CS4122_05 Datasheet, PDF (6/9 Pages) ON Semiconductor – Triple Air−Core Gauge Driver with Serial Input Bus

CS4122
Quadrant IV
ƪ ƫ q + 360° * Tan−1
(VSIN₎)
(VCOS₎)
*
*
(VSIN_*)
(VCOS_*)
For q + 270.176°to 314.824° :
VSIN + *0.748 VBB
VCOS + Tan(q * 270°) 0.748
VBB
For q + 315.176° * 359.824° :
VSIN + *Tan (360° * q) 0.748
VCOS + 0.748 VBB
VBB
270°
V_SIN−
V_COS+
360/0°
0.748 V_BB
IV
0.748 V_BB
q
I
0.748 V_BB
III
II
90°
V_SIN+
0.748 V_BB
180°
V_COS−
Figure 3. Major Gauge Response
The minor gauge coil outputs differ in that only one of the
coils in each movement is driven by the IC. The other is
driven directly by the analog supply voltage, specifically
one−half of this voltage. The common output assures that
this is true. By varying the voltage across the other coil to a
greater voltage, the pointer can be deflected more than 45°
to each side of the externally driven coil. This relationship
is shown in Figure 4.
Note: There are actually eight segments, but only the are
shown here for simplicity.
0°
Max(128)
C+
Output
Min(0)
Degrees of Rotation
14° 28° 42° 56°
70°
84°
Max(128)
C−
Output
Min(0)
00
1F 3F
5F
7F 9F
BF
Code₁₆
Figure 4. Minor Gauge Outputs
98° 112°
DF FF
Quadrant I, II
ƪ ƫ q + 56.1° * Tan−1
(VC₎) * (VC_*)
VBB * V(V_BBń2)
VCOIL + V(V_BBń2) Tan (56.1° * q)
56.1°
V_BB/2
0°
q
(−56.1)
I
V_C+
0.744 V_BB
112.2°
II
0.744 V_BB
V_C−
Figure 5. Minor Gauge Outputs
To drive a gauge’s pointer to a particular angle, the
microcontroller sends a 12 bit digital word to the CS4122.
These 12 bits are divided as shown in Figure 6. However,
from a software programmer’s viewpoint, a 360° circle is
divided into 1024 equal parts of 0.35° each and a 112.2° arc
is divided into 256 parts of 0.44° each. Table 1 shows the
data associated with the 45° divisions of the 360° driver.
Table 2 shows the data for the center and end points of the
112.2° drivers. Setting the address to “11” disables all
outputs.
Major
Gauge
(360°)
MSB
LSB
D11 D10 D9 D8 D7 D6 D5 D4 D3 D2 D1 D0
Gauge D9 − D7
Address ^select
= “00” ^{which octant}
Divides a 45° octant into
128 equal parts to achieve
a 0.35° resolution
Code 0 − 127₁₀
Minor
Gauge
#1
D11 D10 D9 D8 D7 D6 D5 D4 D3 D2 D1 D0
Gauge Set to
Address ^{“00”}
= “01”
Deflection angle 0 − 112.2°,
to achieve a 0.44° resolution
Code 0 − 255₁₀
Minor
Gauge
#2
D11 D10 D9 D8 D7 D6 D5 D4 D3 D2 D1 D0
Gauge Set to
Address ^{“00”}
= “10”
Deflection angle 0 − 112.2°,
to achieve a 0.44° resolution
Code 0 − 255₁₀
All
D11 D10 D9 D8 D7 D6 D5 D4 D3 D2 D1 D0
Gauges
Disabled Gauge All Outputs Disabled; D9 − D0 = “Don’t Care”
Address
= “11”
Figure 6. Definition of Serial Word
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