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MM5837: Documented frequency by supply voltage. [Couriersud]
Measurements done 15.02.2020.
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OUTPUT 3 | | 7 N/C
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OUTPUT 3 | | 7 N/C
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VSS 4 |_______| 8 N/C
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VSS 4 |_______| 8 N/C
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Couriersud , 16.02.2020
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The following measurements were taken on Saturday, 15.02.2020 using
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a MM5837. These deviate significantly from the measurements cited
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below from 'mims circuit scrapbook'. I assume mims has noted down the
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frequencies measured on the output pin and has not taken the effort to
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convert them to the internal frequency.
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Some simple math shows that the internal frequency used to drive the
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lfsr (2^17-1 length) is 4 times the frequency measured at pin 3.
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The lfsr produces 32768 l-h transitions during one lfsr cycle. This can
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either be derived using some debug code or stochastic analysis.
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The frequencies measured are also in the order of the 100kHz the
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S2688 datasheet (MM5837 replacement) states.
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The "sweet spot" of 32768Hz was measured at 12.91 supply voltage.
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V Fpin3 Fint T
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7.2 1 4 32768.0
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7.4 26 104 1260.3
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7.5 110 440 297.9
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7.6 205 820 159.8
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7.7 370 1,480 88.6
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8.0 950 3,800 34.5
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8.5 2,900 11,600 11.3
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9.0 5,570 22,280 5.9
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9.5 8,300 33,200 3.9
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10.0 11,300 45,200 2.9
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10.5 14,800 59,200 2.2
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11.0 18,100 72,400 1.8
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11.5 22,050 88,200 1.5
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12.0 25,800 103,200 1.3
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12.5 29,750 119,000 1.1
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12.91 32,768 131,072 1.0
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13.0 33,670 134,680 1.0
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13.5 37,800 151,200 0.9
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14.0 41,900 167,600 0.8
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14.5 46,050 184,200 0.7
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15.0 49,700 198,800 0.7
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15.5 52,450 209,800 0.6
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16.0 53,800 215,200 0.6
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16.5 53,900 215,600 0.6
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17.0 53,000 212,000 0.6
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17.5 51,500 206,000 0.6
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18.0 49,000 196,000 0.7
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18.5 45,900 183,600 0.7
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19.0 42,500 170,000 0.8
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19.5 39,200 156,800 0.8
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20.0 36,000 144,000 0.9
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20.5 32,900 131,600 1.0
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21.0 29,600 118,400 1.1
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21.5 26,700 106,800 1.2
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22.0 24,200 96,800 1.4
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22.5 21,450 85,800 1.5
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23.0 18,800 75,200 1.7
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23.5 16,650 66,600 2.0
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24.0 13,900 55,600 2.4
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24.5 11,950 47,800 2.7
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Output levels (VGG tied to VDD), RL 22k to VDD
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These were measured using my 30 year old Hameg.
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Vsupply Vmin Vmax
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20 6.0 18.0
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15 4.0 13.5
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12 3.0 10.5
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10 2.5 9.0
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***************************************************************************/
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***************************************************************************/
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#ifndef MAME_SOUND_MM5837_H
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#ifndef MAME_SOUND_MM5837_H
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