View LTC3401EMS_267639.PDF datasheet online --- IC-ON-LINE

Datasheet File OCR Text:

FEATURES
s s s s s
LTC3401 1A, 3MHz Micropower Synchronous Boost Converter DESCRIPTIO
The LTC(R)3401 is a high efficiency, fixed frequency, stepup DC/DC converter that operates from an input voltage below 1V. The device includes a 0.16 N-channel MOSFET switch and a 0.18 P-channel synchronous rectifier. Switching frequencies up to 3MHz are programmed with an external timing resistor and the oscillator can be synchronized to an external clock. An external Schottky diode is optional but will slightly improve efficiency. Quiescent current is only 38A 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 fixed frequency switching is enabled. Other features include 1A shutdown, antiringing control, open-drain power good output, thermal shutdown and current limit. The LTC3401 is available in the 10-lead thermally enhanced MSOP package. Higher current applications should use the 2A rated LTC3402 synchronous boost converter. Applications that require VOUT < 2.6V should use the LTC3423.
, LTC and LT are registered trademarks of Linear Technology Corporation. Burst Mode and OPTI-LOOP are registered trademarks of Linear Technology Corporation.
s s s s s s s s s s
Synchronous Rectification: Up to 97% Efficiency 1A Switch Current Rating Fixed Frequency Operation Up to 3MHz Wide Input Range: 0.5V to 5.5V (Operating) Very Low Quiescent Current: 38A (Burst Mode(R) Operation) 2.6V to 5.5V Adjustable Output Voltage 0.85V (Typ) Start-Up Voltage No External Schottky Diode Required (VOUT < 4.3V) Synchronizable Switching Frequency Burst Mode Enable Control Antiringing Control Reduces Switching Noise PGOOD Output OPTI-LOOP(R) Compensation Very Low Shutdown Current: < 1A Small 10-Pin MSOP Package
APPLICATIO S
s s s s s s s
Pagers Handheld Instruments Cordless Phones Wireless Handsets GPS Receivers Battery Backup CCFL Backlights
TYPICAL APPLICATION
All-Ceramic-Capacitor 2-Cell to 3.3V at 500mA Step-Up Converter
VIN = 1.8V to 3V L1 4.7H VOUT 3.3V 500mA SW VOUT 4 7 8 9 5 C3 470pF R5 82k C4 4.7pF R1 549k
EFFICIENCY (%)
100
3 10
LTC3401 VIN SHDN
R2 909k
Burst Mode 90 OPERATION 80 70 1MHz FIXED FREQUENCY
+2
CELLS
2 6
MODE/SYNC FB PGOOD Rt VC GND
C2 22F
60 50 40 30 20 10 0
C1 4.7F
1
Rt 30.1k
VIN = 2.4V WITH SCHOTTKY 0.1 1 10 IOUT (mA) 100 1000
3401 TA02
0 = FIXED FREQUENCY 1 = Burst Mode OPERATION
C1: TAIYO YUDEN JMK212BJ475MG C2: TAIYO YUDEN JMK325BJ226MM L1: SUMIDA CD43-4R7M
3404 TA01
U
U
U
Efficiency
3401fa
1
LTC3401
ABSOLUTE
(Note 1)
AXI U
RATI GS
PACKAGE/ORDER I FOR ATIO
TOP VIEW Rt MODE VIN SW GND 1 2 3 4 5 10 9 8 7 6 SHDN VC FB VOUT PGOOD
VIN, VOUT Voltages ...................................... - 0.5V to 6V SW Voltage ................................................. - 0.5V to 6V VC, Rt Voltages ......................... - 0.5V to (VOUT + 0.3V) PGOOD, SHDN, FB, MODE Voltages ........... - 0.5V to 6V Operating Temperature Range (Note 2) .. - 40C to 85C Storage Temperature Range ................. - 65C to 125C Lead Temperature (Soldering, 10 sec).................. 300C
ORDER PART NUMBER LTC3401EMS MS PART MARKING LTPG
MS PACKAGE 10-LEAD PLASTIC MSOP TJMAX = 125C JA = 130C/ W 1 LAYER BOARD JA = 100C/ W 4 LAYER BOARD
Consult LTC Marketing for parts specified with wider operating temperature ranges.
ELECTRICAL CHARACTERISTICS
The q denotes specifications that apply over the full operating temperature range, otherwise specifications are at TA = 25C. VIN = 1.2V, VOUT = 3.3V unless otherwise noted.
PARAMETER Minimum Start-Up Voltage Minimum Operating Voltage Output Voltage Adjust Range Feedback Voltage Feedback Input Current Quiescent Current--Burst Mode Operation Quiescent Current--SHDN Quiescent Current--Active NMOS Switch Leakage PMOS Switch Leakage NMOS Switch On Resistance PMOS Switch On Resistance NMOS Current Limit NMOS Burst Current Limit Maximum Duty Cycle Minimum Duty Cycle Frequency Accuracy MODE/SYNC Input High MODE/SYNC Input Low MODE/SYNC Input Current Error Amp Transconductance PGOOD Threshold VMODE/SYNC = 5.5V I = - 5A to 5A, VC = VFB Referenced to Feedback Voltage -6 0.01 85 -9 - 12 Rt = 15k Rt = 15k
q q q q
CONDITIONS ILOAD < 1mA (Note 4)
q q q
MIN
TYP 0.85
MAX 1.0 0.5 5.5
UNITS V V V V nA A A A A A A A %
2.6 1.22 1.25 1 38 0.1 440 0.1 0.1 0.16 0.18 1 80 1.6 1.4 1.6 0.66 85
1.28 50 65 1 800 5 10
VFB = 1.25V VC = 0V, MODE/SYNC = 3.3V (Note 3) SHDN = 0V, Not Including Switch Leakage VC = 0V, MODE/SYNC = 0V, Rt = 300k (Note 3)
0 2 2.4 0.4 1
mhos %
2
U
% MHz V V A
3401fa
W
U
U
WW
W
LTC3401
ELECTRICAL CHARACTERISTICS
The q denotes specifications that apply over the full operating temperature range, otherwise specifications are at TA = 25C. VIN = 1.2V, VOUT = 3.3V unless otherwise noted.
PARAMETER PGOOD Low Voltage PGOOD Leakage SHDN Input High SHDN Input Low SHDN Input Current Thermal Shutdown Note 1: Absolute Maximum Ratings are those values beyond which the life of a device may be impaired. Note 2: The LTC3401 is guaranteed to meet performance specifications from 0C to 70C. Specifications over the -40C to 85C operating temperature range are assured by design, characterization and correlation with statistical process controls. VSHDN = 5.5V 0.01 170 CONDITIONS IPGOOD = 1mA VOUT = 1V, IPGOOD = 20A VPGOOD = 5.5V VSHDN = VIN = VOUT 1 0.4 1 MIN TYP 0.1 0.1 0.01 MAX 0.2 0.4 1 UNITS V V A V V A C
Note 3: Current is measured into VOUT since the supply current is bootstrapped to the VOUT pin and in the application will reflect to the input supply by (VOUT/VIN) * Efficiency. The outputs are not switching. Note 4: Once the output is started, the IC is not dependant upon the VIN supply.
TYPICAL PERFOR A CE CHARACTERISTICS
SW Pin and Inductor Current (IC) in Discontinuous Mode. Ringing Control Circuitry Eliminates High Frequency Ringing
IL 50mA/DIV 0A SW 1V/DIV
Switching Waveform on SW Pin
50ns/DIV
UW
3401 G01
Transient Response 5mA to 50mA
VOUT 100mV/DIV
SW 1V/DIV 50mA IOUT 0V 200ns/DIV
3401 G02
5mA COUT = 22F L = 3.3H fOSC = 1MHz 200s/DIV
3401 G03
3401fa
3
LTC3401 TYPICAL PERFOR A CE CHARACTERISTICS
Transient Response 50mA to 500mA
VOUT AC 100mV/DIV
VOUT 200mV/DIV
550mA IOUT 50mA COUT = 22F L = 3.3H fOSC = 1MHz 200s/DIV
3401 G04
Converter Efficiency 1.2V to 3.3V
100 90 80 70 EFFICIENCY (%) 60 50 40 30 20 10 0 0.1 1 10 100 OUTPUT CURRENT (mA) 1000
3401 G07
300kHz Burst Mode OPERATION 3MHz
EFFICIENCY (%)
1MHz
60 50 40 30 20 10 0 0.1
EFFICIENCY (%)
Start-Up Voltage vs IOUT
500 TA = 25C
14 12
OUTPUT CURRENT (mA)
400
EFFICIENCY LOSS (%)
300
8 6 4 2 0 0.2
CURRENT (A)
200
100
0 0.8 0.9 1 1.1 VIN (V) 1.2 1.3 1.4
3401 G09
4
UW
Burst Mode Operation
VOUT AC 100mV/DIV
Burst Mode Operation
SW 1V/DIV
SW 1V/DIV
5ms/DIV VIN = 1.2V VOUT = 3.3V COUT = 100F IOUT = 250A MODE/SYNC PIN = HIGH
3401 G05
VIN = 1.2V 200s/DIV VOUT = 3.3V COUT = 100F IOUT = 20mA MODE/SYNC PIN = HIGH
3401 G06
Converter Efficiency 2.4V to 3.3V
100 90 80 70 300kHz 3MHz 1MHz Burst Mode OPERATION
Converter Efficiency 3.6V to 5V
100 90 80 70 60 50 40 30 20 10 1MHz FIXED FREQUENCY Burst Mode OPERATION
10 100 1 OUTPUT CURRENT (mA)
1000
3401 G08
0 0.1 1 100 10 LOAD CURRENT (mA) 1000
3401 G10
Efficiency Loss Without Schottky vs Frequency
TA = 25C
Current Limit
1.80 1.75 1.70 1.65 1.60 1.55 1.50 1.45
10
0.6
1.0 1.4 1.8 2.2 FREQUENCY (MHz)
2.6
3.0
1.40 -55
-15
25 65 TEMPERATURE (C)
105 125
3401 G12
3401 G11
3401fa
LTC3401 TYPICAL PERFOR A CE CHARACTERISTICS
EA FB Voltage
1.28 1.27 2.05
FREQUENCY (MHz)
VOLTAGE (V)
1.26 1.25 1.24 1.23 1.22 -55
RESISTANCE ()
-15
65 TEMPERATURE (C)
25
PMOS RDS(ON)
0.30 VOUT = 3.3V 1.1
0.25
RESISTANCE ()
VOLTAGE (V)
0.20
0.9
VOLTAGE (V)
0.15
0.10
0.05 -55
-15
25 65 TEMPERATURE (C)
PGOOD Threshold
-7.0 -7.5
PERCENT FROM VFB (%)
-8.0 -8.5 40
CURRENT (A)
-9.0 -9.5
VOLTAGE (V)
-10.0
-10.5 -11.0 -11.5 -12.0 -55 -15 65 TEMPERATURE (C) 25 105 125
3401 G19
UW
Oscillator Frequency Accuracy
2.10 Rt = 15k 0.30
NMOS RDS(ON)
VOUT = 3.3V
0.25
0.20
2.00
0.15
1.95 0.10
105 125
3401 G13
1.90 -55
-15
65 TEMPERATURE (C)
25
105 125
3401 G14
0.05 -55
-15
25 65 TEMPERATURE (C)
105 125
3401 G22
Start-Up Voltage
1.10 1.05 1.0 1.00 0.95 0.90 0.85 0.80 0.75 0.7 0.70 0.65 105 125
3401 G16
Shutdown Threshold
0.8
0.6 -55
-15
25 65 TEMPERATURE (C)
105 125
3401 G17
0.60 -55
-15
25 65 TEMPERATURE (C)
105 125
3401 G18
Burst Mode Operation Current
44 42 2.50 2.45 2.40 2.35 2.30 2.25 2.20 2.15 2.10 32 30 -55 2.05 -15 65 TEMPERATURE (C) 25 105 125
3401 G20
VOUT Turn-Off Voltage
38 36 34
2.00 -55
-15
25 65 TEMPERATURE (C)
105 125
3401 G21
3401fa
5
LTC3401
PI FU CTIO S
Rt (Pin 1): Timing Resistor to Program the Oscillator Frequency.
fOSC =
3 * 1010 Hz Rt
MODE/SYNC (Pin 2): Burst Mode Select and Oscillator Synchronization. MODE/SYNC = High. Enable Burst Mode operation. The inductor peak inductor current will be 1/3 the current limit value and return to zero current on each cycle. During Burst Mode operation the operation is variable frequency, providing a significant efficiency improvement at light loads. It is recommended the Burst Mode operation only be entered once the part has started up. 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 2s is required to synchronize. VIN (Pin 3): Input Supply Pin. SW (Pin 4): Switch Pin. Connect inductor and Schottky diode here. For applications with output voltages over 4.3V, a Schottky diode is required to ensure that the SW pin voltage does not exceed its absolute maximum rating. Minimize trace length to keep EMI down. For discontinuous inductor current, a controlled impedance is placed
6
U
U
U
from SW to VIN from the IC to eliminate high frequency ringing due to the resonant tank of the inductor and SW node capacitance, therefore reducing EMI radiation. GND (Pin 5): Signal and Power Ground for the IC. PGOOD (Pin 6): Power Good Comparator Output. This open-drain output is low when VFB < - 9% from its regulation voltage. VOUT (Pin 7): Output of the Synchronous Rectifier and Bootstrapped Power Source for the IC. A ceramic capacitor of at least 1F is required and should be located as close to the VOUT and GND pins as possible (Pins 7 and 5). FB (Pin 8): Feedback Pin. Connect resistor divider tap here. The output voltage can be adjusted from 2.6V 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. SHDN (Pin 10): Shutdown. Grounding this pin shuts down the IC. Tie to >1V to enable (VIN or digital gate output). To operate with input voltages below 1V once the converter has started, a 1M resistor from SHDN to VIN, and a 5M resistor from SHDN to VOUT will provide sufficient hysteresis 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 complete disconnect during shutdown then refer to section "Output Disconnect Circuits".
3401fa
LTC3401
BLOCK DIAGRA
3
VIN ANTIRING
SHDN
10
SHUTDOWN
GND
5
PWM LOGIC SLEEP
+
-
9 Burst Mode CONTROL
Rt
1
OSC
SYNC SLOPE COMP
PGOOD 6 N
1.25V - 9%
3401 BD
-
CURRENT COMP
ERROR AMP 8
+
-
-
+
+
-
+
CURRENT LIMIT
1.6A TYP
-
+
W
+
1V TO VOUT + 0.3 4 SW P 7 VOUT VOUT 2.6V TO 5V ANTICROSS COND N 10mV
+ -
IZERO AMP
ISENSE AMP
+
1.25V R1 FB
VC
R2
2 MODE/SYNC 0 = FIXED FREQ 1 = BURST MODE
3401fa
7
LTC3401
APPLICATIO S I FOR ATIO
DETAILED DESCRIPTION
The LTC3401 provides high efficiency, low noise power for applications such as portable instrumentation. 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 provide the pulse width modulation control at high efficiency. The Schottky diode across the synchronous PMOS switch provides a lower drop during the break-before-make time (typically 20ns) of the NMOS to PMOS transition. The Schottky diode improves efficiency (see graph "Efficiency loss without Schottky vs Frequency"). While the IC's quiescent current is a low 38A, high efficiency is achieved at light loads when Burst Mode operation is entered. Low Voltage Start-Up The LTC3401 is designed to start up at input voltages of typically 0.85V. The device can start up under some load, (see graph "Start-Up vs Input Voltage"). Once the output voltage exceeds a threshold of 2.3V, the IC powers itself from VOUT instead of VIN. At this point, the internal circuitry has no dependency on the VIN input voltage, eliminating the requirement for a large input capacitor. The input voltage can drop below 0.5V without affecting the operation, but the limiting factor for the application becomes the availability of the power source to supply sufficient energy to the output at the low voltages. Low Noise Fixed Frequency Operation Oscillator. The frequency of operation is set through a resistor from the Rt pin to ground: 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 2s will ensure that Burst Mode operation is disabled.
8
U
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 the error amplifier output to provide a peak current control command for the PWM. The slope compensation in the IC is adaptive to the input and output voltage. Therefore, the converter provides the proper amount of slope compensation to ensure stability and not an excess causing a loss of phase margin in the converter. Error Amp. The error amplifier is a transconductance amplifier with gm = 0.1ms. A simple compensation network is placed from the VC pin to ground. 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. Zero Current Amp. The zero current amplifier monitors the inductor current to the output and shuts off the synchronous rectifier once the current is below 50mA, preventing negative inductor current. Antiringing Control. The anitringing control will place an impedance across the inductor to damp the ringing on the SW pin during discontinuous mode operation. The LCSW ringing (L = inductor, CSW = capacitance on the switch pin) is low energy, but can cause EMI radiation. 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 38A. In this mode, the output ripple has a variable frequency component with load current and the steady state ripple will be typically below 3%. During the period where the device is delivering energy to the output, the peak current will be equal to 1/3 the current limit value and the inductor current will terminate at zero current for each cycle. In this mode the maximum output current is given by:
W
UU
I OUT(MAXBURST)
VIN Amps 6 * VOUT
3401fa
LTC3401
APPLICATIO S I FOR ATIO
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 The high frequency operation of the LTC3401 allows the use of small surface mount inductors. The minimum inductance value is proportional to the operating frequency and is limited by the following constraints: VIN(MIN) * VOUT(MAX) - VIN(MIN) 3 H L > H and L > f * Ripple * VOUT(MAX) f where f = Operating Frequency (Hz) Ripple = Allowable Inductor Current Ripple (A) VIN(MIN) = Minimum Input Voltage (V) VOUT(MAX) = Maximum Output Voltage (V) The inductor current ripple is typically set to 20% to 40% of the maximum inductor current. For high efficiency, choose an inductor with a high frequency 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 able to handle the peak inductor current at full load without saturating. Molded chokes or chip inductors usually do not have enough core to support the peak inductor currents 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.
Table 1. Inductor Vendor Information
SUPPLIER Coilcraft Coiltronics Murata Sumida USA: (847) 956-0666 (847) 956-0702 Japan: 81-3-3607-5111 81-3-3607-5144 www.japanlink.com sumida PHONE (847) 639-6400 (516) 241-7876 (814) 237-1431 (800) 831-9172 FAX (847) 639-1469 (516) 241-9339 (814) 238-0490 WEBSITE www.coilcraft.com www.coiltronics.com www.murata.com
VOUT
(
U
SHDN Rt MODE VC VIN FB SW VOUT GND PGOOD
3401 F01
W
UU
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 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:
VRBULK = IP * VIN V COUT * VOUT * f
where IP = Peak Inductor Current The ESR can be a significant factor for ripple in most power converters. The ripple due to capacitor ESR is simply given by: VRCESR = IP * RESR V 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, Sanyo POSCAP, or TaiyoYuden ceramic capacitors are recommended. For throughhole applications Sanyo OS-CON capacitors offer low ESR in a small package size. See Table 2 for a list of component suppliers.
Table 2. Capacitor Vendor Information
SUPPLIER AVX Sanyo Taiyo Yuden PHONE (803) 448-9411 (619) 661-6322 (408) 573-4150 FAX (803) 448-1943 (619) 661-1055 (408) 573-4159 WEBSITE www.avxcorp.com www.sanyovideo.com www.t-yuden.com
3401fa
9
LTC3401
APPLICATIO S I FOR ATIO
In some layouts it may be required to place a 1F low ESR capacitor as close to the VOUT and GND pins as possible. Input Capacitor Selection The input filter capacitor reduces peak currents drawn from the input source and reduces input switching noise. Since the IC can operate at voltages below 0.5V once the output is regulated, demand on the input capacitor is much less and in most applications a 3.3F is sufficient. Output Diode For applications with output voltages over 4.3V, a Schottky diode is required to ensure that the SW pin voltage does not exceed its absolute maximum rating. The Schottky diode across the synchronous PMOS switch provides a lower drop during the break-before-make time (typically 20ns) of the NMOS to PMOS transition. The Schottky diode improves peak efficiency (see graph "Efficiency Loss Without Schottky vs Frequency"). Use of a Schottky diode such as a MBRM120T3, 1N5817 or equivalent. Since slow recovery times will compromise efficiency, do not use ordinary rectifier diodes. Operating Frequency Selection There are several considerations in selecting the operating frequency of the converter. The first is determining the sensitive frequency bands that cannot tolerate any spectral noise. For example, in products incorporating RF communications, the 455kHz IF frequency is sensitive to any noise, therefore switching above 600kHz is desired. Some communications have sensitivity to 1.1MHz.
100 90 80 70 EFFICIENCY (%) 60 50 40 30 20 10 0 0.1 1 10 100 OUTPUT CURRENT (mA) 1000
3401 G08
Burst Mode OPERATION 3MHz 300kHz 1MHz
Figure 2. Converter Efficiency 2.4V to 3.3V
3401fa
10
U
In this case, converter frequencies up to 3MHz may be employed. The second consideration is the physical size of the converter. As the operating frequency goes up, the inductor 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. For example in Figure 2, for a 2.4V to 3.3V converter, the efficiency at 100mA is 5% less at 2MHz compared to 300kHz. Another operating frequency consideration is whether the application can allow "pulse skipping." In this mode, the minimum on time of the converter cannot support the duty 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:
fMAX _ NOSKIP = VOUT - VIN Hz VOUT * tON(MIN)
W
UU
where tON(MIN) = minimum on time = 120ns Reducing Output Capacitance with a Load Feed Forward Signal 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 LTC3401 converter at the VC pin with respect to the inductor current is typically 130mA/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 correction, but because of the load feed forward signal, the range over which it must slew is greatly reduced. This results in an improved transient response.
LTC3401
APPLICATIO S I FOR ATIO
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:
V * R5 * VIN * 1.5 R6 FF - R5 VOUT * IOUT
where IOUT = load current change.
VIN VOUT
3 10 2 6 1
LTC3401 VIN SHDN SW VOUT
4 7 8 9 5 C3
MODE/SYNC FB PGOOD Rt VC GND
R5 C5 3.3nF
3404 F03
LOAD FEED FORWARD SIGNAL
R6 VFF
Figure 3
Closing the Feedback Loop The LTC3401 uses current mode control with internal adaptive slope compensation. Current mode control 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. GDC = GCONTROLOUTPUT * GEA
2 * VIN GCONTROL = , GEA 2000 IOUT
The output filter pole is given by:
fFILTERPOLE = IOUT Hz * VOUT * COUT
U
where COUT is the output filter capacitor. The output filter zero is given by:
fFILTERZERO = 1 2 * * RESR * COUT Hz
W
UU
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:
fRHPZ =
VIN2 * RO 2 * * L * VO2
Hz
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. The typical error amp compensation is shown in Figure 4. The equations for the loop dynamics are as follows:
fPOLE1 1
Hz 2 * * 20 * 106 * CC1 which is extremelyclose to DC 1 f ZERO1 = Hz 2 * * RZ * CC1 1 fPOLE2 Hz 2 * * RZ * CC2
VOUT
+
ERROR AMP
1.25V FB 8 VC 9 CC1 RZ
3401 F04
R1
-
R2
CC2
Figure 4
Refer to Application Note AN-76 for more closed loop examples.
3401fa
11
LTC3401
OUTPUT DISCO UU ECT CIRCUITS
Single Cell Output Disconnect
VIN = 0.9V TO 1.5V LTC3401 VIN SHDN SW VOUT ZETEX FMMT717
VOUT
3 10 2 6 1
4 7 8 9 5
RB*
MODE/SYNC FB PGOOD Rt VC GND
C5 1F
3404 TA03
(V - VINMIN - 0.7V) * 100 * SET RB TO FORCE BETA OF 100; RB = OUT IOUTMAX 0 = FIXED FREQUENCY 1 = Burst Mode OPERATION
Dual Cell Output Disconnect Alllowing Full Load Start-Up
VIN = 1.8V TO 3V LTC3401 VIN SHDN SW VOUT IRLML6401 VOUT 3 10 2 6 1 4 7 8 9 5 2N2222 C5 1F RG 1M
R7 1M
MODE/SYNC FB PGOOD Rt VC GND
3404 TA04
0 = FIXED FREQUENCY 1 = Burst Mode OPERATION
3401fa
12
LTC3401
TYPICAL APPLICATIO S
Single Cell to 3V at 50mA, 1.2mm High, 3MHz Step-Up Converter
L1 1H R4 5.1M
VIN = 0.9V TO 1.5V
R3 1M
3 10
LTC3401 VIN SHDN SW VOUT
+1
CELL
EFFICIENCY (%)
2 6
MODE/SYNC FB PGOOD Rt VC GND
C1 2.2F
1
Rt 10k
0 = FIXED FREQUENCY 1 = Burst Mode OPERATION
C1: TAIYO YUDEN JMK212BJ225MG C2: TAIYO YUDEN JMK212BJ475MG D1: CENTRAL SEMICONDUCTOR CMDSH-3 L1: TAIYO YUDEN LB2016
Single Cell to 3V at 200mA, 600kHz Step-Up Converter
L1 10H R4 5.1M
VIN = 0.9V TO 1.5V
R3 1M
3 10
LTC3401 VIN SHDN SW VOUT
EFFICIENCY (%)
+1
CELL
2 6
MODE/SYNC FB PGOOD Rt VC GND
C1 3.3F
1
Rt 50k
0 = FIXED FREQUENCY 1 = Burst Mode OPERATION
C1: TAIYO YUDEN JMK212BJ335MG C2: TAIYO YUDEN JMK325BJ226MM D1: ON SEMICONDUCTOR MBRM120T3 L1: SUMIDA CD54-100
U
D1
Efficiency
VOUT 3V 100mA R2 866k
90 80 70 60 50 40 30 20 10 0 0.1 VIN = 1.2V 1 10 100 OUTPUT CURRENT (mA) 1000
3401 TA05b
Burst Mode OPERATION FIXED FREQUENCY
4 7 8 9 5 C3 470pF R5 39k
C2 4.7F
C4 20pF
R1 619k
3404 TA05a
D1
VOUT 3V 200mA R2 866k
Efficiency
100 90 80 70 60 50 40 30 20 10 0 0.1 1 VIN = 1.2V 100 10 LOAD CURRENT (mA) 1000
3401 TA06b
4 7 8 9 5 C3 470pF R5 82k
Burst Mode OPERATION FIXED FREQUENCY
C2 22F
C4 4.7pF
R1 619k
3404 TA06a
3401fa
13
LTC3401
TYPICAL APPLICATIO S
Li-Ion to 5V at 300mA, 1MHz Step-Up Converter
VIN = 2.5V TO 4.2V L1 10H D1*
R3 1M
3 10
LTC3401 VIN SHDN SW VOUT
EFFICIENCY (%)
Li-Ion C1 4.7F
2 6 1
MODE/SYNC FB PGOOD Rt VC GND
Rt 30k
0 = FIXED FREQUENCY 1 = Burst Mode OPERATION
*LOCATE COMPONENTS AS CLOSE TO IC AS POSSIBLE C1: TAIYO YUDEN JMK212BJ475MG C2: TAIYO YUDEN JMK325BJ226MM D1: ON SEMICONDUCTOR MBRM120T3 L1: SUMIDA CDC5023-100
High Efficiency, Compact CCFL Supply with Remote Dimming
C3 27pF 1kV
VIN = 2.5V TO 4.2V
R5 Li-Ion 1M
C1 10F
C1: TAIYO YUDEN JMK212BJ106MG C2: PANASONIC ECH-U D1: ZETEX ZHCS-1000 D2 TO D4: 1N4148
14
U
Efficiency
VOUT 5V 300mA R2 1.65M
100 90 80 70 60 50 40 30 20 10 0 0.1
3404 TA07a
Burst Mode OPERATION
4 7 8 9 5 C3 470pF R5 82k
C2* 22F
1MHz FIXED FREQUENCY
C4 4.7pF
R1 549k
VIN = 3.6V 1 100 10 LOAD CURRENT (mA) 1000
3401 TA07b
T1 1 10 2
6
5
3
4
R1 300
CCFL C2 Q1 0.22F Q2 L1 33F
D1
D4
R4 20k
DIMMING INPUT 0V TO 2.5V
3 10 2 6 1
LTC3401 VIN SHDN SW VOUT
4 7 D2 8 9 5 C5 1F C4 0.1F
3404 TA08
D3
MODE/SYNC FB PGOOD Rt VC GND
R2 10k R3 1k
Rt 150k L1: SUMIDA CD-54-330MC Q1, Q2: ZETEX FMMT-617 T1: SUMIDA C1Q122
CCFL BACKLIGHT APPLICATION CIRCUITS CONTAINED IN THIS DATA SHEET ARE COVERED BY U.S. PATENT NUMBER 5408162 AND OTHER PATENTS PENDING
3401fa
LTC3401
PACKAGE DESCRIPTION
MS Package 10-Lead Plastic MSOP
(Reference LTC DWG # 05-08-1661)
5.23 (.206) MIN
0.50 0.305 0.038 (.0197) (.0120 .0015) BSC TYP RECOMMENDED SOLDER PAD LAYOUT
0.254 (.010) GAUGE PLANE
0.18 (.007) SEATING PLANE 0.17 - 0.27 (.007 - .011) 0.13 0.05 (.005 .002)
MSOP (MS) 0402
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
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 representation that the interconnection of its circuits as described herein will not infringe on existing patent rights.
U
0.889 0.127 (.035 .005)
3.2 - 3.45 (.126 - .136) 3.00 0.102 (.118 .004) (NOTE 3) 10 9 8 7 6
0.497 0.076 (.0196 .003) REF
DETAIL "A" 0 - 6 TYP
4.88 0.10 (.192 .004)
3.00 0.102 (.118 .004) NOTE 4
12345 0.53 0.01 (.021 .006) DETAIL "A" 1.10 (.043) MAX 0.86 (.034) REF
0.50 (.0197) TYP
3401fa
15
LTC3401
TYPICAL APPLICATIO
VIN =1.8V TO 3V
+
2 CELLS
C1 4.7F
0 = FIXED FREQ 1 = Burst Mode OPERATION
C1: TAIYO YUDEN JMK212BJ475MG C2: TAIYO YUDEN JMK325BJ226MM D1: ON SEMICONDUCTOR MBRM120T3 D2 TO D7: ZETEX FMND7000 DUAL DIODE L1: SUMIDA CD43-4R7M
RELATED PARTS
PART NUMBER LT1306 LT1308A/LT1308B LT1317/LT1317B LT1610 LT1613 LT1615 LT1619 LT1930A LT1949 LTC3400 LTC3402 LTC3423 DESCRIPTION Sync, Fixed Frequency, Step-Up DC/DC Converter High Current, Micropower, Single Cell 600kHz DC/DC Converter Micropower 600kHz PWM DC/DC Converter 1.7MHz, Single Cell Micropower DC/DC Converter 1.4MHz, Single Cell DC/DC Converter in SOT-23 Micropower Step-Up DC/DC Converter in SOT-23 High Efficiency Boost DC/DC Controller 2.2MHz DC/DC Converter in SOT-23 600kHz, 1A Switch PWM DC/DC Converter Single Cell, High Current (600mA) Micropower, Synchronous 1.2MHz Step-Up DC/DC Converter Single Cell, High Current (2A) Micropower, Synchronous 3MHz Step-Up DC/DC Converter Single Cell, High Current (2A) Micropower, Synchronous 3MHz Step-Up DC/DC Converter for VOUT < 2.6V COMMENTS Internal 2A Switches, VIN As Low As 1.8V 5V at 1A from Single Li-Ion Cell VIN As Low As 1.5V, IQ = 100A 3V at 30mA from 1V, 5V at 200mA from 3.3V VIN As Low As 1.1V, 3V at 30mA from Single Cell IQ = 20A, 1A Shutdown Current, VIN As Low As 1V 1A Gate Drive, 1.1V to 20V Input, Separate VCC for Gate Drive VIN = 2.6V to 16V, 5V at 450mA from 3.3V Input 1.1A, 0.5/30V Internal Switch, VIN As Low As 1.8V VIN = 0.85V to 5.5V, Up to 92% Efficiency Synchronizable Oscillator from 100kHz to 1.2MHz, ThinSOTTM Package VIN = 0.5V to 5.5V, Up to 97% Efficiency Synchronizable Oscillator from 100kHz to 3MHz, 10-Lead MSOP Package VOUT = 1.5V, Up to 97% Efficiency Synchronizable Oscillator from 100kHz to 3MHz
ThinSOT is a trademark of Linear Technology Corporation.
3401fa
16
Linear Technology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
(408) 432-1900 q FAX: (408) 434-0507
q
U
Triple Output Converter
D2 D3 D4 D5 8V 2mA 0.1F 0.1F 0.1F 4.7F L1, 4.7H D1 VOUT 3.3V 500mA R2 909k R3 1M 3 10 2 6 1 LTC3401 VIN SHDN SW VOUT 4 7 8 9 5 C3 470pF R5 82k R1 549k C4 4.7pF C2 22F MODE/SYNC FB PGOOD Rt VC GND Rt 30k 0.1F D6 4.7F D7 -2.5V 1mA
3401 TA09
LT/TP 0502 1.5K REV A * PRINTED IN USA
www.linear.com
(c) LINEAR TECHNOLOGY CORPORATION 2001

▲Up To Search▲

Price & Availability of LTC3401EMS

	To Download LTC3401EMS Datasheet File
If you can't view the Datasheet, Please click here to try to view without PDF Reader .