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author couriersud <couriersud@gmx.org>2020-02-16 15:58:24 +0100
committer couriersud <couriersud@gmx.org>2020-02-16 15:58:24 +0100
commit33a12cdd010644c9ba6bda92b78932732d2f6e6c (patch)
tree791ef34b3643cd19422348355db45ecc1a1a0d96
parent6ff40dfeffa5062aaebb995e79321da1a9f3d41b (diff)
MM5837: Documented frequency by supply voltage. [Couriersud]
Measurements done 15.02.2020.
-rw-r--r--src/devices/sound/mm5837.h70
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