LT1613
`1.4MHz, Single Cell DC/DC
`Converter in 5-Lead SOT-23
`
`DESCRIPTIOU
`The LT®1613 is the industry’s first 5-lead SOT-23 current
`mode DC/DC converter. Intended for small, low power
`applications, it operates from an input voltage as low as
`1.1V and switches at 1.4MHz, allowing the use of tiny, low
`cost capacitors and inductors 2mm or less in height. Its
`small size and high switching frequency enables the
`complete DC/DC converter function to take up less than
`0.2 square inches of PC board area. Multiple output power
`supplies can now use a separate regulator for each output
`voltage, replacing cumbersome quasi-regulated ap-
`proaches using a single regulator and a custom trans-
`former.
`A constant frequency, internally compensated current
`mode PWM architecture results in low, predictable output
`noise that is easy to filter. The high voltage switch on the
`LT1613 is rated at 36V, making the device ideal for boost
`converters up to 34V as well as for Single-Ended Primary
`Inductance Converter (SEPIC) and flyback designs. The
`device can generate 5V at up to 200mA from a 3.3V supply
`or 5V at 175mA from four alkaline cells in a SEPIC design.
`The LT1613 is available in the 5-lead SOT-23 package.
`, LTC and LT are registered trademarks of Linear Technology Corporation.
`
`1
`
`Efficiency Curve
`
`VIN = 4.2V
`
`VIN = 3.5V
`
`VIN = 2.8V
`
`VIN = 1.5V
`
`0
`
`50
`
`100 150 200 250 300 350 400
`LOAD CURRENT (mA)
`
`1613 TA01a
`
`100
`95
`90
`85
`80
`75
`70
`65
`60
`55
`50
`
`EFFICIENCY (%)
`
`FEATURES
`n Uses Tiny Capacitors and Inductor
`n Internally Compensated
`n Fixed Frequency 1.4MHz Operation
`n Operates with VIN as Low as 1.1V
`n 3V at 30mA from a Single Cell
`n 5V at 200mA from 3.3V Input
`n 15V at 60mA from Four Alkaline Cells
`n High Output Voltage: Up to 34V
`n Low Shutdown Current: <1m A
`n Low VCESAT Switch: 300mV at 300mA
`n Tiny 5-Lead SOT-23 Package
`
`APPLICATIO SU
`n Digital Cameras
`n Pagers
`n Cordless Phones
`n Battery Backup
`n LCD Bias
`n Medical Diagnostic Equipment
`n Local 5V or 12V Supply
`n External Modems
`n PC Cards
`
`TYPICAL APPLICATIOU
`
`L1
`4.7m H
`
`D1
`
`VIN
`3.3V
`
`+
`
`C1
`15m F
`
`VIN
`
`SW
`
`LT1613
`
`SHDN
`
`SHDN
`
`FB
`
`GND
`
`L1: MURATA LQH3C4R7M24 OR SUMIDA CD43-4R7
`C1: AVX TAJA156M010
`C2: AVX TAJB226M006
`D1: MBR0520
`
`R1
`37.4k
`
`+
`
`R2
`12.1k
`
`VOUT
`5V
`200mA
`
`C2
`22m F
`
`1613 TA01
`
`Figure 1. 3.3V to 5V 200mA DC/DC Converter
`
`FEIT 1007
`Feit v. Philips Lighting
`U.S. Pat. No. 6,586,890
`
`

`

`LT1613
`
`ABSOLUTE MAXIMUM RATINGS
`W
`W W
`U
`(Note 1)
`VIN Voltage .............................................................. 10V
`SW Voltage ................................................–0.4V to 36V
`FB Voltage ..................................................... VIN + 0.3V
`Current into FB Pin ............................................... – 1mA
`SHDN Voltage .......................................................... 10V
`Maximum Junction Temperature .......................... 125(cid:176) C
`Operating Temperature Range
`Commercial ............................................. 0(cid:176) C to 70(cid:176) C
`Extended Commercial (Note 2)........... –40(cid:176) C to 85(cid:176) C
`Storage Temperature Range ................. –65(cid:176) C to 150(cid:176) C
`Lead Temperature (Soldering, 10 sec).................. 300(cid:176) C
`
`PACKAGE/ORDER INFORMATION
`W
`U
`U
`ORDER PART NUMBER
`LT1613CS5
`
`TOP VIEW
`
`SW 1
`GND 2
`FB 3
`
`5 VIN
`
`4 SHDN
`
`S5 PACKAGE
`5-LEAD PLASTIC SOT-23
`
`S5 PART MARKING
`LTED
`
`Consult factory for Industrial and Military grade parts.
`
`ELECTRICAL CHARACTERISTICS The l denotes the specifications which apply over the full operating
`temperature range, otherwise specifications are at TA = 25(cid:176) C. Commercial grade 0(cid:176) C to 70(cid:176) C, VIN = 1.5V, VSHDN = VIN unless
`otherwise noted. (Note 2)
`
`CONDITIONS
`
`VSHDN = 1.5V
`VSHDN = 0V, VIN = 2V
`VSHDN = 0V, VIN = 5V
`1.5V £
` VIN £
` 10V
`
`(Note 3)
`ISW = 300mA
`VSW = 5V
`
`l
`
`l
`
`l
`
`l
`
`MIN
`
`1.205
`
`1.0
`82
`550
`
`1
`
`TYP
`0.9
`
`1.23
`27
`3
`0.01
`0.01
`0.02
`1.4
`86
`800
`300
`0.01
`
`25
`0.01
`
`MAX
`1.1
`10
`1.255
`80
`4.5
`0.5
`1.0
`0.2
`1.8
`
`350
`1
`
`0.3
`50
`0.1
`
`UNITS
`V
`V
`V
`nA
`mA
`m A
`m A
`%/V
`MHz
`%
`mA
`mV
`m A
`V
`V
`m A
`m A
`
`Note 2: The LT1613C is guaranteed to meet performance specifications
`from 0(cid:176) C to 70(cid:176) C. Specifications over the –40(cid:176) C to 85(cid:176) C operating
`temperature range are assured by design, characterization and correlation
`with statistical process controls.
`Note 3: Current limit guaranteed by design and/or correlation to static test.
`
`VSHDN = 3V
`VSHDN = 0V
`Note 1: Absolute Maximum Ratings are those values beyond which the life
`of a device may be impaired.
`
`PARAMETER
`Minimum Operating Voltage
`Maximum Operating Voltage
`Feedback Voltage
`FB Pin Bias Current
`Quiescent Current
`Quiescent Current in Shutdown
`
`Reference Line Regulation
`Switching Frequency
`Maximum Duty Cycle
`Switch Current Limit
`Switch VCESAT
`Switch Leakage Current
`SHDN Input Voltage High
`SHDN Input Voltage Low
`SHDN Pin Bias Current
`
`2
`
`

`

`LT1613
`
`TYPICAL PERFOR A CE CHARACTERISTICS
`UW
`
`Switch VCESAT vs Switch Current
`
`Oscillator Frequency vs
`Temperature
`
`SHDN Pin Current vs VSHDN
`
`TA = 25°C
`
`1
`
`2
`3
`SHDN PIN VOLTAGE (V)
`
`4
`
`5
`
`1613 G03
`
`50
`
`40
`
`30
`
`20
`
`10
`
`0
`
`0
`
`SHDN PIN BIAS CURRENT (µA)
`
`VIN = 5V
`
`VIN = 1.5V
`
`2.00
`
`1.75
`
`1.50
`
`1.25
`
`1.00
`
`0.75
`
`0.50
`
`0.25
`
`SWITCHING FREQUENCY (MHz)
`
`TA = 25°C
`
`100
`
`200
`300
`400
`500
`SWITCH CURRENT (mA)
`
`600
`
`700
`
`0
`–50
`
`–25
`
`0
`25
`50
`TEMPERATURE (°C)
`
`75
`
`100
`
`1613 G01
`
`1613 G02
`
`700
`
`600
`
`500
`
`400
`
`300
`
`200
`
`100
`
`0
`
`0
`
`VCESAT (mV)
`
`Current Limit vs Duty Cycle
`
`Feedback Pin Voltage
`
`VOLTAGE
`
`1.25
`
`1.24
`
`1.23
`
`1.22
`
`1.21
`
`FEEDBACK PIN VOLTAGE (V)
`
`70°C
`
`25°C
`
`–40°C
`
`10
`
`20
`
`30
`
`40
`50
`DUTY CYCLE (%)
`
`60
`
`70
`
`80
`
`1613 G04
`
`1.20
`–50
`
`–25
`
`0
`25
`50
`TEMPERATURE (°C)
`
`75
`
`100
`
`1613 G05
`
`Switching Waveforms, Circuit of Figure 1
`
`1000
`
`900
`
`800
`
`700
`
`600
`
`500
`
`400
`
`300
`
`200
`
`CURRENT LIMIT (mA)
`
`VOUT
`100mV/DIV
`AC COUPLED
`
`VSW
`5V/DIV
`
`ISW
`200mA/DIV
`
`ILOAD = 150mA
`
`200ns/DIV
`
`1613 G06
`
`3
`
`

`

`LT1613
`
`PIN FUNCTIONSUU U
`
`
`SW (Pin 1): Switch Pin. Connect inductor/diode here.
`Minimize trace area at this pin to keep EMI down.
`GND (Pin 2): Ground. Tie directly to local ground plane.
`FB (Pin 3): Feedback Pin. Reference voltage is 1.23V.
`Connect resistive divider tap here. Minimize trace area at
`FB. Set VOUT according to VOUT = 1.23V(1 + R1/R2).
`
`SHDN (Pin 4): Shutdown Pin. Tie to 1V or more to enable
`device. Ground to shut down.
`VIN (Pin 5): Input Supply Pin. Must be locally bypassed.
`
`1
`
`SW
`
`R
`
`FF
`S
`
`Q
`
`DRIVER
`
`Q3
`
`0.15W
`
`2
`
`GND
`1613 • BD
`
`–+
`
`COMPARATOR
`
`A2
`
`– +
`
`SHDN
`4
`
`SHUTDOWN
`
`RC
`
`CC
`
`RAMP
`GENERATOR
`
`1.4MHz
`OSCILLATOR
`
`A1
`gm
`
`–+
`
`BLOCK DIAGRAMW
`
`VIN 5
`
`VIN
`
`R5
`40k
`
`R6
`40k
`
`VOUT
`
`R1
`(EXTERNAL)
`
`FB
`3
`
`Q1
`
`FB
`
`R2
`(EXTERNAL)
`
`Q2
`x10
`
`R3
`30k
`
`R4
`140k
`
`OPERATIOU
`The LT1613 is a current mode, internally compensated,
`fixed frequency step-up switching regulator. Operation
`can be best understood by referring to the Block Diagram.
`Q1 and Q2 form a bandgap reference core whose loop is
`closed around the output of the regulator. The voltage
`drop across R5 and R6 is low enough such that Q1 and Q2
`do not saturate, even when VIN is 1V. When there is no
`load, FB rises slightly above 1.23V, causing VC (the error
`amplifier’s output) to decrease. Comparator A2’s output
`stays high, keeping switch Q3 in the off state. As increased
`output loading causes the FB voltage to decrease, A1’s
`output increases. Switch current is regulated directly on a
`cycle-by-cycle basis by the VC node. The flip flop is set at
`the beginning of each switch cycle, turning on the switch.
`When the summation of a signal representing switch
`current and a ramp generator (introduced to avoid
`
`subharmonic oscillations at duty factors greater than
`50%) exceeds the VC signal, comparator A2 changes
`state, resetting the flip flop and turning off the switch.
`More power is delivered to the output as switch current is
`increased. The output voltage, attenuated by external
`resistor divider R1 and R2, appears at the FB pin, closing
`the overall loop. Frequency compensation is provided
`internally by RC and CC. Transient response can be opti-
`mized by the addition of a phase lead capacitor CPL in
`parallel with R1 in applications where large value or low
`ESR output capacitors are used.
`As the load current is decreased, the switch turns on for a
`shorter period each cycle. If the load current is further
`decreased, the converter will skip cycles to maintain
`output voltage regulation.
`
`4
`
`S
`

`

`LT1613
`
`L1A
`22µH
`
`C3
`1µF
`
`VIN
`4V TO
`7V
`
`+
`
`C1
`15µF
`
`VIN
`
`SW
`
`LT1613
`
`SHDN
`
`SHDN
`
`FB
`
`GND
`
`R1
`100k
`
`R2
`32.4k
`
`C1, C2: AVX TAJA156M016
`C3: TAIYO YUDEN JMK325BJ226MM
`D1: MOTOROLA MBR0520
`L1, L2: MURATA LQH3C220
`
`L1B
`22µH
`
`D1
`
`+
`
`VOUT
`5V/150mA
`C2
`15µF
`
`1613 F03
`
`Figure 3. Single-Ended Primary Inductance Converter (SEPIC)
`Generates 5V from An Input Voltage Above or Below 5V
`
`L1A
`
`+
`
`C1
`
`VIN
`
`SHUTDOWN
`
`5
`
`4
`
`1
`
`2 3
`
`R2
`
`L1B
`
`C3
`
`VOUT
`
`D1
`
`+
`
`C2
`
`VIAS TO
`GROUND
`PLANE
`
`OPERATIOU
`LAYOUT
`The LT1613 switches current at high speed, mandating
`careful attention to layout for proper performance. You
`will not get advertised performance with careless layouts.
`Figure 2 shows recommended component placement for
`a boost (step-up) converter. Follow this closely in your
`PCB layout. Note the direct path of the switching loops.
`Input capacitor C1 must be placed close (< 5mm) to the IC
`package. As little as 10mm of wire or PC trace from CIN to
`VIN will cause problems such as inability to regulate or
`oscillation.
`The ground terminal of output capacitor C2 should tie
`close to Pin 2 of the LT1613. Doing this reduces dI/dt in the
`ground copper which keeps high frequency spikes to a
`minimum. The DC/DC converter ground should tie to the
`PC board ground plane at one place only, to avoid intro-
`ducing dI/dt in the ground plane.
`A SEPIC (single-ended primary inductance converter)
`schematic is shown in Figure 3. This converter topology
`produces a regulated output voltage that spans (i.e., can
`be higher or lower than) the output. Recommended com-
`ponent placement for a SEPIC is shown in Figure 4.
`
`L1
`
`+
`
`C1
`
`VIN
`
`GROUND
`
`R1
`
`1613 F04
`
`Figure 4. Recommended Component Placement for SEPIC
`
`SHUTDOWN
`
`1613 F02
`
`COMPONENT SELECTION
`
`Inductors
`Inductors used with the LT1613 should have a saturation
`current rating (where inductance is approximately 70% of
`zero current inductance) of approximately 0.5A or greater.
`DCR of the inductors should be 0.5W
` or less. For boost
`converters, inductance should be 4.7m H for input voltage
`less than 3.3V and 10m H for inputs above 3.3V. When
`using the device as a SEPIC, either a coupled inductor or
`two separate inductors can be used. If using separate
`inductors, 22m H units are recommended for input voltage
`above 3.3V. Coupled inductors have a beneficial mutual
`inductance, so a 10m H coupled inductor results in the
`same ripple current as two 20m H uncoupled units.
`
`5
`
`VOUT
`
`D1
`
`+
`
`C2
`
`VIAS TO
`GROUND
`PLANE
`
`5
`
`4
`
`1
`
`2 3
`
`R2
`
`GROUND
`
`R1
`
`Figure 2. Recommended Component Placement for Boost
`Converter. Note Direct High Current Paths Using Wide PCB
`Traces. Minimize Area at Pin 3 (FB). Use Vias to Tie Local
`Ground Into System Ground Plane. Use Vias at Location Shown
`to Avoid Introducing Switching Currents Into Ground Plane
`
`

`

`LT1613
`
`OPERATIOU
`Table 1 lists several inductors that will work with the
`LT1613, although this is not an exhaustive list. There are
`many magnetics vendors whose components are suitable
`for use.
`
`Diodes
`A Schottky diode is recommended for use with the LT1613.
`The Motorola MBR0520 is a very good choice. Where the
`input to output voltage differential exceeds 20V, use the
`MBR0530 (a 30V diode). If cost is more important than
`efficiency, the 1N4148 can be used, but only at low current
`loads.
`
`Capacitors
`The input bypass capacitor must be placed physically
`close to the input pin. ESR is not critical and in most cases
`an inexpensive tantalum is appropriate.
`The choice of output capacitor is far more important. The
`quality of this capacitor is the greatest determinant of the
`output voltage ripple. The output capacitor must have
`enough capacitance to satisfy the load under transient
`conditions and it must shunt the switched component of
`current coming through the diode. Output voltage ripple
`results when this switched current passes through the
`finite output impedance of the output capacitor. The
`capacitor should have low impedance at the 1.4MHz
`switching frequency of the LT1613. At this frequency, the
`impedance is usually dominated by the capacitor’s equiva-
`lent series resistance (ESR). Choosing a capacitor with
`
`lower ESR will result in lower output ripple.
`Ceramic capacitors can be used with the LT1613 provided
`loop stability is considered. A tantalum capacitor has
`some ESR and this causes an “ESR zero” in the regulator
`loop. This zero is beneficial to loop stability. The internally
`compensated LT1613 does not have an accessible com-
`pensation node, but other circuit techniques can be em-
`ployed to counteract the loss of the ESR zero, as detailed
`in the next section.
`Some capacitor types appropriate for use with the LT1613
`are listed in Table 2.
`
`OPERATION WITH CERAMIC CAPACITORS
`Because the LT1613 is internally compensated, loop sta-
`bility must be carefully considered when choosing an
`output capacitor. Small, low cost tantalum capacitors
`have some ESR, which aids stability. However, ceramic
`capacitors are becoming more popular, having attractive
`characteristics such as near-zero ESR, small size and
`reasonable cost. Simply replacing a tantalum output ca-
`pacitor with a ceramic unit will decrease the phase margin,
`in some cases to unacceptable levels. With the addition of
`a phase lead capacitor (CPL) and isolating resistor (R3),
`the LT1613 can be used successfully with ceramic output
`capacitors as described in the following figures.
`A boost converter, stepping up 2.5V to 5V, is shown in
`Figure 5. Tantalum capacitors are used for the input and
`output (the input capacitor is not critical and has little
`
`Table 1. Inductor Vendors
`VENDOR
`PHONE
`Sumida
`(847) 956-0666
`
`URL
`www.sumida.com
`
`Murata
`
`(404) 436-1300
`
`www.murata.com
`
`Coiltronics
`
`(407) 241-7876
`
`www.coiltronics.com
`
`Table 2. Capacitor Vendors
`VENDOR
`PHONE
`Taiyo Yuden
`(408) 573-4150
`AVX
`(803) 448-9411
`
`URL
`www.t-yuden.com
`www.avxcorp.com
`
`Murata
`
`(404) 436-1300
`
`www.murata.com
`
`PART
`CLS62-22022
`CD43-220
`LQH3C-220
`LQH3C-100
`LQH3C-4R7
`CTX20-1
`
`PART
`Ceramic Caps
`Ceramic Caps
`Tantalum Caps
`Ceramic Caps
`
`COMMENT
`22m H Coupled
`22m H
`22m H, 2mm Height
`10m H
`4.7m H
`20m H Coupled, Low DCR
`
`COMMENT
`X5R Dielectric
`
`6
`
`

`

`OPERATIOU
`effect on loop stability, as long as minimum capacitance
`requirements are met). The transient response to a load
`step of 50mA to 100mA is pictured in Figure 6. Note the
`“double trace,” due to the ESR of C2. The loop is stable and
`settles in less than 100m s. In Figure 7, C2 is replaced by a
`10m F ceramic unit. Phase margin decreases drastically,
`
`L1
`10µH
`
`D1
`
`VIN
`2.5V
`
`+
`
`C1
`15µF
`
`VIN
`
`SW
`
`LT1613
`
`SHDN
`
`SHDN
`
`FB
`
`GND
`
`C1: AVX TAJA156M010R
`C2: AVX TAJA226M006R
`D1: MOTOROLA MBR0520
`L1: MURATA LQH3C100
`
`R1
`37.4k
`
`R2
`12.1k
`
`VOUT
`5V
`
`+
`
`C2
`22µF
`
`1613 F05
`
`Figure 5. 2.5V to 5V Boost Converter with “A”
`Case Size Tantalum Input and Output Capacitors
`
`VOUT
`20mV/DIV
`AC COUPLED
`
`LOAD CURRENT
`
`100mA
`50mA
`
`200m s/DIV
`Figure 6. 2.5V to 5V Boost Converter Transient
`Response with 22m F Tantalum Output Capacitor.
`Apparent Double Trace on VOUT Is Due to Switching
`Frequency Ripple Current Across Capacitor ESR
`
`1613 F06
`
`LT1613
`
`resulting in a severely underdamped response. By adding
`R3 and CPL as detailed in Figure 8’s schematic, phase
`margin is restored, and transient response to the same
`load step is pictured in Figure 9. R3 isolates the device FB
`pin from fast edges on the VOUT node due to parasitic PC
`trace inductance.
`Figure 10’s circuit details a 5V to 12V boost converter,
`delivering up to 130mA. The transient response to a load
`step of 10mA to 130mA, without CPL, is pictured in
`Figure␣ 11. Although the ringing is less than that of the
`previous example, the response is still underdamped and
`can be improved. After adding R3 and CPL, the improved
`transient response is detailed in Figure 12.
`Figure 13 shows a SEPIC design, converting a 3V to 10V
`input to a 5V output. The transient response to a load step
`of 20mA to 120mA, without CPL and R3, is pictured in
`Figure␣ 14. After adding these two components, the im-
`proved response is shown in Figure 15.
`
`VIN
`2.5V
`
`+
`
`C1
`15µF
`
`L1
`10µH
`
`VIN
`
`SW
`
`LT1613
`
`SHUTDOWN
`
`SHDN
`
`FB
`
`GND
`
`D1
`
`R3
`10k
`
`CPL
`330pF
`
`R1
`37.4k
`
`R2
`12.1k
`
`VOUT
`5V
`
`C2
`10µF
`
`C1: AVX TAJA156M010R
`C2: TAIYO YUDEN LMK325BJ106MN
`D1: MBR0520
`L1: MURATA LQH3C100K04
`Figure 8. 2.5V to 5V Boost Converter with Ceramic
`Output Capacitor. CPL Added to Increase Phase Margin,
`R3 Isolates FB Pin from Fast Edges
`
`1613 F08
`
`VOUT
`20mV/DIV
`AC COUPLED
`
`VOUT
`20mV/DIV
`AC COUPLED
`
`LOAD CURRENT 100mA
`50mA
`
`200m s/DIV
`Figure 7. 2.5V to 5V Boost Converter with
`10m F Ceramic Output Capacitor, No CPL
`
`1613 F07
`
`LOAD CURRENT
`
`100mA
`50mA
`
`200m s/DIV
`Figure 9. 2.5V to 5V Boost Converter with 10m F Ceramic
`Output Capacitor, 330pF CPL and 10k in Series with FB Pin
`
`1613 F09
`
`7
`
`

`

`LT1613
`
`OPERATIOU
`
`VIN
`5V
`
`+
`
`L1
`10µH
`
`C1
`22µF
`
`VIN
`
`SW
`
`LT1613
`
`SHUTDOWN
`
`SHDN
`
`FB
`
`GND
`
`D1
`
`R3
`10k
`
`CPL
`200pF
`
`R1
`107k
`
`R2
`12.3k
`
`C1: AVX TAJB226M010
`C2: TAIYO YUDEN EMK325BJ475MN
`D1: MOTOROLA MBR0520
`L1: MURATA LQH3C100
`Figure 10. 5V to 12V Boost Converter with 4.7m F Ceramic
`Output Capacitor, CPL Added to Increase Phase Margin
`
`1613 F10
`
`VOUT
`12V
`130mA
`
`C2
`4.7µF
`
`VIN
`3V TO
`10V
`
`+
`
`C1
`22µF
`
`L1
`22µH
`
`C3
`1µF
`
`VIN
`
`SW
`
`LT1613
`
`L2
`22µH
`
`CPL
`330pF
`
`D1
`
`R3
`10k
`
`R2
`12.1k
`
`R1
`37.4k
`
`VOUT
`5V
`C2
`10µF
`
`1613 F13
`
`SHUTDOWN
`
`SHDN
`
`FB
`
`GND
`
`C1: AVX TAJB226M010
`C2: TAIYO YUDEN LMK325BJ106MN
`C3: TAIYO YUDEN LMK212BJ105MG
`D1: MOTOROLA MBR0520
`L1, L2: MURATA LQH3C220
`
`Figure 13. 5V Output SEPIC with Ceramic
`Output Capacitor. CPL Adds Phase Margin
`
`VOUT
`100mV/DIV
`AC COUPLED
`
`VOUT
`50mV/DIV
`AC COUPLED
`
`LOAD CURRENT 130mA
`10mA
`
`200m s/DIV
`Figure 11. 5V to 12V Boost Converter
`with 4.7m F Ceramic Output Capacitor
`
`VOUT
`100mV/DIV
`AC COUPLED
`
`LOAD CURRENT 130mA
`10mA
`
`200m s/DIV
`Figure 12. 5V to 12V Boost Converter with 4.7m F
`Ceramic Output Capacitor and 200pF Phase-Lead
`Capacitor CPL and 10k in Series with FB Pin
`
`1613 F11
`
`1613 F12
`
`LOAD CURRENT 120mA
`20mA
`
`200m s/DIV
`Figure 14. 5V Output SEPIC with 10m F
`Ceramic Output Capacitor. No CPL. VIN = 4V
`
`VOUT
`50mV/DIV
`AC COUPLED
`
`LOAD CURRENT 120mA
`20mA
`
`200m s/DIV
`Figure 15. 5V Output SEPIC with 10m F Ceramic Output
`Capacitor, 330pF CPL and 10k in Series with FB Pin
`
`1613 F14
`
`1613 F15
`
`8
`
`

`

`OPERATIOU
`START-UP/SOFT-START
`When the LT1613 SHDN pin voltage goes high, the device
`rapidly increases the switch current until internal current
`limit is reached. Input current stays at this level until the
`output capacitor is charged to final output voltage. Switch
`current can exceed 1A. Figure 16’s oscillograph details
`start-up waveforms of Figure 17’s SEPIC into a 50W
` load
`without any soft-start. The output voltage reaches final
`value in approximately 200m s, while input current reaches
`400mA. Switch current in a SEPIC is 2x the input current,
`so the switch is conducting approximately 800mA peak.
`Soft-start reduces the inrush current by taking more time
`to reach final output voltage. A soft-start circuit consisting
`of Q1, RS1, RS2 and CS1 as shown in Figure 17 can be used
`to limit inrush current to a lower value. Figure 18 pictures
`VOUT and input current with RS2 of 33kW
` and CS of 10nF.
`Input current is limited to a peak value of 200mA as the
`
`LT1613
`
`time required to reach final value increases to 1.7ms. In
`Figure 19, CS is increased to 33nF. Input current does not
`exceed the steady-state current the device uses to supply
`power to the 50W
` load. Start-up time increases to 4.3ms.
`CS can be increased further for an even slower ramp, if
`desired.
`
`VOUT
`2V/DIV
`
`IIN
`200mA/DIV
`
`VS
`5V/DIV
`
`500m s/DIV
`Figure 18. Soft-Start Components in Figure 17’s SEPIC
`Reduces Inrush Current. CSS = 10nF, RLOAD = 50W
`
`1613 F18
`
`VOUT
`2V/DIV
`
`IIN
`200mA/DIV
`
`VSHDN
`5V/DIV
`
`VOUT
`2V/DIV
`
`IIN
`200mA/DIV
`
`200m s/DIV
`Figure 16. Start-Up Waveforms of
`Figure 17’s SEPIC Into 50W
` Load
`
`1613 F16
`
`VS
`5V/DIV
`
`1ms/DIV
`Figure 19. Increasing CS to 33nF Further
`Reduces Inrush Current. RLOAD = 50W
`
`1613 F18
`
`VIN
`4V
`
`+
`
`C1
`22µF
`
`SOFT-START COMPONENTS
`RS1
`33k
`
`VS
`
`Q1
`2N3904
`
`CS
`10nF/
`33nF
`
`RS2
`33k
`
`L1
`22µH
`
`C3
`1µF
`
`VIN
`
`SW
`
`LT1613
`
`SHDN
`
`FB
`
`GND
`
`L2
`22µH
`
`CPL
`330pF
`
`D1
`
`R3
`10k
`
`R2
`12.1k
`
`R1
`37.4k
`
`RLOAD
`
`C2
`10µF
`
`VOUT
`5V
`
`1613 F17
`
`C1: AVX TAJB226M006
`C2: TAIYO YUDEN LMK325BJ106MN
`C3: TAIYO YUDEN LMK212BJ105MG
`Figure 17. 5V SEPIC with Soft-Start Components
`
`D1: MOTOROLA MBR0520
`L1, L2: MURATA LQH3C220
`
`9
`
`

`

`LT1613
`
`TYPICAL APPLICATIO SU
`
`6.5V TO 4V
`
`4-Cell to 5V SEPIC DC/DC Converter
`C3
`1µF
`
`D1
`
`L1
`22µH
`
`+
`
`C1
`15µF
`
`4-CELL
`
`VIN
`
`SW
`
`LT1613
`
`SHDN
`
`SHDN
`
`FB
`
`GND
`
`L2
`22µH
`
`+
`
`374k
`
`121k
`
`L1, L2: MURATA LQH3C220
`C3: AVX 1206YG105 CERAMIC
`D1: MBR0520
`
`VOUT
`5V
`175mA
`
`C2
`22µF
`
`1613 • TA03
`
`Efficiency
`
`VIN = 6.5V
`
`VIN = 3.6V
`
`VIN = 5V
`
`0
`
`10 20 30 40 50 60 70 80 90 100
`LOAD CURRENT (mA)
`
`1613 TA04a
`
`4-Cell to 15V/30mA DC/DC Converter
`
`85
`
`80
`
`75
`
`70
`
`65
`
`60
`
`55
`
`50
`
`EFFICIENCY (%)
`
`VOUT
`15V/30mA
`
`+
`
`C2
`4.7µF
`
`R1
`137k
`1%
`
`R2
`12.1k
`
`1613 TA04
`
`VIN
`3.5V TO
`8V
`
`L1
`10µH
`
`+
`
`C1
`22µF
`
`VIN
`
`SW
`
`LT1613
`
`SHDN
`
`SHDN
`
`FB
`
`GND
`
`D1
`
`1nF
`
`10k
`
`C1: AVX TAJB226M016
`C2: AVX TAJA475M025
`D1: MOTOROLA MBR0520
`L1: MURATA LQH3C100
`
`3.3V to 8V/70mA, –8V/5mA, 24V/5mA TFT LCD Bias Supply Uses All Ceramic Capacitors
`
`D2
`
`0.22µF
`
`1µF
`
`0.22µF
`
`D3
`
`D4
`
`0.22µF: TAIYO YUDEN EMK212BJ224MG
`1µF: TAIYO YUDEN LMK212BJ105MG
`4.7µF: TAIYO YUDEN LMK316BJ475ML
`D1: MOTOROLA MBRO520
`D2, D3, D4: BAT54S
`L1: SUMIDA CDRH5D185R4
`
`0.22µF
`
`D1
`
`L1
`5.4µH
`
`VIN
`3.3V
`
`10
`
`C1
`4.7µF
`
`VIN
`
`SW
`
`LT1613
`
`SHDN
`
`FB
`
`GND
`
`274k
`
`48.7k
`
`VOFF
`–8V
`5mA
`VON
`24V
`5mA
`
`AVDD
`8V
`70mA
`
`1µF
`
`1µF
`
`C2
`4.7µF
`
`1613 TA05
`
`

`

`TYPICAL APPLICATIO SU
`
`LT1613
`
`4-Cell to 5V/50mA, 12V/10mA, 15V/10mA Digital Camera Power Supply
`
`D3
`
`D2
`
`D1
`
`15V/10mA
`
`12V/10mA
`
`5V/50mA
`
`C3
`1µF
`
`C4
`1µF
`
`C5
`4.7µF
`
`2
`
`5
`
`3
`
`4
`
`6T
`
`1
`
`1
`
`C1: TAIYO YUDEN JMK316BJ106ML
`C2, C3, C4: TAIYO YUDEN EMK212BJ105MG
`C5: TAIYO YUDEN JMK212BJ475MG
`D1: MOTOROLA MBR0520
`D2, D3: BAT54
`T1: COILCRAFT CCI8245A (847) 639-6400
`
`VIN 7V TO 3.6V
`
`C1
`10µF
`
`SHUTDOWN
`
`VIN
`
`C2
`1µF
`
`SW
`
`LT1613
`
`SHDN
`
`FB
`
`GND
`
`33.2k
`
`270pF
`
`102k
`
`1613 TA07
`
`4-Cell to 5V/50mA, 15V/10mA, –7.5V/10mA Digital Camera Power Supply
`
`15V/10mA
`
`5V/50mA
`
`–7.5V/10mA
`
`1613 TA08
`
`D2
`
`D1
`
`D3
`
`C3
`1µF
`
`C5
`4.7µF
`
`C4
`1µF
`
`2
`
`5
`
`3
`
`4
`
`6T
`
`1
`
`1
`
`C1: TAIYO YUDEN JMK316BJ106ML
`C2, C3, C4: TAIYO YUDEN EMK212BJ105MG
`C5: TAIYO YUDEN JMK212BJ475MG
`D1: MOTOROLA MBR0520
`D2, D3: BAT54
`T1: COILCRAFT CCI8244A (847) 639-6400
`
`VIN 7V TO 3.6V
`
`C1
`10µF
`
`SHUTDOWN
`
`VIN
`
`C2
`1µF
`
`SW
`
`LT1613
`
`SHDN
`
`FB
`
`GND
`
`33.2k
`
`270pF
`
`102k
`
`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-
`tation that the interconnection of its circuits as described herein will not infringe on existing patent rights.
`
`11
`
`

`

`LT1613
`
`TYPICAL APPLICATIONSU
`
`Li-Ion to 16V/20mA Step-Up DC/DC Converter
`
`L1
`2.2µH
`
`D1
`
`VIN
`2.7V
`TO 4.5V
`
`+
`
`C1
`4.7µF
`
`VIN
`
`SW
`
`LT1613
`
`SHDN
`
`SHDN
`
`FB
`
`GND
`
`C1: AVX TAJA4R7M010
`C2: TAIYO YUDEN LMK212BJ105MG
`D1: BAT54S DUAL DIODE
`L1: MURATA LQH3C2R2
`
`165k
`1%
`
`13.7k
`1%
`
`16V
`20mA
`
`C2
`1µF
`X5R
`CERAMIC
`
`1613 TA06
`
`PACKAGE DESCRIPTIONU Dimensions in inches (millimeters) unless otherwise noted.
`S5 Package
`5-Lead Plastic SOT-23
`(LTC DWG # 05-08-1633)
`
`2.60 – 3.00
`(0.102 – 0.118)
`
`1.50 – 1.75
`(0.059 – 0.069)
`
`0.00 – 0.15
`(0.00 – 0.006)
`
`0.90 – 1.45
`(0.035 – 0.057)
`
`2.80 – 3.00
`(0.110 – 0.118)
`(NOTE 3)
`
`0.35 – 0.55
`(0.014 – 0.022)
`
`0.09 – 0.20
`(0.004 – 0.008)
`(NOTE 2)
`
`0.35 – 0.50
`(0.014 – 0.020)
`FIVE PLACES (NOTE 2)
`
`0.90 – 1.30
`(0.035 – 0.051)
`
`1.90
`(0.074)
`REF
`
`0.95
`(0.037)
`REF
`
` S5 SOT-23 0599
`
`NOTE:
`1. DIMENSIONS ARE IN MILLIMETERS
`2. DIMENSIONS ARE INCLUSIVE OF PLATING
`3. DIMENSIONS ARE EXCLUSIVE OF MOLD FLASH AND METAL BURR
`4. MOLD FLASH SHALL NOT EXCEED 0.254mm
`5. PACKAGE EIAJ REFERENCE IS SC-74A (EIAJ)
`
`RELATED PARTS
`PART NUMBER
`DESCRIPTION
`LT1307
`Single Cell Micropower DC/DC
`LT1317
`2-Cell Micropower DC/DC
`LTC1474
`Low Quiescent Current, High Efficiency Step-Down Converter
`LT1521
`300mA Low Dropout Regulator with Micropower Quiescent
`Current and Shutdown
`Micropower, Regulated Charge Pump
`LTC1517-5
`1.7MHz Single Cell Micropower DC/DC Converter
`LT1610
`Inverting 1.4MHz Switching Regulator
`LT1611
`LT1615/LT1615-1 Micropower DC/DC Converter in 5-Lead SOT-23
`
`12
`
`Linear Technology Corporation
`1630 McCarthy Blvd., Milpitas, CA 95035-7417
`(408) 432-1900 l FAX: (408) 434-0507 l www.linear-tech.com
`
`COMMENTS
`3.3V/75mA From 1V; 600kHz Fixed Frequency
`3.3V/200mA From Two Cells; 600kHz Fixed Frequency
`94% Efficiency, 10m A IQ, 9V to 5V at 250m A
`500mV Dropout, 300mA Output Current, 12m A IQ
`
`3-Cells to 5V at 20mA, SOT-23 Package, 6m A IQ
`30m A IQ, MSOP Package, Internal Compensation
`5V to –5V at 150mA, Low Output Noise
`20V at 12mA from 2.5V Input, Tiny SOT-23 Package
`
`sn1613 1613fs LT/TP 1299 4K • PRINTED IN USA
`
`ª LINEAR TECHNOLOGY CORPORATION 1997
`
`