View LT1946EMS8_812311.PDF datasheet online --- IC-ON-LINE

Datasheet File OCR Text:

LT1946 1.2MHz Boost DC/DC Converter with 1.5A Switch and Soft-Start
FEATURES
s s s s s s s
DESCRIPTIO
1.5A, 36V Internal Switch 1.2MHz Switching Frequency Integrated Soft-Start Function Output Voltage Up to 34V Low VCESAT Switch: 300mV at 1.5A (Typ) 8V at 430mA from a 3.3V Input Small 8-Lead MSOP Package
APPLICATIO S
s s s s
TFT-LCD Bias Supplies GPS Receivers DSL Modems Local Power Supplies
The LT(R)1946 is a fixed frequency step-up DC/DC converter containing an internal 1.5A, 36V switch. Capable of generating 8V at 430mA from a 3.3V input, the LT1946 is ideal for large TFT-LCD panel power supplies. The LT1946 switches at 1.2MHz, allowing the use of tiny, low profile inductors and low value ceramic capacitors. Loop compensation can be either internal or external, giving the user flexibility in setting loop compensation and allowing optimized transient response with low ESR ceramic output capacitors. Soft-start is controlled with an external capacitor, which determines the input current ramp rate during start-up. The 8-lead MSOP package and high switching frequency ensure a low profile overall solution less than 1.2mm high.
, LTC and LT are registered trademarks of Linear Technology Corporation.
TYPICAL APPLICATIO
VIN 3.3V 3 1 L1 4.7H 6 VIN SHDN LT1946 VC SS CSS 100nF 8 7 FB COMP GND 4 OFF ON C1 2.2F RC 49.9k CC 470pF 5 SW
D1
90
VOUT 8V 430mA
85 80
EFFICIENCY (%)
R1 28.7k 2 R2 5.23k C2 20F
75 70 65 60 55
C1: 2.2F, X5R OR X7R, 6.3V C2: 2 x 10F, X5R OR X7R, 10V D1: MICROSEMI UPS120 OR EQUIVALENT L1: TDK RLF5018T-4R7M1R4
1946 F01
50
0
100
Figure 1. 3.3V to 8V, 430mA Step-Up DC/DC Converter
U
Efficiency
200 400 300 LOAD CURRENT (mA) 500
1946 F01b
U
U
sn1946 1946fs
1
LT1946
ABSOLUTE
(Note 1)
AXI U
RATI GS
PACKAGE/ORDER I FOR ATIO
TOP VIEW VC FB SHDN GND 1 2 3 4 8 7 6 5 SS COMP VIN SW
VIN Voltage ............................................................. 16V SW Voltage ............................................... - 0.4V to 36V FB Voltage ............................................................. 2.5V SHDN Voltage ......................................................... 16V Current Into FB Pin .............................................. 1mA 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 LT1946EMS8 MS8 PART MARKING LTUG
MS8 PACKAGE 8-LEAD PLASTIC MSOP
TJMAX = 125C, JA = 125C/W (4-LAYER BOARD)
Consult LTC Marketing for parts specified with wider operating temperature ranges.
ELECTRICAL CHARACTERISTICS
SYMBOL Minimum Operating Voltage Maximum Operating Voltage Feedback Voltage CONDITIONS
The q denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25C. VIN = 3V, VSHDN = VIN unless otherwise specified. (Note 2)
MIN TYP 2.45 1.230 1.220 1.250 20 40 300 VSHDN = 2.5V, Not Switching VSHDN = 0V, VIN = 3V 2.6V VIN 16V
q
MAX 2.6 16 1.270 1.270 120
UNITS V V V V nA mhos V/V
q
FB Pin Bias Current Error Amp Transconductance Error Amp Voltage Gain Quiescent Current Quiescent Current in Shutdown Reference Line Regulation Switching Frequency Switching Frequency in Foldback Maximum Duty Cycle Switch Current Limit Switch VCESAT Switch Leakage Current Soft-Start Charging Current SHDN Input Voltage High SHDN Input Voltage Low SHDN Pin Bias Current
VFB = 1.250V (Note 3) I = 2A
q
3.2 0 0.01 0.9 0.8 86 1.5 1.2 0.4
q
5 1 0.05 1.4 1.5
VFB = 0V (Note 4) ISW = 1A VSW = 5V VSS = 0.5V 2.5 2.4
q
90 2.1 240 0.01 4 3.1 340 1 6 0.5
VSHDN = 3V VSHDN = 0V
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 LT1946E 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.
Note 3: Current flows out of FB pin. Note 4: Current limit guaranteed by design and/or correlation to static test. Current limit is independent of duty cycle and is guaranteed by design.
sn1946 1946fs
2
U
mA A %/V MHz MHz MHz % A mV A A V V A A
W
U
U
WW
W
LT1946 TYPICAL PERFOR A CE CHARACTERISTICS
Feedback Pin Voltage
1.28 1400 1.27 1200
FEEDBACK VOLTAGE (V)
1.26 1.25 1.24 1.23 1.22 1.21 1.20 - 50 - 25 0 75 50 25 TEMPERATURE (C) 100 125
OSCILLATOR FREQUENCY (kHz)
TA = -30C 800 600 400 200 0 0 0.2
TA = 100C TA = 25C
CURRENT LIMIT (A)
Switch Saturation Voltage
0.35 0.30 0.25
VCESAT (V)
QUIESCENT CURRENT (mA)
3.8 3.6 3.4 3.2 3.0 2.8 2.6 2.4 2.2
0.20 0.15 0.10 0.05 0 0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 SWITCH CURRENT (A)
1946 G04
UW
1946 G01
Oscillator Frequency
Current Limit
2.6 2.4 2.2 2.0 1.8 1.6 1.4 1.2 1.0 0.8 0.6 0.4 0.2 0 -50
1000
0.8 0.6 1.0 0.4 FEEDBACK VOLTAGE (V)
1.2
1946 G02
-25
75 0 50 25 TEMPERATURE (C)
100
125
1946 G03
Quiescent Current
VOUT 20mV/DIV AC COUPLED VSW 5V/DIV 0V ILI 0.5A/DIV AC COUPLED
Switching Waveforms for Figure 1 Circuit
0.5s/DIV
1946 G06
2.0 -50
-25
0 25 50 75 TEMPERATURE (C)
100
125
1946 G05
sn1946 1946fs
3
LT1946
PI FU CTIO S
VC (Pin 1): Error Amplifier Output Pin. Tie external compensation network to this pin, or use the internal compensation network by shorting the VC pin to the COMP pin. FB (Pin 2): Feedback Pin. Reference voltage is 1.250V. Connect resistive divider tap here. Minimize trace area at FB. Set VOUT according to VOUT = 1.250(1 + R1/R2). SHDN (Pin 3): Shutdown Pin. Tie to 2.4V or more to enable device. Ground to shut down. Do not float this pin. GND (Pin 4): Ground. Tie directly to local ground plane. SW (Pin 5): Switch Pin. This is the collector of the internal NPN power switch. Minimize the metal trace area connected to this pin to minimize EMI. VIN (Pin 6): Input Supply Pin. Must be locally bypassed. COMP (Pin 7): Internal Compensation Pin. Provides an internal compensation network. Tie directly to the VC pin for internal compensation. Tie to GND if not used. SS (Pin 8): Soft-Start Pin. Place a soft-start capacitor here. Upon start-up, 4A of current charges the capacitor to 1.5V. Use a larger capacitor for slower start-up. Leave floating if not in use.
BLOCK DIAGRA
VIN 6 1.250V REFERENCE
+
A1
-
RAMP GENERATOR 4
VOUT R1 (EXTERNAL) FB R2 (EXTERNAL) 0.5V
-
+
A3
/3
1.2MHz OSCILLATOR
-
SHUTDOWN 3 SHDN 2 FB
Figure 2. Block Diagram
4
+
-
W
U
U
U
SS 8
VC 1
COMP 7 120k
4A
90pF
SW 5 COMPARATOR DRIVER A2 R S Q Q1
+
0.01
GND
1946 BD
sn1946 1946fs
LT1946
OPERATIO
The LT1946 uses a constant frequency, current mode control scheme to provide excellent line and load regulation. Please refer to Figure 2 for the following description of the part's operation. At the start of the oscillator cycle, the SR latch is set, turning on the power switch Q1. The switch current flows through the internal current sense resistor generating a voltage. This voltage 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 (VC pin) is set by the error amplifier (A1) and is simply an amplified version of the difference between the feedback voltage and the reference voltage of 1.250V. In this manner, the error amplifier sets the correct peak current level to keep the output in regulation. Two functions are provided to enable a very clean start-up for the LT1946. Frequency foldback is used to reduce the oscillator frequency by a factor of 3 when the FB pin is
APPLICATIO S I FOR ATIO
Inductor Selection
Several inductors that work well with the LT1946 are listed in Table 1. This table is not exclusive; there are many other manufacturers and inductors that can be used. Consult each manufacturer for more detailed information and for their entire selection of related parts, as many different sizes and shapes are available. Ferrite core inductors should be used to obtain the best efficiency, as core losses at 1.2MHz are much lower for ferrite cores than for the cheaper powdered-iron ones. Choose an inductor that can handle at least 1.5A without saturating, and ensure that the inductor has a low DCR (copper wire resistance) to minimize I2R power losses. A 4.7H to 10H inductor will be the best choice for most LT1946 designs. Note that in some applications, the current handling requirements of the inductor can be lower, such as in the SEPIC topology where each inductor only carries one-half of the total switch current.
U
W
UU
U
below a nominal value of 0.5V. This is accomplished via comparator A3. This feature reduces the minimum duty cycle that the part can achieve thus allowing better control of the switch current during start-up. When the FB pin voltage exceeds 0.5V, the oscillator returns to the normal frequency of 1.2MHz. A soft-start function is also provided by the LT1946. When the part is brought out of shutdown, 4A of current is sourced out of the SS pin. By connecting an external capacitor to the SS pin, the rate of voltage rise on the pin can be set. Typical values for the soft-start capacitor range from 10nF to 200nF. The SS pin directly limits the rate of rise on the VC pin, which in turn limits the peak switch current. Current limit is not shown in Figure 2. The switch current is constantly monitored and not allowed to exceed the nominal value of 2.1A. If the switch current reaches 2.1A, the SR latch is reset regardless of the output of comparator A2. This current limit helps protect the power switch as well as the external components connected to the LT1946. The inductors shown in Table 1 were chosen for small size. For better efficiency, use similar valued inductors with a larger volume.
Table 1. Recommended Inductors
L (H) 4.1 5.4 5.3 6.2 8.2 4.7 5.6 6.8 4.7 MAX DCR (m) 57 76 38 45 53 50 59 62 45 SIZE LxWxH (mm) 5.7 x 5.7 x 2 5.7 x 5.7 x 3 PART CDRH5D18-4R1 CDRH5D18-5R4 CDRH5D28-5R3 CDRH5D28-6R2 CDRH5D28-8R2 ELL6SH-4R7M ELL6SH-5R6M ELL6SH-6R8M RLF5018T4R7M1R4 VENDOR Sumida (847) 956-0666 www.sumida.com 6.4 x 6 x 3 Panasonic (408) 945-5660 www.panasonic.com TDK (847) 803-6100 www.tdk.com 5.6 x 5.2 x 1.8
sn1946 1946fs
5
LT1946
APPLICATIO S I FOR ATIO
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 the capacitance over wide voltage and temperature ranges. A 4.7F to 20F output capacitor is sufficient for most applications, but systems with very low output currents may need only a 1F or 2.2F output capacitor. 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 LT1946. A 2.2F to 4.7F input capacitor is sufficient for most applications. Table 2 shows a list of several ceramic capacitor manufacturers. Consult the manufacturers for detailed information on their entire selection of ceramic parts.
Table 2. 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
VOUT 20mV/DIV AC COUPLED
Compensation--Adjustment To compensate the feedback loop of the LT1946, a series resistor-capacitor network should be connected from the COMP pin to GND. For most applications, a capacitor in the range of 220pF to 680pF will suffice. A good starting value for the compensation capacitor, CC, is 470pF. The compensation resistor, RC, is usually in the range of 20k to 100k. A good technique to compensate a new application is to use a 100k potentiometer in place of RC, and use a 470pF capacitor for CC. By adjusting the potentiometer while observing the transient response, the optimum value for RC can be found. Figures 3a to 3c illustrate this process for the circuit of Figure 1 with a load current stepped from 250mA to 300mA. Figure 3a shows the transient response with RC equal to 7.5k. The phase margin is
ILI 0.5A/DIV AC COUPLED RC = 49.9k 200s/DIV
1946 F03b
6
U
ILI 0.5A/DIV AC COUPLED RC = 7.5k 200s/DIV
1946 F03a
W
UU
Figure 3a. Transient Response Shows Excessive Ringing
VOUT 20mV/DIV AC COUPLED
ILI 0.5A/DIV AC COUPLED RC = 18k 200s/DIV
1946 F03b
Figure 3b. Transient Response is Better
VOUT 20mV/DIV AC COUPLED
Figure 3c. Transient Response is Well Damped
poor as evidenced by the excessive ringing in the output voltage and inductor current. In Figure 3b, the value of R C is increased to 18k, which results in a more damped response. Figure 3c shows the results when RC is increased further to 49.9k. The transient response is nicely damped and the compensation procedure is complete. The COMP pin provides access to an internal resistor (120k) and capacitor (90pF). For some applications, these values will suffice and no external RC and CC will be needed.
sn1946 1946fs
LT1946
APPLICATIO S I FOR ATIO
Compensation--Theory
+
Like all other current mode switching regulators, the LT1946 needs to be compensated for stable and efficient operation. Two feedback loops are used in the LT1946: a fast current loop which does not require compensation, and a slower voltage loop which does. Standard Bode plot analysis can be used to understand and adjust the voltage feedback loop. As with any feedback loop, identifying the gain and phase contribution of the various elements in the loop is critical. Figure 4 shows the key equivalent elements of a boost converter. Because of the fast current control loop, the power stage of the IC, inductor and diode have been replaced by the equivalent transconductance amplifier gmp. gmp acts as a current source where the output current is proportional to the VC voltage. Note that the maximum output current of gmp is finite due to the current limit in the IC. From Figure 4, the DC gain, poles and zeroes can be calculated as follows: 2 2 * *RL * C OUT 1 Error Amp Pole: P2 = 2 * *RO * C C 1 Error Amp Zero: Z1= 2 * *RC * C C 1.25 DC GAIN: A = * gma * RO * gmp * RL VOUT 1 ESR Zero: Z2 = 2 * * ESR * C OUT Output Pole: P1= RHP Zero: Z3 = VIN2 * RL
2
VC RC CC RO
CC: COMPENSATION CAPACITOR COUT: OUTPUT CAPACITOR gma: TRANSCONDUCTANCE AMPLIFIER INSIDE IC gmp: POWER STAGE TRANSCONDUCTANCE AMPLIFIER RC: COMPENSATION RESISTOR RL: OUTPUT RESISTANCE DEFINED AS VOUT DIVIDED BY ILOAD(MAX) RO: OUTPUT RESISTANCE OF gma R1, R2: FEEDBACK RESISTOR DIVIDER NETWORK
Figure 4. Boost Converter Equivalent Model
The Current Mode zero is a right half plane zero which can be an issue in feedback control design, but is manageable with proper external component selection. Using the circuit of Figure 1 as an example, the following table shows the parameters used to generate the Bode plot shown in Figure 5.
Table 3. Bode Plot Parameters
Parameter RL COUT RO CC RC VOUT VIN gma gmp L fS Value 18.6 20 10 470 49.9 8 3.3 40 5 5.4 1.2 Units F M pF k V V mho mho H MHz Comment Application Specific Application Specific Not Adjustable Adjustable Adjustable Application Specific Application Specific Not Adjustable Not Adjustable Application Specific Not Adjustable
2 * * VOUT * L f High Frequency Pole: P3 > S 3
From Figure 5, the phase is 120 when the gain reaches 0dB giving a phase margin of 60. This is more than adequate. The crossover frequency is 25kHz, which is about three times lower than the frequency of the right half plane zero Z2. It is important that the crossover frequency be at least three times lower than the frequency of the RHP zero to achieve adequate phase margin.
sn1946 1946fs
-
U
gmp COUT RL VOUT
W
UU
+
gma
1.250V REFERENCE R1
-
R2
1946 F04
7
LT1946
APPLICATIO S I FOR ATIO
100
50 GAIN (dB)
0
-50 100
1k
10k 25k 100k FREQUENCY (Hz)
1M
1946 F05a
0
PHASE (DEG)
-100
60 -180 -200 100 1k 10k 25k 100k FREQUENCY (Hz) 1M
1946 F05b
Figure 5. Bode Plot of Figure 1's Circuit
GROUND PLANE
R1 2 R2 SHUTDOWN 3 4 MULTIPLE VIAs GND C2 VOUT LT1946 7 6 5 L1
Figure 6. Recommended Component Placement for Boost Converter. Note Direct High Current Paths Using Wide PC Traces. Minimize Trace Area at Pin 1 (VC) and Pin 2 (FB). Use Multiple Vias to Tie Pin 4 Copper to Ground Plane. Use Vias at One Location Only to Avoid Introducing Switching Currents Into the Ground Plane
sn1946 1946fs
8
U
Diode Selection A Schottky diode is recommended for use with the LT1946. The Microsemi UPS120 is a very good choice. Where the input to output voltage differential exceeds 20V, use the UPS140 (a 40V diode). These diodes are rated to handle an average forward current of 1A. For applications where the average forward current of the diode is less than 0.5A, an ON Semiconductor MBR0520 diode can be used Setting Output Voltage To set the output voltage, select the values of R1 and R2 (see Figure 1) according to the following equation: V R1 = R2 OUT - 1 1.25V A good range for R2 is from 5k to 30k. Layout Hints The high speed operation of the LT1946 demands careful attention to board layout. You will not get advertised performance with careless layout. Figure 6 shows the recommended component placement for a boost converter.
CSS C1 CC RC 1 8
W
UU
+
VIN
1946 F06
LT1946
TYPICAL APPLICATIO S
Low Profile, Triple Output TFT Supply (10V, -10V, 20V)
D2 D3 VON 20V 5mA
VIN 3.3V TO 5V 3 8
OFF ON
+
C1 4.7F CSS 100nF
C1 TO C6: X5R OR X7R C1: 4.7F, 6.3V C2: 2 x 10F, 10V C3: 1F, 25V C4: 2.2F, 10V C5, C6: 0.1F, 10V D1: MICROSEMI UPS120 OR EQUIVALENT D2 TO D5: ZETEX BAT54S OR EQUIVALENT L1: SUMIDA CDRH5D18-5R4
Efficiency
90 85 80
EFFICIENCY (%)
VIN = 3.3V
75 70 65 60 55 50 0 VON LOAD = 5mA VOFF LOAD = 10mA 100 400 300 AVDD LOAD CURRENT (mA) 200 500
1946 TA01a
U
C5 0.1F L1 5.4H 6 VIN SHDN SS LT1946 FB GND 4 R2 10.5k 2 5 SW D1 AVDD 10V 450mA, VIN = 5V 275mA, VIN = 3.3V R1 75k C2 20F C3 1F
7
COMP VC 1 RC 33.3k CC 470pF
C6 0.1F
D4 C4 2.2F D5 VOFF -10V 10mA
1946 TA01
Transient Response
VIN = 5V
AVDD 50mV/DIV AC COUPLED
ILI 0.5A/DIV
AVDD 150mA LOAD 100mA
VIN = 5V
100s/DIV
1946 TA01b
sn1946 1946fs
9
LT1946
TYPICAL APPLICATIO S
12V Output Boost Converter
L1 4.7H 6 VIN SHDN LT1946 VC SS CSS 100nF 8 7 FB COMP GND 4 2 R2 9.76k 5 SW
VIN 3.3V TO 5V 3 1
Efficiency
90 VIN = 5V 85 80 VIN = 3.3V
EFFICIENCY (%)
75 70 65 60 55 50 0 100 200 400 300 LOAD CURRENT (mA) 500
1946 TA02a
10
U
D1
VOUT 12V 410mA, VIN = 5V 275mA, VIN = 3.3V R1 84.5k C2 4.7F
OFF ON C1 4.7F RC 33.3k CC 470pF
C1: 4.7F, X5R OR X7R, 6.3V C2: 4.7F, X5R OR X7R, 16V D1: MICROSEMI UPS120 OR EQUIVALENT L1: TDK RLF5018T-4R7M1R4
1946 TA02
Transient Response
VOUT 100mV/DIV AC COUPLED
ILI 0.5A/DIV
ILOAD 175mA 100mA VIN = 3.3V 100s/DIV
1946 TA02b
sn1946 1946fs
LT1946
PACKAGE DESCRIPTIO U
MS8 Package 8-Lead Plastic MSOP
(Reference LTC DWG # 05-08-1660)
0.889 0.127 (.035 .005) 3.2 - 3.45 (.126 - .136) 0.65 (.0256) BSC 3.00 0.102 (.118 .004) (NOTE 3) 8 7 65 0.52 (.206) REF DETAIL "A" 0 - 6 TYP 4.88 0.1 (.192 .004) 3.00 0.102 (.118 .004) NOTE 4 0.53 0.015 (.021 .006) DETAIL "A" 0.18 (.077) SEATING PLANE 0.22 - 0.38 (.009 - .015) 0.13 0.05 (.005 .002)
MSOP (MS8) 1001
5.23 (.206) MIN
0.42 0.04 (.0165 .0015) TYP
RECOMMENDED SOLDER PAD LAYOUT
0.254 (.010) GAUGE PLANE
1 1.10 (.043) MAX
23
4 0.86 (.034) REF
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
0.65 (.0256) BCS
sn1946 1946fs
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.
11
LT1946
TYPICAL APPLICATIO U
Low Profile, Triple Output TFT Supply (8V, - 8V, 23V)
D2 D3 D4 D5 VON 23V 5mA C5 0.1F C6 0.1F C7 0.1F L1 5.4H 6 OFF ON 3 8 VIN SHDN SS LT1946 FB GND 4 R3 5.23k 2 5 SW R2 28.7k C2 20F C4 1F D1 AVDD 8V 375mA 7 COMP VC 1 RC 49.9k CC 470pF C8 0.1F D7 C3 2.2F D6 VOFF -8V 10mA
1946 TA03
VIN 3.3V
+
C1 4.7F CSS 100nF
C1 TO C8: X5R OR X7R C1: 4.7F, 6.3V C2: 2 x 10F, 10V C3: 2.2F, 10V C4: 1F, 25V C5, C6, C8: 0.1F, 10V C7: 0.1F, 16V D1: MICROSEMI UPS120 OR EQUIVALENT D2 TO D5: ZETEX BAT54S OR EQUIVALENT L1: SUMIDA CDRH5D18-5R4
Efficiency
85 80 75
EFFICIENCY (%) AVDD 2V/DIV
Start-Up Waveforms
70 65 60 55 50 0 100 200 300 AVDD LOAD CURRENT (mA) 400 VON LOAD = 5mA VOFF LOAD = 10mA
VON 10V/DIV VOFF 5V/DIV
IIN 200mA/V 1ms/DIV
1946 TA03a
1946 TA04
RELATED PARTS
PART NUMBER LT1613 LT1615 LT1930/LT1930A LT1944/LT1944-1 LT1945 LT1946A LT1947 DESCRIPTION 1.4MHz Switching Regulator in 5-Lead ThinSOT
TM
COMMENTS 5V at 200mA from 3.3V Input, ThinSOT Package 20V at 12mA from 2.5V, ThinSOT Package 12V at 300mA from 5V Input, ThinSOT Package VIN = 1.2V to 15V, VOUT to 34V, MS10 Package VIN = 1.2V to 15V, VOUT to 34V, MS10 Package VIN = 2.45V to 16V, VOUT to 34V, MS8E Package 8V at 200mA from 3.3V Input, 10-Lead MSOP Package
sn1946 1946fs LT/TP 1002 2K * PRINTED IN USA
Micropower Constant Off-Time DC/DC Converter in 5-Lead ThinSOT 1.2MHz/2.2MHz, 1A Switching Regulator in 5-Lead ThinSOT Dual 350mA Boost Converter Dual 250mA Boost Converter 12.7MHz, 1.5A Boost DC/DC Converter 3MHz, Dual Switching Regulator
Burst Mode and ThinSOT are trademarks 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.com
(c) LINEAR TECHNOLOGY CORPORATION 2001

▲Up To Search▲

Price & Availability of LT1946EMS8

	To Download LT1946EMS8 Datasheet File
If you can't view the Datasheet, Please click here to try to view without PDF Reader .