lt1961 Linear Technology Corporation, lt1961 Datasheet
lt1961
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lt1961 Summary of contents
Page 1
... Synchronization allows an external logic level signal to increase the internal oscillator from 1.5MHz to 2MHz. The LT1961 is available in an exposed pad, 8-pin MSOP package. Full cycle-by-cycle switch current limit protec- tion and thermal shutdown are provided. High frequency operation allows the reduction of input and output filtering components and permits the use of chip inductors ...
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... Switch Voltage ......................................................... 35V SHDN Pin ............................................................... 25V FB Pin Current ....................................................... 1mA SYNC Pin Current .................................................. 1mA Operating Junction Temperature Range (Note 2) LT1961E, LT1961I ........................... – 40°C to 125°C Storage Temperature Range ................ – 65°C to 150°C Lead Temperature (Soldering, 10 sec)................. 300° ORDER I FOR ATIO ...
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... Specifications over the – 40°C to 125°C operating junction temperature range are assured by design, characterization and correlation with statistical process controls. The LT1961I is guaranteed over the – 40ºC to 125ºC operating junction temperature range. The ● ...
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... LT1961 W U TYPICAL PERFORMANCE CHARACTERISTICS FB vs Temperature 1.22 1.21 1.20 1.19 1.18 –50 – 100 TEMPERATURE (°C) 1961 G01 SHDN Threshold vs Temperature 1.40 1.38 1.36 1.34 1.32 1.30 –50 – 100 TEMPERATURE (°C) 1961 G04 SHDN Supply Current 300 T = 25° 15V IN 250 200 150 100 ...
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... C C input of the peak switch current comparator normally used for frequency compensation, but can do double duty as a current clamp or control loop override. This pin sits at about 0.3V for very light loads and 0.9V at maximum load. LT1961 1961fa 5 ...
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... LT1961 W BLOCK DIAGRAM The LT1961 is a constant frequency, current-mode boost converter. This means that there is an internal clock and two feedback loops that control the duty cycle of the power switch. In addition to the normal error amplifier, there is a current sense amplifier that monitors switch current on a cycle-by-cycle basis ...
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... Y5V or similar type ceramics can be used since the absolute value of capacitance is less important and has no significant effect on loop stability. If operation is required close to the minimum input voltage required by either the output or the LT1961, a larger value may be necessary. loop compen- C This is to prevent excessive ripple causing dips below the minimum operating voltage resulting in erratic operation ...
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... INDUCTOR CHOICE AND MAXIMUM OUTPUT CURRENT When choosing an inductor, there are 2 conditions that limit the minimum inductance; required output current, and avoidance of subharmonic oscillation. The maximum output current for the LT1961 in a standard boost con- verter configuration with an infinitely large inductor is: η V • ...
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... SHUTDOWN AND UNDERVOLTAGE LOCKOUT Figure 4 shows how to add undervoltage lockout (UVLO) to the LT1961. Typically, UVLO is used in situations where the input supply is current limited , or has a relatively high source resistance. A switching regulator draws constant power from the source, so source current increases as source voltage drops ...
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... Board layout also has a significant effect on thermal resistance. The exposed pad is the copper plate that runs under the LT1961 die. This is the best thermal path for heat out of the package. Soldering the pad onto the board will reduce die temperature and increase the power capability of the LT1961 ...
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... R3 6.8k INPUT GND C3 LT1961EMS8E U1 GND PLACE FEEDTHROUGHS AROUND GROUND PIN FOR GOOD THERMAL CONDUCTIVITY OUTPUT 12V 0.5A* R1 90. 10μF 10k CERAMIC KEEP FB AND V COMPONENTS AWAY FROM HIGH FREQUENCY, HIGH INPUT COMPONENTS R2 R1 SOLDER EXPOSED GROUND PAD TO BOARD LT1961 C 1961fa 11 ...
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... U APPLICATIONS INFORMATION THERMAL CALCULATIONS Power dissipation in the LT1961 chip comes from four sources: switch DC loss, switch AC loss, drive current, and input quiescent current. The following formulas show how to calculate each of these losses. These formulas assume continuous mode operation, so they should not be used for calculating efficiency at light load currents. − ...
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... UPS140 T1* V OUT 15V 7 + • C4 47μF 4 • 47μF • 1 –V OUT –15V UPS140 LT1961 • TA02 D1 UPS120 † V OUT 5V R2 31.6k 1% • L1B* 47μF 10μH 10V R3 10k 1% LT1961 • TA03 OUT LT1961 1961fa 13 ...
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... LT1961 U TYPICAL APPLICATIO S + SINGLE Li-Ion CELL 14 Single Li-Ion Cell UPS120 4.7μ S/S SW OFF LT1961 + FB C1 10μF GND 2.2nF C3 R3 100pF 10k I V OUT IN 0.75A 2.7V 0.93A 3.3V 1.0A 3.6V V OUT 5V R1 31. 47μF 10V R2 10k 1% LT1961 • TA04 1961fa ...
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... TYP 0.53 ± 0.152 1.10 (.021 ± .006) (.043) DETAIL “A” MAX SEATING PLANE 0.22 – 0.38 (.009 – .015) TYP (.0256) LT1961 BOTTOM VIEW OF 2.06 ± 0.102 (.081 ± .004) 1 1.83 ± 0.102 (.072 ± .004) 8 0.52 (.0205 REF 3.00 ± 0.102 (.118 ± ...
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... Q1 ZETEX ZTX849 1% 0.47μF = WIMA 3X 0.15μF TYPE MKP-20 HV DIODES = SEMTECH-FM-50 LASER = HUGHES 3121H-P COILTRONICS (407) 241-7876 LT1961 • TA05 = 1V to 6V, Low Battery Comparator 2.75V to 18V 35V, MS10E Package IN OUT = 2.7V, S8 Package IN(MIN 34V, Integrated SS, MS8 Package OUT to 5.5V 95% Efficiency, OUT to 5 ...