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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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| 257 | jelle | 4 | Description: V REG ADJ +1.25/15V, SMD, 1117 |
| 5 | Supplier: http://uk.farnell.com/1202824/semiconductors-integrated-circuits/product.us0?sku=stmicroelectronics-ld1117str-e |
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| 6 | Datasheet: http://www.st.com/stonline/products/literature/ds/2572/ld1117xx.pdf |
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| 7 | Catalogue Page: 436 / EBU |
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| 88 | jelle | 8 | |
| 257 | jelle | 9 | ------------------------------------------------------------------------ |
| 88 | jelle | 10 | |
| 11 | VOUT = VREF (1 + R2 / R1) |
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| 12 | |||
| 13 | VREF = 1.25V |
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| 14 | |||
| 15 | # notes |
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| 16 | |||
| 17 | The power dissipated by the device will be equal to: |
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| 18 | IOUT(MAX)(VIN(MAX) – VOUT) + IGND(VIN(MAX)) |
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| 19 | where, |
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| 20 | IOUT(MAX) = 250mA |
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| 21 | VIN(MAX) = 6V |
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| 22 | IGND at (IOUT = 250mA, VIN = 6V) = 5mA |
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| 23 | So, |
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| 24 | P = 250mA(6V – 3.3V) + 5mA(6V) = 0.71W |
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| 25 | |||
| 26 | page 7: Thermal resistance junction-case: 14 C/W |
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| 27 | |||
| 28 | |||
| 29 | === 3.0 V ==== |
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| 30 | |||
| 106 | jelle | 31 | R1 = 220 |
| 88 | jelle | 32 | R2 = 330 |
| 33 | |||
| 34 | VOUT = VREF (1 + R2 / R1) |
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| 35 | 3.000 = 1.25 * (1 + 280 / 200) |
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| 97 | jelle | 36 | 2.969 = 1.25 * (1 + 330 / 240) |
| 88 | jelle | 37 | 3.125 = 1.25 * (1 + 330 / 220) |
| 38 | |||
| 39 | ( (VOUT / VREF) -1 ) = (R2 / R1) |
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| 40 | |||
| 41 | I = U / R |
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| 42 | 3 / 200 = 0.015 |
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| 43 | |||
| 44 | P = I * U |
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| 45 | |||
| 46 | 0.015 * 3 = 0.045 W |
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| 47 | 0603 Case Size = 0.063 W |
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| 48 | |||
| 49 | |||
| 50 | === 3.3 V === |
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| 51 | |||
| 52 | R1 = 240 |
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| 53 | R2 = 390 |
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| 54 | |||
| 55 | VOUT = VREF (1 + R2 / R1) |
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| 56 | 3.281 = 1.25 * (1 + 390 / 240) |
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| 97 | jelle | 57 | |
| 100 | jelle | 58 | == +3.0V Limits == |
| 97 | jelle | 59 | |
| 60 | VOUT = VREF (1 + R2 / R1) |
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| 61 | R1 = 240 |
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| 62 | R2 = 330 |
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| 63 | R1 = 99% = 237.6 |
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| 64 | R1 = 101% = 242.4 |
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| 65 | R2 = 99% = 326.7 |
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| 66 | R2 = 101% = 333.3 |
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| 67 | |||
| 68 | MIN(2.940) = 1.238 * (1 + 326.7 / 237.6) |
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| 69 | TYP(2.969) = 1.250 * (1 + 330.0 / 240.0) |
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| 70 | MAX(3.004) = 1.262 * (1 + 333.3 / 242.4) |
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| 71 | |||
| 100 | jelle | 72 | == +3.125 V Limits == |
| 97 | jelle | 73 | |
| 74 | VOUT = VREF (1 + R2 / R1) |
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| 100 | jelle | 75 | R1 = 220 |
| 76 | R2 = 330 |
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| 77 | R1 = 99% = 217.8 |
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| 78 | R1 = 101% = 222.2 |
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| 79 | R2 = 99% = 326.7 |
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| 80 | R2 = 101% = 333.3 |
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| 81 | |||
| 82 | MIN(3.095) = 1.238 * (1 + 326.7 / 217.8) |
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| 83 | TYP(3.125) = 1.250 * (1 + 330.0 / 220.0) |
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| 84 | MAX(3.115) = 1.262 * (1 + 333.3 / 222.2) |
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| 85 | |||
| 86 | 3.125 = 1.25 * (1 + 330 / 220) |
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| 87 | |||
| 88 | |||
| 89 | == +3.3V Limits == |
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| 90 | |||
| 91 | VOUT = VREF (1 + R2 / R1) |
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| 97 | jelle | 92 | R1 = 240 |
| 93 | R2 = 390 |
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| 94 | R1 = 99% = 237.6 |
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| 95 | R1 = 101% = 242.4 |
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| 96 | R2 = 99% = 386.1 |
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| 97 | R2 = 101% = 393.9 |
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| 98 | MIN(3.250) = 1.238 * (1 + 386.1 / 237.6) |
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| 99 | TYP(3.281) = 1.238 * (1 + 386.1 / 237.6) |
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| 100 | MAX(3.313) = 1.262 * (1 + 393.9 / 242.4) |