CS8191 Просмотр технического описания (PDF) - ON Semiconductor
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CS8191 Datasheet PDF : 12 Pages
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CS8191
Table 1. Function Generator Output Nominal Angle vs. Ideal Angle (After Calibrating at 2705)
Nominal
Nominal
Nominal
Nominal
Nominal
Nominal
Ideal Q
Q
Ideal Q
Q
Ideal Q
Q
Ideal Q
Q
Ideal Q
Q
Ideal Q
Q
Degrees Degrees Degrees Degrees Degrees Degrees Degrees Degrees Degrees Degrees Degrees Degrees
0
0
17
17.98
34
33.04
75
74.00
160
159.14
245
244.63
1
1.09
18
18.96
35
34.00
80
79.16
165
164.00
250
249.14
2
2.19
19
19.92
36
35.00
85
84.53
170
169.16
255
254.00
3
3.29
20
20.86
37
36.04
90
90.00
175
174.33
260
259.16
4
4.38
21
21.79
38
37.11
95
95.47
180
180.00
265
264.53
5
5.47
22
22.71
39
38.21
100
100.84
185
185.47 270
270.00
6
6.56
23
23.61
40
39.32
105
106.00
190
190.84 275
275.47
7
7.64
24
24.50
41
40.45
110
110.86
195
196.00 280
280.84
8
8.72
25
25.37
42
41.59
115
115.37
200
200.86 285
286.00
9
9.78
26
26.23
43
42.73
120
119.56
205
205.37 290
290.86
10
10.84
27
27.07
44
43.88
125
124.00
210
209.56 295
295.37
11
11.90
28
27.79
45
45.00
130
129.32
215
214.00 300
299.21
12
12.94
29
28.73
50
50.68
135
135.00
220
219.32 305
303.02
13
13.97
30
29.56
55
56.00
140
140.68
225
225.00
14
14.99
31
30.39
60
60.44
145
146.00
230
230.58
15
16.00
32
31.24
65
64.63
150
150.44
235
236.00
16
17.00
33
32.12
70
69.14
155
154.63
240
240.44
Note: Temperature, voltage and nonlinearity not included.
CIRCUIT DESCRIPTION and APPLICATION NOTES
The CS8191 is specifically designed for use with air–core
meter movements. It includes an input comparator for
sensing an input signal from an ignition pulse or speed
sensor, a charge pump for frequency to voltage conversion,
a bandgap voltage regulator for stable operation, and a
function generator with sine and cosine amplifiers to
differentially drive the meter coils.
From the partial schematic of Figure 7, the input signal is
applied to the FREQIN lead, this is the input to a high
impedance comparator with a typical positive input
threshold of 2.7 V and typical hysteresis of 0.4 V. The output
of the comparator, SQOUT, is applied to the charge pump
input CP+ through an external capacitor CCP. When the
input signal changes state, CCP is charged or discharged
through R3 and R4. The charge accumulated on CCP is
mirrored to C4 by the Norton Amplifier circuit comprising
of Q1, Q2 and Q3. The charge pump output voltage, F/VOUT,
ranges from 2.0 V to 6.3 V depending on the input signal
frequency and the gain of the charge pump according to the
formula:
FńVOUT + 2.0 V ) 2.0 FREQ CCP RT (VREG * 0.7 V)
RT is a potentiometer used to adjust the gain of the F/V
output stage and give the correct meter deflection. The F/V
output voltage is applied to the function generator which
generates the sine and cosine output voltages. The output
voltage of the sine and cosine amplifiers are derived from the
on–chip amplifier and function generator circuitry. The
various trip points for the circuit (i.e., 0°, 90°, 180°, 270°)
are determined by an internal resistor divider and the
bandgap voltage reference. The coils are differentially
driven, allowing bidirectional current flow in the outputs,
thus providing up to 305° range of meter deflection. Driving
the coils differentially offers faster response time, higher
current capability, higher output voltage swings, and
reduced external component count. The key advantage is a
higher torque output for the pointer.
The output angle, Θ, is equal to the F/V gain multiplied by
the function generator gain:
Q + AFńV AFG,
where:
AFG + 77°ńV(typ)
The relationship between input frequency and output
angle is:
Q + AFG 2.0 FREQ CCP RT (VREG * 0.7 V)
or, Q + 970 FREQ CCP RT
The ripple voltage at the F/V converter’s output is
determined by the ratio of CCP and C4 in the formula:
DV
+
CCP(VREG
C4
*
0.7
V)
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