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MM5837: Documented frequency by supply voltage. [Couriersud]

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Measurements done 15.02.2020.
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couriersud 2020-02-16 15:58:24 +01:00
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src/devices/sound/mm5837.h
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@ -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