Input. The LT1936 Runs Only When the Input
is Present
PCB Layout
For proper operation and minimum EMI, care must be
taken during printed circuit board layout. Figure 7 shows
the recommended component placement with trace,
ground plane and via locations. Note that large, switched
ThedietemperatureiscalculatedbymultiplyingtheLT1936
power dissipation by the thermal resistance from junction
to ambient. Power dissipation within the LT1936 can be
estimated by calculating the total power loss from an
efficiency measurement and subtracting the catch diode
loss. The resulting temperature rise at full load is nearly
independentofinputvoltage. Thermalresistancedepends
on the layout of the circuit board, but values from 40°C/W
to 60°C/W are typical.
currents flow in the LT1936’s V and SW pins, the catch
IN
diode (D1) and the input capacitor (C2). The loop formed
bythesecomponentsshouldbeassmallaspossible.These
components,alongwiththeinductorandoutputcapacitor,
should be placed on the same side of the circuit board,
and their connections should be made on that layer. Place
a local, unbroken ground plane below these components.
The SW and BOOST nodes should be as small as possible.
Die temperature rise was measured on a 4-layer, 5cm ×
6.5cm circuit board in still air at a load current of 1.4A.
For 12V input to 3.3V output the die temperature elevation
above ambient was 26°C; for 24V in to 3.3V out the rise
was 31°C; for 12V in to 5V the rise was 31°C and for 24V
in to 5V the rise was 34°C.
Finally, keep the FB and V nodes small so that the ground
C
traces will shield them from the SW and BOOST nodes.
The Exposed Pad on the bottom of the package must be
soldered to ground so that the pad acts as a heat sink. To
keep thermal resistance low, extend the ground plane as
much as possible, and add thermal vias under and near
the LT1936 to additional ground planes within the circuit
board and on the bottom side.
1936fd
14
LT1936
APPLICATIONS INFORMATION
Hot Plugging Safely
input voltage, possibly exceeding the LT1936’s rating and
damaging the part. If the input supply is poorly controlled
or the user will be plugging the LT1936 into an energized
supply, the input network should be designed to prevent
this overshoot.
The small size, robustness and low impedance of ceramic
capacitors make them an attractive option for the input
bypasscapacitorofLT1936circuits.However,thesecapaci-
tors can cause problems if the LT1936 is plugged into a
live supply (see Linear Technology Application Note 88 for
a complete discussion). The low loss ceramic capacitor
combined with stray inductance in series with the power
sourceformsanunderdampedtankcircuit,andthevoltage
Figure 8 shows the waveforms that result when an LT1936
circuit is connected to a 24V supply through six feet of
24-gauge twisted pair. The first plot is the response with
a 4.7μF ceramic capacitor at the input. The input voltage
rings as high as 50V and the input current peaks at 26A.
at the V pin of the LT1936 can ring to twice the nominal
IN
CLOSING SWITCH
DANGER
SIMULATES HOT PLUG
V
IN
I
IN
20V/DIV
V
IN
RINGING V MAY EXCEED
IN
ABSOLUTE MAXIMUM
RATING OF THE LT1936
LT1936
4.7μF
+
I
IN
LOW
STRAY
10A/DIV
IMPEDANCE
ENERGIZED
24V SUPPLY
INDUCTANCE
DUE TO 6 FEET
(2 METERS) OF
TWISTED PAIR
20μs/DIV
(8a)
V
IN
20V/DIV
LT1936
4.7μF
+
+
22μF
35V
AI.EI.
I
IN
10A/DIV
(8b)
20μs/DIV
0.7Ω
V
IN
20V/DIV
LT1936
4.7μF
+
0.1μF
I
IN
10A/DIV
1936 F08
20μs/DIV
(8c)
Figure 8. A Well Chosen Input Network Prevents Input Voltage Overshoot and
Ensures Reliable Operation When the LT1936 is Connected to a Live Supply
1936fd
15
LT1936
APPLICATIONS INFORMATION
One method of damping the tank circuit is to add another
capacitor with a series resistor to the circuit. In Figure 8b
an aluminum electrolytic capacitor has been added. This
capacitor’s high equivalent series resistance damps the
circuit and eliminates the voltage overshoot. The extra
capacitor improves low frequency ripple filtering and
can slightly improve the efficiency of the circuit, though
it is likely to be the largest component in the circuit. An
alternative solution is shown in Figure 8c. A 0.7Ω resistor
is added in series with the input to eliminate the voltage
overshoot (it also reduces the peak input current). A 0.1μF
capacitor improves high frequency filtering. This solution
issmallerandlessexpensivethantheelectrolyticcapacitor.
For high input voltages its impact on efficiency is minor,
reducing efficiency by one percent for a 5V output at full
load operating from 24V.
Other Linear Technology Publications
Application Notes 19, 35 and 44 contain more detailed
descriptions and design information for buck regulators
and other switching regulators. The LT1376 data sheet
has a more extensive discussion of output ripple, loop
compensation and stability testing. Design Note 100
shows how to generate a bipolar output supply using a
buck regulator.
Outputs Greater Than 6V
For outputs greater than 6V, add a resistor of 1k to 2.5k
across the inductor to damp the discontinuous ringing
of the SW node, preventing unintended SW current. The
12V Step-Down Converter circuit in the Typical Applica-
tions section shows the location of this resistor. Also note
that for outputs above 6V, the input voltage range will be
limited by the maximum rating of the BOOST pin. The 12V
circuit shows how to overcome this limitation using an
additional Zener diode.
TYPICAL APPLICATIONS
3.3V Step-Down Converter
D2
V
IN
4.5V TO 36V
C3
0.22μF
L1
V
BOOST
SW
IN
10μH
V
3.3V
1.2A
OUT
SHDN
ON OFF
C1
4.7μF
D1
R1
17.4k
LT1936
COMP
FB
GND
V
C
R2
10k
C2
47μF
1936 TA03
1936fd
16
LT1936
TYPICAL APPLICATIONS
5V Step-Down Converter
D2
V
IN
6.3V TO 36V
C3
0.22μF
L1
V
BOOST
SW
IN
15μH
V
OUT
SHDN
5V
ON OFF
1.2A
C1
4.7μF
D1
R1
31.6k
LT1936
COMP
FB
GND
V
C
R2
10k
C2
22μF
1936 TA04
1.8V Step-Down Converter
Efficiency, 1.8V Output
90
2.0
1.5
1.0
0.5
D2
V
A
= 1.8V
OUT
V
IN
T
= 25°C
3.6V TO 20V
C3
L1
V
BOOST
SW
IN
0.22μF
80
70
60
V
= 5V
IN
4.7μH
V
1.8V
1.3A
OUT
SHDN
ON OFF
C1
4.7μF
D1
V
= 12V
IN
R1
10k
LT1936
COMP
FB
GND
C2
47μF
×2
V
C
R2
20k
POWER LOSS
1
D1: DFLS140L
D2: 1N4148
L1: TOKO D63CB
1936 TA05a
50
0
0
0.5
1.5
LOAD CURRENT (A)
1936 TA05b
1.2V Step-Down Converter
Efficiency, 1.2V Output
2.0
1.5
1.0
0.5
0
D2
80
75
70
65
60
55
50
V
= 1.2V
OUT
V
IN
T
= 25°C
A
3.6V TO 20V
C3
L1
V
BOOST
SW
IN
0.22μF
V
= 5V
3.3μH
IN
V
1.2V
1.3A
OUT
SHDN
ON OFF
C1
D1
LT1936
4.7μF
V
= 12V
IN
COMP
FB
GND
C2
47μF
×2
V
C
100k
POWER LOSS
D1: DFLS140L
D2: 1N4148
1936 TA06a
L1: TOKO D63CB
0
0.5
1
1.5
LOAD CURRENT (A)
1936 TA06b
1936fd
17
LT1936
TYPICAL APPLICATIONS
2.5V Step-Down Converter
D2
V
IN
3.6V TO 36V
C3
1μF
L1
V
BOOST
SW
IN
V
OUT
6.2μH
2.5V
1.2A
SHDN
ON OFF
C1
4.7μF
T
> 0°C
D1
A
R1
11k
LT1936
COMP
FB
GND
V
C
R2
10k
C2
47μF
D1: DFLS140L
D2: MBRO540
L1: TOKO D63CB
1936 TA07a
Efficiency, 2.5V Output
Minimum Input Voltage
5.5
100
90
V
= 2.5V
V
A
= 2.5V
OUT
OUT
T
= 25°C
5.0
4.5
4.0
3.5
3.0
TO START
T
A
= –45°C
V
= 5V
IN
80
V
= 12V
IN
TO START
= 25°C
T
A
TO RUN
= –45°C
T
A
70
TO RUN
= 25°C
T
A
60
100
1000
1
0
0.5
1.0
1.5
10
LOAD CURRENT (A)
LOAD CURRENT (mA)
1936 TA07b
1936 TA07c
12V Step-Down Converter
D3
D2 6.8V
V
IN
14.5V TO 36V
C3
0.22μF
L1
22μH
V
BOOST
SW
IN
SHDN
ON OFF
V
1.8k
OUT
C1
2.2μF
D1
LT1936
12V
1.2A
COMP
FB
GND
R1
182k
V
C
R2
20k
C2
22μF
D1: MBRM140
D2: 1N4148
D3: CMDZ5235B
1936 TA08
1936fd
18
LT1936
PACKAGE DESCRIPTION
MS8E Package
8-Lead Plastic MSOP, Exposed Die Pad
(Reference LTC DWG # 05-08-1662 Rev E)
BOTTOM VIEW OF
EXPOSED PAD OPTION
2.06 ± 0.102
(.081 ± .004)
1
0.29
REF
1.83 ± 0.102
(.072 ± .004)
0.889 ± 0.127
(.035 ± .005)
2.794 ± 0.102
(.110 ± .004)
0.05 REF
DETAIL “B”
5.23
(.206)
MIN
3.20 – 3.45
2.083 ± 0.102
(.082 ± .004)
CORNER TAIL IS PART OF
THE LEADFRAME FEATURE.
FOR REFERENCE ONLY
(.126 – .136)
DETAIL “B”
8
NO MEASUREMENT PURPOSE
3.00 ± 0.102
0.52
(.0205)
REF
(.118 ± .004)
(NOTE 3)
0.65
(.0256)
BSC
0.42 ± 0.038
(.0165 ± .0015)
TYP
8
7 6 5
RECOMMENDED SOLDER PAD LAYOUT
3.00 ± 0.102
(.118 ± .004)
(NOTE 4)
4.90 ± 0.152
(.193 ± .006)
DETAIL “A”
0° – 6° TYP
0.254
(.010)
GAUGE PLANE
1
2
3
4
0.53 ± 0.152
(.021 ± .006)
1.10
(.043)
MAX
0.86
(.034)
REF
DETAIL “A”
0.18
(.007)
SEATING
PLANE
0.22 – 0.38
(.009 – .015)
TYP
0.1016 ± 0.0508
(.004 ± .002)
0.65
(.0256)
BSC
MSOP (MS8E) 0908 REV E
NOTE:
1. DIMENSIONS IN MILLIMETER/(INCH)
2. DRAWING NOT TO SCALE
3. DIMENSION DOES NOT INCLUDE MOLD FLASH, PROTRUSIONS OR GATE BURRS.
MOLD FLASH, PROTRUSIONS OR GATE BURRS SHALL NOT EXCEED 0.152mm (.006") PER SIDE
4. DIMENSION DOES NOT INCLUDE INTERLEAD FLASH OR PROTRUSIONS.
INTERLEAD FLASH OR PROTRUSIONS SHALL NOT EXCEED 0.152mm (.006") PER SIDE
5. LEAD COPLANARITY (BOTTOM OF LEADS AFTER FORMING) SHALL BE 0.102mm (.004") MAX
1936fd
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 representa-
tion that the interconnection of its circuits as described herein will not infringe on existing patent rights.
19
LT1936
TYPICAL APPLICATION
2.5V Step-Down Converter
Minimum Input Voltage
5.5
5.0
4.5
4.0
3.5
3.0
D2
V
= 2.5V
OUT
V
IN
3.6V TO 20V
C3
L1
CONNECTING THE BOOST CIRCUIT TO THE
INPUT LOWERS THE MINIMUM INPUT
VOLTAGE TO RUN AND TO START TO LESS
THAN 3.7V AT ALL LOADS
V
BOOST
SW
IN
0.22μF
8.2μH
V
2.5V
1.3A
OUT
SHDN
ON OFF
C1
D1
R1
11k
LT1936
4.7μF
COMP
FB
GND
V
C
R2
10k
C2
47μF
D1: DFLS140L
D2: 1N4148
1936 TA09a
L1: TOKO D63CB
100
10
LOAD CURRENT (mA)
1000
1
1936 TA09b
RELATED PARTS
PART NUMBER
DESCRIPTION
COMMENTS
LT1676
60V, 440mA (I ), 100kHz, High Efficiency Step-Down
V : 7.4V to 60V, V
= 1.24V, I = 3.2mA, I = 2.5μA,
OUT(MIN) Q SD
OUT
IN
DC/DC Converter
SO-8 Package
LT1765
25V, 2.75A (I ), 1.25MHz, High Efficiency Step-Down
V : 3V to 25V, V
= 1.20V, I = 1mA, I = 15μA,
OUT
IN
OUT(MIN) Q SD
DC/DC Converter
SO-8 and 16-Lead TSSOPE Packages
LT1766
60V, 1.2A (I ), 200kHz, High Efficiency Step-Down
V : 5.5V to 60V, V = 1.20V, I = 2.5mA, I = 25μA,
OUT
IN
OUT(MIN)
Q
SD
DC/DC Converter
16-Lead TSSOP/TSSOPE Packages
LT1767
25V, 1.2A (I ), 1.25MHz, High Efficiency Step-Down
V : 3V to 25V, V = 1.20V, I = 1mA, I = 6μA,
OUT
IN
OUT(MIN)
Q
SD
DC/DC Converter
MS8/MS8E Packages
LT1776
40V, 550mA (I ), 200kHz, High Efficiency Step-Down
V : 7.4V to 40V, V
= 1.24V, I = 3.2mA, I = 30μA,
Q SD
OUT
IN
OUT(MIN)
DC/DC Converter
N8/SO-8 Packages
LT1933
600mA, 500kHz, Step-Down Switching Regulator in SOT-23 V : 3.6V to 36V, V
= 1.25V, I = 1.6mA, I < 1μA,
Q SD
IN
OUT(MIN)
ThinSOT™ Package
LT1940
25V, Dual 1.4A (I ), 1.1MHz, High Efficiency Step-Down
V : 3V to 25V, V
= 1.2V, I = 3.8mA, I < 1μA,
OUT(MIN) Q SD
OUT
IN
DC/DC Converter
16-Lead TSSOPE Package
V : 5.5V to 60V, V = 1.20V, I = 2.5mA, I = 25μA,
OUT(MIN) Q SD
LT1956
60V, 1.2A (I ), 500kHz, High Efficiency Step-Down
OUT
IN
DC/DC Converter
16-Lead TSSOP/TSSOPE Packages
LT1976
60V, 1.2A (I ), 200kHz, High Efficiency Step-Down
V : 3.3V to 60V, V = 1.20V, I = 100μA, I < 1μA,
OUT
IN
OUT(MIN)
Q
SD
DC/DC Converter with Burst Mode® Operation
80V, 50mA, Low Noise Linear Regulator
16-Lead TSSOPE Package
LT3010
V : 1.5V to 80V, V = 1.28V, I = 30μA, I < 1μA,
OUT(MIN) Q SD
IN
MS8E Package
LTC®3407
LTC3412
LTC3414
LT3430/LT3431
Dual 600mA (I ), 1.5MHz, Synchronous Step-Down
V : 2.5V to 5.5V, V
= 0.6V, I = 40μA, I < 1μA,
OUT
IN
OUT(MIN) Q SD
DC/DC Converter
10-Lead MSE Package
2.5A (I ), 4MHz, Synchronous Step-Down DC/DC
V : 2.5V to 5.5V, V
= 0.8V, I = 60μA, I < 1μA,
Q SD
OUT
IN
OUT(MIN)
Converter
16-Lead TSSOPE Package
4A (I ), 4MHz, Synchronous Step-Down DC/DC Converter V : 2.3V to 5.5V, V
= 0.8V, I = 64μA, I < 1μA,
Q SD
OUT
IN
OUT(MIN)
20-Lead TSSOPE Package
60V, 2.75A (I ), 200kHz/500kHz, High Efficiency
V : 5.5V to 60V, V
= 1.20V, I = 2.5mA, I = 30μA,
Q SD
OUT
IN
OUT(MIN)
Step-Down DC/DC Converters
16-Lead TSSOPE Package
Burst Mode is a registered trademark of Linear Technology Corporation. ThinSOT is a trademark of Linear Technology Corporation.
1936fd
LT 1108 REV D • PRINTED IN USA
LinearTechnology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
20
●
●
© LINEAR TECHNOLOGY CORPORATION 2006
(408) 432-1900 FAX: (408) 434-0507 www.linear.com
相关型号：
SI9130DB
5- and 3.3-V Step-Down Synchronous ConvertersWarning: Undefined variable $rtag in /www/wwwroot/website_ic37/www.icpdf.com/pdf/pdf/index.php on line 217
-
VISHAY
SI9135LG-T1
SMBus Multi-Output Power-Supply ControllerWarning: Undefined variable $rtag in /www/wwwroot/website_ic37/www.icpdf.com/pdf/pdf/index.php on line 217
-
VISHAY
SI9135LG-T1-E3
SMBus Multi-Output Power-Supply ControllerWarning: Undefined variable $rtag in /www/wwwroot/website_ic37/www.icpdf.com/pdf/pdf/index.php on line 217
-
VISHAY
SI9135_11
SMBus Multi-Output Power-Supply ControllerWarning: Undefined variable $rtag in /www/wwwroot/website_ic37/www.icpdf.com/pdf/pdf/index.php on line 217
-
VISHAY
SI9136_11
Multi-Output Power-Supply ControllerWarning: Undefined variable $rtag in /www/wwwroot/website_ic37/www.icpdf.com/pdf/pdf/index.php on line 217
-
VISHAY
SI9130CG-T1-E3
Pin-Programmable Dual Controller - Portable PCsWarning: Undefined variable $rtag in /www/wwwroot/website_ic37/www.icpdf.com/pdf/pdf/index.php on line 217
-
VISHAY
SI9130LG-T1-E3
Pin-Programmable Dual Controller - Portable PCsWarning: Undefined variable $rtag in /www/wwwroot/website_ic37/www.icpdf.com/pdf/pdf/index.php on line 217
-
VISHAY
SI9130_11
Pin-Programmable Dual Controller - Portable PCsWarning: Undefined variable $rtag in /www/wwwroot/website_ic37/www.icpdf.com/pdf/pdf/index.php on line 217
-
VISHAY
SI9137
Multi-Output, Sequence Selectable Power-Supply Controller for Mobile ApplicationsWarning: Undefined variable $rtag in /www/wwwroot/website_ic37/www.icpdf.com/pdf/pdf/index.php on line 217
-
VISHAY
SI9137DB
Multi-Output, Sequence Selectable Power-Supply Controller for Mobile ApplicationsWarning: Undefined variable $rtag in /www/wwwroot/website_ic37/www.icpdf.com/pdf/pdf/index.php on line 217
-
VISHAY
SI9137LG
Multi-Output, Sequence Selectable Power-Supply Controller for Mobile ApplicationsWarning: Undefined variable $rtag in /www/wwwroot/website_ic37/www.icpdf.com/pdf/pdf/index.php on line 217
-
VISHAY
SI9122E
500-kHz Half-Bridge DC/DC Controller with Integrated Secondary Synchronous Rectification DriversWarning: Undefined variable $rtag in /www/wwwroot/website_ic37/www.icpdf.com/pdf/pdf/index.php on line 217
-
VISHAY
©2020 ICPDF网 联系我们和版权申明