LT3693 [Linear]
36V, 3.5A, 2.4MHz Step-Down Switching Regulator; 36V ， 3.5A ， 2.4MHz是降压型开关稳压器
| 型号： | LT3693 |
| 厂家： | 
Linear |
| 描述： | 36V, 3.5A, 2.4MHz Step-Down Switching Regulator |
| 文件： | 总24页 (文件大小：308K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
LT3693
36V, 3.5A, 2.4MHz
Step-Down Switching Regulator
U
DESCRIPTIO
FEATURES
The LT®3693 is an adjustable frequency (200kHz to
2.4MHz)monolithicbuckswitchingregulatorthataccepts
■
Wide Input Range: 3.6V to 36V
■
3.5A Maximum Output Current
■
Adjustable Switching Frequency: 200kHz to 2.4MHz
Low Shutdown Current: I < 1μA
Integrated Boost Diode
Synchronizable Between 250kHz to 2MHz
Power Good Flag
Saturating Switch Design: 95m On-Resistance
0.790V Feedback Reference Voltage
Output Voltage: 0.79V to 30V
Thermal Protection
input voltages up to 36V. A high efficiency 95m switch
is included on the die along with a boost Schottky diode
and the necessary oscillator, control, and logic circuitry.
Current mode topology is used for fast transient response
and good loop stability. Shutdown reduces input supply
current to less than 1μA while a resistor and capacitor on
the RUN/SS pin provide a controlled output voltage ramp
■
■
■
■
■
■
■
■
■
■
Q
(soft-start). A power good flag signals when V
reaches
OUT
91% of the programmed output voltage. The LT3693 is
available in 10-Pin MSOP and 3mm × 3mm DFN packages
with exposed pads for low thermal resistance.
Soft-Start Capability
Small 10-Pin Thermally Enhanced MSOP and
(3mm × 3mm) DFN Packages
, LT, LTC and LTM are registered trademarks of Linear Technology Corporation.
All other trademarks are the property of their respective owners.
U
APPLICATIO S
■
Automotive Battery Regulation
■
Power for Portable Products
■
Distributed Supply Regulation
■
Industrial Supplies
■
Wall Transformer Regulation
U
TYPICAL APPLICATIO
5V Step-Down Converter
Efficiency
V
OUT
100
90
80
70
60
50
V
IN
5V
6.3V TO 36V
3.5A
V
= 12V
IN
V
IN
BD
RUN/SS
BOOST
OFF ON
15k
V
= 34V
IN
V
= 24V
IN
0.47 F
4.7 H
V
C
SW
LT3693
GND
10 F
RT
680pF
PG
V
= 5V
OUT
536k
63.4k
L = 4.7μH
SYNC
FB
f = 600kHz
100k
47 F
0
0.5
1
1.5
2
2.5
3
3.5
OUTPUT CURRENT (A)
3693 G01
3693 TA01a
3693f
1
LT3693
W W U W
ABSOLUTE AXI U RATI GS
(Note 1)
Operating Junction Temperature Range (Note 2)
LT3693E............................................. –40°C to 125°C
LT3693I.............................................. –40°C to 125°C
Storage Temperature Range................... –65°C to 150°C
Lead Temperature (Soldering, 10 sec)
V , RUN/SS Voltage.................................................36V
IN
BOOST Pin Voltage ...................................................56V
BOOST Pin Above SW Pin.........................................30V
FB, RT, V Voltage.......................................................5V
C
PG, BD Voltage .........................................................30V
(MSE Only) ....................................................... 300°C
SYNC Voltage............................................................20V
PIN CONFIGURATION
TOP VIEW
TOP VIEW
BD
BOOST
SW
1
2
3
4
5
10 RT
BD
BOOST
SW
1
2
3
4
5
10 RT
9
8
7
6
V
C
9
8
7
6
V
C
11
11
FB
FB
V
PG
SYNC
IN
V
IN
PG
RUN/SS
RUN/SS
SYNC
MSE PACKAGE
10-LEAD PLASTIC MSOP
= 45°C/W, θ = 10°C/W
JC
EXPOSED PAD (PIN 11) IS GND, MUST BE SOLDERED TO PCB
DD PACKAGE
θ
JA
10-LEAD (3mm × 3mm) PLASTIC DFN
= 45°C/W, θ = 10°C/W
JC
EXPOSED PAD (PIN 11) IS GND, MUST BE SOLDERED TO PCB
θ
JA
ORDER INFORMATION
LEAD FREE FINISH
LT3693EDD#PBF
LT3693IDD#PBF
LT3693EMSE#PBF
LT3693IMSE#PBF
TAPE AND REEL
PART MARKING*
LDGB
PACKAGE DESCRIPTION
TEMPERATURE RANGE
LT3693EDD#TRPBF
LT3693IDD#TRPBF
LT3693EMSE#TRPBF
LT3693IMSE#TRPBF
10-Lead (3mm × 3mm) Plastic DFN
10-Lead (3mm × 3mm) Plastic DFN
10-Lead Plastic MSOP
–40°C to 125°C
–40°C to 125°C
–40°C to 125°C
–40°C to 125°C
LDGB
LTDFZ
LTDFZ
10-Lead Plastic MSOP
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/
ELECTRICAL CHARACTERISTICS The ● denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C. VIN = 10V, VRUN/SS = 10V, VBOOST = 15V, VBD = 3.3V unless otherwise
noted. (Note 2)
PARAMETER
CONDITIONS
MIN
TYP
3
MAX
3.6
0.5
1.2
2.3
0.5
1.8
UNITS
V
●
●
Minimum Input Voltage
Quiescent Current from V
V
V
V
V
V
= 0.2V
0.01
0.45
1.3
μA
IN
RUN/SS
= 3V, Not Switching
= 0, Not Switching
mA
mA
μA
BD
BD
Quiescent Current from BD
= 0.2V
0.01
0.9
RUN/SS
●
= 3V, Not Switching
mA
3693f
BD
2
LT3693
ELECTRICAL CHARACTERISTICS
The ● denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C. VIN = 10V, VRUN/SS = 10V, VBOOST = 15V, VBD = 3.3V unless otherwise
noted. (Note 2)
PARAMETER
CONDITIONS
MIN
TYP
1
MAX
10
UNITS
μA
V
BD
= 0, Not Switching
Minimum Bias Voltage (BD Pin)
Feedback Voltage
2.7
3
V
780
775
790
790
800
805
mV
mV
●
●
FB Pin Bias Current (Note 3)
FB Voltage Line Regulation
V
= 0.8V, V = 0.4V
10
0.002
525
2000
60
40
nA
%/V
FB
C
4V < V < 36V
0.01
IN
Error Amp g
μMho
m
Error Amp Gain
V Source Current
μA
μA
A/V
V
C
V Sink Current
C
60
V Pin to Switch Current Gain
C
5.3
V Clamp Voltage
C
2.0
Switching Frequency
R = 8.66k
2.2
1.0
200
2.45
1.1
230
2.7
1.25
260
MHz
MHz
kHz
T
R = 29.4k
T
R = 187k
T
●
●
Minimum Switch Off-Time
Switch Current Limit
60
5.4
335
0.02
1.5
35
150
6.0
nS
A
Duty Cycle = 5%
4.6
Switch V
I
= 3.5A
SW
mV
μA
V
CESAT
Boost Schottky Reverse Leakage
Minimum Boost Voltage (Note 4)
BOOST Pin Current
V
SW
= 10V, V = 0V
2
BD
2.0
60
8
I
= 1A
mA
μA
V
SW
RUN/SS Pin Current
V
= 2.5V
5
RUN/SS
RUN/SS Input Voltage High
RUN/SS Input Voltage Low
PG Threshold Offset from Feedback Voltage
PG Hysteresis
2.5
0.2
V
V
FB
Rising
65
10
mV
mV
μA
μA
V
PG Leakage
V
V
= 5V
0.1
800
1
PG
●
PG Sink Current
= 0.4V
200
0.5
PG
SYNC Low Threshold
SYNC High Threshold
SYNC Pin Bias Current
0.8
V
V
SYNC
= 0V
0.1
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.
Note 3: Bias current flows out of the FB pin.
Note 4: This is the minimum voltage across the boost capacitor needed to
guarantee full saturation of the switch.
Note 2: The LT3693E is guaranteed to meet performance specifications
from 0°C to 125°C. Specifications over the –40°C to 125°C operating
temperature range are assured by design, characterization and correlation
with statistical process controls. The LT3693I specifications are
guaranteed over the –40°C to 125°C temperature range.
3693f
3
LT3693
U W
TA = 25°C unless otherwise noted.
TYPICAL PERFOR A CE CHARACTERISTICS
Efficiency
Efficiency
Efficiency
100
90
80
70
60
50
100
3.0
2.5
2.0
1.5
1.0
0.5
100
90
80
70
60
50
V
= 12V
IN
V
= 12V
IN
90
80
70
V
= 34V
IN
V
= 34V
IN
V
= 24V
IN
V
= 24V
IN
V
V
= 12V
= 5V
IN
OUT
L = 4.7μH
60
50
V
= 5V
V
= 3.3V
OUT
OUT
L = 4.7μH
L = 3.3μH
f = 600kHz
f = 600kHz
f = 600kHz
0
0.5
1
1.5
2
2.5
3
3.5
0
0.5
1
1.5
2
2.5
3.5
0
0.5
1
1.5
2
2.5
3
3.5
3
OUTPUT CURRENT (A)
OUTPUT CURRENT (A)
OUTPUT CURRENT (A)
3693 G01
3693 G03
3693 G02
Switch Current Limit
Maximum Load Current
Maximum Load Current
5.5
5.0
4.5
5.5
5.0
4.5
4.0
3.5
3.0
6.0
5.5
5.0
TYPICAL
TYPICAL
MINIMUM
MINIMUM
4.0
3.5
4.5
4.0
V
T
= 3.3V
V
T
= 5V
OUT
A
OUT
A
= 25°C
= 25°C
3.0
2.5
3.5
3.0
L = 4.7μH
L = 4.7μH
f = 600kHz
f = 600kHz
5
10
15
20
25
30
10
20
INPUT VOLTAGE (V)
25
30
20
60
40
DUTY CYCLE (%)
80
100
5
15
0
INPUT VOLTAGE (V)
3693 G06
3693 G07
3693 G08
Switch Current Limit
Switch Voltage Drop
Boost Pin Current
6.5
6.0
5.5
5.0
4.5
4.0
3.5
3.0
2.5
2.0
700
600
120
105
90
75
60
45
30
15
0
DUTY CYCLE = 10 %
500
400
300
200
100
DUTY CYCLE = 90 %
0
–50 –25
0
25 50 75 100 125 150
TEMPERATURE (°C)
3693 G09
0
1
2
3
4
5
0
1
2
3
4
5
SWITCH CURRENT (A)
SWITCH CURRENT (A)
3693 G10
3693 G11
3693f
4
LT3693
U W
TYPICAL PERFOR A CE CHARACTERISTICS
TA = 25°C unless otherwise noted.
Switching Frequency
Frequency Foldback
Feedback Voltage
1200
1.20
1.15
1.10
1.05
1.00
0.95
0.90
0.85
0.80
840
820
800
780
760
R
= 34.0k
R
= 34.0k
T
T
1000
800
600
400
200
0
–50 –25
0
25 50 75 100 125 150
TEMPERATURE (oC)
3693 G13
700 800 900
0
100 200 300 400 500 600
–50 –25
0
25 50 75 100 125 150
TEMPERATURE (°C)
3693 G12
FB PIN VOLTAGE (mV)
3693 G14
Soft-Start
RUN/SS Pin Current
Minimum Switch On-Time
140
120
7
6
5
4
3
2
1
0
12
10
8
100
80
60
40
20
6
4
2
0
0
–50 –25
0
25 50 75 100 125 150
TEMPERATURE (°C)
3693 G15
20
RUN/SS PIN VOLTAGE (V)
30
35
0.5
1
2
2.5
3
3.5
0
15
25
0
1.5
5
10
RUN/SS PIN VOLTAGE (V)
3693 G16
3693 G17
Boost Diode
Error Amp Output Current
Minimum Input Voltage
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0
50
40
5.0
4.5
4.0
3.5
3.0
2.5
2.0
30
20
10
0
–10
–20
–30
–40
–50
V
A
= 3.3V
OUT
T
= 25oC
L = 4.7MH
f = 600kHz
0
0.5
1.0
1.5
2.0
1
10
100
1000
10000
–200
–100
0
100
200
BOOST DIODE CURRENT (A)
FB PIN ERROR VOLTAGE (mV)
LOAD CURRENT (mA)
3693 G18
3693 G20
3693 G19
3693f
5
LT3693
U W
TA = 25°C unless otherwise noted.
TYPICAL PERFOR A CE CHARACTERISTICS
VC Voltages
Power Good Threshold
Minimum Input Voltage
2.50
95
6.5
2.00
1.50
6.0
5.5
5.0
90
85
80
75
CURRENT LIMIT CLAMP
SWITCHING THRESHOLD
1.00
0.50
0
V
A
= 5V
OUT
4.5
4.0
T
= 25 oC
L = 4.7MH
f = 600kHz
–50 –25
0
25 50 75 100 125 150
TEMPERATURE (°C)
–50 –25
0
25 50 75 100 125 150
TEMPERATURE (°C)
3693 G23
1
10
100
1000
10000
LOAD CURRENT (mA)
3693 G22
3693 G21
Switching Waveforms;
Discontinuous Operation
Switching Waveforms;
Continuous Operation
V
SW
V
5V/DIV
SW
5V/DIV
I
I
L
L
0.2A/DIV
0.5A/DIV
V
OUT
V
OUT
10mV/DIV
10mV/DIV
3693 G25
3693 G26
V
V
LOAD
= 12V
1μs/DIV
1μs/DIV
IN
V
V
LOAD
= 12V
IN
OUT
= 3.3V
OUT
= 3.3V
= 1A
I
= 110mA
I
3693f
6
LT3693
U
U
U
PI FU CTIO S
BD (Pin 1): This pin connects to the anode of the boost
Schottky diode. BD also supplies current to the internal
regulator.
SYNC (Pin 6): This is the external clock synchronization
input. Ground this pin when notused. Tie to a clock source
for synchronization. Clock edges should have rise and
fall times faster than 1μs. Do not leave pin floating. See
synchronizing section in Applications Information.
BOOST (Pin 2): This pin is used to provide a drive
voltage,higherthantheinputvoltage,totheinternalbipolar
NPN power switch.
PG (Pin 7): The PG pin is the open collector output of an
internal comparator. PG remains low until the FB pin is
within9%ofthefinalregulationvoltage. PGoutputisvalid
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.
when V is above 3.6V and RUN/SS is high.
IN
FB (Pin 8): The LT3693 regulates the FB pin to 0.790V.
Connect the feedback resistor divider tap to this pin.
V (Pin 4): The V pin supplies current to the LT3693’s
IN
IN
internal regulator and to the internal power switch. This
pin must be locally bypassed.
V (Pin 9): The V pin is the output of the internal error
C
C
amplifier. The voltage on this pin controls the peak switch
current. Tie an RC network from this pin to ground to
compensate the control loop.
RUN/SS (Pin 5): The RUN/SS pin is used to put the
LT3693 in shutdown mode. Tie to ground to shut down
the LT3693. Tie to 2.5V or more for normal operation. If
the shutdown feature is not used, tie this pin to the V
RT(Pin10):OscillatorResistorInput.Connectingaresistor
to ground from this pin sets the switching frequency.
IN
pin. RUN/SS also provides a soft-start function; see the
Applications Information section.
Exposed Pad (Pin 11): Ground. The Exposed Pad must
be soldered to PCB.
W
BLOCK DIAGRA
V
IN
V
IN
4
–
+
C1
BD
1
INTERNAL 0.79V REF
RUN/SS
5
SLOPE COMP
SWITCH
LATCH
BOOST
SW
2
3
C3
R
RT
OSCILLATOR
200kHzTO2.4MHz
Q
10
6
S
L1
R
T
V
OUT
SYNC
C2
D1
SOFT-START
PG
7
V
C
CLAMP
ERROR AMP
+
–
+
–
0.7V
V
C
9
C
C
C
F
R
C
GND
11
FB
8
R2
R1
3693 BD
3693f
7
LT3693
OPERATION
The LT3693 is a constant frequency, current mode step-
down regulator. An oscillator, with frequency set by RT,
enables an RS flip-flop, turning on the internal power
switch. An amplifier and comparator monitor the current
efficiency. The RUN/SS pin is used to place the LT3693
in shutdown, disconnecting the output and reducing the
input current to less than 0.5μA.
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.
flowing between the V and SW pins, turning the switch
IN
off when this current reaches a level determined by the
voltage at V . An error amplifier measures the output
C
voltage through an external resistor divider tied to the FB
pin and servos the V pin. If the error amplifier’s output
C
increases, more current is delivered to the output; if it
The oscillator reduces the LT3693’s operating frequency
when the voltage at the FB pin is low. This frequency
foldbackhelpstocontroltheoutputcurrentduringstartup
and overload.
decreases,lesscurrentisdelivered.Anactiveclamponthe
V pinprovidescurrentlimit. TheV pinisalsoclampedto
C
C
the voltage on the RUN/SS pin; soft-start is implemented
by generating a voltage ramp at the RUN/SS pin using an
external resistor and capacitor.
TheLT3693containsapowergoodcomparatorwhichtrips
when the FB pin is at 91% of its regulated value. The PG
output is an open-collector transistor that is off when the
output is in regulation, allowing an external resistor to pull
the PG pin high. Power good is valid when the LT3693 is
Aninternalregulatorprovidespowertothecontrolcircuitry.
The bias regulator normally draws power from the V pin,
but if the BD pin is connected to an external voltage higher
than 3V bias power will be drawn from the external source
(typically the regulated output voltage). This improves
IN
enabled and V is above 3.6V.
IN
3693f
8
LT3693
APPLICATIONS INFORMATION
FB Resistor Network
where V is the typical input voltage, V
is the output
IN
OUT
voltage, V is the catch diode drop (~0.5V) and V is the
D
SW
The output voltage is programmed with a resistor divider
between the output and the FB pin. Choose the 1% resis-
tors according to:
internal switch drop (~0.5V at max load). This equation
shows that slower switching frequency is necessary to
safely accommodate high V /V
ratio. Also, as shown
IN OUT
VOUT
0.79V
⎛
⎞
⎠
inthenextsection,lowerfrequencyallowsalowerdropout
voltage. The reason input voltage range depends on the
switchingfrequencyisbecausetheLT3693switchhasfinite
minimum on and off times. The switch can turn on for a
minimumof~150nsandturnoffforaminimumof~150ns.
Typical minimum on time at 25°C is 80ns. This means that
the minimum and maximum duty cycles are:
R1=R2
–1
⎜
⎝
⎟
Reference designators refer to the Block Diagram.
Setting the Switching Frequency
The LT3693 uses a constant frequency PWM architecture
thatcanbeprogrammedtoswitchfrom200kHzto2.4MHz
by using a resistor tied from the RT pin to ground. A table
showing the necessary RT value for a desired switching
frequency is in Figure 1.
DCMIN = fSWtON MIN
(
)
DCMAX =1– fSWtOFF MIN
(
)
where f is the switching frequency, the t
is the
ON(MIN)
SW
SWITCHING FREQUENCY (MHz)
R VALUE (kΩ)
T
minimum switch on time (~150ns), and the t
is
OFF(MIN)
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1.0
1.2
1.4
1.6
1.8
2.0
2.2
2.4
215
140
100
78.7
63.4
53.6
45.3
39.2
34
26.7
22.1
18.2
15
the minimum switch off time (~150ns). These equations
show that duty cycle range increases when switching
frequency is decreased.
A good choice of switching frequency should allow ad-
equate input voltage range (see next section) and keep
the inductor and capacitor values small.
Input Voltage Range
The maximum input voltage for LT3693 applications
depends on switching frequency and Absolute Maxi-
12.7
10.7
9.09
mum Ratings of the V and BOOST pins (36V and 56V
IN
respectively).
Figure 1. Switching Frequency vs. RT Value
While the output is in start-up, short-circuit, or other
overload conditions, the switching frequency should be
chosen according to the following equation:
Operating Frequency Tradeoffs
Selection of the operating frequency is a tradeoff between
efficiency,componentsize,minimumdropoutvoltage,and
maximum input voltage. The advantage of high frequency
operationisthatsmallerinductorandcapacitorvaluesmay
be used. The disadvantages are lower efficiency, lower
maximum input voltage, and higher dropout voltage. The
VOUT + VD
V
=
– VD + VSW
IN MAX
(
)
fSWtON MIN
(
)
where V
OUT
is the maximum operating input voltage,
IN(MAX)
V
is the output voltage, V is the catch diode drop
D
highest acceptable switching frequency (f
given application can be calculated as follows:
) for a
SW(MAX)
(~0.5V), V is the internal switch drop (~0.5V at max
SW
load), f is the switching frequency (set by R ), and
SW
ON(MIN)
T
VD + VOUT
t
istheminimumswitchontime(~100ns).Notethat
fSW MAX
=
(
)
tON MIN V + V – V
(
)
a higher switching frequency will depress the maximum
D
IN
SW
(
)
3693f
9
LT3693
APPLICATIONS INFORMATION
operating input voltage. Conversely, a lower switching
frequency will be necessary to achieve safe operation at
high input voltages.
ripple current. The LT3693’s switch current limit (I ) is
LIM
5.5A at low duty cycles and decreases linearly to 4.5A at
DC = 0.8. The maximum output current is a function of
the inductor ripple current:
If the output is in regulation and no short-circuit, start-
up, or overload events are expected, then input voltage
transients of up to 36V are acceptable regardless of the
switching frequency. In this mode, the LT3693 may enter
pulse skipping operation where some switching pulses
are skipped to maintain output regulation. In this mode
the output voltage ripple and inductor current ripple will
be higher than in normal operation.
I
= I – ΔI /2
LIM L
OUT(MAX)
Be sure to pick an inductor ripple current that provides
sufficient maximum output current (I ).
OUT(MAX)
The largest inductor ripple current occurs at the highest
V . To guarantee that the ripple current stays below the
IN
specified maximum, the inductor value should be chosen
according to the following equation:
The minimum input voltage is determined by either the
LT3693’s minimum operating voltage of ~3.6V or by its
maximum duty cycle (see equation in previous section).
The minimum input voltage due to duty cycle is:
⎛
⎞
⎛
⎞
VOUT + VD
fSWΔIL
VOUT + VD
L =
1–
⎜
⎟
⎜
⎟
V
⎝
⎠
⎝
⎠
IN(MAX)
VOUT + VD
where V is the voltage drop of the catch diode (~0.4V),
D
V
=
– VD + VSW
IN MIN
(
)
V
is the maximum input voltage, V
is the output
1– fSWtOFF MIN
IN(MAX)
OUT
(
)
voltage, f is the switching frequency (set by RT), and
SW
L is in the inductor value.
whereV
istheminimuminputvoltage,andt
OFF(MIN)
IN(MIN)
is the minimum switch off time (150ns). Note that higher
switching frequency will increase the minimum input
voltage. If a lower dropout voltage is desired, a lower
switching frequency should be used.
The inductor’s RMS current rating must be greater than
the maximum load current and its saturation current
should be about 30% higher. For robust operation in fault
conditions (start-up or short circuit) and high input volt-
age (>30V), the saturation current should be above 5A.
To keep the efficiency high, the series resistance (DCR)
should be less than 0.05 , and the core material should
be intended for high frequency applications. Table 1 lists
several vendors and suitable types.
Inductor Selection
For a given input and output voltage, the inductor value
and switching frequency will determine the ripple current.
The ripple current ΔI increases with higher V or V
L
IN
OUT
and decreases with higher inductance and faster switch-
ing frequency. A reasonable starting point for selecting
the ripple current is:
Table 1. Inductor Vendors
VENDOR URL
PART SERIES
TYPE
Murata
TDK
www.murata.com
LQH55D
Open
www.componenttdk.com SLF10145
Shielded
ΔI = 0.4(I
)
OUT(MAX)
L
Toko
www.toko.com
D75C
D75F
Shielded
Open
where I
is the maximum output load current. To
OUT(MAX)
guarantee sufficient output current, peak inductor current
Sumida
NEC
www.sumida.com
CDRH74
CR75
Shielded
Open
mustbelowerthantheLT3693’sswitchcurrentlimit(I ).
The peak inductor current is:
LIM
CDRH8D43
Shielded
www.nec.com
MPLC073
MPBI0755
Shielded
Shielded
I
= I
+ ΔI /2
OUT(MAX) L
L(PEAK)
where I
is the peak inductor current, I
is
L(PEAK)
OUT(MAX)
the maximum output load current, and ΔI is the inductor
L
3693f
10
LT3693
APPLICATIONS INFORMATION
Of course, such a simple design guide will not always re-
sult in the optimum inductor for your application. A larger
value inductor provides a slightly higher maximum load
current and will reduce the output voltage ripple. If your
load is lower than 3.5A, 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. 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 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 opera-
tion, see Linear Technology Application Note 44. Finally,
ceramic input capacitor concerns the maximum input
voltage rating of the LT3693. A ceramic input capacitor
combined with trace or cable inductance forms a high
quality (under damped) tank circuit. If the LT3693 circuit
is plugged into a live supply, the input voltage can ring to
twice its nominal value, possibly exceeding the LT3693’s
voltage rating. This situation is easily avoided (see the Hot
Plugging Safety section).
For space sensitive applications, a 4.7μF ceramic capaci-
tor can be used for local bypassing of the LT3693 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 LT3693 to ~3.7V.
for duty cycles greater than 50% (V /V > 0.5), there
OUT IN
Output Capacitor and Output Ripple
is a minimum inductance required to avoid subharmonic
The output capacitor has two essential functions. Along
withtheinductor,itfiltersthesquarewavegeneratedbythe
LT3693toproducetheDCoutput. Inthisroleitdetermines
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
LT3693’s control loop. Ceramic capacitors have very low
equivalent series resistance (ESR) and provide the best
ripple performance. A good starting value is:
oscillations. See AN19.
Input Capacitor
Bypass the input of the LT3693 circuit with a ceramic
capacitor of X7R or X5R type. Y5V types have poor
performance over temperature and applied voltage, and
should not be used. A 10μF to 22μF ceramic capacitor is
adequate to bypass the LT3693 and will easily handle the
ripplecurrent.Notethatlargerinputcapacitanceisrequired
when a lower switching frequency is used. 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 lower performance electrolytic capacitor.
100
COUT
=
VOUT SW
f
where f is in MHz, and C
is the recommended
OUT
SW
output capacitance in μF. Use X5R or X7R types. This
choice will provide low output ripple and good transient
response. Transient performance can be improved with
a higher value capacitor if the compensation network is
also adjusted to maintain the loop bandwidth. A lower
value of output capacitor can be used to save space and
cost but transient performance will suffer. See the Fre-
quency Compensation section to choose an appropriate
compensation network.
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 LT3693 and to force this very high frequency
switching current into a tight local loop, minimizing EMI.
A 10μF capacitor is capable of this task, but only if it is
placed close to the LT3693 and the catch diode (see the
PCB Layout section). A second precaution regarding the
3693f
11
LT3693
APPLICATIONS INFORMATION
Table 2. Capacitor Vendors
VENDOR
PHONE
URL
PART SERIES
Ceramic,
Polymer,
Tantalum
Ceramic,
Tantalum
Ceramic,
Polymer,
Tantalum
Ceramic
COMMANDS
Panasonic
(714) 373-7366
www.panasonic.com
EEF Series
Kemet
Sanyo
(864) 963-6300
(408) 749-9714
www.kemet.com
T494, T495
POSCAP
www.sanyovideo.com
Murata
AVX
(408) 436-1300
(864) 963-6300
www.murata.com
www.avxcorp.com
Ceramic,
Tantalum
Ceramic
TPS Series
Taiyo Yuden
www.taiyo-yuden.com
When choosing a capacitor, look carefully through the
data sheet to find out what the actual capacitance is under
operating conditions (applied voltage and temperature).
A physically larger capacitor, or one with a higher volt-
age rating, may be required. High performance tantalum
or electrolytic capacitors can be used for the output
capacitor. Low ESR is important, so choose one that is
intended for use in switching regulators. The ESR should
be specified by the supplier, and should be 0.05 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.
where I
is the output load current. The only reason to
OUT
consideradiodewithalargercurrentratingthannecessary
for nominal operation is for the worst-case condition of
shorted output. The diode current will then increase to the
typical peak switch current. Peak reverse voltage is equal
to the regulator input voltage. Use a schottky diode with a
reverse voltage rating greater than the input voltage. Table
3 lists several Schottky diodes and their manufacturers.
Table 3. Diode Vendors
V
I
V AT 3A
R
AVE
F
PART NUMBER
(V)
(A)
(mV)
On Semiconductor
MBRA340
40
3
500
Diodes Inc.
PDS340
B340A
40
40
40
3
3
3
500
500
450
Catch Diode
B340LA
The catch diode conducts current only during switch off
time. Average forward current in normal operation can be
calculated from:
I
= I (V – V )/V
OUT IN OUT IN
D(AVG)
3693f
12
LT3693
APPLICATIONS INFORMATION
Frequency Compensation
well as long as the value of the inductor is not too high
and the loop crossover frequency is much lower than the
The LT3693 uses current mode control to regulate the
output.Thissimplifiesloopcompensation.Inparticular,the
LT3693 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. Frequency
compensation is provided by the components tied to the
switching frequency. A phase lead capacitor (C ) across
PL
the feedback divider may improve the transient response.
Figure 3 shows the transient response when the load cur-
rent is stepped from 1A to 3A and back to 1A.
LT3693
V pin, as shown in Figure 2. Generally a capacitor (C )
C
C
and a resistor (R ) in series to ground are used. In addi-
CURRENT MODE
SW
C
OUTPUT
POWER STAGE
tion, there may be lower value capacitor in parallel. This
ERROR
g
m
= 5.3mho
C
R1
AMPLIFIER
PL
capacitor (C ) is not part of the loop compensation but
F
FB
–
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.
g
=
m
525Mmho
ESR
+
0.8V
C1
+
3M
C1
Loop compensation determines the stability and transient
performance.Designingthecompensationnetworkisabit
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 stabil-
ity using a transient load. Figure 2 shows an equivalent
circuit for the LT3693 control loop. The error amplifier is a
transconductance amplifier with finite output impedance.
The power section, consisting of the modulator, power
switch and inductor, is modeled as a transconductance
amplifier generating an output current proportional to
POLYMER
OR
CERAMIC
V
GND
C
TANTALUM
R
C
R2
C
F
C
C
3693 F02
Figure 2. Model for Loop Response
V
OUT
100mV/DIV
I
L
1A/DIV
the voltage at the V pin. Note that the output capacitor
C
integratesthiscurrent, andthatthecapacitorontheV pin
C
10Ms/DIV
3693 F03
(C )integratestheerroramplifieroutputcurrent,resulting
C
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 . This simple model works
Figure 3. Transient Load Response of the LT3693 Front Page
Application as the Load Current is Stepped from 1A to 3A.
VOUT = 5V
C
C
3693f
13
LT3693
APPLICATIONS INFORMATION
V
is marginally adequate to support the boosted drive stage
whileusingtheinternalboostdiode.ForreliableBOOSTpin
operation with 2.5V outputs use a good external Schottky
diode (such as the ON Semi MBR0540), and a 1μF boost
capacitor (see Figure 4b). For lower output voltages the
boost diode can be tied to the input (Figure 4c), or to
OUT
BD
BOOST
V
V
IN
IN
LT3693
GND
C3
SW
4.7MF
another supply greater than 2.8V. Tying BD to V reduces
IN
the maximum input voltage to 28V. The circuit in Figure 4a
is more efficient because the BOOST pin current and BD
pin quiescent current comes from a lower voltage source.
You must also be sure that the maximum voltage ratings
of the BOOST and BD pins are not exceeded.
(4a) For V
> 2.8V
OUT
V
OUT
D2
BD
BOOST
V
V
IN
IN
LT3693
C3
SW
6.0
GND
4.7MF
5.5
5.0
4.5
4.0
3.5
3.0
TO START
(WORST CASE)
(4b) For 2.5V < V
< 2.8V
OUT
TO RUN
V
OUT
BD
BOOST
V
V
A
= 3.3V
OUT
T
= 25oC
2.5
2.0
L = 8.2MH
V
IN
LT3693
IN
C3
f = 600kHz
SW
1
10
100
1000
10000
GND
4.7MF
LOAD CURRENT (mA)
8.0
7.0
6.0
5.0
4.0
3.0
2.0
3693 FO5
TO START
(WORST CASE)
(4c) For V
< 2.5V; V
= 28V
IN(MAX)
OUT
Figure 4. Three Circuits For Generating The Boost Voltage
TO RUN
BOOST and BIAS Pin Considerations
Capacitor C3 and the internal boost Schottky diode (see
the Block Diagram) are used to generate a boost volt-
age that is higher than the input voltage. In most cases
a 0.47μF capacitor will work well. Figure 2 shows three
ways to arrange the boost circuit. The BOOST pin must be
more than 2.3V above the SW pin for best efficiency. For
outputs of 3V and above, the standard circuit (Figure 4a)
is best. For outputs between 2.8V and 3V, use a 1μF boost
capacitor. A 2.5V output presents a special case because it
V
T
= 5V
OUT
A
= 25oC
L = 8.2MH
f = 600kHz
1
10
100
1000
10000
LOAD CURRENT (mA)
3693 F06
Figure 5. The Minimum Input Voltage Depends on
Output Voltage, Load Current and Boost Circuit
3693f
14
LT3693
APPLICATIONS INFORMATION
The minimum operating voltage of an LT3693 application
is limited by the minimum input voltage (3.6V) and by the
maximum duty cycle as outlined in a previous section. For
proper startup, the minimum input voltage is also limited
by the boost circuit. If the input voltage is ramped slowly,
or the LT3693 is turned on with its RUN/SS 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 5 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
I
L
RUN
15k
1A/DIV
RUN/SS
GND
V
RUN/SS
2V/DIV
V
OUT
2V/DIV
3693 F07
2ms/DIV
Figure 6. To Soft-Start the LT3693, Add a Resisitor
and Capacitor to the RUN/SS Pin
Synchronization
Synchronizing the LT3693 oscillator to an external fre-
quency can be done by connecting a square wave (with
20% to 80% duty cycle) to the SYNC pin. The square
wave amplitude should have valleys that are below 0.3V
and peaks that are above 0.8V (up to 6V).
start. The plots show the worst-case situation where V
IN
is ramping very slowly. For lower start-up voltage, the
boost diode can be tied to V ; however, this restricts the
IN
The LT3693 may be synchronized over a 250kHz to 2MHz
input range to one-half of the absolute maximum rating
range. The R resistor should be chosen to set the LT3693
T
of the BOOST pin.
switchingfrequency20%belowthelowestsynchronization
input. For example, if the synchronization signal will be
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
250kHz and higher, the R should be chosen for 200kHz.
T
To assure reliable and safe operation the LT3693 will only
synchronize when the output voltage is near regulation
as indicated by the PG flag. It is therefore necessary to
choosealargeenoughinductorvaluetosupplytherequired
300mV above V . At higher load currents, the inductor
OUT
current is continuous and the duty cycle is limited by the
maximum duty cycle of the LT3693, requiring a higher
input voltage to maintain regulation.
output current at the frequency set by the R resistor. See
T
Inductor Selection section. It is also important to note that
Soft-Start
slope compensation is set by the R value: When the sync
T
frequency is much higher than the one set by R , the slope
T
The RUN/SS pin can be used to soft-start the LT3693,
reducing the maximum input current during start-up.
The RUN/SS pin is driven through an external RC filter to
create a voltage ramp at this pin. Figure 6 shows the start-
up and shut-down waveforms with the soft-start circuit.
By choosing a large RC time constant, the peak start-up
current can be reduced to the current that is required to
regulate the output, with no overshoot. Choose the value
oftheresistorsothatitcansupply20μAwhentheRUN/SS
pin reaches 2.5V.
compensation will be significantly reduced which may
require a larger inductor value to prevent subharmonic
oscillation.
3693f
15
LT3693
APPLICATIONS INFORMATION
Shorted and Reversed Input Protection
PCB Layout
If the inductor is chosen so that it won’t saturate exces-
sively, an LT3693 buck regulator will tolerate a shorted
output. There is another situation to consider in systems
where the output will be held high when the input to the
LT3693 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 LT3693’s
For proper operation and minimum EMI, care must be
taken during printed circuit board layout. Figure 8 shows
the recommended component placement with trace,
ground plane and via locations. Note that large, switched
currents flow in the LT3693’s V and SW pins, the catch
IN
diode (D1) and the input capacitor (C1). 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.
output. If the V pin is allowed to float and the RUN/SS
IN
pin is held high (either by a logic signal or because it is
tied to V ), then the LT3693’s internal circuitry will pull
IN
its quiescent current through its SW pin. This is fine if
your system can tolerate a few mA in this state. If you
ground the RUN/SS pin, the SW pin current will drop to
Finally, keep the FB and V nodes small so that the ground
C
essentially zero. However, if the V pin is grounded while
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 LT3693 to additional ground planes within the circuit
board and on the bottom side.
IN
the output is held high, then parasitic diodes inside the
LT3693 can pull large currents from the output through
the SW pin and the V pin. Figure 7 shows a circuit that
IN
will run only when the input voltage is present and that
protects against a shorted or reversed input.
D4
MBRS140
L1
C2
V
IN
V
BOOST
SW
V
OUT
IN
LT3693
V
OUT
RUN/SS
C
C
R
RT
V
C
GND FB
BACKUP
R
C
R2
3693 F08
R1
C1
D1
Figure 7. Diode D4 Prevents a Shorted Input from
R
PG
GND
Discharging a Backup Battery Tied to the Output. It Also
Protects the Circuit from a Reversed Input. The LT3693
Runs Only When the Input is Present
3693 F09
VIAS TO V
VIAS TO LOCAL GROUND PLANE
VIAS TO V
VIAS TO RUN/SS
VIAS TO PG
IN
OUTLINE OF LOCAL
GROUND PLANE
VIAS TO SYNC
OUT
Figure 8. A Good PCB Layout Ensures Proper, Low EMI Operation
3693f
16
LT3693
APPLICATIONS INFORMATION
Hot Plugging Safely
energized supply, the input network should be designed
to prevent this overshoot. Figure 9 shows the waveforms
that result when an LT3693 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. A good solution is shown
in Figure 9b. A 0.7 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. For high input voltages its impact on
efficiency is minor, reducing efficiency by 1.5 percent for
a 5V output at full load operating from 24V.
The small size, robustness and low impedance of ceramic
capacitors make them an attractive option for the input
bypasscapacitorofLT3693circuits.However,thesecapaci-
tors can cause problems if the LT3693 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
source, forms an under damped tank circuit, and the
voltage at the V pin of the LT3693 can ring to twice the
IN
nominal input voltage, possibly exceeding the LT3693’s
rating and damaging the part. If the input supply is poorly
controlled or the user will be plugging the LT3693 into an
CLOSING SWITCH
DANGER
SIMULATES HOT PLUG
V
IN
20V/DIV
I
IN
V
IN
RINGING V MAY EXCEED
IN
ABSOLUTE MAXIMUM RATING
LT3693
4.7MF
+
I
IN
10A/DIV
LOW
STRAY
IMPEDANCE
ENERGIZED
24V SUPPLY
INDUCTANCE
DUE TO 6 FEET
(2 METERS) OF
TWISTED PAIR
20Ms/DIV
(9a)
0.77
V
IN
20V/DIV
LT3693
4.7MF
+
0.1MF
I
IN
10A/DIV
20Ms/DIV
(9b)
V
IN
20V/DIV
LT3693
4.7MF
+
+
22MF
35V
AI.EI.
I
IN
10A/DIV
3693 F10
20Ms/DIV
(9c)
Figure 9. A Well Chosen Input Network Prevents Input Voltage Overshoot and
Ensures Reliable Operation when the LT3693 is Connected to a Live Supply
3693f
17
LT3693
APPLICATIONS INFORMATION
High Temperature Considerations
Power dissipation within the LT3693 can be estimated by
calculatingthetotalpowerlossfromanefficiencymeasure-
ment and subtracting the catch diode loss and inductor
loss. The die temperature is calculated by multiplying the
LT3693 power dissipation by the thermal resistance from
junction to ambient.
The PCB must provide heat sinking to keep the LT3693
cool. The Exposed Pad on the bottom of the package must
be soldered to a ground plane. This ground should be tied
to large copper layers below with thermal vias; these lay-
ers will spread the heat dissipated by the LT3693. Place
additionalviascanreducethermalresistancefurther.With
these steps, the thermal resistance from die (or junction)
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.
to ambient can be reduced to
= 35°C/W or less. With
JA
100LFPMairflow, thisresistancecanfallbyanother25%.
Further increases in airflow will lead to lower thermal re-
sistance. Because of the large output current capability of
the LT3693, it is possible to dissipate enough heat to raise
thejunctiontemperaturebeyondtheabsolutemaximumof
125°C. Whenoperatingathighambienttemperatures, the
maximum load current should be derated as the ambient
temperature approaches 125°C.
TYPICAL APPLICATIONS
5V Step-Down Converter
V
OUT
V
IN
5V
6.5V TO 36V
3.5A
V
BD
IN
RUN/SS
BOOST
ON OFF
L
0.47MF
4.7MH
V
SW
C
LT3693
GND
10MF
D
RT
15k
PG
536k
SYNC
FB
63.4k
680pF
47MF
100k
f = 600kHz
3693 TA02
D: ON SEMI MBRA340
L: NEC MPLC0730L4R7
3693f
18
LT3693
TYPICAL APPLICATIONS
3.3V Step-Down Converter
V
3.3V
3.5A
OUT
V
IN
4.6V TO 36V
V
IN
BD
RUN/SS
BOOST
ON OFF
L
0.47MF
3.3MH
V
SW
C
LT3693
GND
4.7MF
D
RT
19k
PG
316k
SYNC
63.4k
FB
680pF
47MF
100k
f = 600kHz
3693 TA03
D: ON SEMI MBRA340
L: NEC MPLC0730L3R3
2.5V Step-Down Converter
V
OUT
V
IN
2.5V
4V TO 36V
3.5A
V
IN
BD
D2
RUN/SS
BOOST
ON OFF
L
1 F
3.3 H
V
SW
C
4.7 F
LT3693
GND
D1
RT
15.4k
PG
215k
SYNC
FB
63.4k
680pF
47 F
100k
f = 600kHz
3693 TA04
D1: ON SEMI MBRA340
D2: MBR0540
L: NEC MPLC0730L3R3
3693f
19
LT3693
TYPICAL APPLICATIONS
5V, 2MHz Step-Down Converter
V
V
OUT
IN
5V
8.6V TO 22V
2.5A
TRANSIENT TO 36V
V
IN
BD
RUN/SS
BOOST
ON OFF
L
0.47 F
2.2 H
V
SW
C
LT3693
GND
4.7 F
D
RT
15k
PG
536k
SYNC
FB
12.7k
680pF
22 F
100k
f = 2MHz
3693 TA05
D: ON SEMI MBRA340
L: NEC MPLC0730L2R2
12V Step-Down Converter
V
OUT
V
IN
12V
15V TO 36V
3.5A
V
IN
BD
RUN/SS
BOOST
ON OFF
L
0.47 F
8.2 H
V
SW
C
LT3693
GND
10 F
D
RT
17.4k
PG
715k
SYNC
FB
63.4k
680pF
47 F
50k
f = 600kHz
3693 TA06
D: ON SEMI MBRA340
L: NEC MBP107558R2P
3693f
20
LT3693
TYPICAL APPLICATIONS
1.8V Step-Down Converter
V
1.8V
3.5A
OUT
V
IN
3.6V TO 27V
V
BD
IN
RUN/SS
BOOST
ON OFF
L
0.47MF
3.3MH
V
SW
C
LT3693
GND
4.7MF
D
RT
16.9k
PG
127k
SYNC
FB
78.7k
680pF
47MF
100k
f = 500kHz
3693 TA08
D: ON SEMI MBRA340
L: NEC MPLC0730L3R3
3693f
21
LT3693
PACKAGE DESCRIPTION
DD Package
10-Lead Plastic DFN (3mm × 3mm)
(Reference LTC DWG # 05-08-1699)
0.675 0.05
3.50 0.05
2.15 0.05 (2 SIDES)
1.65 0.05
PACKAGE
OUTLINE
0.25 0.05
0.50
BSC
2.38 0.05
(2 SIDES)
RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS
R = 0.115
0.38 0.10
TYP
6
10
3.00 0.10
(4 SIDES)
1.65 0.10
(2 SIDES)
PIN 1
TOP MARK
(SEE NOTE 6)
(DD) DFN 1103
5
1
0.25 0.05
0.50 BSC
0.75 0.05
0.200 REF
2.38 0.10
(2 SIDES)
0.00 – 0.05
BOTTOM VIEW—EXPOSED PAD
NOTE:
1. DRAWING TO BE MADE A JEDEC PACKAGE OUTLINE M0-229 VARIATION OF (WEED-2).
CHECK THE LTC WEBSITE DATA SHEET FOR CURRENT STATUS OF VARIATION ASSIGNMENT
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
3693f
22
LT3693
PACKAGE DESCRIPTION
MSE Package
10-Lead Plastic MSOP, Exposed Die Pad
(Reference LTC DWG # 05-08-1664 Rev B)
BOTTOM VIEW OF
EXPOSED PAD OPTION
2.06 0.102
2.794 0.102
(.110 .004)
0.889 0.127
(.035 .005)
(.081 .004)
1
1.83 0.102
(.072 .004)
5.23
(.206)
MIN
2.083 0.102 3.20 – 3.45
(.082 .004) (.126 – .136)
10
0.50
(.0197)
BSC
0.305 0.038
(.0120 .0015)
TYP
3.00 0.102
(.118 .004)
(NOTE 3)
0.497 0.076
(.0196 .003)
REF
10 9
8
7 6
RECOMMENDED SOLDER PAD LAYOUT
3.00 0.102
(.118 .004)
(NOTE 4)
4.90 0.152
(.193 .006)
DETAIL “A”
0.254
(.010)
0° – 6° TYP
1
2
3
4 5
GAUGE PLANE
0.53 0.152
(.021 .006)
0.86
(.034)
REF
1.10
(.043)
MAX
DETAIL “A”
0.18
(.007)
SEATING
PLANE
0.17 – 0.27
(.007 – .011)
TYP
0.1016 0.0508
(.004 .002)
0.50
(.0197)
BSC
MSOP (MSE) 0307 REV B
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
3693f
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.
23
LT3693
U
TYPICAL APPLICATIO
1.2V Step-Down Converter
V
1.2V
3.5A
OUT
V
IN
3.6V TO 27V
V
IN
BD
RUN/SS
BOOST
ON OFF
L
0.47 F
3.3 H
V
SW
C
LT3693
GND
4.7 F
D
RT
17k
PG
52.3k
SYNC
FB
78.7k
470pF
100k
100 F
f = 500kHz
3693 TA09
D: ON SEMI MBRA340
L: NEC MPLC0730L3R3
RELATED PARTS
PART NUMBER DESCRIPTION
COMMENTS
LT1766
LT1933
LT1936
LT1938
LT1940
60V, 1.2A (I ), 200kHz, High Efficiency Step-Down DC/DC Converter V : 5.5V to 60V, V
= 1.2V, I = 2.5mA, I = 25μA,
OUT
IN
OUT(MIN) Q SD
TSSOP16/E Package
500mA (I ), 500kHz Step-Down Switching Regulator in SOT-23
V : 3.6V to 36V, V
= 1.2V, I = 1.6mA, I < 1μA,
Q SD
OUT
IN
OUT(MIN)
ThinSOTTM Package
36V, 1.4A (I ), 500kHz, High Efficiency Step-Down DC/DC Converter V : 3.6V to 36V, V
= 1.2V, I = 1.9mA, I < 1μA,
OUT
IN
OUT(MIN)
Q
SD
3mm × 3mm DFN Package
2.5V, 2.2A (I ), 2.8MHz, High Efficiency Step-Down DC/DC Converter V : 3.6V to 25V, V
= 0.8V, I = 0.8mA, I < 1μA,
Q SD
OUT
IN
OUT(MIN)
OUT(MIN)
MS8E Package
Dual 25V, 1.4A (I ), 1.1MHz, High Efficiency Step-Down DC/DC
V : 3.6V to 25V, V
= 1.2V, I = 3.8mA, I < 30μA,
Q SD
OUT
IN
Converter
TSSOP16E Package
LT1976/LT1967 60V, 1.2A (I ), 200kHz/500kHz, High Efficiency Step-Down DC/DC
V : 3.3V to 60V, V
= 1.2V, I = 100μA, I < 1μA,
Q SD
OUT
IN
OUT(MIN)
Converters with Burst Mode Operation
TSSOP16E Package
LT3434/LT3435 60V, 2.4A (I ), 200kHz/500kHz, High Efficiency Step-Down DC/DC
V : 3.3V to 60V, V
= 1.2V, I = 100μA, I < 1μA,
Q SD
OUT
IN
OUT(MIN)
Converters with Burst Mode Operation
TSSOP16 Package
LT3437
LT3480
LT3481
LT3493
LT3505
LT3508
LT3680
LT3684
LT3685
60V, 400mA (I ), Micropower Step-Down DC/DC Converter with
V : 3.3V to 60V, V
= 1.25V, I = 100μA, I < 1μA,
Q SD
OUT
IN
OUT(MIN)
Burst Mode Operation
3mm × 3mm DFN10 and TSSOP16E Packages
36V with Transient Protection to 60V, 2A (I ), 2.4MHz, High Efficiency V : 3.6V to 38V, V
= 0.78V, I = 70μA, I < 1μA,
OUT
IN
OUT(MIN)
Q
SD
Step-Down DC/DC Converter with Burst Mode Operation
3mm × 3mm DFN10 and MSOP10E Packages
34V with Transient Protection to 36V, 2A (I ), 2.8MHz, High Efficiency V : 3.6V to 34V, V
= 1.26V, I = 50μA, I < 1μA,
OUT
IN
OUT(MIN)
Q
SD
Step-Down DC/DC Converter with Burst Mode Operation
3mm × 3mm DFN10 and MSOP10E Packages
36V, 1.4A (I ), 750kHz High Efficiency Step-Down
V : 3.6V to 36V, V = 0.8V, I = 1.9mA, I < 1μA,
OUT
IN
OUT(MIN)
Q
SD
DC/DC Converter
2mm x 3mm DFN6 Package
36V with Transient Protection to 40V, 1.4A (I ), 3MHz,
V : 3.6V to 34V, V = 0.78V, I = 2mA, I = 2μA,
OUT
IN
OUT(MIN)
Q
SD
High Efficiency Step-Down DC/DC Converter
3mm × 3mm DFN8 and MSOP8E Packages
36V with Transient Protection to 40V, Dual 1.4A (I ), 3MHz,
V : 3.7V to 37V, V = 0.8V, I = 4.6mA, I = 1μA,
OUT
IN
OUT(MIN)
Q
SD
High Efficiency Step-Down DC/DC Converter
4mm × 4mm QFN24 and TSSOP16E Packages
36V, 3.5A, 2.4MHz High Efficiency Step-Down DC/DC Converter
V : 3.6V to 34V, V = 0.78V, I = 75μA, I = 1μA,
IN
OUT(MIN)
Q
SD
3mm × 3mm DFN10 and MSOP10E Packages
34V with Transient Protection to 36V, 2A (I ), 2.8MHz,
V : 3.6V to 34V, V = 1.26V, I = 850μA, I < 1μA,
OUT
IN
OUT(MIN)
Q
SD
High Efficiency Step-Down DC/DC Converter
3mm × 3mm DFN10 and MSOP10E Packages
36V with Transient Protection to 60V, Dual 2A (I ), 2.4MHz,
V : 3.6V to 38V, V = 0.78V, I = 70μA, I < 1μA,
OUT
IN
OUT(MIN)
Q
SD
High Efficiency Step-Down DC/DC Converter
3mm × 3mm DFN10 and MSOP10E Packages
3693f
LT 0907 • PRINTED IN USA
LinearTechnology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
24
●
●
© LINEAR TECHNOLOGY CORPORATION 2007
(408) 432-1900 FAX: (408) 434-0507 www.linear.com
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