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CS4122XDWF24

P1-P3P4-P6P7-P9
CS4122
http://onsemi.com
4
PIN FUNCTION DESCRIPTION
PIN # PIN SYMBOL FUNCTION
1 SCLK Serial clock for shifting in/out of data. Rising edge shifts data on SI into the shift register and the
falling edge changes the data on SO.
2 CS When High, allows data at SI to be shifted into the internal shift register with the rising edge of
SCLK. The falling edge transfers the shift register contents into the DAC and multiplexer to update
the output buffers. The falling edge also re−enables the output drivers if they have been disabled by
a fault.
3 SIN− Negative output for SINE coil.
4 SIN+ Positive output for SINE coil.
5, 6, 7, 8,
17, 18, 19, 20
GND Ground for V
BB
and V
CC
supplies; device substrate. In the power SOIC package they aid in removing
internally generated heat from the package and as such should be soldered to as large a PCB area
as possible.
9 V
BB
/2 1/2 V
BB
output for biasing the minor coils.
10 C1+ Positive output for the #1 minor coil.
11 C1− Negative output for the #1 minor coil.
12 V
CC
5.0 V logic supply. The internal registers and latches are reset by a POR generated by the rising
edge of the voltage on this lead.
13 FAULT Open−drain fault flag. A logic low on this lead indicates that an output is shorted or the device is in
thermal shutdown.
14 V
BB
Analog supply. Nominally 12 V.
15 C2+ Positive output for the #2 minor coil.
16 C2− Negative output for the #2 minor coil.
21 COS− Negative output for COSINE coil.
22 COS+ Positive output for COSINE coil.
23 SI Serial data input. Data present at the rising edge of the clock signal is shifted into the internal shift
register.
24 SO Serial data output. Existing 12 bit data is shifted out when new data is shifted in. Allows cascading
of multiple devices on common serial port.
ORDERING INFORMATION
Device Package Shipping
†
CS4122XDWF24 SOIC−24 WB 31 Units / Rail
CS4122XDWF24G SOIC−24 WB
(Pb−Free)
31 Units / Rail
CS4122XDWFR24 SOIC−24 WB 1000 Tape & Reel
CS4122XDWFR24G SOIC−24 WB
(Pb−Free)
1000 Tape & Reel
†For information on tape and reel specifications, including part orientation and tape sizes, please refer to our Tape and Reel Packaging
Specifications Brochure, BRD8011/D.
CS4122
http://onsemi.com
5
APPLICATIONS INFORMATION
THEORY OF OPERATION
The CS4122 is for interfacing between a microcontroller
or microprocessor and air−core meters commonly used in
automotive vehicles for speedometers, tachometers and
auxiliary gauges. These meters are built using 2 coils placed
at 90° orientation to each other. A magnetized disc floats in
the middle of the coils and responds to the magnetic field
generated by each coil. The disc has a shaft attached to it that
protrudes out of the assembly. A pointer indicator is attached
to this shaft and in conjunction with a separate printed scale
displays the vehicle’s speed, engine’s speed or other
information such as fuel quantity or battery voltage.
The disc (and pointer) respond to the vector sum of the
voltages applied to the coils. Ideally, this relationship
follows a sine/cosine equation. Since this is a transcendental
and non−linear function, devices of this type use an
approximation for this relationship. The CS4122 uses a
tangential algorithm as shown in Figure 2 for the major
(360°) gauge. Only one output varies in any 45° range.
Note: The actual slopes are segmented but are shown here
as straight lines for simplicity.
S
IN+
O
utput
Max(128)
S
IN−
O
utput
C
OS+
O
utput
C
OS−
O
utput
Max(128)
Max(128)
Max(128)
Min(0)
Min(0)
Min(0)
Min(0)
0° 45° 90° 135° 180° 225° 270° 315° 360°
000 001 010 011 100 101 110 111 00
0
MUX bits (D9−D7)
Degrees of Rotation
Figure 2. Major Gauge Outputs
Quadrant I
q + Tan
−1
ƪ
(V
SIN)
) * (V
SIN*
)
(V
COS)
) * (V
COS*
)
ƫ
For q + 0.176°to 44.824° :
V
SIN
+ Tanq 0.748 V
BB
V
COS
+ 0.748 V
BB
For q + 45.176°to 89.824° :
V
SIN
+ 0.748 V
BB
V
COS
+ Tan(90° * q) 0.748 V
BB
Quadrant II
q + 180° * Tan
−1
ƪ
(V
SIN)
) * (V
SIN*
)
(V
COS)
) * (V
COS*
)
ƫ
For q + 90.176°to 134.824° :
V
SIN
+ 0.748 V
BB
V
COS
+*Tan (q * 90°) 0.748 V
BB
For q + 135.176°to 179.824° :
V
SIN
+ Tan(180° * q) 0.748 V
BB
V
COS
+*0.748 V
BB
Quadrant III
q + 180° ) Tan
−1
ƪ
(V
SIN)
) * (V
SIN*
)
(V
COS)
) * (V
COS*
)
ƫ
For q + 180.176°to 224.824° :
V
SIN
+*Tan (q * 180°) 0.748 V
BB
V
COS
+*0.748 V
BB
For q + 225.176°to 269.824° :
V
SIN
+*0.748 V
BB
V
COS
+*Tan (270° * q) 0.748 V
BB
CS4122
http://onsemi.com
6
Quadrant IV
q + 360° * Tan
−1
ƪ
(V
SIN)
) * (V
SIN*
)
(V
COS)
) * (V
COS*
)
ƫ
For q + 270.176°to 314.824° :
V
SIN
+*0.748 V
BB
V
COS
+ Tan(q * 270°) 0.748 V
BB
For q + 315.176° * 359.824° :
V
SIN
+*Tan (360° * q) 0.748 V
BB
V
COS
+ 0.748 V
BB
270°
V
SIN−
V
SIN+
90°
V
COS−
V
COS+
180°
360/0°
0.748 V
BB
0.748 V
BB
0.748 V
BB
0.748 V
BB
q
IV
III II
I
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° 14° 28° 42° 56° 70° 84° 98° 112°
Degrees of Rotation
C
+
O
utput
Max(128)
C
−
O
utput
Max(128)
Min(0)
Min(0)
00 1F 3F 5F 7F 9F BF DF FF
Code
16
Figure 4. Minor Gauge Outputs
Quadrant I, II
q + 56.1° * Tan
−1
ƪ
(V
C)
) * (V
C*
)
V
BB
* V
(V
BBń2)
ƫ
V
COIL
+ V
(VBBń2)
Tan (56.1° * q)
Figure 5. Minor Gauge Outputs
V
C−
V
C+
0.744 V
BB
0.744 V
BB
0°
(−56.1)
112.2°
56.1°
V
BB
/2
q
III
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.
Gauge
Address
= “00”
D9 − D7
select
which octant
Divides a 45° octant into
128 equal parts to achieve
a 0.35° resolution
Code 0 − 127
10
Major
Gauge
(360°)
MSB LSB
D9 D8 D7 D6 D5 D4 D3 D2 D1 D0D10D11
Gauge
Address
= “01”
Set to
“00”
Deflection angle 0 − 112.2°,
to achieve a 0.44° resolution
Code 0 − 255
10
Minor
Gauge
#1
D9 D8 D7 D6 D5 D4 D3 D2 D1 D0D10D11
Gauge
Address
= “10”
Set to
“00”
Deflection angle 0 − 112.2°,
to achieve a 0.44° resolution
Code 0 − 255
10
Minor
Gauge
#2
D9 D8 D7 D6 D5 D4 D3 D2 D1 D0D10D11
Gauge
Address
= “11”
All Outputs Disabled; D9 − D0 = “Don’t Care”
All
Gauges
Disabled
D9 D8 D7 D6 D5 D4 D3 D2 D1 D0D10D11
Figure 6. Definition of Serial Word
P1-P3P4-P6P7-P9

CS4122XDWF24

Mfr. #:
Buy CS4122XDWF24
Manufacturer:
ON Semiconductor
Description:
Motor / Motion / Ignition Controllers & Drivers Air Core Gauge DRVR
Lifecycle:
New from this manufacturer.
Delivery:
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