LT1173 LINER [Linear Technology], LT1173 Datasheet
LT1173
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LT1173 Summary of contents
Page 1
... The LT1173 functions equally well in step-up, step- down or inverting applications. The LT1173 consumes just 110 A supply current at standby, making it ideal for applications where low quies- cent current is important. The device can deliver 5V at 80mA from a 3V input in step-up mode 200mA from a 12V input in step-down mode ...
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... SW1 SW2 Pin Voltage (V ) ............................. – 0. SW2 Feedback Pin Voltage (LT1173) ................................. 5V Sense Pin Voltage (LT1173, -5, -12) ....................... 36V Maximum Power Dissipation ............................. 500mW Maximum Switch Current ....................................... 1.5A Operating Temperature Range ..................... Storage Temperature Range .................. – 150 C Lead Temperature, (Soldering, 10 sec.)................ 300 C ...
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... TYPICAL PERFOR A Saturation Voltage Step-Up Mode (SW2 Pin Grounded) 1.2 1 3. 0.6 0.4 0 0.2 0.4 0.6 0.8 1.0 1.2 I (A) SWITCH LT1173 • TPC01 Maximum Switch Current vs R Step-Down Mode LIM 1000 OUT 900 V = 24V 800 500 H 700 600 V = 12V IN 500 L = 250 H 400 300 200 100 0 ...
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... SET (Pin 7): GB input amp with positive input connected to SET pin and negative input connected to 1.245V reference. FB/SENSE (Pin 8): On the LT1173 (adjustable) this pin goes to the comparator input. On the LT1173-5 and LT1173-12, this pin goes to the internal application resis- tor that sets output voltage ...
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... Measuring Input Current at Zero or Light Load Obtaining meaningful numbers for quiescent current and efficiency at low output current involves understanding how the LT1173 operates. At very low or zero load current, the device is idling for seconds at a time. When the output voltage falls enough to trip the comparator, the power switch comes on for a few cycles until the output voltage rises sufficiently to overcome the comparator hysteresis ...
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... These equations assume that inductor current is zero. This situation is called “discon- tinuous mode operation” in switching regulator parlance. Setting “t” to the switch ON time from the LT1173 speci- fication table (typically 23 s) will yield i “L” and V IN ...
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... We recommend OS-CON capacitors from Sanyo Corporation (San Diego, CA). These units are physically quite small and have extremely low ESR. To illustrate, Figures 2, 3, and 4 show the output voltage of an LT1173 based converter with three 100 F capacitors. The peak switch current is 500mA in all cases. Figure 2 shows a Sprague 501D, 25V aluminum capacitor ...
Page 8
... Although they are rated at 1A, the switching time of a 1N4001 is in the 10 s-50 s range. At best, efficiency will be severely compromised when these diodes are used; at worst, the circuit may not work at all. Most LT1173 circuits will be well served by a 1N5818 Schottky diode. The combination of 500mV forward drop at 1A current, fast turn ON and turn OFF time, and leakage current fit nicely with LT1173 requirements ...
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... R2 set the output voltage according to the formula 245 . V . OUT R 1 Step-Down (Buck Mode) Operation A step-down DC-DC converter converts a higher voltage to a lower voltage. The usual hookup for an LT1173 based step-down converter is shown in Figure 100 + V I SW1 LIM ...
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... Figure 8. Negative-to-Positive Converter Using the I Pin LIM The LT1173 switch can be programmed to turn off at a set switch current, a feature not found on competing devices. This enables the input to vary over a wide range without exceeding the maximum switch rating or saturating the inductor. Consider the case where analysis shows the LT1173 must operate at an 800mA peak switch current with a 2 ...
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... S I FOR ATIO Using the Gain Block The gain block (GB) on the LT1173 can be used as an error amplifier, low battery detector or linear post regulator. The gain block itself is a very simple PNP input op amp with an open collector NPN output. The negative input of the gain block is tied internally to the 1 ...
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... RL1284 –22V LCD Bias Generator L1* 1N4148 100 H R1 100 I V LIM IN SW1 LT1173 FB GND SW2 + 4.7 F 1N5818 1N5818 + PART NUMBERS OS-CON Series PL Series 150D Solid Tantalums 550D Tantalex 2.21M 1% 0.1 F 118k 220k –22V OUTPUT 7mA AT 2.0V INPUT 70% EFFICIENCY LT1173 • TA19 ...
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... Step-Down Converter +V IN 100 I V LIM IN SW1 LT1173-5 SENSE GND SW2 L1* 220 H 5V OUTPUT 300mA + 100 F 1N5818 * L1 = GOWANDA GA20-223K LT1173 • TA21 L1* MUR110 500 H + 390k 220 F 10V 2N5400 IRF530 1N4148 V IN SW1 FB SW2 110k LT1173 • TA22 LT1173 LT1173 • TA18 +5V 100mA 13 ...
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... L1 100k I V LIM IN 100k 100 SW1 AO 2.2M LT1173 301k SET FB GND SW2 † 100k SI9405DY +5V OUTPUT 470k 75k + 470 F 240 470 F 24k LT1173 • TA23 1N5820 220 2N4403 +5V OUTPUT † 300mA LOCKOUT AT 1.85V INPUT 5 + 100 F MJE200 OS-CON 47 LT1173 • TA24 ...
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... V IN SW1 0.02 F 100M FB SW2 1.3M L1* + 100 F –V = –5.13 • V OUT C 2W MAXIMUM OUTPUT 39k V (0V TO 5V) C LT1173 • TA25 L1 500mA + 1N5820 470 F 121k 500mA LOAD 150 A Q LT1173 • TA26 95V REGULATED 0.02 F NE-2 0.68 F BLINKS AT 200V 0.5Hz 3.3M LT1173 • TA27 LT1173 15 ...
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LT1 173 PACKAGE DESCRIPTIO 0.300 – 0.325 (7.620 – 8.255) 0.009 – 0.015 (0.229 – 0.381) +0.025 0.325 –0.015 +0.635 8.255 –0.381 *THESE DIMENSIONS DO NOT INCLUDE MOLD FLASH OR PROTRUSIONS. MOLD FLASH OR PROTURSIONS SHALL NOT EXCEED 0.010 INCH ...