LT1931 Linear Technology, LT1931 Datasheet
LT1931
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LT1931 Summary of contents
Page 1
... LT1931A switches at 2.2MHz. These high speeds enable the use of tiny, low cost capacitors and inductors 2mm or less in height. The LT1931 is capable of generating – 350mA or –12V at 150mA from a 5V supply, while the LT1931A can generate –5V at 300mA using significantly smaller induc- tors ...
Page 2
... SHDN Pin Bias Current V SHDN V SHDN Note 1: Absolute Maximum Ratings are those values beyond which the life of a device may be impaired. Note 2: The LT1931E/LT1931AE are guaranteed to meet performance specifications from Specifications over the – PACKAGE/ORDER I FOR ATIO SW 1 GND 2 ...
Page 3
... LT1931A –10 100 SHDN PIN VOLTAGE (V) 1931 G02 Oscillator Frequency 2.5 2.3 LT1931A 2.1 1.9 1.7 1.5 1.3 1.1 0.9 0.7 0.5 –50 – 1.2 TEMPERATURE ( C) 1931 G05 | V | – 255 OUT 255 . – • LT1931 5 6 1931 G03 LT1931 75 100 1931 G06 3 ...
Page 4
... SR latch is reset regardless of the state of comparator A2. This current limit protects the power switch as well as various external components connected to the LT1931. ) and m The Block Diagram for the LT1931A is identical except that the oscillator is 2.2MHz and resistors are one-half the LT1931 values. 1 COMPARATOR – ...
Page 5
... A 4 coupled inductor uncoupled inductor will usually be the best choice for most LT1931 designs. For the LT1931A 4.7 H coupled inductor uncoupled inductor will usually suffice. In certain applications such as the “Charge Pump” inverting DC/DC converter, only a single inductor is used ...
Page 6
... X7R, as these materials retain their capacitance over wide voltage and temperature ranges output capacitor is sufficient for most LT1931 applications while a 4 capacitor will suffice for the LT1931A. 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 ...
Page 7
... C1: TAIYO YUDEN X5R JMK212BJ475MG C2: TAIYO YUDEN X5R LMK212BJ105MG C3: TAIYO YUDEN XR5 JMK325BJ226MM OUT D1: ON SEMICONDUCTOR MBR0520 L1: SUMIDA CLS62-100 and C at SHDN Pin Provide Soft-Start to LT1931 Inverting Converter SS LT1931/LT1931A 500 s/DIV 1931 F06 Reaches – OUT = 15k and C = 33nF. Input current, measured ...
Page 8
... W U DIODE SELECTION A Schottky diode is recommended for use with the LT1931/ LT1931A. The Motorola MBR0520 is a very good choice. Where the input to output voltage differential exceeds 20V, use the MBR0530 (a 30V diode). These diodes are rated to handle an average forward current of 0 applications ...
Page 9
... SHDN R1 220pF LT1931 29.4k C1 4.7 F NFB GND R2 10k L2 4 OUT –5V 300mA C4 180pF C3 4.7 F 1931 TA05a LT1931/LT1931A Efficiency 100 100 125 150 50 LOAD CURRENT (mA) 1931 TA03 OUT –5V 300mA ...
Page 10
... 3 OUT –5V 200mA C4 68pF C3 4 10k 1931 TA06a LT1931 SHDN NFB GND 25. 68nF C6 R4 1000pF 2.7k *TOTAL OUTPUT POWER NOT TO EXCEED 3. C5: X5R OR X7R D1, D2: BAV99 OR EQUIVALENT L1: SUMIDA CR43-220 Efficiency ...
Page 11
... MAX) .00 – .15 .01 – .10 A1 (.00 – .006) (.0004 – .004) .90 – 1.30 .80 – .90 A2 (.035 – .051) (.031 – .035) .35 – .55 .30 – .50 REF L (.014 – .021) (.012 – .019 REF) LT1931/LT1931A 35V COM C5 4 25V V OUT1 –21.6V 48mA* ...
Page 12
... Linear Technology Corporation 12 1630 McCarthy Blvd., Milpitas, CA 95035-7417 (408) 432-1900 FAX: (408) 434-0507 www.linear-tech.com C2 L1A 0 SHDN R1 LT1931A 28.7k C1 2.2 F NFB GND R2 10k C1: TAIYO YUDEN Y5V EMK212F225ZG C2: 0.1 F 25V X5R C3: TAIYO YUDEN X5R JMK212BJ475MG D1: ON SEMICONDUCTOR MBR0520 L1: SUMIDA CLQ4D10-4R7 DRAWING #5382-T039 Efficiency ...