LT1073 Linear Technology Corporation, LT1073 Datasheet
LT1073
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LT1073 Summary of contents
Page 1
... The device requires only three external components to deliver a fixed output 12V. The very low minimum supply voltage of 1V allows the use of the LT1073 in applications where the primary power source is a single cell. An on-chip auxiliary gain block can function as a low- battery detector or linear post-regulator ...
Page 2
... Supply Voltage, Step-Up Mode ................................ 15V Supply Voltage, Step-Down Mode ........................... 36V SW1 Pin Voltage ...................................................... 50V SW2 Pin Voltage ........................................... –0 Feedback Pin Voltage (LT1073) ................................. 5V Switch Current ........................................................ 1.5A Maximum Power Dissipation ............................. 500mW Operating Temperature Range ..................... Storage Temperature Range ................. – 150 C Lead Temperature (Soldering, 10 sec) ...
Page 3
... LIM IN Measured at SW1 Pin Switch Off SW1 Note 4: 100k resistor connected between a 5V source and the AO pin. Note 5: The LT1073 is guaranteed to withstand continuous application of 1.6V applied to the GND and SW2 pins while V grounded. Switch ON Voltage Step-Down Mode (SW1 Pin Connected ...
Page 4
... SET (Pin 7): GB Input amp with positive input connected to SET pin and negative input connected to 212mV reference. FB/SENSE (Pin 8): On the LT1073 (adjustable) this pin goes to the comparator input. On the LT1073-5 and LT1073-12, this pin goes to the internal application resis- tor that sets output voltage 212mV ...
Page 5
... Output ripple, inherently present in gated-oscillator de- signs, will typically run around 150mV for the LT1073-5 and 350mV for the LT1073-12 with the proper inductor/ capacitor selection. This output ripple can be reduced considerably by using the gain block amp as a preamplifier in front of the FB pin ...
Page 6
... Measuring Input Current at Zero or Light Load Obtaining meaningful numbers for quiescent current and efficiency at low output current involves understanding how the LT1073 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 ...
Page 7
... 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 3, 4, and 5 show the output voltage of an LT1073 based converter with three 100 F capacitors. The peak switch current is 500mA in all cases. Figure 3 shows a Sprague 501D aluminum capacitor ...
Page 8
... Most LT1073 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 LT1073 requirements ...
Page 9
... Figure 7. Step-Down Mode Hookup switch is in series with the output. Step-down converters are characterized by low output voltage ripple but high input current ripple. The usual hookup for an LT1073- based step-down converter is shown in Figure 7. When the switch turns on, SW2 pulls puts a voltage across L1 equal to V causing a current to build ...
Page 10
... Figure 11, keeping output ripple to a minimum. Using the Gain Block The gain block (GB) on the LT1073 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 (–) input of the gain LIM block is tied internally to the 212mV reference ...
Page 11
... GND SW2 R1 1073 F13 212mV OUT R1 PART NUMBERS OS-CON Series PL Series 150D Solid Tantalums 550D Tantalex 1. Step-Up Converter † L1 1N5818 120 H 9V OUTPUT 7mA AT V BATTERY 16mA LIM IN 1M* SW1 + 47 F LT1073 FB GND SW2 24.3k* 1073 TA04 = 1V = 1.5V BATTERY 11 ...
Page 12
... GND SW2 1073 TA06 3V to 15V Step-Up Converter † L1 1N5818 68 H 15V OUTPUT 27mA AT V BATTERY 100 1M LIM IN SW1 + 47 F LT1073 FB GND SW2 14.3k* 1073 TA08 5V to 15V Step-Up Converter † L1 1N5818 150 H 15V OUTPUT 100mA AT 4. LIM IN + SW1 100 F ...
Page 13
... LIM IN + SET SW1 100 F LT1073-5 AO SENSE GND SW2 1073 TA12 Step-Down Converter 220 I V LIM IN SW1 LT1073-5 9V SENSE 5V OUTPUT BATTERY † L1 GND SW2 100 H + 100 F 1N5818 L1 = GOWANDA GA10-103k 1073 TA14 OR CADDELL-BURNS 7300-13 Memory Backup Supply 5V TO MEMORY, 5V MAIN 4.5V WHEN MAIN ...
Page 14
... SELECT Q1 AND C1 FOR OPTIMUM RISE AND FALL 1073 TA21 1. Low Noise Step-Up Converter † L1 1N5818 OUTPUT 20mV I V LIM IN 909k* SW1 + FB 100 F LT1073 OS-CON AO SET GND SW2 40.2k* 1073 TA18 OR CADDELL-BURNS 7300-12 † 220 909k* 1N5818 I V SW1 LIM ...
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... Plastic Small Outline (Narrow 0.150) (LTC DWG # 05-08-1610) 0.053 – 0.069 (1.346 – 1.752) 0.004 – 0.010 (0.101 – 0.254) 0.050 0.014 – 0.019 (1.270) (0.355 – 0.483) TYP BSC LT1073 0.400* (10.160) MAX 0.255 0.015* (6.477 0.381 ...
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... 1N976 1M 3M 330 4 1N4148 LIM SW1 NC LT1073 1 10k AO SET 2 NC GND SW2 68pF 1N5818 600V R1 210k 0.01 F 500M 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 – ...