LT1110 Linear Technology, LT1110 Datasheet
LT1110
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LT1110 Summary of contents
Page 1
... The LT1110 is a versatile micropower DC-DC converter. The device requires only three external components to deliver a fixed output 12V. The very low minimum supply voltage of 1.0V allows the use of the LT1110 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
... U Supply Voltage, Step-Up Mode ................................ 15V Supply Voltage, Step-Down Mode ........................... 36V SW1 Pin Voltage ...................................................... 50V SW2 Pin Voltage ......................................... – 0. Feedback Pin Voltage (LT1110) .............................. 5.5V Switch Current ........................................................ 1.5A Maximum Power Dissipation ............................. 500mW Operating Temperature Range ..................... Storage Temperature Range .................. – 150 C Lead Temperature (Soldering, 10 sec.)................. 300 C ...
Page 3
... Between I and V LIM IN Measured at SW1 Pin Switch Off SW1 Note 3: 100k resistor connected between a 5V source and the AO pin. Note 4: The LT1110 is guaranteed to withstand continuous application of +1.6V applied to the GND and SW2 pins while V grounded. C HARA TERISTICS C CE Oscillator Frequency 80 ...
Page 4
... SWITCH ON TIME ( s) LT1110 • TPC08 Maximum Switch Current vs R Step-Up LIM 1.5 1.3 1.1 STEP-UP MODE 0 0.7 0.5 0.3 0.1 10 100 LIM LT1110 • TPC11 Saturation Voltage Step-Up Mode 1 2.0V 1 1.5V IN 1.0 0 1. 1.0V IN 0.4 0 0.2 0.4 0.6 0.8 1.0 75 100 I (A) SWITCH Quiescent Current 400 380 ...
Page 5
... SET (Pin 7): GB input amp with positive input connected to SET pin and negative input connected to 220mV reference. FB/SENSE (Pin 8): On the LT1110 (adjustable) this pin goes to the comparator input. On the LT1110-5 and LT1110-12, this pin goes to the internal application resistor that sets output voltage. W ...
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... The LT1110-5 and LT1110-12 fixed output voltage ver- sions have the gain setting resistors on-chip. Only three external components are required to construct 12V output converter flows through R1 and R2 in the LT1110-5, and 39 A flows in the LT1110-12. This current I SW1 LIM represents a load and the converter must cycle from time to time to maintain the proper output voltage ...
Page 7
... 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 LT1110 speci- fication table (typically 10 s) will yield I “L” and V at the end of the switch ON time can be calculated as ...
Page 8
... LT1110 PPLICATI S I FOR ATIO Picking an inductor value with 0.2 DCR results in a peak switch current PEAK Substituting I into Equation 05 results in PEAK 862 . Since 17.5 J > 13.7 J, the 47 H inductor will work. This trial-and-error approach can be used to select the opti- mum inductor ...
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... Corporation (San Diego, CA). These units are physically ( ) 15 quite small and have extremely low ESR. To illustrate, Figures 1, 2 and 3 show the output voltage of an LT1110 based converter with three 100 F capacitors. The peak switch current is 500mA in all cases. Figure 1 shows a Sprague 501D, 25V aluminum capacitor. V over 120mV when the switch turns off, followed by a drop in voltage as the inductor dumps into the capacitor ...
Page 10
... V at the internal reference voltage of 220mV and R2 set the output voltage according to the formula V OUT Step-Down (Buck Mode) Operation A step-down DC-DC converter converts a higher voltage to a lower voltage. The usual hookup for an LT1110 based step-down converter is shown in Figure – IN ...
Page 11
... PPLICATI S I FOR ATIO dissipation inside the LT1110. Output voltage is deter- mined 220 mV . OUT programs switch current limit. This is especially im- portant in applications where the input varies over a wide range. Without R3, the switch stays on for a fixed time each cycle ...
Page 12
... Figure 10. Current Limit Keeps Inductor Current Under Control feature, LIM Using the Gain Block The gain block (GB) on the LT1110 can be used as an error amplifier, low battery detector or linear post regulator. The across gain block itself is a very simple PNP input op amp with an LIM open collector NPN output ...
Page 13
... Sumida Electric Co. USA 708-956-0666 W U Output ripple of the LT1110, normally 90mV reduced significantly by placing the gain block in front of the FB input as shown in Figure 13. This effectively reduces the comparator hysteresis by the gain of the gain block. Output ripple can be reduced to just a few millivolts using this technique ...
Page 14
... Powered Laser Diode Driver 220 4.7k + 2N3906 MJE210 LIM SW1 LT1110 1N5818 SET GND SW2 1.5V Powered Laser Diode Driver MBRS12OT3 V PP 12V 120MA + 47 F 20V LT1110 • TA18 TOSHIBA TOLD-9211 0.22 F CERAMIC C1 100 F OS-CON 2 LT1110 • TA13 ...
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... MBRL120 *L1 = COILCRAFT 1812LS-823 LT1110 • TA11 All Surface Mount Step-Down Converter 220 I V LIM IN SW1 LT1110-5 9V SENSE L1* GND SW2 MBRL120 10 F LT1110 • TA10 All Surface Mount L1 LIM IN SW1 4.7 F LT1110 SENSE GND SW2 + 4.7 F LT1110 5V 40mA +5V 4mA –5V 4mA 4 ...
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... LT1110 PACKAGE DESCRIPTIO 0.300 – 0.320 (7.620 – 8.128) 0.065 (1.651) 0.009 – 0.015 TYP (0.229 – 0.381) +0.025 0.045 ± 0.015 0.325 –0.015 (1.143 ± 0.381) +0.635 8.255 –0.381 0.010 – 0.020 45 (0.254 – 0.508) 0.008 – 0.010 0° ...