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| Rev | Author | Line No. | Line |
|---|---|---|---|
| 88 | jelle | 1 | Manufacturer: STMICROELECTRONICS |
| 2 | Order Code: 1202824 |
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| 3 | Manufacturer Part No: LD1117STR-E |
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| 4 | V REG ADJ +1.25/15V, SMD, 1117 |
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| 5 | |||
| 6 | http://uk.farnell.com/1202824/semiconductors-integrated-circuits/product.us0?sku=stmicroelectronics-ld1117str-e |
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| 7 | http://www.st.com/stonline/products/literature/ds/2572/ld1117xx.pdf |
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| 8 | |||
| 9 | VOUT = VREF (1 + R2 / R1) |
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| 10 | |||
| 11 | VREF = 1.25V |
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| 12 | |||
| 13 | # notes |
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| 14 | |||
| 15 | The power dissipated by the device will be equal to: |
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| 16 | IOUT(MAX)(VIN(MAX) – VOUT) + IGND(VIN(MAX)) |
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| 17 | where, |
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| 18 | IOUT(MAX) = 250mA |
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| 19 | VIN(MAX) = 6V |
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| 20 | IGND at (IOUT = 250mA, VIN = 6V) = 5mA |
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| 21 | So, |
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| 22 | P = 250mA(6V – 3.3V) + 5mA(6V) = 0.71W |
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| 23 | |||
| 24 | page 7: Thermal resistance junction-case: 14 C/W |
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| 25 | |||
| 26 | |||
| 27 | === 3.0 V ==== |
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| 28 | |||
| 29 | R1 = 240 |
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| 30 | R2 = 330 |
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| 31 | |||
| 32 | VOUT = VREF (1 + R2 / R1) |
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| 33 | 3.000 = 1.25 * (1 + 280 / 200) |
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| 34 | 2.968 = 1.25 * (1 + 330 / 240) |
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| 35 | 3.125 = 1.25 * (1 + 330 / 220) |
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| 36 | |||
| 37 | ( (VOUT / VREF) -1 ) = (R2 / R1) |
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| 38 | |||
| 39 | I = U / R |
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| 40 | 3 / 200 = 0.015 |
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| 41 | |||
| 42 | P = I * U |
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| 43 | |||
| 44 | 0.015 * 3 = 0.045 W |
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| 45 | 0603 Case Size = 0.063 W |
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| 46 | |||
| 47 | |||
| 48 | === 3.3 V === |
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| 49 | |||
| 50 | R1 = 240 |
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| 51 | R2 = 390 |
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| 52 | |||
| 53 | VOUT = VREF (1 + R2 / R1) |
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| 54 | 3.281 = 1.25 * (1 + 390 / 240) |