LTC3424 [Linear Systems]
Low Output Voltage 3MHz Micropower Synchronous Boost Converters; 低输出电压为3MHz微功率同步升压转换器
| 型号： | LTC3424 |
| 厂家： | 
Linear Systems |
| 描述： | Low Output Voltage 3MHz Micropower Synchronous Boost Converters |
| 文件： | 总12页 (文件大小：200K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
LTC3423/LTC3424
Low Output Voltage,
3MHz Micropower Synchronous
Boost Converters
U
FEATURES
DESCRIPTIO
The LTC®3423 and LTC3424 are high efficiency, fixed
frequency, step-up DC/DC converters that can regulate
output voltages as low as 1.5V from a single cell. An
applied voltage of at least 2.7V to the VDD pin is required
to power the internal control circuitry.
■
1.5V to 5.5V Adjustable Output Voltage
■
Synchronous Rectification: Up to 95% Efficiency
■
1A Switch Current (LTC3423) or
2A Switch Current (LTC3424)
■
Fixed Frequency Operation Up to 3MHz
■
Wide Input Range: 0.5V to 5.5V (Operating)
The devices include a 0.16Ω N-channel MOSFET switch
anda0.21ΩP-channelsynchronousrectifier.TheLTC3423
is intended for applications requiring less than 0.75W of
outputpowerandtheLTC3424for1.5Worless.Switching
frequencies up to 3MHz are programmed with an external
timing resistor and the oscillator can be synchronized to
an external clock.
Very Low Quiescent Current: 38µA (Burst Mode®
■
Operation)
■
No External Schottky Diode Required
■
Synchronizable Switching Frequency
■
Burst Mode Enable Control
OPTI-LOOP® Compensation
■
■
Very Low Shutdown Current: <1µA
■
Quiescent current is only 38µA in Burst Mode operation,
maximizing battery life in portable applications. Burst
Mode operation is user controlled and can be enabled by
driving the MODE/SYNC pin high. If the MODE/SYNC pin
has either a clock or is driven low then the operation is at
constant fixed frequency.
Small 10-Pin MSUOP Package
APPLICATIO S
■
Pagers
Handheld Instruments
Cordless Phones
Wireless Handsets
GPS Receivers
Battery Backup
■
■
■
Otherfeaturesincludea1µAshutdown,thermalshutdown
and current limit. The LTC3423 and LTC3424 are available
in the 10-lead MSOP package. For applications requiring
an output voltage greater than 2.6V, the LTC3401 and
LTC3402arerecommendedwithouttheneedofaseparate
voltage for the VDD pin.
■
■
, LTC and LT are registered trademarks of Linear Technology Corporation.
Burst Mode and OPTI-LOOP are registered trademarks of Linear Technology Corporation.
U
TYPICAL APPLICATIO
1-Cell to 1.8V at 600mA Step-Up Converter
V
= 2.7V TO 5.5V
DD
L1
2.2µH
Efficiency
V
DD
V
OUT
V
= 0.9V TO 1.5V
IN
1.8V
100
V
= 1.5V
600mA
IN
90
80
70
60
50
40
30
20
10
0
LTC3424
Burst Mode
OPERATION
6
10
3
4
7
8
9
5
R1
V
SW
DD
110k
V
= 1.2V
V = 0.9V
IN
IN
SHDN
V
OUT
FB
+
–
1
C3
CELL
V
IN
44µF
(2× 22µF)
2
MODE/SYNC
V
C
C4
C1
2.2µF
C2
10µF
1
470pF
R2
249k
R
GND
t
C5
4.7pF
V
V
= 3.3V
= 1.8V
DD
OUT
R
30.1k
RC
82k
t
WITH MBRM120T3 SCHOTTKY
0.1
1
10
100
1000
C1: TAIYO YUDEN JMK212BJ225MG
C2: TAIYO YUDEN JMK212BJ106MM
C3: TAIYO YUDEN JMK325BJ226MM
L1: SUMIDA CD43-2R2M
OUTPUT CURRENT (mA)
0 = FIXED FREQ
1 = Burst Mode OPERATION
3223/24 TA02
3423/24 TA01
34234f
1
LTC3423/LTC3424
W W
U W
U W
U
ABSOLUTE AXI U RATI GS
PACKAGE/ORDER I FOR ATIO
(Note 1)
VIN, VOUT, VDD Voltages.............................. –0.5V to 6V
SW Voltage ................................................. –0.5V to 6V
VC, Rt Voltages ......................... –0.5V to (VOUT + 0.3V)
SHDN, FB, MODE Voltages ......................... –0.5V to 6V
Operating Temperature Range (Note 2) .. –40°C to 85°C
Storage Temperature Range ................. –65°C to 125°C
Lead Temperature (Soldering, 10 sec).................. 300°C
ORDER PART
TOP VIEW
NUMBER
R
1
2
3
4
5
10 SHDN
t
MODE
9
8
7
6
V
C
LTC3423EMS
LTC3424EMS
V
FB
V
V
IN
SW
OUT
DD
GND
MS PACKAGE
10-LEAD PLASTIC MSOP
MS PART MARKING
TJMAX = 125°C
θJA = 130°C/ W 1 LAYER BOARD
θJA = 100°C/ W 4 LAYER BOARD
LTQM
LTQN
Consult LTC Marketing for parts specified with wider operating temperature ranges.
ELECTRICAL CHARACTERISTICS
The ● denotes specifications that apply over the full operating temperature range, otherwise specifications are at TA = 25°C.
VIN = 1.2V, VDD = 3.3V, VOUT = 1.8V, unless otherwise noted.
PARAMETER
CONDITIONS
MIN
2.7
TYP
MAX
5.5
5.5
5.5
1.28
50
UNITS
V
V
V
Input Voltage Range
●
●
●
●
DD
IN
Operating Voltage Range
(Note 4)
0.5
V
Output Voltage Adjust Range
Feedback Voltage
1.5
V
1.22
1.25
1
V
Feedback Input Current
V
= 1.25V
nA
µA
µA
µA
µA
µA
Ω
FB
Quiescent Current—Burst Mode Operation
Quiescent Current—SHDN
Quiescent Current—Active
NMOS Switch Leakage
V = 0V, MODE/SYNC = 3.3V (Note 3)
C
38
65
SHDN = 0V, Not Including Switch Leakage
0.1
440
0.1
0.1
0.16
0.21
1
V = 0V, MODE/SYNC = 0V, R = 300k (Note 3)
C
800
5
t
PMOS Switch Leakage
10
NMOS Switch On Resistance
PMOS Switch On Resistance
NMOS Current Limit
Ω
LTC3423
LTC3424
●
●
1
2
1.6
2.8
A
A
Maximum Duty Cycle
R = 15k
●
●
●
80
85
%
%
t
Minimum Duty Cycle
0
Frequency Accuracy
R = 15k
t
1.6
1.4
2
2.4
MHz
V
MODE/SYNC Input High
MODE/SYNC Input Low
MODE/SYNC Input Current
Error Amp Transconductance
0.4
1
V
V
= 5.5V
0.01
85
µA
MODE/SYNC
∆I = –5µA to 5µA, V = V
µmhos
C
FB
34234f
2
LTC3423/LTC3424
ELECTRICAL CHARACTERISTICS
The ● denotes specifications that apply over the full operating temperature range, otherwise specifications are at TA = 25°C.
VIN = 1.2V, VOUT = 3.3V unless otherwise noted.
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
SHDN Input High
SHDN Input Low
SHDN Input Current
V
= V = V
1
V
V
SHDN
IN
OUT
0.4
1
V
= 5.5V
0.01
µA
SHDN
Note 1: Absolute Maximum Ratings are those values beyond which the life
of a device may be impaired.
Note 3: Current is measured into V since the supply current is
DD
bootstrapped to the V pin. The outputs are not switching.
DD
Note 2: The LTC3423/LTC3424 are guaranteed to meet performance
specifications from 0°C to 70°C. Specifications over the –40°C to 85°C
operating temperature range are assured by design, characterization and
correlation with statistical process controls.
Note 4: Once the output is started, the IC is not dependant upon the V
supply.
IN
U W
TYPICAL PERFOR A CE CHARACTERISTICS
Transient Response
150mA to 450mA
Switching Waveform on SW Pin
VOUT
100mV/DIV
ACCOUPLED
SW
0.5V/DIV
450mA
IOUT
150mA
0V
COUT = 44µF
L = 2.2µH
fOSC = 1MHz
200µs/DIV
3423/24 G02
I
LOAD = 500mA 100ns/DIV
3423/24 G01
VOUT 1.8V
Burst Mode Operation
at 500µA Load
Burst Mode Operation
at 10mA Load
VOUT
100mV/DIV
AC COUPLED
VOUT
100mV/DIV
AC COUPLED
SW
1V/DIV
SW
1V/DIV
VIN = 1.2V
VOUT = 1.8V
COUT = 44µF
1ms/DIV
3423/24 G03
V
IN = 1.2V
500µs/DIV
3423/24 G04
VOUT = 1.8V
COUT = 44µF
MODE/SYNC PIN = HIGH
MODE/SYNC PIN = HIGH
34234f
3
LTC3423/LTC3424
U W
TYPICAL PERFOR A CE CHARACTERISTICS
Converter Efficiency 1.2V to 1.8V
LTC3424 Current Limit
LTC3423 Current Limit
100
90
80
70
60
50
40
30
20
10
0
3.4
3.2
3.0
2.8
2.6
2.4
2.2
2.0
1.80
1.75
1.70
1.65
300MHz
Burst Mode
OPERATION
3MHz
1MHz
1.60
1.55
1.50
1.45
1.40
WITH MBRM120T3 SCHOTTKY
10 100 1000
OUTPUT CURRENT (mA)
0.1
1
–15
25
TEMPERATURE (°C)
105
125
–55
–15
25
TEMPERATURE (°C)
105
125
65
–55
65
3223/24 G05
3423/24 G06
3423/24 G07
EA FB Voltage
Oscillator Frequency Accuracy
NMOS RDS(ON)
1.28
1.27
1.26
1.25
1.24
1.23
1.22
2.10
2.05
2.00
1.95
1.90
0.30
0.25
0.20
0.15
0.10
0.05
R
= 15k
V
= 1.8V
OUT
DD
T
V
= 3.3V
–15
25
TEMPERATURE (°C)
105
–15
25
TEMPERATURE (°C)
105
–15
25
TEMPERATURE (°C)
105
125
–55
125
–55
125
–55
65
65
65
3423/24 G08
3423/24 G09
3423/24 G10
Efficiency Loss Without Schottky
vs Frequency
PMOS RDS(ON)
14
12
10
8
0.40
0.35
0.30
0.25
0.20
0.15
V
V
= 1.8V
OUT
DD
T = 25°C
A
= 3.3V
6
4
2
0
–15
25
105
1.8
FREQUENCY (MHz)
2.6 3.0
–55
125
0.2 0.6
1.0 1.4
2.2
65
TEMPERATURE (°C)
3423/24 G11
3423/24 G12
34234f
4
LTC3423/LTC3424
U W
TYPICAL PERFOR A CE CHARACTERISTICS
Shutdown Threshold
Burst Mode Operation Current
1.10
1.05
1.00
0.95
0.90
0.85
0.80
0.75
0.70
0.65
0.60
44
42
40
38
36
34
32
30
–15
25
105
–15
25
TEMPERATURE (°C)
105
125
–55
125
–55
65
65
TEMPERATURE (°C)
3423/24 G13
3423/24 G14
U
U
U
PI FU CTIO S
Rt (Pin 1): Timing Resistor to Program the Oscillator
Frequency.
SW (Pin 4): Switch Pin. Connect inductor and optional
Schottky diode here. Minimize trace length to keep EMI
down.
3 •1010
fOSC
=
Hz
GND (Pin 5): Signal and Power Ground for the IC.
Rt
VDD (Pin 6): Power Source for the IC. Typically derived
fromahighervoltagepowerconverter. Requiresaninput
of 2.7V to 5.5V. A 2.2µF ceramic bypass capacitor is
recommended as close to the pins as possible.
MODE/SYNC (Pin 2): Burst Mode Select and Oscillator
Synchronization.
MODE/SYNC = High. Enable Burst Mode operation. The
inductor peak inductor current will be 400mA and
returntozerocurrentoneachcycle. DuringBurstMode
operationtheoperationisvariablefrequency,providing
a significant efficiency improvement at light loads. It is
recommended the Burst Mode operation only be en-
tered once the part has started up.
VOUT (Pin 7): Output of the Synchronous Rectifier.
FB (Pin 8): Feedback Pin. Connect resistor divider tap
here. The output voltage can be adjusted from 1.5V to
5.5V. The feedback reference voltage is typically 1.25V.
VC (Pin 9): Error Amp Output. A frequency compensation
network is connected to this pin to compensate the loop.
See the section “Compensating the Feedback Loop” for
guidelines.
MODE/SYNC = Low. Disable Burst Mode operation and
maintain low noise, constant frequency operation.
MODE/SYNC = External CLK. Synchronization of the
internal oscillator and Burst Mode operation disable. A
clock pulse width of 100ns to 2µs is required to
synchronize.
SHDN(Pin10):Shutdown.Groundingthispinshutsdown
the IC. Tie to >1V to enable (VDD or digital gate output).
During shutdown the output voltage will hold up to VIN
minus a diode drop due to the body diode of the PMOS
synchronous switch. If the application requires a com-
plete disconnect during shutdown then refer to section
“Output Disconnect”.
VIN (Pin 3): Voltage Sense for Internal Circuitry.
34234f
5
LTC3423/LTC3424
W
BLOCK DIAGRA
+
1V TO
+ 0.3
V
OUT
OPTIONAL
V
SW
IN
3
4
P
V
OUT
V
OUT
7
1.5V TO 5.5V
ANTICROSS
CONDITION
SHDN
SHUTDOWN
10
+
+
N
10mV
I
SENSE
AMP
+
–
–
I
ZERO
AMP
+
CURRENT
LIMIT
GND
5
6
1
–
1.6A TYP (LTC3423)
2.8A TYP (LTC3424)
+
–
1.25V
–
ERROR
AMP
R1
FB
CURRENT
COMP
8
9
V
+
DD
V
DD
2.7V TO 5.5V
PWM
LOGIC
+
–
SLEEP
V
C
Σ
Burst Mode
CONTROL
R2
SYNC
R
t
OSC
2
MODE/SYNC
SLOPE COMP
3423/24 BD
34234f
6
LTC3423/LTC3424
W U U
APPLICATIO S I FOR ATIO
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DETAILED DESCRIPTION
ZeroCurrentAmp.Thezerocurrentamplifiermonitorsthe
inductor current to the output and shuts off the synchro-
nous rectifier once the current is below 50mA, preventing
negative inductor current.
TheLTC3423/LTC3424provideshighefficiency,lownoise
power for applications such as portable instrumentation
andareidealforapplicationsthatrequireanoutputvoltage
between 1.5V and 2.6V from a single cell. These products
are an addition to the LTC3401 and LTC3402 family of
synchronous boost converters, with the differences being
theomissionofthepowergoodfunction(PGOOD)andthe
addition of a VDD input to provide internal power. The IC
will not start up until the applied voltage on the VDD pin is
above 2.7V.
Burst Mode Operation
Burst Mode operation is when the IC delivers energy to the
output until it is regulated and then goes into a sleep mode
where the outputs are off and the IC is consuming only
38µA. In this mode, the output ripple has a variable
frequency component with load current and the steady
state ripple will be typically below 3%.
The current mode architecture with adaptive slope
compensation provides ease of loop compensation with
excellent transient load response. The low RDS(ON), low
gate charge synchronous switches provides the pulse
width modulation control at high efficiency.
During the period where the device is delivering energy to
theoutput, thepeakcurrentwillbeequalto400mAandthe
inductorcurrentwillterminateatzerocurrentforeachcycle.
In this mode the maximum output current is given by:
V
IN
Low Noise Fixed Frequency Operation
IOUT(MAXBURST)
≈
Amps
6•VOUT
Oscillator. The frequency of operation is set through a
resistor from the Rt pin to ground where f = 3 • 1010/Rt. An
internally trimmed timing capacitor resides inside the IC.
The oscillator can be synchronized with an external clock
inserted on the MODE/SYNC pin. When synchronizing the
oscillator, the free running frequency must be set to
approximately 30% lower than the desired synchronized
frequency. Keeping the sync pulse width below 2µs will
ensure that Burst Mode operation is disabled.
Burst Mode operation is user controlled by driving the
MODE/SYNC pin high to enable and low to disable. It is
recommended that Burst Mode operation be entered after
the part has started up.
COMPONENT SELECTION
Inductor Selection
Current Sensing. Lossless current sensing converts the
peak current signal to a voltage to sum in with the internal
slope compensation. This summed signal is compared to
theerroramplifieroutputtoprovideapeakcurrentcontrol
command for the PWM. The slope compensation in the IC
is adaptive to the input and output voltage. Therefore, the
converterprovidestheproperamountofslopecompensa-
tion to ensure stability and not an excess causing a loss of
phase margin in the converter.
The high frequency operation of the LTC3423/LTC3424
allows the use of small surface mount inductors. The
minimum inductance value is proportional to the operat-
ing frequency and is limited by the following constraints:
V
IN(MIN) • VOUT(MAX) – V
(
IN(MIN)
)
k
f
L > µH and L >
H
f •Ripple •VOUT(MAX)
where
k = 3 for LTC3423, 2 for LTC3424
Error Amp. The error amplifier is a transconductance
amplifier with gm = 85µmhos. A simple compensation
network is placed from the VC pin to ground.
f = Operating Frequency (Hz)
Ripple = Allowable Inductor Current Ripple (A)
VIN(MIN) = Minimum Input Voltage (V)
VOUT(MAX) = Maximum Output Voltage (V)
Current Limit. The current limit amplifier will shut the
NMOS switch off once the current exceeds its threshold.
The current amplifier delay to output is typically 50ns.
34234f
7
LTC3423/LTC3424
W U U
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APPLICATIO S I FOR ATIO
The inductor current ripple is typically set to 20% to 40%
of the maximum inductor current.
where
IL = Average Inductor Current
IP = Peak Inductor Current
For high efficiency, choose an inductor with a high fre-
quency core material, such as ferrite, to reduce core
losses. The inductor should have low ESR (equivalent
series resistance) to reduce the I2R losses and must be
abletohandlethepeakinductorcurrentatfullloadwithout
saturating. Molded chokes or chip inductors usually do
not have enough core to support the peak inductor cur-
rents in the 1A to 2A region. To minimize radiated noise,
use a toroid, pot core or shielded bobbin inductor. See
Table 1 for a list of component suppliers.
The ESR is usually the most dominant factor for ripple in
most power converters. The ripple due to capacitor ESR is
simply given by:
VRCESR = IP • RESR Volts
where
RESR = Capacitor Series Resistance
Low ESR capacitors should be used to minimize output
voltage ripple. For surface mount applications, AVX TPS
series tantalum capacitors and Sanyo POSCAP or Taiyo-
Yudenceramiccapacitorsarerecommended.Forthrough-
hole applications Sanyo OS-CON capacitors offer low ESR
in a small package size. See Table 2 for a list of component
suppliers.
Table 1. Inductor Vendor Information
SUPPLIER
Coilcraft
PHONE
FAX
WEBSITE
(847) 639-6400 (847) 639-1469 www.coilcraft.com
(516) 241-7876 (516) 241-9339 www.coiltronics.com
Coiltronics
Murata
(814) 237-1431 (814) 238-0490 www.murata.com
(800) 831-9172
Sumida
In some layouts it may be required to place a 1µF low ESR
capacitor as close to the VOUT and GND pins as possible.
USA: (847) 956-0666 (847) 956-0702 www.japanlink.com
Japan: 81-3-3607-5111 81-3-3607-5144 sumida
Table 2. Capacitor Vendor Information
SUPPLIER
AVX
PHONE
FAX
WEBSITE
R
SHDN
t
(803) 448-9411 (803) 448-1943 www.avxcorp.com
(619) 661-6322 (619) 661-1055 www.sanyovideo.com
MODE
V
C
V
SW
FB
OUT
V
DD
IN
Sanyo
V
IN
V
DD
2.7V
TO 5.5V
GND
Taiyo Yuden (408) 573-4150 (408) 573-4159 www.t-yuden.com
Input Capacitor Selection
V
OUT
Theinputfiltercapacitorreducespeakcurrentsdrawnfrom
theinputsourceandreducesinputswitchingnoise.Inmost
applications a 3.3µF is sufficient.
3423/24 F01
Figure 1. Recommended Component Placement. Traces
Carrying High Current Are Direct. Trace Area FB and VC Pins
Are Kept Low. Lead Length to Battery Should be Kept Short
Output Diode
The Schottky diode across the synchronous PMOS switch
isnotrequired,butprovidesalowerdropduringthebreak-
before-make time (typically 20ns) of the NMOS to PMOS
transition. The addition of the Schottky diode will improve
peak efficiency (see graph “Efficiency Loss Without
Schottky vs Frequency”). Use of a Schottky diode such as
a MBRM120T3, 1N5817 or equivalent. Since slow recov-
ery times will compromise efficiency, do not use ordinary
rectifier diodes.
Output Capacitor Selection
The output voltage ripple has several components. The
bulk value of the capacitor is set to reduce the ripple due
to charge into the capacitor each cycle. The max ripple due
to charge is given by:
IL •V (VOUT – V )
COUT •VOUT •VOUT • f
IN
IN
Volts
VRBULK
=
34234f
8
LTC3423/LTC3424
W U U
APPLICATIO S I FOR ATIO
U
Operating Frequency Selection
130mA/100mV, and the LTC3424 is typically 170mA/
100mV, so the amount of signal injected is proportional to
the anticipated change of inductor current with load. The
outer voltage loop performs the remainder of the correc-
tion, butbecauseoftheloadfeedforwardsignal, therange
over which it must slew is greatly reduced. This results in
an improved transient response. A logic level feed forward
signal, VFF, is coupled through components C5 and R6.
The amount of feed forward signal is attenuated with
resistor R6 and is given by the following relationship:
There are several considerations in selecting the operat-
ingfrequencyoftheconverter.Thefirstisdeterminingthe
sensitive frequency bands that cannot tolerate any spec-
tral noise. For example, in products incorporating RF
communications, the 455kHz IF frequency is sensitive to
any noise, therefore switching above 600kHz is desired.
Somecommunicationshavesensitivityto1.1MHz. Inthis
case, converter frequencies up to 3MHz may be em-
ployed.
The second consideration is the physical size of the
converter. As the operating frequency goes up, the induc-
tor and filter caps go down in value and size. The trade off
is in efficiency since the switching losses due to gate
charge are going up proportional with frequency.
VFF •R5•V •1.5
VOUT • ∆IOUT
IN
R6 ≈
– R5
where ∆IOUT = load current change.
Another operating frequency consideration is whether the
application can allow “pulse skipping.” In this mode, the
minimumontimeoftheconvertercannotsupporttheduty
cycle, so the converter ripple will go up and there will be
a low frequency component of the output ripple. In many
applications where physical size is the main criterion then
running the converter in this mode is acceptable. In
applications where it is preferred not to enter this mode,
then the maximum operating frequency is given by:
V
V
OUT
IN
LTC3423/LTC3424
V
DD
IN
6
10
3
4
7
8
9
5
V
DD
SW
SHDN
V
OUT
V
IN
FB
2
MODE/SYNC
V
C
C3
1
R
t
GND
R5
VOUT – V
OUT • tON(MIN)
IN
fMAX_NOSKIP
=
Hz
C5
3.3nF
V
LOAD FEED
FORWARD
SIGNAL
R6
V
FF
3423/24 F02
where tON(MIN) = minimum on time = 140ns
Figure 2
Reducing Output Capacitance with a Load Feed
Forward Signal
Closing the Feedback Loop
In many applications the output filter capacitance can be
reduced for the desired transient response by having the
device commanding the change in load current, (i.e.
system microcontroller), inform the power converter of
the changes as they occur. Specifically, a “load feed
forward” signal coupled into the VC pin gives the inner
current loop a head start in providing the change in output
current. The transconductance of the LTC3423 converter
attheVC pinwithrespecttotheinductorcurrentistypically
The LTC3423/LTC3424 uses current mode control with
internal adaptive slope compensation. Current mode con-
trol eliminates the 2nd order filter due to the inductor and
output capacitor exhibited in voltage mode controllers,
and simplifies it to a single-pole filter response. The
product of the modulator control to output DC gain plus
the error amp open-loop gain equals the DC gain of the
system.
34234f
9
LTC3423/LTC3424
W U U
U
APPLICATIO S I FOR ATIO
GDC = GCONTROLOUTPUT • GEA
The typical error amp compensation is shown in Figure 3.
The equations for the loop dynamics are as follows:
2•V
IOUT
IN
GCONTROL
=
, GEA ≈ 2000
1
fPOLE1
≈
Hz
2• π •20•106 •CC1
The output filter pole is given by:
whichisextremelyclose toDC
1
IOUT
π •VOUT •COUT
fFILTERPOLE
=
Hz
fZERO1
=
Hz
2• π •RZ •CC1
1
where COUT is the output filter capacitor.
The output filter zero is given by:
fPOLE2
≈
Hz
2• π •RZ •CC2
1
fFILTERZERO
=
Hz
Refer to Application Note AN76 for more closed loop
examples.
2 • π •RESR •COUT
where RESR is the capacitor equivalent series resistance.
A troublesome feature of the boost regulator topology is
the right half plane zero (RHP) and is given by:
V
OUT
1.25V
+
–
ERROR
AMP
R1
FB
8
V
IN
2 •RO
R2
V
C
fRHPZ
=
Hz
2
9
2• π •L•VO
C
C1
C
C2
R
Z
At heavy loads this gain increase with phase lag can occur
at a relatively low frequency. The loop gain is typically
rolled off before the RHP zero frequency.
3423/24 F03
Figure 3
U
TYPICAL APPLICATIO
Typical Application with Output Disconnect
ZETEX
FMMT717
V
IN
= 0.9V TO 1.5V
V
OUT
LTC3423/LTC3424
3
10
2
4
7
8
9
5
V
SW
OUT
RB*
IN
SHDN
V
C5
1µF
MODE/SYNC FB
6
V
DD
V
DD
V
C
1
R
GND
t
3423/24 TA03
(V
– V
– 0.7V) • 100
OUTMAX
OUT
INMIN
I
* SET RB TO FORCE BETA OF ≤100; RB =
0 = FIXED FREQ
1 = Burst Mode OPERATION
34234f
10
LTC3423/LTC3424
U
TYPICAL APPLICATIO
Single Cell to 1.8V at 300mA, 1.8mm High
V
= 2.7V TO 5.5V
V
DD
L1
4.7µH
DD
IN
D1
V
OUT
V
= 0.9V TO 1.5V
IN
1.8V
300mA
LTC3423
6
10
3
4
7
8
9
5
R1
V
SW
DD
110k
SHDN
V
OUT
FB
+
–
1
C3
22µF
CELL
V
IN
2
MODE/SYNC
V
C
C4
C1
2.2µF
C2
4.7µF
1
470pF
R2
249k
R
GND
= 1MHz
t
C5
4.7pF
R
30.1k
R
f
t
C
OSC
82k
C1: TAIYO YUDEN JMK212BJ225MG
C2: TAIYO YUDEN JMK212BJ475MM
C3: TAIYO YUDEN JMK325BJ226MM
D1: ON SEMICONDUCTOR MBRM120T3
L1: SUMIDA CDRH3D16-4R7M
3423/24 TA04
0 = FIXED FREQ
1 = Burst Mode OPERATION
U
PACKAGE DESCRIPTIO
MS Package
10-Lead Plastic MSOP
(Reference LTC DWG # 05-08-1661)
0.889 ± 0.127
(.035 ± .005)
5.23
(.206)
MIN
3.2 – 3.45
(.126 – .136)
3.00 ± 0.102
(.118 ± .004)
(NOTE 3)
0.497 ± 0.076
(.0196 ± .003)
REF
0.50
3.05 ± 0.38
(.0120 ± .0015)
TYP
(.0197)
10 9
8
7 6
BSC
RECOMMENDED SOLDER PAD LAYOUT
3.00 ± 0.102
(.118 ± .004)
NOTE 4
4.88 ± 0.10
(.192 ± .004)
DETAIL “A”
0° – 6° TYP
0.254
(.010)
GAUGE PLANE
1
2
3
4 5
0.53 ± 0.01
(.021 ± .006)
0.86
(.034)
REF
1.10
(.043)
MAX
DETAIL “A”
0.18
(.007)
SEATING
PLANE
0.17 – 0.27
(.007 – .011)
0.13 ± 0.05
(.005 ± .002)
MSOP (MS) 1001
0.50
(.0197)
TYP
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
34234f
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 represen-
tationthattheinterconnectionofitscircuitsasdescribedhereinwillnotinfringeonexistingpatentrights.
11
LTC3423/LTC3424
U
TYPICAL APPLICATIO
Triple Output Converter
D2
D3
D4
D5
3.6V
2mA
4.7µF
0.1µF
0.1µF
0.1µF
0.1µF
D6
D7
V
= 2.7V TO 5.5V
DD
V
L1
2.2µH
DD
IN
4.7µF
D1
V
OUT
V
= 0.9V TO 1.5V
IN
1.8V
700mA
–1.1V
1mA
LTC3423
6
10
3
4
7
8
9
5
R1
V
SW
DD
110k
SHDN
V
OUT
FB
+
1
C3
CELL
–
V
44µF
IN
(2× 22µF)
2
MODE/SYNC
V
C
C4
C1
2.2µF
C2
10µF
1
470pF
R2
249k
R
GND
= 1MHz
t
C5
4.7pF
R
30.1k
RC
82k
t
f
OSC
C1: TAIYO YUDEN JMK212BJ225MG
C2: TAIYO YUDEN JMK212BJ106MM
C3: TAIYO YUDEN JMK325BJ226MM
D1: ON SEMICONDUCTOR MBRM120T3
3423/24 TA05
0 = FIXED FREQ
1 = Burst Mode OPERATION
D2 TO D7: ZETEX FMND7000 DUAL DIODE
L1: SUMIDA CD43-2R2M
RELATED PARTS
PART NUMBER
DESCRIPTION
COMMENTS
LT1306
Sync, Fixed Frequency, Step-Up DC/DC Converter
High Current, Micropower, Single Cell 600kHz DC/DC Converter
Micropower 600kHz PWM DC/DC Converter
Internal 2A Switches, V As Low As 1.8V
IN
LT1308A/LT1308B
LT1317/LT1317B
LT1610
5V at 1A from Single Li-Ion Cell
V
As Low As 1.5V, I = 100µA
Q
IN
1.7MHz, Single Cell Micropower DC/DC Converter
3V at 30mA from 1V, 5V at 200mA from 3.3V
As Low As 1.1V, 3V at 30mA from Single Cell
TM
LT1613
1.4MHz, Single Cell DC/DC Converter in ThinSOT
V
IN
LT1615
Micropower Step-Up DC/DC Converter in ThinSOT
600kHz, 1A Switch PWM DC/DC Converter
ThinSOT, 600mA, 1.2MHz Boost Converter
I = 20µA, 1µA Shutdown Current, V As Low As 1V
Q IN
LT1949
1.1A, 0.5Ω/30V Internal Switch, V As Low As 1.8V
IN
LTC3400/LTC3400B
LTC3401
92% Efficiency, 0.85V ≤ V , 2.6V ≤ V
≤ 5V
IN
OUT
Single Cell, High Current (1A) Micropower, Synchronous
3MHz Step-Up DC/DC Converter
V = 0.5V to 5.5V, Up to 97% Efficiency Synchronizable
IN
Oscillator from 100kHz to 3MHz
LTC3402
Single Cell, High Current (2A) Micropower, Synchronous
3MHz Step-Up DC/DC Converter
V
IN
= 0.5V to 5.5V, Up to 97% Efficiency Synchronizable
Oscillator from 100kHz to 3MHz
ThinSOT is a trademark of Linear Technology Corporation.
34234f
LT/TP 0302 2K • PRINTED IN USA
LinearTechnology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
12
●
●
(408) 432-1900 FAX: (408) 434-0507 www.linear.com
LINEAR TECHNOLOGY CORPORATION 2001
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