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