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LT1931/LT1931A 1.2MHz/2.2MHz Inverting DC/DC Converters in ThinSOT
FEATURES
s s s s s s s s s s
DESCRIPTIO
Fixed Frequency 1.2MHz/2.2MHz Operation Very Low Noise: 1mVP-P Output Ripple - 5V at 350mA from 5V Input -12V at 150mA from 5V Input Uses Small Surface Mount Components Wide Input Range: 2.6V to 16V Low Shutdown Current: <1A Low VCESAT Switch: 400mV at 1A Low Profile (1mm) ThinSOTTM Package Pin-for-Pin Compatible with the LT1611
APPLICATIO S
s s s s s
The LT(R)1931/LT1931A are the industry's highest power inverting SOT-23 current mode DC/DC converters. Both parts include a 1A integrated switch allowing high current outputs to be generated in a small footprint. The LT1931 switches at 1.2MHz while the LT1931A switches at 2.2MHz. These high speeds enable the use of tiny, low cost capacitors and inductors 2mm or less in height. The LT1931 is capable of generating - 5V at 350mA or -12V at 150mA from a 5V supply, while the LT1931A can generate -5V at 300mA using significantly smaller inductors. Both parts are easy pin-for-pin upgrades for higher power LT1611 applications. The LT1931/LT1931A operate in a dual inductor inverting topology that filters both the input side and output side current. Very low output voltage ripple approaching 1mVP-P can be achieved when ceramic output capacitors are used. Fixed frequency switching ensures a clean output free from low frequency noise typically present with charge pump solutions. The low impedance output remains within 1% of nominal during large load steps. The 36V switch allows VIN to VOUT differential of up to 34V. The LT1931/LT1931A are available in the 5-lead ThinSOT package.
, LTC and LT are registered trademarks of Linear Technology Corporation. ThinSOT is a trademark of Linear Technology Corporation.
Disk Drive MR Head Bias Digital Camera CCD Bias LCD Bias GaAs FET Bias Local Low Noise/Low Impedance Negative Supply
TYPICAL APPLICATIO
VIN 5V VIN SHDN C1 4.7F LT1931 NFB GND L1A 10H
C2 1F
L1B 10H
100 95
D1 SW R1 29.4k R2 10k C4 220pF
EFFICIENCY (%)
VOUT -5V 350mA C3 22F
90 85 80 75 70 65 60
C1: TAIYO YUDEN X5R JMK212BJ475MG C2: TAIYO YUDEN X5R LMK212BJ105MG C3: TAIYO YUDEN X5R JMK325BJ226MM D1: ON SEMICONDUCTOR MBR0520 L1: SUMIDA CLS62-100
1931 F01
55 50 0 50 100 150 200 250 LOAD CURRENT (mA) 300 350
Figure 1. 5V to -5V, 350mA Inverting DC/DC Converter
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Efficiency
1931 TA01
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LT1931/LT1931A
ABSOLUTE
(Note 1)
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RATI GS
PACKAGE/ORDER I FOR ATIO
TOP VIEW SW 1 GND 2 NFB 3 4 SHDN 5 VIN
VIN Voltage .............................................................. 16V SW Voltage ................................................- 0.4V to 36V NFB Voltage ............................................................. - 2V Current Into NFB Pin ............................................ 1mA SHDN Voltage .......................................................... 16V Maximum Junction Temperature .......................... 125C Operating Temperature Range (Note 2) .. - 40C to 85C Storage Temperature Range ................. - 65C to 150C Lead Temperature (Soldering, 10 sec).................. 300C
ORDER PART NUMBER LT1931ES5 LT1931AES5 S5 PART MARKING LTRA LTSP
S5 PACKAGE 5-LEAD PLASTIC SOT-23
TJMAX = 125C, JA = 256C/ W
Consult factory for parts specified with wider operating temperature ranges.
ELECTRICAL CHARACTERISTICS
The q denotes specifications which apply over the full operating temperature range, otherwise specifications are TA = 25C. VIN = 3V, VSHDN = VIN, unless otherwise noted. (Note 2)
PARAMETER Minimum Operating Voltage Maximum Operating Voltage Feedback Voltage
q
CONDITIONS
MIN
LT1931 TYP 2.45
MAX 2.6 16
MIN
LT1931A TYP MAX 2.45 2.6 16
UNITS V V V V A mA A %/V MHz MHz % A mV A V V A A
- 1.275 - 1.255 - 1.235 - 1.280 - 1.230 4 4.2 0.01 0.01 1 0.85 84 1 1.2 90 1.2 400 0.01 2.4 0.5 2 600 1 8 6 1 0.05 1.4 1.6
-1.275 -1.255 -1.235 -1.280 -1.230 8 5.8 0.01 0.01 1.8 1.6 75 1 2.2 82 1.2 400 0.01 2.4 0.5 35 0 70 0.1 2.5 600 1 16 8 1 0.05 2.6 2.9
NFB Pin Bias Current Quiescent Current Quiescent Current in Shutdown Reference Line Regulation Switching Frequency
VNFB = -1.255V VSHDN = 2.4V, Not Switching VSHDN = 0V, VIN = 3V 2.6V VIN 16V
q
q
Maximum Duty Cycle Switch Current Limit Switch VCESAT Switch Leakage Current SHDN Input Voltage, High SHDN Input Voltage, Low SHDN Pin Bias Current VSHDN = 3V VSHDN = 0V (Note 3) ISW = 1A VSW = 5V
q
16 0
32 0.1
Note 1: Absolute Maximum Ratings are those values beyond which the life of a device may be impaired. Note 2: The LT1931E/LT1931AE are 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. Note 3: Current limit guaranteed by design and/or correlation to static test.
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LT1931/LT1931A TYPICAL PERFOR A CE CHARACTERISTICS
Quiescent Current
7.0 6.5
QUIESCENT CURRENT (mA)
NOT SWITCHING
-1.27
6.0 5.5 5.0 4.5 4.0 3.5 3.0 -50 -25
LT1931A
SHDN PIN CURRENT (A)
FEEDBACK VOLTAGE (V)
LT1931
50 25 TEMPERATURE (C)
0
Current Limit
1.6 1.4
CURRENT LIMIT (A)
1.2 VCESAT (V) 1.0 0.8 0.6 0.4 0.2 0 10 20 30 40 50 60 70 DUTY CYCLE (%) 80 90
0.30 0.25 0.20 0.15 0.10 0.05 0 0 0.2 0.4 0.6 0.8 SWITCH CURRENT (A) 1.0 1.2
FREQUENCY (MHz)
PI FU CTIO S
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. NFB (Pin 3): Feedback Pin. Reference voltage is -1.255V. Connect resistive divider tap here. Minimize trace area. The NFB bias current flows out of the pin. Set R1 and R2 according to: For LT1931: R1 = | VOUT | - 1.255 1.255 + 4 * 10 - 6 R2 For LT1931A: R1 = | VOUT | - 1.255 1.255 + 8 * 10 - 6 R2
UW
75
1931 G01
Feedback Pin Voltage
-1.28 90 80 70 60 50 40 30 20 10 0
Shutdown Pin Current
TA = 25C LT1931A
-1.26 -1.25 -1.24 -1.23 -1.22 -50
LT1931
100
-25
0 25 50 TEMPERATURE (C)
75
100
1931 G02
-10 0 1 3 4 2 SHDN PIN VOLTAGE (V) 5 6
1931 G03
Switch Saturation Voltage
0.45 TA = 25C 0.40 0.35 TA = 25C
Oscillator Frequency
2.5 2.3 2.1 1.9 1.7 1.5 1.3 1.1 0.9 0.7 0.5 -50 -25 25 50 0 TEMPERATURE (C) 75 100
1931 G06
LT1931A
LT1931
1931 G04
1931 G05
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(
)
SHDN (Pin 4): Shutdown Pin. Tie to 2.4V or more to enable device. Ground to shut down. VIN (Pin 5): Input Supply Pin. Must be locally bypassed.
(
)
3
LT1931/LT1931A
BLOCK DIAGRA
VIN 5
-
Q1 VOUT R1 (EXTERNAL) NFB R2 (EXTERNAL) Q2 x10 R3 30k R4 150k 3 NFB
CC
CPL (OPTIONAL)
1.2MHz OSCILLATOR SHDN 4 SHUTDOWN
Figure 2
OPERATIO
The LT1931 uses a constant frequency, current mode control scheme to provide excellent line and load regulation. Operation can be best understood by referring to the Block Diagram in Figure 2. At the start of each oscillator cycle, the SR latch is set, turning on the power switch Q3. A voltage proportional to the switch current is added to a stabilizing ramp and the resulting sum is fed into the positive terminal of the PWM comparator A2. When this voltage exceeds the level at the negative input of A2, the SR latch is reset, turning off the power switch. The level at the negative input of A2 is set by the error amplifier (gm) and is simply an amplified version of the difference between the feedback voltage and the reference voltage of -1.255V. In this manner, the error amplifier sets the correct peak
current level to keep the output in regulation. If the error amplifier's output increases, more current is taken from the output; if it decreases, less current is taken. One function not shown in Figure 2 is the current limit. The switch current is constantly monitored and not allowed to exceed the nominal value of 1.2A. If the switch current reaches 1.2A, the SR latch is reset regardless of the state of comparator A2. This current limit protects the power switch as well as various external components connected to the LT1931. The Block Diagram for the LT1931A is identical except that the oscillator is 2.2MHz and resistors R3 to R6 are one-half the LT1931 values.
4
+
RC
RAMP GENERATOR
-
W
VIN R5 80k R6 80k 1 SW COMPARATOR A1 gm LATCH S DRIVER Q Q3
+
A2
R
+
0.01
-
2 GND
1931 BD
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LT1931/LT1931A
APPLICATIO S I FOR ATIO
LT1931A AND LT1931 DIFFERENCES: Switching Frequency
The key difference between the LT1931A and LT1931 is the faster switching frequency of the LT1931A. At 2.2MHz, the LT1931A switches at nearly twice the rate of the LT1931. Care must be taken in deciding which part to use. The high switching frequency of the LT1931A allows smaller cheaper inductors and capacitors to be used in a given application, but with a slight decrease in efficiency and maximum output current when compared to the LT1931. Generally, if efficiency and maximum output current are critical, the LT1931 should be used. If application size and cost are more important, the LT1931A will be the better choice. In many applications, tiny inexpensive chip inductors can be used with the LT1931A, reducing solution cost. Duty Cycle The maximum duty cycle (DC) of the LT1931A is 75% compared to 84% for the LT1931. The duty cycle for a given application using the dual inductor inverting topology is given by: | VOUT | DC = | VIN | + | VOUT | For a 5V to -5V application, the DC is 50% indicating that the LT1931A can be used. A 5V to -16V application has a DC of 76.2% making the LT1931 the right choice. The LT1931A can still be used in applications where the DC, as calculated above, is above 75%. However, the part must be operated in the discontinuous conduction mode so that the actual duty cycle is reduced. INDUCTOR SELECTION Several inductors that work well with the LT1931 are listed in Table 1 and those for the LT1931A are listed in Table 2. Besides these, there are many other inductors that can be used. Consult each manufacturer for detailed information and for their entire selection of related parts. Ferrite core inductors should be used to obtain the best efficiency, as
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core losses at frequencies above 1MHz are much lower for ferrite cores than for powdered-iron units. When using coupled inductors, choose one that can handle at least 1A of current without saturating, and ensure that the inductor has a low DCR (copper-wire resistance) to minimize I2R power losses. If using uncoupled inductors, each inductor need only handle one-half of the total switch current so that 0.5A per inductor is sufficient. A 4.7H to 15H coupled inductor or a 15H to 22H uncoupled inductor will usually be the best choice for most LT1931 designs. For the LT1931A, a 2.2H to 4.7H coupled inductor or a 3.3H to 10H uncoupled inductor will usually suffice. In certain applications such as the "Charge Pump" inverting DC/DC converter, only a single inductor is used. In this case, the inductor must carry the entire 1A switch current.
Table 1. Recommended Inductors--LT1931
PART CLS62-100 CR43-150 CR43-220 CTX10-1 CTX15-1 LQH3C100K24 LQH4C150K04 L (H) 10 15 22 10 15 10 15 Size (L x W x H) mm 6.8 x 6.6 x 2.5 4.5 x 4.0 x 3.2 8.9 x 11.4 x 4.2 VENDOR Sumida (847) 956-0666 www.sumida.com Coiltronics (407) 241-7876 www. coiltronics.com Murata (404) 436-1300 www.murata.com 3.2 x 2.5 x 2.0
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Table 2. Recommended Inductors--LT1931A
PART ELJPC3R3MF ELJPC4R7MF CLQ4D10-4R71 CLQ4D10-6R82 LB20164R7M LB20163R3M LQH3C4R7K24 LQH4C100K24 L (H) 3.3 4.7 4.7 6.8 4.7 3.3 4.7 10 Size (L x W x H) mm 2.5 x 2.0 x 1.6 VENDOR Panasonic (408) 945-5660 www.panasonic.com Sumida (847) 956-0666 www.sumida.com Taiyo Yuden (408) 573-4150 www.t-yuden.com Murata (404) 436-1300 www.murata.com
7.6 x 4.8 x 1.8
2.0 x 1.6 x 1.6
3.2 x 2.5 x 2.0
1Use drawing #5382-T039 2Use drawing #5382-T041
5
LT1931/LT1931A
APPLICATIO S I FOR ATIO
The inductors shown in Table 2 for use with the LT1931A were chosen for their small size. For better efficiency, use similar valued inductors with a larger volume. For instance, the Sumida CR43 series, in values ranging from 3.3H to 10H, will give a LT1931A application a few percentage points increase in efficiency. CAPACITOR SELECTION Low ESR (equivalent series resistance) capacitors should be used at the output to minimize the output ripple voltage. Multilayer ceramic capacitors are an excellent choice, as they have an extremely low ESR and are available in very small packages. X5R dielectrics are preferred, followed by X7R, as these materials retain their capacitance over wide voltage and temperature ranges. A 10F to 22F output capacitor is sufficient for most LT1931 applications while a 4.7F to 10F capacitor will suffice for the LT1931A. Solid tantalum or OS-CON capacitors can be used, but they will occupy more board area than a ceramic and will have a higher ESR. Always use a capacitor with a sufficient voltage rating. Ceramic capacitors also make a good choice for the input decoupling capacitor, which should be placed as close as possible to the LT1931/LT1931A. A 1F to 4.7F input capacitor is sufficient for most applications. Table 3 shows a list of several ceramic capacitor manufacturers. Consult the manufacturers for detailed information on their entire selection of ceramic parts.
Table 3. Ceramic Capacitor Manufacturers
Taiyo Yuden AVX Murata (408) 573-4150 www.t-yuden.com (803) 448-9411 www.avxcorp.com (714) 852-2001 www.murata.com
The decision to use either low ESR (ceramic) capacitors or the higher ESR (tantalum or OS-CON) capacitors can effect the stability of the overall system. The ESR of any capacitor, along with the capacitance itself, contributes a
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zero to the system. For the tantalum and OS-CON capacitors, this zero is located at a lower frequency due to the higher value of the ESR, while the zero of a ceramic capacitor is at a much higher frequency and can generally be ignored. A phase lead zero can be intentionally introduced by placing a capacitor (C4) in parallel with the resistor (R1) between VOUT and VNFB as shown in Figure 1. The frequency of the zero is determined by the following equation. Z = 1 2 * R1 * C4 By choosing the appropriate values for the resistor and capacitor, the zero frequency can be designed to improve the phase margin of the overall converter. The typical target value for the zero frequency is between 20kHz to 60kHz. Figure 3 shows the transient response of the inverting converter from Figure 1 without the phase lead capacitor C4. The phase margin is reduced as evidenced by more ringing in both the output voltage and inductor current. A 220pF capacitor for C4 results in better phase margin, which is revealed in Figure 4 as a more damped response and less overshoot. Figure 5 shows the transient response when a 22F tantalum capacitor with no phase lead capacitor is used on the output. The higher output voltage ripple is revealed in the upper waveform as a thicker line. The transient response is adequate which implies that the ESR zero is improving the phase margin.
VOUT 20mV/DIV AC COUPLED IL1A + IL1B 0.5A/DIV AC COUPLED LOAD 200mA CURRENT 100mA 100s/DIV
1931 F03
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Figure 3. Transient Response of Inverting Converter Without Phase Lead Capacitor
LT1931/LT1931A
APPLICATIO S I FOR ATIO
VOUT 20mV/DIV AC COUPLED IL1A + IL1B 0.5A/DIV AC COUPLED LOAD 200mA CURRENT 100mA 100s/DIV
1931 F04
Figure 4. Transient Response of Inverting Converter with 220pF Phase Lead Capacitor
VOUT 0.1V/DIV AC COUPLED
IL1A + IL1B 0.5A/DIV AC COUPLED LOAD 200mA CURRENT 100mA 50s/DIV
1931 F05
Figure 5. Transient Response of Inverting Converter with 22F Tantalum Output Capacitor and No Phase Lead Capacitor
START-UP/SOFT-START For most LT1931/LT1931A applications, the start-up inrush current can be high. This is an inherent feature of switching regulators in general since the feedback loop is saturated due to VOUT being far from its final value. The
CURRENT PROBE VIN 5V L1A 10H
+
RSS 15k VSS D2 1N4148 CSS 33nF/68nF VOUT
C1 4.7F
C1: TAIYO YUDEN X5R JMK212BJ475MG C2: TAIYO YUDEN X5R LMK212BJ105MG C3: TAIYO YUDEN XR5 JMK325BJ226MM D1: ON SEMICONDUCTOR MBR0520 L1: SUMIDA CLS62-100
Figure 7. RSS and CSS at SHDN Pin Provide Soft-Start to LT1931 Inverting Converter
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VOUT 2V/DIV IIN 0.5A/DIV AC COUPLED VSHDN 5V 0V 500s/DIV
1931 F06
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Figure 6. Start-Up Waveforms for 5V to - 5V Application (Figure 1). No Soft-Start Circuit. VOUT Reaches - 5V in 500s; Input Current Peaks at 800mA
regulator tries to charge up the output capacitor as quickly as possible, which results in a large inrush current. Figure 6 shows a typical oscillograph of the start-up waveform for the application of Figure 1 starting into a load of 33. The lower waveform shows SHDN being pulsed from 0V to 5V. The middle waveform shows the input current, which reaches as high as 0.8A. The total time required for the output to reach its final value is approximately 500s. For some applications, this initial inrush current may not be acceptable. If a longer start-up time is acceptable, a soft-start circuit consisting of RSS and CSS, as shown in Figure 7, can be used to limit inrush current to a lower value. Figure 8 shows the relevant waveforms with RSS = 15k and CSS = 33nF. Input current, measured at VIN, is limited to a peak value of 0.5A as the time required to reach final value increases to 1ms. In Figure 9, CSS is
C2 1F L1B 10H
D1 VIN LT1931 SHDN GND NFB R2 10k SW R1 29.4k C4 220pF VOUT -5V C3 22F
1931 F07
7
LT1931/LT1931A
APPLICATIO S I FOR ATIO
VOUT 2V/DIV
IIN 0.5A/DIV AC COUPLED VSS 5V 0V 200s/DIV
1931 F08
Figure 8. RSS = 15k, CSS = 33nF; VOUT Reaches - 5V in 1ms; Input Current Peaks at 500mA
VOUT 2V/DIV
IIN 0.5A/DIV AC COUPLED VSS 5V 0V 500s/DIV
1931 F09
Figure 9. RSS = 15k, CSS = 68nF; VOUT Reaches - 5V in 1.6ms; Input Current Peaks at 350mA
GND
Figure 10. Suggested Component Placement. Note Cut in Ground Copper at D1's Cathode
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increased to 68nF, resulting in a lower peak input current of 350mA with a VOUT ramp time of 1.6ms. CSS or RSS can be increased further for an even slower ramp, if desired. Diode D2 serves to quickly discharge CSS when VSS is driven low to shut down the device. D2 can be omitted, resulting in a "soft-stop" slow discharge of the output capacitor.
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DIODE SELECTION A Schottky diode is recommended for use with the LT1931/ LT1931A. The Motorola MBR0520 is a very good choice. Where the input to output voltage differential exceeds 20V, use the MBR0530 (a 30V diode). These diodes are rated to handle an average forward current of 0.5 A. In applications where the average forward current of the diode exceeds 0.5A, a Microsemi UPS5817 rated at 1A is recommended. LAYOUT HINTS The high-speed operation of the LT1931/LT1931A demands careful attention to board layout. You will not get advertised performance with careless layout. Figure 10 shows the recommended component placement. The ground cut at the cathode of D1 is essential for low noise operation.
L1B -VOUT D1 C3 1 2 3 R2 4 SHUTDOWN 5 C2 VIN L1A C1
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1931 F10
LT1931/LT1931A
TYPICAL APPLICATIO S
5V to -12V Inverting Converter
L1A 10H C2 1F L1B 10H
100 95 90
VIN 5V VIN SHDN C1 4.7F
EFFICIENCY (%)
SW LT1931 NFB GND R2 10k R1 84.5k
C1: TAIYO YUDEN X5R JMK212BJ475MG C2: TAIYO YUDEN X5R TMK316BJ105ML C3: TAIYO YUDEN X5R EMK325BJ106MM D1: ON SEMICONDUCTOR MBR0520 L1: SUMIDA CLS62-100
VIN 5V VIN SHDN C1 4.7F
C1: TAIYO YUDEN X5R JMK212BJ475MG C2: TAIYO YUDEN X5R LMK212BJ105MG C3: TAIYO YUDEN X5R JMK212BJ226MM D1: ON SEMICONDUCTOR MBR0520 L1, L2: MURATA LQH3C100K04
2.2MHz, 5V to - 5V Inverting Converter
L1 4.7H C2 1F L2 4.7H
80 75
VIN 5V VIN
SHDN C1 4.7F LT1931A NFB GND
R1 28.7k R2 10k
C4 180pF
EFFICIENCY (%)
SW
C1: TAIYO YUDEN X5R JMK212BJ475MG C2: TAIYO YUDEN X5R LMK212BJ105MG C3: TAIYO YUDEN X5R JMK212BJ475MG D1: ON SEMICONDUCTOR MBR0520 L1, L2: MURATA LQH3C4R7M24
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Efficiency
D1
VOUT -12V 150mA C3 10F
85 80 75 70 65 60 55
1931 TA02
50 0 25 75 100 50 LOAD CURRENT (mA) 125 150
1931 TA03
5V to - 5V Inverting Converter Using Uncoupled Inductors
L1 10H C2 1F L2 10H
D1 SW LT1931 NFB GND R2 10k R1 29.4k 220pF
VOUT -5V 300mA C3 22F
1931 TA04
Efficiency
D1
VOUT -5V 300mA C3 4.7F
70 65 60 55
1931 TA05a
50 0 50 100 150 200 250 LOAD CURRENT (mA) 300 350
1931 TA05b
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LT1931/LT1931A
TYPICAL APPLICATIO S
2.2MHz, 5V to -5V Converter Uses Tiny Chip Inductors
L1 3.3H C2 1F L2 3.3H
80 75
VIN 5V VIN
SHDN C1 2.2F LT1931A NFB GND
R1 28.7k R2 10k
C4 68pF
EFFICIENCY (%)
SW
C1: TAIYO YUDEN X5R JMK212BJ225MG C2: TAIYO YUDEN X5R LMK212BJ105MG C3: TAIYO YUDEN X5R JMK212BJ475MG D1: ON SEMICONDUCTOR MBR0520 L1, L2: PANASONIC ELJPC3R3MF
SLIC Power Supply with - 33V and - 68V Outputs, Uses Soft-Start
L1 22H C1 4.7F 16V RSS 15k VSS
VIN 12V
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Efficiency
D1
VOUT -5V 200mA C3 4.7F
70 65 60 55
1931 TA06a
50 0 50 100 150 200 LOAD CURRENT (mA) 250
1931 TA06b
R1 1 C2 1F 35V D1 3 NFB 2 C4 4.7F 35V
VIN LT1931 SHDN GND CSS 68nF
SW
COM
1 R2 1k R3 25.5k C6 1000pF R4 2.7k C3 1F 35V 3
VOUT1 -33V 100mA*
D2 2 1 C5 4.7F 35V
1931 TA08
*TOTAL OUTPUT POWER NOT TO EXCEED 3.3W C1 TO C5: X5R OR X7R D1, D2: BAV99 OR EQUIVALENT L1: SUMIDA CR43-220
VOUT2 -66V 48mA*
LT1931/LT1931A
TYPICAL APPLICATIO S
SLIC Power Supply with - 21.6V and - 65V Outputs, Uses Soft-Start
L1 10H C1 4.7F 16V R1 1 C2 1F 35V D1 RSS 15k VSS LT1931 SHDN GND R2 1k CSS 68nF R3 16.2k C8 1000pF R4 2.7k C3 1F 35V 3 *TOTAL OUTPUT POWER NOT TO EXCEED 1.3W C1 TO C7: X5R OR X7R D1, D2: BAV99 OR EQUIVALENT L1: SUMIDA CR43-100 NFB 1 3 2 C5 4.7F 25V COM
VIN 5V
PACKAGE DESCRIPTIO
.20 (.008) DATUM `A' A A2 2.60 - 3.00 (.102 - .118) 1.90 (.074) REF SOT-23 (Original) .90 - 1.45 (.035 - .057) .00 - .15 (.00 - .006) .90 - 1.30 (.035 - .051) .35 - .55 (.014 - .021) SOT-23 (ThinSOT) 1.00 MAX (.039 MAX) .01 - .10 (.0004 - .004) .80 - .90 (.031 - .035) .30 - .50 REF (.012 - .019 REF) 1.50 - 1.75 (.059 - .069) (NOTE 3)
L NOTE: 1. CONTROLLING DIMENSION: MILLIMETERS MILLIMETERS 2. DIMENSIONS ARE IN (INCHES)
.09 - .20 (.004 - .008) (NOTE 2)
3. DRAWING NOT TO SCALE 4. DIMENSIONS ARE INCLUSIVE OF PLATING 5. DIMENSIONS ARE EXCLUSIVE OF MOLD FLASH AND METAL BURR 6. MOLD FLASH SHALL NOT EXCEED .254mm 7. PACKAGE EIAJ REFERENCE IS: SC-74A (EIAJ) FOR ORIGINAL JEDEL MO-193 FOR THIN
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.
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VIN
SW
VOUT1 -21.6V 48mA*
D2 2 1 D3 C6 4.7F 25V
C4 1F 35V 3
2 1
C7 4.7F 25V
1931 TA09
VOUT2 - 65V 20mA*
S5 Package 5-Lead Plastic SOT-23
(LTC DWG # 05-08-1633) (LTC DWG # 05-08-1635)
2.80 - 3.10 (.110 - .118) (NOTE 3)
A1
PIN ONE .95 (.037) REF
A A1 A2 L
.25 - .50 (.010 - .020) (5PLCS, NOTE 2)
S5 SOT-23 0501
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LT1931/LT1931A
TYPICAL APPLICATIO
2.2MHz, 12V to - 5V Converter Uses Low Profile Coupled Inductor
L1A 4.7H C2 0.1F L1B 4.7H
VIN 12V VIN
EFFICIENCY (%)
RELATED PARTS
PART NUMBER LT1307 LT1316 LT1317 LT1610 LT1611 LT1613 LT1615 LT1617 LT1930/LT1930A DESCRIPTION Single Cell Micropower 600kHz PWM DC/DC Converter Burst ModeTM Operation DC/DC with Programmable Current Limit 2-Cell Micropower DC/DC with Low-Battery Detector Single Cell Micropower DC/DC Converter Inverting 1.4MHz Switching Regulator in 5-Lead ThinSOT 1.4MHz Switching Regulator in 5-Lead ThinSOT Micropower Constant Off-Time DC/DC Converter in 5-Lead ThinSOT Micropower Inverting DC/DC Converter in 5-Lead ThinSOT 1.2MHz/2.2MHz, 1A Switching Regulators in 5-Lead ThinSOT COMMENTS 3.3V at 75mA from One Cell, MSOP Package 1.5V Minimum, Precise Control of Peak Current Limit 3.3V at 200mA from Two Cells, 600kHz Fixed Frequency 3V at 30mA from 1V, 1.7MHz Fixed Frequency -5V at 150mA from 5V Input. Tiny SOT-23 Package 5V at 200mA from 3.3V Input. Tiny SOT-23 Package 20V at 12mA from 2.5V. Tiny SOT-23 Package -15V at 12mA from 2.5V. Tiny SOT-23 Package 5V at 450mA from 3.3V Input. Tiny SOT-23 Package
Burst Mode operation is a trademark of Linear Technology Corporation.
12
Linear Technology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
(408)432-1900 q FAX: (408) 434-0507 q www.linear-tech.com
U
D1 SW LT1931A NFB GND R2 10k R1 28.7k SHDN C1 2.2F VOUT -5V 450mA C3 4.7F C1: TAIYO YUDEN Y5V EMK212F225ZG C2: 0.1F 25V X5R C3: TAIYO YUDEN X5R JMK212BJ475MG D1: ON SEMICONDUCTOR MBR0520 L1: SUMIDA CLQ4D10-4R7 DRAWING #5382-T039
1931 TA07a
Efficiency
80 75 70 65 60 55 50 0 100 200 300 400 LOAD CURRENT (mA) 500
1931 TA07b
1931f LT/TP 0601 2K * PRINTED IN USA
(c) LINEAR TECHNOLOGY CORPORATION 2000

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