diff options
author | couriersud <couriersud@gmx.org> | 2020-02-16 15:58:24 +0100 |
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committer | couriersud <couriersud@gmx.org> | 2020-02-16 15:58:24 +0100 |
commit | 33a12cdd010644c9ba6bda92b78932732d2f6e6c (patch) | |
tree | 791ef34b3643cd19422348355db45ecc1a1a0d96 | |
parent | 6ff40dfeffa5062aaebb995e79321da1a9f3d41b (diff) |
MM5837: Documented frequency by supply voltage. [Couriersud]
Measurements done 15.02.2020.
-rw-r--r-- | src/devices/sound/mm5837.h | 70 |
1 files changed, 70 insertions, 0 deletions
diff --git a/src/devices/sound/mm5837.h b/src/devices/sound/mm5837.h index 543f92be033..594a782d4f9 100644 --- a/src/devices/sound/mm5837.h +++ b/src/devices/sound/mm5837.h @@ -12,6 +12,76 @@ OUTPUT 3 | | 7 N/C VSS 4 |_______| 8 N/C + + Couriersud , 16.02.2020 + + The following measurements were taken on Saturday, 15.02.2020 using + a MM5837. These deviate significantly from the measurements cited + below from 'mims circuit scrapbook'. I assume mims has noted down the + frequencies measured on the output pin and has not taken the effort to + convert them to the internal frequency. + + Some simple math shows that the internal frequency used to drive the + lfsr (2^17-1 length) is 4 times the frequency measured at pin 3. + The lfsr produces 32768 l-h transitions during one lfsr cycle. This can + either be derived using some debug code or stochastic analysis. + + The frequencies measured are also in the order of the 100kHz the + S2688 datasheet (MM5837 replacement) states. + + The "sweet spot" of 32768Hz was measured at 12.91 supply voltage. + + V Fpin3 Fint T + 7.2 1 4 32768.0 + 7.4 26 104 1260.3 + 7.5 110 440 297.9 + 7.6 205 820 159.8 + 7.7 370 1,480 88.6 + 8.0 950 3,800 34.5 + 8.5 2,900 11,600 11.3 + 9.0 5,570 22,280 5.9 + 9.5 8,300 33,200 3.9 + 10.0 11,300 45,200 2.9 + 10.5 14,800 59,200 2.2 + 11.0 18,100 72,400 1.8 + 11.5 22,050 88,200 1.5 + 12.0 25,800 103,200 1.3 + 12.5 29,750 119,000 1.1 + 12.91 32,768 131,072 1.0 + 13.0 33,670 134,680 1.0 + 13.5 37,800 151,200 0.9 + 14.0 41,900 167,600 0.8 + 14.5 46,050 184,200 0.7 + 15.0 49,700 198,800 0.7 + 15.5 52,450 209,800 0.6 + 16.0 53,800 215,200 0.6 + 16.5 53,900 215,600 0.6 + 17.0 53,000 212,000 0.6 + 17.5 51,500 206,000 0.6 + 18.0 49,000 196,000 0.7 + 18.5 45,900 183,600 0.7 + 19.0 42,500 170,000 0.8 + 19.5 39,200 156,800 0.8 + 20.0 36,000 144,000 0.9 + 20.5 32,900 131,600 1.0 + 21.0 29,600 118,400 1.1 + 21.5 26,700 106,800 1.2 + 22.0 24,200 96,800 1.4 + 22.5 21,450 85,800 1.5 + 23.0 18,800 75,200 1.7 + 23.5 16,650 66,600 2.0 + 24.0 13,900 55,600 2.4 + 24.5 11,950 47,800 2.7 + + Output levels (VGG tied to VDD), RL 22k to VDD + These were measured using my 30 year old Hameg. + + Vsupply Vmin Vmax + 20 6.0 18.0 + 15 4.0 13.5 + 12 3.0 10.5 + 10 2.5 9.0 + ***************************************************************************/ #ifndef MAME_SOUND_MM5837_H |