LTC3637_15 [Linear]
76V, 1A Step-Down Regulator;
| 型号： | LTC3637_15 |
| 厂家： | 
Linear |
| 描述： | 76V, 1A Step-Down Regulator |
| 文件： | 总26页 (文件大小：357K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
LTC3637
76V, 1A Step-Down
Regulator
FEATURES
DESCRIPTION
The LTC®3637 is a high efficiency step-down DC/DC
regulator with an internal high side power switch that
draws only 12μA DC supply current while maintaining a
regulated output voltage at no load.
n
Wide Operating Input Voltage Range: 4V to 76V
n
Internal 350mΩ Power MOSFET
n
No Compensation Required
Adjustable 100mA to 1A Maximum Output Current
Low Dropout Operation: 100% Duty Cycle
Low Quiescent Current: 12µA
Wide Output Range: 0.8V to V
n
n
TheLTC3637cansupplyupto1Aloadcurrentandfeatures
a programmable peak current limit that provides a simple
method for optimizing efficiency and for reducing output
ripple and component size. The LTC3637’s combination
of Burst Mode® operation, integrated power switch, low
quiescent current, and programmable peak current limit
provideshighefficiencyoverabroadrangeofloadcurrents.
n
n
IN
n
n
n
n
n
n
n
0.8V 1% Feedback Voltage Reference
Precise RUN Pin Threshold
Internal and External Soft-Start
Programmable 1.8V, 3.3V, 5V or Adjustable Output
Few External Components Required
Programmable Input Overvoltage Lockout
Low Profile (0.75mm) 3mm × 5mm DFN and
Thermally-Enhanced MSE16 Packages
With its wide input range of 4V to 76V, and programmable
overvoltage lockout, the LTC3637 is a robust regulator
suitedforregulatingfromawidevarietyofpowersources.
Additionally, theLTC3637 includesaprecise runthreshold
and soft-start feature to guarantee that the power system
start-up is well-controlled in any environment.
APPLICATIONS
n
Industrial Control Supplies
The LTC3637 is available in the thermally-enhanced
3mm × 5mm DFN and the MSE16 packages.
L, LT, LTC, LTM, Burst Mode, Linear Technology and the Linear logo are registered trademarks
of Linear Technology Corporation. All other trademarks are the property of their respective
owners.
n
Medical Devices
n
Distributed Power Systems
n
Portable Instruments
n
Battery-Operated Devices
n
Automotive
Avionics
n
TYPICAL APPLICATION
Efficiency and Power Loss vs Load Current
100
12.5V to 76V Input to 12V Output, 1A Regulator
V
= 12V
OUT
EFFICIENCY
90
80
70
60
50
40
30
20
10
0
10µH
V
12V
1A
OUT
V
IN
V
SW
LTC3637
IN
12.5V TO 76V
47µF
2.2µF
200k
1000
100
10
RUN
V
FB
SS
PRG1
PRG2
35.7k
POWER LOSS
FBO
V
V
OVLO
I
SET
V
V
V
= 24V
= 48V
= 76V
IN
IN
IN
GND
3637 TA01a
0
0.1
1.0
10
100
1000
LOAD CURRENT (mA)
3637 TA01b
3637fa
1
For more information www.linear.com/LTC3637
LTC3637
ABSOLUTE MAXIMUM RATINGS (Note 1)
V Supply Voltage..................................... –0.3V to 80V
Storage Temperature Range .................. –65°C to 150°C
Lead Temperature (Soldering, 10 sec)
IN
RUN Voltage............................................... –0.3V to 80V
SS, FBO, I
Voltages................................. –0.3V to 6V
MSOP ...............................................................300°C
SET
, V
V , V
, OVLO Voltages .............. –0.3V to 6V
FB PRG1 PRG2
Operating Junction Temperature Range (Notes 2, 3, 4)
LTC3637E, LTC3637I......................... –40°C to 125°C
LTC3637H.......................................... –40°C to 150°C
LTC3637MP ....................................... –55°C to 150°C
PIN CONFIGURATION
TOP VIEW
SW
NC
1
2
3
4
5
6
7
8
16 GND
15 NC
TOP VIEW
1
3
SW
16 GND
14 RUN
12 OVLO
V
14 RUN
13 NC
IN
V
IN
NC
17
GND
17
GND
5
6
7
8
FBO
PRG2
PRG1
GND
FBO
12 OVLO
V
V
11
I
SET
10 SS
V
V
11
I
SET
PRG2
9
V
FB
10 SS
PRG1
GND
MSE PACKAGE
VARIATION: MSE16 (12)
16-LEAD PLASTIC MSOP
9
V
FB
DHC PACKAGE
T
= 150°C, θ = 45°C/W, θ = 10°C/W
JA JC
JMAX
16-LEAD (5mm × 3mm) PLASTIC DFN
EXPOSED PAD (PIN 17) IS GND, MUST BE SOLDERED TO PCB
(NOTE 6)
T
= 150°C, θ = 43°C/W, θ = 5°C/W
JA JC
JMAX
EXPOSED PAD (PIN 17) IS GND, MUST BE SOLDERED TO PCB
ORDER INFORMATION
LEAD FREE FINISH
LTC3637EMSE#PBF
LTC3637IMSE#PBF
LTC3637HMSE#PBF
LTC3637MPMSE#PBF
LTC3637EDHC#PBF
LTC3637IDHC#PBF
LTC3637HDHC#PBF
LTC3637MPDHC#PBF
TAPE AND REEL
PART MARKING*
PACKAGE DESCRIPTION
TEMPERATURE RANGE
LTC3637EMSE#TRPBF
LTC3637IMSE#TRPBF
LTC3637HMSE#TRPBF
3637
3637
3637
16-Lead Plastic MSOP
–40°C to 125°C
–40°C to 125°C
–40°C to 150°C
–55°C to 150°C
–40°C to 125°C
–40°C to 125°C
–40°C to 150°C
–55°C to 150°C
16-Lead Plastic MSOP
16-Lead Plastic MSOP
LTC3637MPMSE#TRPBF 3637
16-Lead Plastic MSOP
LTC3637EDHC#TRPBF
LTC3637IDHC#TRPBF
LTC3637HDHC#TRPBF
3637
3637
3637
16-Lead (5mm × 3mm) Plastic DFN
16-Lead (5mm × 3mm) Plastic DFN
16-Lead (5mm × 3mm) Plastic DFN
16-Lead (5mm × 3mm) Plastic DFN
LTC3637MPDHC#TRPBF 3637
Consult LTC Marketing for parts specified with wider operating temperature ranges. *The temperature grade is identified by a label on the shipping container.
Consult LTC Marketing for information on non-standard lead based finish parts.
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/
3637fa
2
For more information www.linear.com/LTC3637
LTC3637
ELECTRICAL CHARACTERISTICS The l denotes the specifications which apply over the specified operating
junction temperature range, otherwise specifications are at TA = 25°C (Note 2). VIN = 12V, unless otherwise noted.
SYMBOL
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
Input Supply (V )
IN
V
V
Input Voltage Operating Range
Output Voltage Operating Range
4
76
V
V
IN
0.8
V
IN
OUT
l
l
UVLO
V
IN
Undervoltage Lockout
V
V
Rising
Falling
3.45
3.30
3.65
3.5
150
3.85
3.70
V
V
mV
IN
IN
Hysteresis
I
DC Supply Current (Note 5)
Active Mode
Q
165
12
3
350
20
10
µA
µA
µA
Sleep Mode
No Load
RUN = 0V
Shutdown Mode
RUN and OVLO Pin Threshold Voltage
Rising
1.17
1.06
1.21
1.10
110
1.25
1.14
V
V
mV
Falling
Hysteresis
RUN Pin Leakage Current
RUN = 1.3V
–10
0
10
nA
Output Supply (V
)
FB
Feedback Comparator Threshold Voltage
(Adjustable Output)
V
Rising, V
= V
PRG2
= 0V
= 0V
FB
PRG1
l
l
LTC3637E, LTC3637I
0.792
0.788
0.800
0.800
0.808
0.812
V
V
LTC3637H, LTC3637MP
l
Feedback Comparator Hysteresis
(Adjustable Output)
V
V
Falling, V
= V
PRG2
2.5
5
7
mV
FB
PRG1
Feedback Pin Current
= 1V, V
= 0V, V
= 0V
PRG2
–10
0
10
nA
FB
PRG1
l
l
Feedback Comparator Threshold Voltages
(Fixed Output)
V
V
Rising, V
Falling, V
= SS, V
= SS, V
= 0V
= 0V
4.940
4.910
5.015
4.985
5.090
5.060
V
V
FB
FB
PRG1
PRG1
PRG2
PRG2
l
l
V
V
Rising, V
Falling, V
= 0V, V
= 0V, V
= SS
= SS
3.250
3.230
3.310
3.290
3.370
3.350
V
V
FB
FB
PRG1
PRG1
PRG2
PRG2
l
l
V
V
Rising, V
Falling, V
= V
= V
= SS
= SS
1.775
1.765
1.805
1.795
1.835
1.825
V
V
FB
FB
PRG1
PRG1
PRG2
PRG2
Feedback Voltage Line Regulation
Peak Current Comparator Threshold
V
= 4V to 76V
0.001
%/V
IN
Operation
l
l
l
I
Floating
2
0.9
0.17
2.4
1.2
0.24
2.8
1.5
0.31
A
A
A
SET
100k Resistor from I to GND
SET
I
Shorted to GND
SET
Power Switch On-Resistance
Switch Pin Leakage Current
Soft-Start Pin Pull-Up Current
Internal Soft-Start Time
I
= –200mA
0.35
0.1
5
Ω
μA
μA
ms
SW
V
= 65V, SW = 0V
1
6
IN
SS Pin < 2.5V
3
SS Pin Floating
0.8
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.
High junction temperatures degrade operating lifetimes; operating lifetime
is derated for junction temperatures greater than 125°C. Note that the
maximum ambient temperature consistent with these specifications is
determined by specific operating conditions in conjunction with board
layout, the rated package thermal impedance and other environmental
factors.
Note 2: The LTC3637 is tested under pulsed load conditions such that
T ≈ T . The LTC3637E is guaranteed to meet performance specifications
J
A
from 0°C to 85°C. Specifications over the –40°C to 125°C operating
junction temperature range are assured by design, characterization and
correlation with statistical process controls. The LTC3637I is guaranteed
over the –40°C to 125°C operating junction temperature range, the
LTC3637H is guaranteed over the –40°C to 150°C operating junction
temperature range and the LTC3637MP is tested and guaranteed over the
–55°C to 150°C operating junction temperature range.
Note 3: The junction temperature (T , in °C) is calculated from the ambient
J
temperature (T , in °C) and power dissipation (P , in Watts) according to
A
D
the formula:
T = T + (P • θ )
JA
J
A
D
where θ is 43°C/W for the DFN or 45°C/W for the MSOP.
JA
3637fa
3
For more information www.linear.com/LTC3637
LTC3637
ELECTRICAL CHARACTERISTICS
Note that the maximum ambient temperature consistent with these
specifications is determined by specific operating conditions in
conjunction with board layout, the rated package thermal impedance and
other environmental factors.
junction temperature may impair device reliability or permanently damage
the device. The overtemperature protection level is not production tested.
Note 5: Dynamic supply current is higher due to the gate charge being
delivered at the switching frequency. See Applications Information.
Note 4: This IC includes over temperature protection that is intended to
protect the device during momentary overload conditions. The maximum
rated junction temperature will be exceeded when this protection is active.
Continuous operation above the specified absolute maximum operating
Note 6: For application concerned with pin creepage and clearance
distances at high voltages, the MSOP package should be used. See
Applications Information.
TYPICAL PERFORMANCE CHARACTERISTICS
Efficiency and Power Loss
vs Load Current, VOUT = 5V
Efficiency and Power Loss
Efficiency and Power Loss
vs Load Current, VOUT = 3.3V
vs Load Current, VOUT = 1.8V
100
90
80
70
60
50
40
30
20
10
0
100
90
80
70
60
50
40
30
20
10
0
100
90
80
70
60
50
40
30
20
10
0
V
= 3.3V
V
= 1.8V
V
= 5V, FIGURE 13 CIRCUIT
OUT
FIGURE 13 CIRCUIT
OUT
FIGURE 13 CIRCUIT
OUT
EFFICIENCY
EFFICIENCY
EFFICIENCY
1000
100
10
1000
100
10
1000
100
10
POWER LOSS
POWER LOSS
POWER LOSS
V
V
V
= 12V
= 24V
= 70V
V
V
V
= 12V
= 24V
= 68V
V
V
V
= 12V
= 24V
= 67V
IN
IN
IN
IN
IN
IN
IN
IN
IN
0
0
0
1000
0.1
1.0
10
100
1000
0.1
1.0
10
100
1000
0.1
1.0
10
100
LOAD CURRENT (mA)
LOAD CURRENT (mA)
LOAD CURRENT (mA)
3637 G01
3637 G02
3637 G03
Efficiency vs Input Voltage
Line Regulation vs Input Voltage
Load Regulation vs Load Current
0.05
100
90
80
70
60
50
5.02
5.01
5.00
4.99
4.98
V
= 5V
V
LOAD
FIGURE 13 CIRCUIT
= 5V
= 1A
V
V
= 12V
OUT
FIGURE 13 CIRCUIT
OUT
FIGURE 13 CIRCUIT
OUT
IN
0.04
0.03
0.02
0.01
0
I
= 5V
–0.01
–0.02
–0.03
–0.04
–0.05
I
I
I
I
= 1A
LOAD
LOAD
LOAD
LOAD
= 100mA
= 10mA
= 1mA
40
INPUT VOLTAGE (V)
0
10 20 30
50 60 70 80
45
INPUT VOLTAGE (V)
5
25
35
55
65
75
15
0
100 200 300 400 500 600 700 800 9001000
LOAD CURRENT (mA)
3637 G04
3637 G05
3637 G06
3637fa
4
For more information www.linear.com/LTC3637
LTC3637
TYPICAL PERFORMANCE CHARACTERISTICS
Feedback Comparator Trip
Voltage vs Temperature
Feedback Comparator Hysteresis
vs Temperature
RUN and OVLO Comparator
Threshold Voltages vs Temperature
5.5
5.4
5.3
5.2
5.1
5.0
4.9
4.8
4.7
4.6
4.5
1.24
1.22
1.20
1.18
1.16
1.14
1.12
1.10
1.08
0.804
0.802
0.800
0.798
V
= 12V
V
= 12V
IN
IN
RISING
FALLING
0.796
1.06
–55 –25
5
35
65
95 125 155
–55
5
35
65
95 125
–25
155
–55 –25
5
35
155
65
95 125
TEMPERATURE (°C)
TEMPERATURE (°C)
TEMPERATURE (°C)
3637 G07
3637 G08
3637 G09
Peak Current Trip Threshold
vs RISET
Peak Current Trip Threshold
vs Temperature
Peak Current Trip Threshold
vs Input Voltage
2800
2400
2000
1600
1200
800
2800
2400
2000
1600
1200
800
2800
2400
V
= 12V
V
= 12V
IN
IN
ISET OPEN
ISET OPEN
2000
1600
1200
800
R
ISET
= 100k
R
ISET
= 100k
400
400
400
ISET = 0V
ISET = GND
0
0
0
0
50
100
R
150
(kΩ)
200
250
95 125 155
TEMPERATURE (°C)
35
65
0
10 20
30 40 50 60 70
INPUT VOLTAGE (V)
–55 –25
5
ISET
3637 G10
3637 G11
3637 G12
Quiescent VIN Supply Current
vs Input Voltage
Quiescent VIN Supply Current
vs Temperature
UVLO Threshold Voltages
vs Temperature
20
16
12
8
30
25
20
15
3.70
3.65
3.60
3.55
3.50
3.45
V
IN
= 12V
RISING
SLEEP
SLEEP
10
5
SHUTDOWN
FALLING
4
SHUTDOWN
0
0
5
15
25
35
45
55
65
75
–55
35
65
95
125 155
–25
5
–55 –25
5
35
65
95 125 155
INPUT VOLTAGE (V)
TEMPERATURE (°C)
TEMPERATURE (°C)
3637 G13
3637 G14
3637 G15
3637fa
5
For more information www.linear.com/LTC3637
LTC3637
TYPICAL PERFORMANCE CHARACTERISTICS
Switch Leakage Current
vs Temperature
Switch On-Resistance
vs Input Voltage
Switch On-Resistance
vs Temperature
1.0
0.8
0.6
0.4
0.2
0
35
25
15
5
0.55
0.45
0.35
0.25
V
= 65V
V
= 12V
IN
IN
150°C
SW = 65V
25°C
–55°C
SW = 0V
–5
0.15
–15
0
10 20 30 40 50 60 70
INPUT VOLTAGE (V)
–55 –25
5
35
65
95 125 155
–55 –25
5
35
65
95 125 155
TEMPERATURE (°C)
TEMPERATURE (°C)
3637 G17
3637 G18
3637 G16
Load Step Transient Response
Operating Waveforms, VIN = 76V
Short Circuit and Recovery
OUTPUT
VOLTAGE
50mV/DIV
SWITCH
VOLTAGE
25V/DIV
INDUCTOR
CURRENT
2A/DIV
OUTPUT
VOLTAGE
2V/DIV
OUTPUT
VOLTAGE
50mV/DIV
LOAD
CURRENT
500mA/DIV
INDUCTOR
CURRENT
1A/DIV
3637 G19
3637 G21
V
V
= 12V
= 5V
100µs/DIV
V
V
= 12V
= 5V
200µs/DIV
3637 G20
IN
OUT
IN
OUT
OUT
V
= 5V
= 1A
10µs/DIV
OUT
OUT
I
5mA TO 1A LOAD STEP
FIGURE 13 CIRCUIT
I
= 50mA (NON SHORT CIRCUIT)
FIGURE 13 CIRCUIT
FIGURE 13 CIRCUIT
3637fa
6
For more information www.linear.com/LTC3637
LTC3637
PIN FUNCTIONS
SW (Pin 1): Switch Node Connection to Inductor. This
pin connects to the drains of the internal power MOSFET
switches.
I
(Pin 11): Peak Current Set Input and Voltage Output
SET
Ripple Filter. A resistor from this pin to ground sets the
peak current comparator threshold. Leave floating for the
maximum peak current (2.4A typical) or short to ground
for minimum peak current (0.24A typical). The maximum
outputcurrentisone-halfthepeakcurrent.The5µAcurrent
that is sourced out of this pin when switching, is reduced
to 1µA in sleep. Optionally, a capacitor can be placed from
this pin to GND to trade off efficiency for light load output
voltage ripple. See Applications Information.
NC (Pins 2, 4, 13, 15 DHC Package Only): No Internal
Connection. Leave these pins open.
V
(Pin 3): Main Input Supply Pin. A ceramic bypass
IN
capacitor should be tied between this pin and GND.
FBO (Pin 5): Feedback Comparator Output. The typical
pull-up current is 20µA. The typical pull- down imped-
ance is 70Ω.
OVLO (Pin 12): Overvoltage Lockout Input. Connect to
the input supply through a resistor divider to set the over-
voltage lockout level. A voltage on this pin above 1.21V
disables the internal MOSFET switch. Normal operation
resumes when the voltage on this pin decreases below
1.10V. A transient exceeding the OVLO threshold triggers
a soft-start reset, resulting in a graceful recovery from
an input supply transient. Connect this pin to ground to
disable the overvoltage lockout.
V
, V
(Pins 6, 7): Output Voltage Selection. Short
PRG2 PRG1
both pins to ground for an external resistive divider pro-
grammable output voltage. Short V to SS and short
PRG1
V
PRG2
to ground for a 5V output voltage. Short V
to
PRG1
ground and short V
to SS for a 3.3V output voltage.
PRG2
Short both pins to SS for a 1.8V output voltage.
GND (Pins 8, 16, Exposed Pad Pin 17): Ground. The ex-
posed backside pad must be soldered to the PCB ground
plane for optimal thermal performance.
RUN (Pin 14): Run Control Input. A voltage on this pin
above 1.21V enables normal operation. Forcing this pin
below 0.7V shuts down the LTC3637, reducing quiescent
current to approximately 3µA. Optionally, connect to the
input supply through a resistor divider to set the under-
voltage lockout.
V
FB
(Pin 9): Output Voltage Feedback. When configured
for an adjustable output voltage, connect to an external
resistive divider to divide the output voltage down for
comparison to the 0.8V reference. For the fixed output
configuration,directlyconnectthispintotheoutputsupply.
SS (Pin 10): Soft-Start Control Input. A capacitor to
ground at this pin sets the output voltage ramp time. A
50µA current initially charges the soft-start capacitor until
switching begins, at which time the current is reduced to
its nominal value of 5µA. The output voltage ramp time
from zero to its regulated value is 1ms for every 16.5nF
of capacitance from SS to GND. If left floating, the ramp
time defaults to an internal 0.8ms soft-start.
3637fa
7
For more information www.linear.com/LTC3637
LTC3637
BLOCK DIAGRAM
1.3V
V
IN
ACTIVE: 5µA
SLEEP: 1µA
V
3
IN
+
I
SET
11
C
IN
PEAK CURRENT
COMPARATOR
+
–
RUN
14
+
–
1.21V
LOGIC
L1
SW
1
V
OUT
+
–
D1
C
OUT
GND
OVLO
16
12
+
–
INTV
*
CC
REVERSE CURRENT
COMPARATOR
20µA
FEEDBACK
COMPARATOR
VOLTAGE
INTV
*
CC
REFERENCE
FBO
START-UP: 50µA
NORMAL: 5µA
0.800V
+
+
–
5
SS
70Ω
SOFTSTART
10
R1
V
FB
9
7
6
V
V
PRG1
PRG2
R2
GND
GND
8
V
V
V
R1
R2
PRG2
PRG1
OUT
17
GND GND ADJUSTABLE 1.0M
∞
IMPLEMENT DIVIDER
EXTERNALLY FOR
ADJUSTABLE VERSION
GND
SS
SS
SS
GND
SS
5V FIXED 4.2M 800k
3.3V FIXED 2.5M 800k
1.8V FIXED 1.0M 800k
3637 BD
*WHEN V > 5V, INTV = 5V
IN
CC
WHEN V ≤ 5V, INTV FOLLOWS V
IN
IN
CC
3637fa
8
For more information www.linear.com/LTC3637
LTC3637
(Refer to Block Diagram)
OPERATION
The LTC3637 is a step-down DC/DC regulator with an
internal high side power switch that uses Burst Mode
control. The low quiescent current and high switching
frequency results in high efficiency across a wide range
of load currents. Burst Mode operation functions by us-
ing short “burst” cycles to switch the inductor current
through the internal power MOSFET, followed by a sleep
cycle where the power switch is off and the load current
is supplied by the output capacitor. During the sleep cycle,
the LTC3637 draws only 12µA of supply current. At light
loads, the burst cycles are a small percentage of the total
cycle time which minimizes the average supply current,
greatly improving efficiency. Figure 1 shows an example
of Burst Mode operation. The switching frequency and the
number of switching cycles during Burst Mode operation
are dependent on the inductor value, peak current, load
current, input voltage and output voltage.
reducing the V pin supply current to only 12µA. As the
IN
load current discharges the output capacitor, the voltage
on the V pin decreases. When this voltage falls 5mV
FB
below the 800mV reference, the feedback comparator
trips and enables burst cycles.
At the beginning of the burst cycle, the internal high side
power switch (P-channel MOSFET) is turned on and the
inductor current begins to ramp up. The inductor current
increases until either the current exceeds the peak current
comparatorthresholdorthevoltageontheV pinexceeds
FB
800mV, at which time the high side power switch is turned
off and the external catch diode turns on. The inductor
current ramps down until the reverse current compara-
tor trips, signaling that the current is close to zero. If the
voltage on the V pin is still less than the 800mV refer-
FB
ence, the high side power switch is turned on again and
another cycle commences. The average current during a
burst cycle will normally be greater than the average load
current.Forthisarchitecture,themaximumaverageoutput
current is equal to half of the peak current.
SLEEP
CYCLE
SWITCHING
FREQUENCY
BURST
CYCLE
The hysteretic nature of this control architecture results
in a switching frequency that is a function of the input
voltage, output voltage, and inductor value. This behavior
provides inherent short-circuit protection. If the output is
shorted to ground, the inductor current will decay very
slowly during a single switching cycle. Since the high side
switch turns on only when the inductor current is near
zero,theLTC3637inherentlyswitchesatalowerfrequency
during start-up or short-circuit conditions.
INDUCTOR
CURRENT
BURST
FREQUENCY
OUTPUT
VOLTAGE
∆V
3637 F01
OUT
Figure 1. Burst Mode Operation
Start-Up and Shutdown
Main Control Loop
IfthevoltageontheRUNpinislessthan0.7V, theLTC3637
enters a shutdown mode in which all internal circuitry is
disabled,reducingtheDCsupplycurrentto3µA.Whenthe
voltage on the RUN pin exceeds 1.21V, normal operation
of the main control loop is enabled. The RUN pin com-
parator has 110mV of internal hysteresis, and therefore
must fall below 1.1V to stop switching and disable the
main control loop.
The LTC3637 uses the V
and V
control pins to
PRG2
PRG1
connect internal feedback resistors to the V pin. This
FB
enables fixed outputs of 1.8V, 3.3V or 5V without increas-
ing component count, input supply current or exposure to
noise on the sensitive input to the feedback comparator.
External feedback resistors (adjustable mode) can still
be used by connecting both V
and V
to ground.
PRG1
PRG2
In adjustable mode the feedback comparator monitors
An internal 0.8ms soft-start function limits the ramp rate
oftheoutputvoltageonstart-uptopreventexcessiveinput
supply droop. If a longer ramp time and consequently less
the voltage on the V pin and compares it to an inter-
FB
nal 800mV reference. If this voltage is greater than the
reference,thecomparatoractivatesasleepmodeinwhich
the power switch and current comparators are disabled,
supply droop is desired, a capacitor can be placed from
3637fa
9
For more information www.linear.com/LTC3637
LTC3637
(Refer to Block Diagram)
OPERATION
the SS pin to ground. The 5µA current that is sourced
out of this pin will create a smooth voltage ramp on the
capacitor. If this ramp rate is slower than the internal
0.8ms soft-start, then the output voltage will be limited
by the ramp rate on the SS pin instead. The internal and
external soft-start functions are reset on start-up and after
an undervoltage or overvoltage event on the input supply.
Input Voltage and Overtemperature Protection
When using the LTC3637, care must be taken not to
exceed any of the ratings specified in the Absolute Maxi-
mum Ratings section. As an added safeguard, however,
the LTC3637 incorporates an overtemperature shutdown
feature.Ifthejunctiontemperaturereachesapproximately
180°C, the LTC3637 will enter thermal shutdown mode.
Both power switches will be turned off and the SW node
will become high impedance. After the part has cooled
below 160°C, it will restart. The overtemperature level is
not production tested.
The peak inductor current is not limited by the internal or
external soft-start functions; however, placing a capacitor
from the I pin to ground does provide this capability.
SET
Peak Inductor Current Programming
The LTC3637 additionally implements protection features
whichinhibitswitchingwhentheinputvoltageisnotwithin
a programmed operating range. By using a resistive di-
vider from the input supply to ground, the RUN and OVLO
pins can serve as a precise input supply voltage monitor.
Switching is disabled when either the RUN pin falls below
1.1V or the OVLO pin rises above 1.21V, which can be
configured to limit switching to a specific range of input
supply voltage. Pulling the RUN pin below 700mV forces
a low quiescent current shutdown (3µA). Furthermore, if
theinputvoltagefallsbelow3.5Vtypical(3.7Vmaximum),
an internal undervoltage detector disables switching.
The peak current comparator nominally limits the peak
inductor current to 2.4A. This peak inductor current can
be adjusted by placing a resistor from the I
pin to
SET
ground. The 5µA current sourced out of this pin through
the resistor generates a voltage that adjusts the peak cur-
rent comparator threshold.
During sleep mode, the current sourced out of the I pin
SET
isreducedto1µA.TheI currentisincreasedbackto5µA
SET
on the first switching cycle after exiting sleep mode. The
I
current reduction in sleep mode, along with adding
SET
a filtering capacitor, C , from the I
pin to ground,
ISET
SET
provides a method of reducing light load output voltage
ripple at the expense of lower efficiency and slightly de-
graded load step transient response.
Whenswitchingisdisabled,theLTC3637cansafelysustain
input voltages up to the absolute maximum rating of 80V.
Input supply undervoltage or overvoltage events trigger a
soft-start reset, which results in a graceful recovery from
an input supply transient.
Dropout Operation
When the input supply decreases toward the output sup-
ply, the duty cycle increases to maintain regulation. The
P-channel MOSFET top switch in the LTC3637 allows
the duty cycle to increase all the way to 100%. At 100%
duty cycle, the P-channel MOSFET stays on continuously,
providing output current equal to the peak current, which
can be greater than 2A. The power dissipation of the
LTC3637 can increase dramatically during dropout opera-
tionespeciallyatinputvoltageslessthan10V.Theincreased
power dissipation is due to higher potential output current
and increased P-channel MOSFET on-resistance. See
the Thermal Considerations section of the Applications
Information for a detailed example.
High Input Voltage Considerations
Whenoperatingwithaninputvoltagetooutputvoltagedif-
ferential of more than 65V, a minimum output load current
of 10mA is required to maintain a well-regulated output
voltageunderalloperatingconditions,includingshutdown
mode. If this 10mA minimum load is not available, then
the minimum output voltage that can be maintained by
the LTC3637 is limited to V – 65V.
IN
3637fa
10
For more information www.linear.com/LTC3637
LTC3637
APPLICATIONS INFORMATION
ThebasicLTC3637applicationcircuitisshownonthefront
page of the data sheet. External component selection is
determinedbythemaximumloadcurrentrequirementand
beginswiththeselectionofthepeakcurrentprogramming
The internal 5μA current source is reduced to 1μA in sleep
mode to maximize efficiency and to facilitate a trade-off
between efficiency and light load output voltage ripple, as
described in the Optimizing Output Voltage Ripple section
of the Applications Information. For maximum efficiency,
resistor,R .TheinductorvalueLcanthenbedetermined,
ISET
minimize the capacitance on the I
pin and place the
followed by capacitors C and C
.
SET
IN
OUT
R
ISET
resistor as close to the pin as possible.
Peak Current Resistor Selection
Thetypicalpeakcurrentisinternallylimitedtobewithinthe
Thepeakcurrentcomparatorhasaguaranteedpeakcurrent
limit of 2A (2.4A typical), which guarantees a maximum
average load current of 1A. For applications that demand
less current, the peak current threshold can be reduced to
aslittleas200mA(240mAtypical).Thislowerpeakcurrent
allows the use of lower value, smaller components (input
capacitor, output capacitor, and inductor), resulting in
lower supply ripple and a smaller overall DC/DC regulator.
range of 240mA to 2.4A. Shorting the I pin to ground
SET
programs the current limit to 240mA, and leaving it float
sets the current limit to the maximum value of 2.4A. When
selecting this resistor value, be aware that the maximum
average output current for this architecture is limited to
halfofthepeakcurrent.Therefore,besuretoselectavalue
that sets the peak current with enough margin to provide
adequate load current under all conditions. Selecting the
peak current to be 2.2 times greater than the maximum
load current is a good starting point for most applications.
The threshold can be easily programmed using a resis-
tor (R ) between the I pin and ground. The voltage
ISET
SET
pin by R
generated on the I
and the internal 5µA
SET
ISET
Inductor Selection
current source sets the peak current. The voltage on the
The inductor, input voltage, output voltage, and peak cur-
rent determine the switching frequency during a burst
cycle of the LTC3637. For a given input voltage, output
voltage, and peak current, the inductor value sets the
switching frequency during a burst cycle when the output
is in regulation. Generally, switching between 50kHz and
250kHz yields high efficiency, and 200kHz is a good first
choice for many applications. The inductor value can be
determined by the following equation:
I
pin is internally limited within the range of 0.1V to
SET
1.0V. The value of resistor for a particular peak current can
be selected by using Figure 2 or the following equation:
R
ISET
= 140k • I
– 24k
PEAK
where 200mA < I
< 2A.
PEAK
260
240
220
200
180
160
140
120
100
80
VOUT
f •I
VOUT
V
IN
L =
• 1–
PEAK
The variation in switching frequency during a burst cycle
withinputvoltageandinductanceisshowninFigure3. For
lower values of I
, multiply the frequency in Figure 3
PEAK
60
40
20
by 2.4A/I
.
PEAK
An additional constraint on the inductor value is the
LTC3637’s150nsminimumon-timeofthehighsideswitch.
Therefore, in order to keep the current in the inductor
well-controlled, the inductor value must be chosen so that
0
0
400
600
800
1000
200
MAXIMUM LOAD CURRENT (mA)
3637 F02
Figure 2. RISET Selection
3637fa
11
For more information www.linear.com/LTC3637
LTC3637
APPLICATIONS INFORMATION
300
1000
100
10
V
SET
= 5.0V
OUT
I
OPEN
L = 5.6µH
L = 10µH
200
100
0
L = 22µH
L = 47µH
1
20 30 40 50
INPUT VOLTAGE (V)
0
10
60 70
100
1000
V
IN
PEAK INDUCTOR CURRENT (mA)
3637 F03
3637 F04
Figure 4. Recommended Inductor Values for Maximum Efficiency
Figure 3. Switching Frequency for VOUT = 5.0V
it is larger than a minimum value which can be computed
as follows:
largercorescanbeused,whichextendstherecommended
range of Figure 4 to larger values.
V
IN(MAX) • tON(MIN)
Inductor Core Selection
L >
•1.2
IPEAK
Once the value for L is known, the type of inductor must
be selected. High efficiency regulators generally cannot
affordthecorelossfoundinlowcostpowderedironcores,
forcing the use of the more expensive ferrite cores. Actual
core loss is independent of core size for a fixed inductor
value but is very dependent of the inductance selected.
As the inductance increases, core losses decrease. Un-
fortunately, increased inductance requires more turns of
wire and therefore copper losses will increase.
whereV
isthemaximuminputsupplyvoltagewhen
IN(MAX)
switching is enabled, t
is 150ns, I
is the peak
ON(MIN)
PEAK
current, and the factor of 1.2 accounts for typical inductor
tolerance and variation over temperature. For applications
that have large input supply transients, the OVLO pin can
be used to disable switching above the maximum operat-
ing voltage, V
, so that the minimum inductor value
IN(MAX)
is not artificially limited by a transient condition. Inductor
values that violate the above equation will cause the peak
current to overshoot and permanent damage to the part
may occur.
Ferrite designs have very low core losses and are pre-
ferred at high switching frequencies, so design goals
can concentrate on copper loss and preventing satura-
tion. Ferrite core material saturates “hard,” which means
that inductance collapses abruptly when the peak design
current is exceeded. This results in an abrupt increase in
inductor ripple current and consequently output voltage
ripple. Do not allow the core to saturate!
Although the above equation provides the minimum in-
ductor value, higher efficiency is generally achieved with
a larger inductor value, which produces a lower switching
frequency.Foragiveninductortype,however,asinductance
is increased, DC resistance (DCR) also increases. Higher
DCRtranslatesintohighercopperlossesandlowercurrent
rating,bothofwhichplaceanupperlimitontheinductance.
The recommended range of inductor values for small sur-
facemountinductorsasafunctionofpeakcurrentisshown
inFigure4.Thevaluesinthisrangeareagoodcompromise
between the trade-offs discussed above. For applications
where board area is not a limiting factor, inductors with
Different core materials and shapes will change the size/
currentandprice/currentrelationshipofaninductor.Toroid
or shielded pot cores in ferrite or permalloy materials are
small and do not radiate energy but generally cost more
than powdered iron core inductors with similar charac-
teristics. The choice of which style inductor to use mainly
3637fa
12
For more information www.linear.com/LTC3637
LTC3637
APPLICATIONS INFORMATION
depends on the price versus size requirements and any
radiated field/EMI requirements. New designs for surface
mount inductors are available from Würth, Coilcraft, TDK,
Toko, and Sumida.
switch and supply current to the output. The output ripple
can be approximated by:
IPEAK
2
4 •10–6 VOUT
∆VOUT
≈
–I
LOAD
•
+
COUT
160
C and C
Selection
IN
OUT
Theoutputrippleisamaximumatnoloadandapproaches
lower limit of V /160 at full load. Choose the output
The input capacitor, C , is needed to filter the trapezoidal
IN
OUT
current at the source of the top high side MOSFET. C
IN
capacitor C
to limit the output voltage ripple ∆V
OUT
OUT
should be sized to provide the energy required to charge
using the following equation:
the inductor without causing a large decrease in input
IPEAK • 2 •10–6
voltage (∆V ). The relationship between C and ∆V
IN
IN
IN
COUT
≥
VOUT
is given by:
∆VOUT
–
160
2
L •IPEAK
CIN >
2 • V • ∆V
The value of the output capacitor must be large enough
to accept the energy stored in the inductor without a large
change in output voltage during a single switching cycle.
IN
IN
It is recommended to use a larger value for C than
calculated by the above equation since capacitance de-
creases with applied voltage. In general, a 4.7µF X7R
ceramiccapacitorisagoodchoiceforC inmostLTC3637
applications.
IN
Setting this voltage step equal to 1% of the output voltage,
the output capacitor must be:
IN
2
IPEAK
V
OUT
COUT > 50 •L •
To minimize large ripple voltage, a low ESR input capaci-
tor sized for the maximum RMS current should be used.
RMS current is given by:
Typically, a capacitor that satisfies the voltage ripple
requirement is adequate to filter the inductor ripple. To
avoidoverheating,theoutputcapacitormustalsobesized
to handle the ripple current generated by the inductor.
The worst-case ripple current in the output capacitor is
VOUT
V
V
IN
VOUT
IRMS = IOUT(MAX)
•
•
– 1
IN
This formula has a maximum at V = 2V , where I =
RMS
IN
OUT
given by I
= I
/2. Multiple capacitors placed in
RMS
PEAK
I /2.Thissimpleworst-caseconditioniscommonlyused
OUT
parallel may be needed to meet the ESR and RMS current
handling requirements.
fordesignbecauseevensignificantdeviationsdonotoffer
muchrelief.Notethatripplecurrentratingsfromcapacitor
manufacturers are often based only on 2000 hours of life
which makes it advisable to further derate the capacitor,
or choose a capacitor rated at a higher temperature than
required.Severalcapacitorsmayalsobeparalleledtomeet
size or height requirements in the design.
Dry tantalum, special polymer, aluminum electrolytic,
and ceramic capacitors are all available in surface mount
packages. Special polymer capacitors offer very low ESR
but have lower capacitance density than other types.
Tantalum capacitors have the highest capacitance density
but it is important only to use types that have been surge
tested for use in switching power supplies. Aluminum
electrolytic capacitors have significantly higher ESR but
can be used in cost-sensitive applications provided that
consideration is given to ripple current ratings and long-
termreliability.CeramiccapacitorshaveexcellentlowESR
characteristics but can have high voltage coefficient and
The output capacitor, C , filters the inductor’s ripple
OUT
current and stores energy to satisfy the load current when
the LTC3637 is in sleep. The output ripple has a lower limit
of V /160 due to the 5mV typical hysteresis of the feed-
OUT
back comparator. The time delay of the comparator adds
an additional ripple voltage that is a function of the load
current. During this delay time, the LTC3637 continues to
audible piezoelectric effects. The high quality factor (Q)
3637fa
13
For more information www.linear.com/LTC3637
LTC3637
APPLICATIONS INFORMATION
of ceramic capacitors in series with trace inductance can
also lead to significant input voltage ringing.
with a series resistor may be required in parallel with
to dampen the ringing of the input supply. Figure
C
IN
6 shows this circuit and the typical values required to
Input Voltage Steps
dampen the ringing.
If the input voltage falls below the regulated output volt-
age, the body diode of the internal high side MOSFET will
conduct current from the output supply to the input sup-
ply. If the input voltage falls rapidly, the voltage across the
inductorwillbesignificantandmaysaturatetheinductor.A
large current will then flow through the high side MOSFET
body diode, resulting in excessive power dissipation that
may damage the part.
Ceramic capacitors are also piezoelectric sensitive. The
LTC3637’s burst frequency depends on the load current,
and in some applications at light load the LTC3637 can
excite the ceramic capacitor at audio frequencies, gen-
erating audible noise. If the noise is unacceptable, use
a high performance tantalum or electrolytic capacitor at
the output.
L
LTC3637
IN
V
IN
If rapid voltage steps are expected on the input supply, put
LIN
CIN
R=
a small silicon or Schottky diode in series with the V pin
3637 F05
IN
C
IN
to prevent reverse current and inductor saturation, shown
below as D2 in Figure 5. The diode should be sized for a
reverse voltage of greater than the input voltage, and to
withstand repetitive currents higher than the maximum
peak current of the LTC3637.
4 • C
IN
Figure 6. Series RC to Reduce VIN Ringing
Output Voltage Programming
The LTC3637 has three fixed output voltage modes that
can be selected with the V and V pins and an
adjustable mode. The fixed output modes use an internal
feedback divider which enables higher efficiency, higher
noise immunity, and lower output voltage ripple for 5V,
3.3V and 1.8V applications. To select the fixed 5V output
LTC3637
D2
L
V
SW
IN
INPUT
V
OUT
SUPPLY
PRG1
PRG2
C
C
OUT
IN
3637 F05
Figure 5. Preventing Current Flow to the Input
voltage, connect V
to SS and V
to GND. For 3.3V,
PRG1
to GND and V
PRG2
Ceramic Capacitors and Audible Noise
connect V
to SS. For 1.8V, connect
PRG1
PRG2
Higher value, lower cost ceramic capacitors are now be-
coming available in smaller case sizes. Their high ripple
current, high voltage rating, and low ESR make them ideal
for switching regulator applications. However, care must
be taken when these capacitors are used at the input and
output. When a ceramic capacitor is used at the input and
thepowerissuppliedbyawalladapterthroughlongwires,
a load step at the output can induce ringing at the input,
both V
and V
to SS. For any of the fixed output
PRG1
PRG2
voltage options, directly connect the V pin to V
.
FB
OUT
For the adjustable output mode (V
= 0V, V
= 0V),
PRG1
PRG2
the output voltage is set by an external resistive divider
according to the following equation:
R1
R2
VOUT = 0.8V • 1+
V . At best, this ringing can couple to the output and be
IN
mistaken as loop instability. At worst, a sudden inrush
The resistive divider allows the V pin to sense a fraction
FB
of current through the long wires can potentially cause
of the output voltage as shown in Figure 7. The output
a voltage spike at V large enough to damage the part.
IN
voltage can range from 0.8V to V . Be careful to keep the
IN
divider resistors very close to the V pin to minimize the
FB
For application with inductive source impedance, such as
alongwire,anelectrolyticcapacitororaceramiccapacitor
trace length and noise pick-up on the sensitive V signal.
FB
3637fa
14
For more information www.linear.com/LTC3637
LTC3637
APPLICATIONS INFORMATION
V
OUT
RUN Pin and External Input Overvoltage/Undervoltage
Lockout
R1
0.8V
V
FB
The RUN pin has two different threshold voltage levels.
Pulling the RUN pin below 0.7V puts the LTC3637 into a
LTC3637
R2
V
PRG1
V
PRG2
low quiescent current shutdown mode (I ~ 3µA). When
Q
3637 F06
theRUNpinisgreaterthan1.21V,thecontrollerisenabled.
Figure 9 shows examples of configurations for driving the
RUN pin from logic.
Figure 7. Setting the Output Voltage with External Resistors
To minimize the no-load supply current, resistor values in
the megohm range may be used; however, large resistor
values should be used with caution. The feedback divider
is the only load current when in shutdown. If PCB leakage
currenttotheoutputnodeorswitchnodeexceedstheload
current, the output voltage will be pulled up. In normal
operation, this is generally a minor concern since the load
current is much greater than the leakage.
The RUN and OVLO pins can alternatively be configured
as precise undervoltage (UVLO) and overvoltage (OVLO)
lockoutsontheV supplywitharesistivedividerfromV
IN
IN
toground. Asimpleresistivedividercanbeusedasshown
in Figure 10 to meet specific V voltage requirements.
IN
The current that flows through the R3-R4-R5 divider will
directly add to the shutdown, sleep, and active current of
the LTC3637, and care should be taken to minimize the
impact of this current on the overall efficiency of the ap-
plicationcircuit.Resistorvaluesinthemegohmrangemay
berequiredtokeeptheimpactonquiescentshutdownand
sleep currents low. To pick resistor values, the sum total
To avoid excessively large values of R1 in high output volt-
age applications (V
≥ 10V), a combination of external
OUT
and internal resistors can be used to set the output volt-
age. This has an additional benefit of increasing the noise
immunity on the V pin. Figure 8 shows the LTC3637
FB
of R3 + R4 + R5 (R
) should be chosen first based on
TOTAL
with the V pin configured for a 5V fixed output with an
FB
the allowable DC current that can be drawn from V . The
IN
external divider to generate a higher output voltage. The
internal 5M resistance appears in parallel with R2, and the
value of R2 must be adjusted accordingly. R2 should be
chosen to be less than 200k to keep the output voltage
variationlessthan1%duetothetoleranceoftheLTC3637’s
internal resistor.
V
IN
SUPPLY
LTC3637
RUN
LTC3637
RUN
3637 F09
V
OUT
Figure 9. RUN Pin Interface to Logic
R1
LTC3637
4.2M
V
5V
FB
V
IN
R2
R3
R4
R5
0.8V
RUN
LTC3637
800k
SS
V
PRG1
V
PRG2
OVLO
3637 F10
3637 F08
Figure 8. Setting the Output Voltage with
External and Internal Resistors
Figure 10. Adjustable UV and OV Lockout
3637fa
15
For more information www.linear.com/LTC3637
LTC3637
APPLICATIONS INFORMATION
individual values of R3, R4 and R5 can then be calculated
from the following equations:
by the LTC3637 will be optimized by using a catch diode
with minimum reverse leakage current. Low leakage
Schottky diodes often have larger forward voltage drops
at a given current, so a trade-off can exist between low
load and high load efficiency. Often Schottky diodes with
larger reverse bias ratings will have less leakage at a given
output voltage than a diode with a smaller reverse bias
rating. Therefore, superior leakage performance can be
achieved at the expense of diode size.
1.21V
R5= RTOTAL
•
Rising V OVLO Threshold
IN
1.21V
R4= RTOTAL
•
–R5
Rising V UVLO Threshold
IN
R3= RTOTAL –R5–R4
Soft-Start
For applications that do not need a precise external OVLO,
the OVLO pin can be tied directly to ground. The RUN pin
in this type of application can be used as an external UVLO
using the above equations with R5 = 0Ω.
Soft-start is implemented by ramping the effective refer-
ence voltage from 0V to 0.8V. To increase the duration of
soft-start, place a capacitor from the SS pin to ground.
An internal 5µA pull-up current will charge this capacitor.
The value of the soft-start capacitor can be calculated by
the following equation:
Similarly, for applications that do not require a precise
UVLO, theRUNpincanbetiedtoV . Inthisconfiguration,
IN
the UVLO threshold is limited to the internal V UVLO
IN
thresholdsasshownintheElectricalCharacteristicstable.
The resistor values for the OVLO can be computed using
the above equations with R3 = 0Ω.
5µA
0.35V
CSS = Soft-Start Time •
The minimum soft-start time is limited to the internal soft-
start timer of 0.8ms. When the LTC3637 detects a fault
condition(inputsupplyundervoltageorovertemperature)
or when the RUN pin falls below 1.1V, or when the OVLO
pinrisesabove1.21V,theSSpinisquicklypulledtoground
and the internal soft-start timer is reset. This ensures an
orderly restart when using an external soft-start capacitor.
Be aware that the OVLO pin cannot be allowed to exceed
its absolute maximum rating of 6V. To keep the voltage
on the OVLO pin from exceeding 6V, the following relation
should be satisfied:
R5
V
•
< 6V
IN(MAX)
R3+ R4+ R5
Note that the soft-start capacitor may not be the limiting
factor in the output voltage ramp. The maximum output
current, which is equal to half the peak current, must
charge the output capacitor from 0V to its regulated value.
For small peak currents or large output capacitors, this
ramptimecanbesignificant.Therefore,theoutputvoltage
Catch Diode Selection
ThecatchdiodeD1conductscurrentonlyduringswitch-off
time. Use a Schottky diode to limit forward voltage drop to
increase efficiency. The Schottky diode must have a peak
reverse voltage that is equal to the regulator maximum
input voltage or OVLO set voltage and must be sized for
average forward current in normal operation. Average
forward current can be calculated from:
ramp time from 0V to the regulated V
to a minimum of:
value is limited
OUT
2 •COUT
IPEAK
Ramp Time ≥
VOUT
IOUT •V
IN
ID(AVG)
=
V – V
(
)
IN
OUT
Optimizing Output Voltage Ripple
An additional consideration is reverse leakage current.
When the catch diode is reversed biased, any leakage
current will appear as load current. When operating under
light load conditions, the low supply current consumed
Once the peak current resistor, R , and inductor are se-
ISET
lectedtomeettheloadcurrentandfrequencyrequirements,
an optional capacitor, C , can be added in parallel with
ISET
3637fa
16
For more information www.linear.com/LTC3637
LTC3637
APPLICATIONS INFORMATION
2
R
. This will boost efficiency at mid-loads and reduce
2. I R losses are calculated from the resistances of the
internal switches, R and external inductor R . When
ISET
theoutputvoltagerippledependencyonloadcurrentatthe
expenseofslightlydegradedloadsteptransientresponse.
SW
L
switching, the average output current flowing through
the inductor is “chopped” between the high side PMOS
switch and the external catch diode. Thus, the series
resistance looking back into the switch pin is a function
of the top and bottom switch R
duty cycle (DC = V /V ) as follows:
The peak inductor current is controlled by the voltage on
the I
pin. Current out of the I
pin is 5µA while the
SET
SET
LTC3637 is switching and is reduced to 1µA during sleep
mode. The I current will return to 5µA on the first cycle
values and the
DS(ON)
SET
OUT IN
after sleep mode. Placing a parallel RC from the I pin to
SET
ground filters the I voltage as the LTC3637 enters and
R
SW
= (R )DC + (R ) • (1 – DC)
DS(ON)TOP DS(ON)BOT
SET
exits sleep mode which in turn will affect the output volt-
The R
for both the top and bottom MOSFETs can
DS(ON)
ageripple, efficiencyandloadsteptransientperformance.
be obtained from the Typical Performance Characteris-
2
Ingeneral,whenR
isgreaterthan120kaC
capacitor
tics curves. Thus, to obtain the I R losses, simply add
ISET
ISET
inthe47pFto100pFrangewillimprovemostperformance
R
to R and multiply the result by the square of the
SW L
parameters.WhenR
islessthan100k,thecapacitance
average output current:
ISET
on the I pin should be minimized.
2
2
SET
I R Loss = I (R + R )
O
SW
L
Efficiency Considerations
Other losses, including C and C
losses and inductor core losses, generally account for
less than 2% of the total power loss.
ESR dissipative
OUT
IN
Theefficiencyofaswitchingregulatorisequaltotheoutput
power divided by the input power times 100%. It is often
useful to analyze individual losses to determine what is
limiting the efficiency and which change would produce
the most improvement. Efficiency can be expressed as:
Thermal Considerations
Inmostapplications,theLTC3637doesnotdissipatemuch
heat due to its high efficiency. But, in applications where
the LTC3637 is running at high ambient temperature with
low supply voltage and high duty cycles, such as dropout,
the heat dissipated may exceed the maximum junction
temperature of the part.
Efficiency = 100% – (L1 + L2 + L3 + ...)
where L1, L2, etc. are the individual losses as a percent-
age of input power.
Although all dissipative elements in the circuit produce
losses, two main sources usually account for most of
To prevent the LTC3637 from exceeding the maximum
junctiontemperature,theuserwillneedtodosomethermal
analysis. The goal of the thermal analysis is to determine
whether the power dissipated exceeds the maximum
junction temperature of the part. The temperature rise
from ambient to junction is given by:
2
the losses: V operating current and I R losses. The V
IN
IN
operating current dominates the efficiency loss at very
2
low load currents whereas the I R loss dominates the
efficiency loss at medium to high load currents.
1. The V operating current comprises two components:
IN
The DC supply current as given in the electrical charac-
teristics and the internal MOSFET gate charge currents.
The gate charge current results from switching the gate
capacitance of the internal power MOSFET switches.
Each time the gate is switched from high to low to
T = P • θ
R D JA
where P is the power dissipated by the regulator and θ
D
JA
is the thermal resistance from the junction of the die to
the ambient temperature.
The junction temperature is given by:
high again, a packet of charge, ∆Q, moves from V to
IN
ground. The resulting ∆Q/dt is the current out of V
IN
T = T + T
R
J
A
that is typically larger than the DC bias current.
3637fa
17
For more information www.linear.com/LTC3637
LTC3637
APPLICATIONS INFORMATION
Generally, the worst-case power dissipation is in dropout
at low input voltage. In dropout, the LTC3637 can provide
a DC current as high as the full 2.4A peak current to the
output. At low input voltage, this current flows through a
higher resistance MOSFET, which dissipates more power.
Therefore, the minimum inductor requirement is satisfied
and the 4.7μH inductor value may be used.
Next,C andC areselected.Forthisdesign,C should
IN
OUT
IN
be sized for a current rating of at least:
3.3V
24V
24V
3.3V
As an example, consider the LTC3637 in dropout at an
input voltage of 5V, a load current of 1A and an ambient
temperatureof85°C.FromtheTypicalPerformancegraphs
IRMS = 1A •
•
– 1≅ 350mARMS
The value of C is selected to keep the input from droop-
IN
of Switch On-Resistance, the R
of the top switch
DS(ON)
ing less than 240mV (1%):
at V = 5V and 100°C is approximately 0.6Ω. Therefore,
IN
4.7µH• 2.4A2
2 • 24V • 240mV
the power dissipated by the part is:
CIN >
≅ 2.2µF
2
2
P = (I
) • R
= (1A) • 0.6Ω = 0.6W
D
LOAD
DS(ON)
C
will be selected based on a value large enough to
For the MSOP package the θ is 45°C/W. Thus, the junc-
OUT
JA
satisfy the output voltage ripple requirement. For a 50mV
output ripple, the value of the output capacitor can be
calculated from:
tion temperature of the regulator is:
45°C
W
TJ = 85°C+ 0.6W •
= 112°C
4.7µH• 2.4A2
which is below the maximum junction temperature of
150°C.
COUT
>
≅ 100µF
2 • 3.3V • 50mV
NotethatthewhiletheLTC3637isindropout,itcanprovide
output current that is equal to the peak current of the part.
This can increase the chip power dissipation dramatically
and may cause the internal overtemperature protection
circuitry to trigger at 180°C and shut down the LTC3637.
C
also needs an ESR that will satisfy the output voltage
OUT
ripplerequirement.TherequiredESRcanbecalculatedfrom:
50mV
ESR <
≅ 20mΩ
2.4A
A 100µF ceramic capacitor has significantly less ESR
than 20mΩ.
Design Example
As a design example, consider using the LTC3637 in an ap-
Since an output voltage of 3.3V is one of the standard
output configurations, the LTC3637 can be configured
plication with the following specifications: typical V = 24V,
IN
OUT
maximum applied V = 80V, V
= 3.3V, I
= 1A,
IN
OUT
by connecting V
to ground and V
to the SS pin.
PRG1
PRG2
f = 200kHz. Furthermore, assume for this example that
switching should start when V is greater than 6V and
The undervoltage and overvoltage lockout requirements
IN
stop switching when V is greater than 48V.
on V can be satisfied with a resistive divider from V to
IN
IN
IN
the RUN and OVLO pins (refer to Figure 9). Pick R
TOTAL
First, calculate the inductor value that gives the required
switching frequency:
= 1M = R3 + R4 + R5 to minimize the loading on V and
IN
calculate R3, R4 and R5 as follows (standard values):
3.3V
200kHz • 2.4A
3.3V
24V
1.21V
48V
L =
• 1–
≅ 4.7µH
R5= 1M•
R4= 1M•
= 24.9k
Next, verify that this value meets the L
requirement.
MIN
1.21V
6V
–24.9k = 174k
For this input voltage and peak current, the minimum
inductor value is:
R3= 1M− 24.9k –174k = 806k
48V •150ns
LMIN
=
•1.2 ≅ 4µH
2.4A
3637fa
18
For more information www.linear.com/LTC3637
LTC3637
APPLICATIONS INFORMATION
L1
D1
Note that the V falling thresholds for both UVLO and
IN
V
IN
V
OUT
V
SW
IN
OVLO will be 10% less than the rising thresholds or 5.4V
R3
R4
R1
R2
and 43V respectively.
V
FB
RUN
The absolute maximum rating on the OVLO pin (6V) is
not violated based on the following:
LTC3637
R
C
ISET
I
OVLO
SET
ISET
C
C
OUT
IN R5
24.9k
806k+ 174k+ 24.9k
OVLO(MAX)= 80V •
= 2V
C
SS
(
)
FBO
SS
V
V
PRG2
PRG1
The I pin should be left open in this example to select
SET
maximum peak current (2.4A typical). Figure 11 shows a
complete schematic for this design example.
4.7µH
V
3.3V
1A
OUT
V
IN
V
SW
LTC3637
IN
24V
806k
174k
24.9k
V
FB
L1
RUN
SS
100µF
2.2µF
V
V
PRG2
OVLO
FBO
PRG1
I
3637 F11
SET
GND
C
OUT
C
IN
Figure 11. 24V to 3.3V, 1A Regulator at 200kHz
D1
PC Board Layout Checklist
When laying out the printed circuit board, the following
checklist should be used to ensure proper operation of
the LTC3637. Check the following in your layout:
1. Large switched currents flow in the power switches
and input capacitor. The loop formed by these compo-
nents should be as small as possible. A ground plane
is recommended to minimize ground impedance.
3637 F12
VIAS TO GROUND PLANE
Figure 12. Example PCB Layout
Pin Clearance/Creepage Considerations
2. Connect the (+) terminal of the input capacitor, C , as
IN
close as possible to the V pin. This capacitor provides
The LTC3637 is available in two packages (MSE16 and
DHC)bothwithidenticalfunctionality.However,the0.2mm
(minimum space) between pins and paddle on the DHC
package may not provide sufficient PC board trace clear-
ance between high and low voltage pins in some higher
voltage applications. In applications where clearance is
required, the MSE16 package should be used. The MSE16
package has removed pins between all the adjacent high
voltage and low voltage pins, providing 0.657mm clear-
ance which will be sufficient for most applications. For
more information, refer to the printed circuit board design
IN
the AC current into the internal power MOSFETs.
3. Keep the switching node, SW, away from all sensitive
smallsignalnodes.Therapidtransitionsontheswitching
node can couple to high impedance nodes, in particular
V , and create increased output ripple.
FB
4. Flood all unused area on all layers with copper except
for the area under the inductor. Flooding with copper
will reduce the temperature rise of power components.
You can connect the copper areas to any DC net (V ,
IN
V
, GND, or any other DC rail in your system).
OUT
standards described in IPC-2221 (www.ipc.org).
3637fa
19
For more information www.linear.com/LTC3637
LTC3637
TYPICAL APPLICATIONS
L1
Soft-Start Waveform
10µH
V
5V
1A
OUT
V
IN
V
SW
IN
5V TO 76V
C
C
OUT
IN
D1
100µF
4.7µF
LTC3637
×2
RUN
FBO
V
FB
OUTPUT
VOLTAGE
1V/DIV
SS
PRG1
PRG2
V
V
C
I
SS
SET
150nF
OVLO
GND
C
R
ISET
255k
ISET
47pF
3637 F13
3637 F13b
2ms/DIV
C
: TDK C5750X7R2A-475M
OUT
IN
C
: 2 × MURATA GRM32ER61A107ME20L
D1: DIODES INC. SBR3U100LP
L1: SUMIDA CDRH105R-100
Figure 13. 5V-76V Input to 5V Output, 1A Regulator with Soft-Start
36.5V to 76V Input to 36V Output, 1A Regulator
L1
10µH
V
OUT
36V
1A
V
IN
V
SW
LTC3637
IN
OUTPUT VOLTAGE
1V/DIV
36.5V TO 76V
C
C
OUT
10µF
IN
D1
R1
200k
2.2µF
AC-COUPLED
RUN
FBO
V
FB
SS
R2
32.4k
SW VOLTAGE
50V/DIV
V
V
PRG1
I
SET
PRG2
OVLO
INDUCTOR CURRENT
2A/DIV
GND
3637 TA02a
3637 TA02b
V
V
= 76V
5µs/DIV
IN
= 36V
OUT
= 1A
OUT
C
C
: TDK CGA6N3X7R2A225M
OUT
IN
I
: TAIYO YUDEN UMK325BJ106MM
D1: DIODES INC. ES2BA-13-F
L1: TDK SLF10145T-100M
3637fa
20
For more information www.linear.com/LTC3637
LTC3637
TYPICAL APPLICATIONS
4V to 64V Input to –12V Output Positive-to-Negative Regulator
Maximum Load Current vs Input Voltage
L1
1000
800
600
400
V
= –12V
OUT
4.7µH
V
IN
V
SW
LTC3637
RUN
IN
4V TO 63V
C
IN
2.2µF
D1
R1
200k
V
FB
C
OUT
R2
147k
I
SS
SET
22µF
FBO
OVLO
V
PRG1
V
PRG2
GND
V
OUT
200
0
–12V
3637 TA03a
C
C
: KEMET C1210C225M1RAC
IN
: AVX 1210YC226MAT
OUT
D1: AVX SD3220S100S5R0
0
20
30
40
50
60
10
L1: COOPER BUSSMANN DR7-4R7-R
INPUT VOLTAGE (V)
3637 TA03b
V
IPEAK
2
IN
MAXIMUM LOAD CURRENT ≈
•
V
IN+ |VOUT
|
24.5V to 76V Input to 24V Output with 350mA Input Current Limit
Maximum Input and Load Current vs Input Voltage
L1
1000
22µH
V
V
900
IN
OUT
V
SW
LTC3637
IN
24.5V TO 76V
24V
MAXIMUM
OUTPUT CURRENT
C
C
OUT
10µF
IN
800
D1
R1
1µF
200k
700
600
R3
806k
RUN
V
FB
I
SS
R2
53.6k
SET
R4
11.5k
500
V
PRG1
MAXIMUM
INPUT CURRENT
OVLO
FBO
400
V
PRG2
300
200
100
0
R4
R3+R4
GND
INPUT CURRENT LIMIT ≈ VOUT
MAXIMUM LOAD CURRENT ≈
•
3637 TA04a
V
R4
R3+R4
IN
•
2
C
C
: TAIYO YUDEN HMK325B7105MN
: TDK C3225X7R1H106M
D1: DIODES INC. SBR3U100LP
L1: WÜRTH 7447714220
IN
OUT
25
35
45
55
65
75
INPUT VOLTAGE (V)
3637 TA04b
3637fa
21
For more information www.linear.com/LTC3637
LTC3637
TYPICAL APPLICATIONS
4V to 76V Input to 15V Output* Clamp, 1A High Efficiency Surge Stopper
L1
6.8µH
V
*
V
*
IN
OUT
V
SW
LTC3637
IN
76V INPUT SURGE
4V TO 76V
1A
C
OUT
D1
R1
200k
22µF
V
IN
20V/DIV
RUN
FB0
V
FB
SS
R2
27.4k
V
V
I
PRG1
PRG2
SET
OVLO
15V OUTPUT CLAMP
V
OUT
GND
20V/DIV
3637 TA05b
I = 1A
LOAD
100ms/DIV
C
: TDK C3225X7R1C226M
3637 TA05a
OUT
D1: VISHAY 10MQ100NPBF
L1: VISAHY IHLP-2525CZ-01
*WHEN V > 15V, LTC3637 SWITCHES AND V
IS REGULATED TO 15V;
OUT
IN
WHEN V ≤ 15V, LTC3637 OPERATES IN DROPOUT AND V
FOLLOWS V
IN
IN
OUT
RUN
2V/DIV
4V to 76V Input to 1.8V SuperCap Charger
V
OUT
500mV/DIV
L1
6.2µH
D2
V
V
IN
OUT
INDUCTOR
CURRENT
2A/DIV
V
IN
SW
4V TO 76V
1.8V
C
OUT
C
SC
D1
100µF
LTC3637
1F
×2
V
= 48V
IN
RUN
FBO
V
3637 TA05b
FB
100ms/DIV
ZOOM
SS
I
V
V
GND
SET
PRG1
PRG2
RUN
2V/DIV
OVLO
3637 TA06
V
OUT
C
C
: TDK C3225X5R0J107M
OUT
SC
500mV/DIV
: COOPER BUSSMANN M0810-2R5105-R
INDUCTOR
CURRENT
2A/DIV
D1: VISHAY VSSA310S-E3
D2: VISHAY 10MDQ100NPBF
L1: WÜRTH 744 066 0062
V
= 48V
IN
3637 TA05c
200µs/DIV
3637fa
22
For more information www.linear.com/LTC3637
LTC3637
PACKAGE DESCRIPTION
Please refer to http://www.linear.com/designtools/packaging/ for the most recent package drawings.
MSE Package
Variation: MSE16 (12)
16-Lead Plastic MSOP with 4 Pins Removed
Exposed Die Pad
(Reference LTC DWG # 05-08-1871 Rev D)
BOTTOM VIEW OF
EXPOSED PAD OPTION
2.845 ±0.102
(.112 ±.004)
2.845 ±0.102
(.112 ±.004)
0.889 ±0.127
(.035 ±.005)
1
8
0.35
REF
5.10
(.201)
MIN
1.651 ±0.102
(.065 ±.004)
1.651 ±0.102
(.065 ±.004)
3.20 – 3.45
(.126 – .136)
0.12 REF
DETAIL “B”
CORNER TAIL IS PART OF
THE LEADFRAME FEATURE.
FOR REFERENCE ONLY
DETAIL “B”
16
9
0.305 ±0.038
0.50
NO MEASUREMENT PURPOSE
4.039 ±0.102
(.159 ±.004)
(NOTE 3)
(.0120 ±.0015)
(.0197)
1.0
(.039)
BSC
TYP
BSC
0.280 ±0.076
(.011 ±.003)
16 14 121110
9
RECOMMENDED SOLDER PAD LAYOUT
REF
DETAIL “A”
0.254
(.010)
3.00 ±0.102
(.118 ±.004)
(NOTE 4)
0° – 6° TYP
4.90 ±0.152
(.193 ±.006)
GAUGE PLANE
0.53 ±0.152
(.021 ±.006)
1
3 5 6 7 8
1.0
DETAIL “A”
0.86
(.034)
REF
1.10
(.043)
MAX
0.18
(.007)
(.039)
BSC
SEATING
PLANE
0.17 – 0.27
(.007 – .011)
TYP
0.1016 ±0.0508
(.004 ±.002)
MSOP (MSE16(12)) 0213 REV D
0.50
(.0197)
BSC
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
6. EXPOSED PAD DIMENSION DOES INCLUDE MOLD FLASH. MOLD FLASH ON E-PAD SHALL
NOT EXCEED 0.254mm (.010") PER SIDE.
3637fa
23
For more information www.linear.com/LTC3637
LTC3637
PACKAGE DESCRIPTION
Please refer to http://www.linear.com/designtools/packaging/ for the most recent package drawings.
DHC Package
16-Lead Plastic DFN (5mm × 3mm)
(Reference LTC DWG # 05-08-1706 Rev Ø)
0.65 ±0.05
3.50 ±0.05
1.65 ±0.05
2.20 ±0.05 (2 SIDES)
PACKAGE
OUTLINE
0.25 ± 0.05
0.50 BSC
4.40 ±0.05
(2 SIDES)
RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS
R = 0.115
TYP
0.40 ±0.10
5.00 ±0.10
(2 SIDES)
9
16
R = 0.20
TYP
3.00 ±0.10
(2 SIDES)
1.65 ±0.10
(2 SIDES)
PIN 1
TOP MARK
(SEE NOTE 6)
PIN 1
NOTCH
(DHC16) DFN 1103
8
1
0.25 ±0.05
0.75 ±0.05
0.200 REF
0.50 BSC
4.40 ±0.10
(2 SIDES)
0.00 – 0.05
BOTTOM VIEW—EXPOSED PAD
NOTE:
1. DRAWING PROPOSED TO BE MADE VARIATION OF VERSION (WJED-1) IN JEDEC
PACKAGE OUTLINE MO-229
2. DRAWING NOT TO SCALE
3. ALL DIMENSIONS ARE IN MILLIMETERS
4. DIMENSIONS OF EXPOSED PAD ON BOTTOM OF PACKAGE DO NOT INCLUDE
MOLD FLASH. MOLD FLASH, IF PRESENT, SHALL NOT EXCEED 0.15mm ON ANY SIDE
5. EXPOSED PAD SHALL BE SOLDER PLATED
6. SHADED AREA IS ONLY A REFERENCE FOR PIN 1 LOCATION ON THE
TOP AND BOTTOM OF PACKAGE
3637fa
24
For more information www.linear.com/LTC3637
LTC3637
REVISION HISTORY
REV
DATE
DESCRIPTION
PAGE NUMBER
A
05/14 Clarify FBO and UVLO pin description
Fix typos on Block Diagram. Clarify SS operation.
Clarify FBO operation
7
8
10
18
Clarify Design Example
3637fa
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.
25
LTC3637
TYPICAL APPLICATION
5.5V to 76V Input to 5V Output, 1A Step-Down Regulator
Efficiency vs Load Current
L1
100
90
80
70
60
50
40
30
20
10
0
V
= 5V
OUT
5.2µH
V
5V
1A
OUT
V
IN
V
SW
LTC3637
IN
5.5V TO 76V
C
C
OUT
47µF
IN
D1
2.2µF
RUN
V
FB
OVLO
SS
V
FBO
V
PRG1
PRG2
I
SET
GND
3637 TA07a
V
V
V
= 12V
= 24V
= 70V
IN
IN
IN
C
C
: TDK CGA6N3X7R2A225K
IN
OUT
: MURATA GCM32ER70J476KE19L
D1: VISHAY SS2H10
L1: COILCRAFT MSS1038T-522
0.1
1
10
100
1000
LOAD CURRENT (mA)
3637 TA07b
RELATED PARTS
PART NUMBER DESCRIPTION
COMMENTS
LTC3639
LTC3630A
LTC3642
LTC3631
LTC3632
LT®3990
LTC3891
150V, 100mA Synchronous Step-Down Regulator
V : 4V to 150V, V
= 0.8V, I = 12µA, I = 1.4µA,
OUT(MIN) Q SD
IN
MSOP-16(12)E
76V, 500mA Synchronous Step-Down DC/DC Converter
V : 4V to 76V, V
= 0.8V, I = 12µA, I = 3µA,
IN
OUT(MIN) Q SD
3 × 5 DFN-16, MSOP-16(12)E
45V (Transient to 60V) 50mA Synchronous Step-Down
DC/DC Converter
V : 4.5V to 45V, V = 0.8V, I = 12µA, I = 3µA,
IN
OUT(MIN)
Q
SD
3 × 3 DFN-8, MSOP-8
45V (Transient to 60V) 100mA Synchronous Step-Down
DC/DC Converter
V : 4.5V to 45V, V
= 0.8V, I = 12µA, I = 3µA,
Q SD
IN
OUT(MIN)
3 × 3 DFN-8, MSOP-8
50V (Transient to 60V) 20mA Synchronous Step-Down
DC/DC Converter
V : 4.5V to 50V, V
= 0.8V, I = 12µA, I = 3µA,
Q SD
IN
OUT(MIN)
3 × 3 DFN-8, MSOP-8
62V, 350mA, 2.2MHz High Efficiency Micropower Step-Down V : 4.2V to 62V, V
= 1.21V, I = 2.5µA, I < 1µA,
Q SD
IN
OUT(MIN)
DC/DC Converter with I = 2.5µA
3 × 3 DFN-10, MSOP-16E
Q
Low I , 60V Synchronous Step-Down Regulator
V : 4V to 60V, V = 0.8V, I = 50µA, I = 14µA,
Q
IN
OUT(MIN)
Q
SD
3 × 4 QFN-20, TSSOP-20E
3637fa
LT 0514 • PRINTED IN USA
LinearTechnology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
26
●
●
(408)432-1900 FAX: (408) 434-0507 www.linear.com/LTC3637
LINEAR TECHNOLOGY CORPORATION 2013
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