1
Features
Output
Amplifiers
Gnd
SCLK
SI
COS
COS
+
SIN
SIN
+
V
BB
V
CC
POR
Serial
to
Parallel
Shift
Register
POR
OC
7 Bit
DAC
SO
D0 D6
V
TOP
V
VAR
MUX
OE
CS
V
BAT
FAULT
Latch
LOGIC
ST
R
S
S
D7 D9
s
Serial Input Bus
s
2 MHz Operating
Frequency
s
Tangential Drive
Algorithm
s
80mA Drive Circuits
s
0.5 Accuracy (Typ.)
s
Power-On-Reset
s
Protection Features
Output Short Circuit
Overtemperature
Package Options
Single Air-Core Gauge Driver
CS4172
Description
The CS4172 is a monolithic BiCMOS
integrated circuit used to translate a
digital 10-bit word from a micropro-
cessor/microcontroller to complemen-
tary DC outputs. The DC outputs
drive an air-core meter commonly
used in vehicle instrument panels. The
10 bits of data are used to linearly con-
trol the quadrature coils of the meter
directly with a 0.35 resolution and
1.0 accuracy over the full 360 range
of the gauge. The interface from the
microcontroller is by a Serial Periph-
eral Interface (SPI) compatible serial
connection using up to a 2MHz shift
clock rate.
The digital code, which is directly pro-
portional to the desired gauge pointer
deflection, is shifted into a DAC and
multiplexer. These two blocks provide
a tangential conversion function to
change the digital data into the appro-
priate DC coil voltage for the angle
demanded. The tangential algorithm
creates approximately 40% more
torque in the meter movement than
does a sin-cos algorithm at 45, 135,
225, and 315 angles. This increased
torque reduces the error due to pointer
droop at these critical angles.
Each output buffer is capable of sup-
plying up to 80mA per coil and are
controlled by a common enable pin.
When OE is low the output buffers are
turned off but the logic portion of the
chip remains powered and continues
to operate normally.
The Serial Gauge Driver is self-protect-
ed against output short circuit condi-
tions. The output drivers are disabled
anytime the on-chip protection circuit-
ry detects a short circuit condition. The
outputs remain off until a falling edge
is presented on CS. If the short circuit
is still present the output drivers auto-
matically disable themselves again. A
thermal protection circuit limits the
junction temperature to approximately
160C for conditions of high supply
voltage and high ambient temperature.
The status pin (ST) reflects the state of
the outputs and is low whenever the
outputs are disabled.
Block Diagram
16 Lead PDIP
SIN
-
SIN
+
Gnd
V
BB
Gnd
NC
SO
SI
V
CC
COS
+
COS
-
CS
SCLK
OE
1
Gnd
ST
SIN
-
SIN
+
Gnd
V
BB
Gnd
Gnd
SO
SI
V
CC
COS
+
COS
-
CS
SCLK
OE
1
Gnd
ST
16 Lead SO Wide
(internally fused leads)
Rev. 4/19/99
CS4172
Cherry Semiconductor Corporation
2000 South County Trail, East Greenwich, RI 02818
Tel: (401)885-3600 Fax: (401)885-5786
Email: info@cherry-semi.com
Web Site: www.cherry-semi.com
A Company
2
Absolute Maximum Ratings
Supply Voltage
V
BB
....................................................................................................................................................................-1.0V to 15.0V
V
CC
......................................................................................................................................................................-1.0V to 6.0V
Digital Inputs ..............................................................................................................................................................-1.0V to 6.0V
Ground Potential Difference (|AGnd-DGnd|)....................................................................................................................0.5V
Steady State Output Current ............................................................................................................................................100mA
Forced Injection Current (Inputs and Supply).................................................................................................................10mA
Operating Junction Temperature (T
J
) ..................................................................................................................................150C
Storage Temperature Range .................................................................................................................................-65C to 150C
Lead Temperature Soldering
Wave Solder (through hole styles only) .....................................................................................10 sec. max, 260C peak
Reflow (SMD styles only) ......................................................................................60 sec. max above 183C, 230C peak
ESD Susceptibility (Human Body Model)..............................................................................................................................2kV
CS4172
Electrical Characteristics: -40C T
A
105C; 7.5V V
BB
14V; 4.5V V
CC
5.5V (unless otherwise specified)
PARAMETER
TEST CONDITIONS
MIN
TYP
MAX
UNIT
s Supply Voltages and Currents
V
BB
Quiescent Current
Output disabled (OE = 0V)
1
5
mA
[R
COS
, R
SIN
= R
L(MIN)
] @45
175
mA
(code = X080) V
BB
= 14V
V
CC
Quiescent Current
OE = high, V
BB
= 0V
SCLK = 2.0MHz
1
mA
s Digital Inputs and Outputs
Output High Voltage
SO, I
OH
= 0.8mA
V
CC
- 0.8
V
Output Low Voltage
SO, I
OL
=0.8mA
0.4
V
ST, I
OL
= 2.5mA
0.8
V
Output High Current
ST, V
CC
= 5.0V
25
A
Input High Voltage
CS, SCLK, SI, OE
0.7
V
CC
V
Input Low Voltage
CS, SCLK, SI, OE
0.3
V
CC
V
Input High Current
CS, SCLK, SI, OE; V
IN
= 0.7
V
CC
1
A
Input Low Current
CS, SCLK, SI, OE; V
IN
= 0.3
V
CC
1
A
s Analog Outputs
Output Function Accuracy
-1.2
+1.2
deg
Output Shutdown Current,
V
BB
= 14.0V
70
250
mA
Source
Output Shutdown Current,
V
BB
= 14.0V
70
250
mA
Sink
Output Shutdown Current,
V
BB
= 7.5V
43
250
mA
Source
Output Shutdown Current,
V
BB
= 7.5V
43
250
mA
Sink
Coil Drive Output Voltage
0.748
V
BB
V
Minimum Load Resistance
T
A
= 105C
229
T
A
= 25C
171
T
A
= -40C
150
3
Package Pin Description
PACKAGE PIN#
PIN SYMBOL
FUNCTION
PARAMETER
TEST CONDITIONS
MIN
TYP
MAX
UNIT
Shift Clock Frequency
2.0
MHz
SCLK High Time
175
ns
SCLK Low Time
175
ns
SO Rise Time
0.75V to V
CC
- 1.2V; C
L
= 90pF
150
ns
SO Fall Time
0.75V to V
CC
- 1.2V; C
L
= 90pF
150
ns
SO Delay Time
C
L
= 90pF
150
ns
SI Setup Time
75
ns
SI Hold Time
75
ns
CS Setup Time
0
ns
CS Hold Time
75
ns
16 Lead SO Wide
16 Lead PDIP
1
1
SIN
-
Negative output for SINE coil.
2
2
SIN
+
Positive output for SINE coil.
3
4
V
BB
Analog supply. Nominally 13.5V.
4,5,12,13
3,13,14
Gnd
Ground.
6
6
SI
Serial data input. Data present at the rising edge of the
clock signal is shifted into the internal shift register.
7
7
V
CC
5V logic supply. The internal registers and latches are
reset by a POR generated by the rising edge of the voltage
on this pin.
8
8
OE
Controls the state of the output buffers. A logic low on
this pin turns them off.
9
9
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.
10
10
CS
When high allows data at SI to be shifted into part with
the rising edges 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.
11
11
ST
STATUS reflects the state of the outputs and is low any-
time the outputs are disabled, either by OE or the internal
protection circuitry. Requires external pull-up resistor.
14
5
SO
Serial data output. Existing 10-bit data is shifted out when
new data is shifted in. Allows cascading of multiple
devices on common serial port.
15
15
COS
-
Negative output for COSINE coil.
16
16
COS
+
Positive output for COSINE coil.
12
NC
No connection.
Electrical Characteristics: -40C T
A
105C; 7.5V V
BB
14V; 4.5V V
CC
5.5V (unless otherwise specified)
CS4172
4
The SACD is for interfacing between a microcontroller or
microprocessor and air-core meter movements commonly
used in automotive vehicles for speedometers and
tachometers. These movements are built using 2 coils
placed at a 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 point-
er indicator is attached to this shaft and in conjunction
with a separate printed scale displays the vehicles speed
or the engines speed.
The disc (and pointer) respond to the vector sum of the
voltages applied to the coils. Ideally, this relationship fol-
lows a
equation. Since this is a transcendental and
non-linear function, devices of this type use an approxi-
mation for this relationship. The SACD uses a tangential
algorithm as shown in Figure 1. Only 1 output varies in
any 45 degree range.
Figure 1. Major gauge outputs.
Quadrant I
q = Tan
-1
For
q = 0.176 to 44.824:
V
SIN
= Tan
q 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
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
For
q = 180.176 to 224.824:
V
SIN
= -Tan(
q 180) 0.748 V
BB
V
COS
= -0.748
V
BB
For
q = 225.176 269.824:
V
SIN
= -0.748
V
BB
V
COS
= -Tan(270
q) 0.748 V
BB
Quadrant IV
q = 360 Tan
-1
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
Graph 1. Major gauge response.
II
V
COS+
360/0
I
q
270
V
SIN
90
V
SIN+
III
IV
180
V
COS-
0.748V
BB
0.748V
BB
0.748V
BB
0.748V
BB
]
V
SIN+
V
SIN-
V
COS+
V
COS-
[
]
V
SIN+
V
SIN-
V
COS+
V
COS-
[
]
V
SIN+
V
SIN-
V
COS+
V
COS-
[
]
V
SIN+
V
SIN-
V
COS+
V
COS-
[
0
45
90
135
180
225
270
315
360
Max (128)
Min (0)
Max (128)
Min (0)
Max (128)
Min (0)
Max (128)
Min (0)
SIN
+
Output
SIN
Output
COS
+
Output
COS
Output
Degrees of Rotation
MUX bits (D9 D7)
000
001
010
011
100
101
110
111
000
sine
cosine
Theory of Operation
Applications Information
CS4172
CS4172
Applications Information: continued
5
To drive the gauges pointer to a particular angle, the
microcontroller sends a 10-bit digital word into the serial
port. These 10 bits are divided as shown in Figure 2.
However, from a software programmers viewpoint, a
360 circle is divided into 1024 equal parts of .35 each.
Table 1 shows the data associated with the 45 divisions
of the 360 driver.
Figure 2. Definition of serial word.
Table 1. Nominal output for major gauge (V
BB
= 14V).
The 10 bits are shifted into the devices shift register MSB
first using an SPI compatible scheme. This method is
shown in Figure 3. The CS must be high and remain high
for SCLK to be enabled. Data on SI is shifted in on the ris-
ing edge of the synchronous clock signal. Data in the shift
register changes at SO on the falling edge of SCLK. This
arrangement allows the cascading of devices. SO is
always enabled. Data shifts through without affecting the
outputs until CS is brought low. At this time the internal
DAC is updated and the outputs change accordingly.
Figure 3. Serial data timing diagram.
Figure 4. Power-up sequence.
10 Bits
V
CC
CS
SI
OE
ST
10 Bits
OUTPUTS
ENABLED
REGISTERS
SET
T
O
ZERO
REGISTERS
SET
T
O
ZERO
OUTPUTS
ENABLED
SO
(tpd)
SO
(Rise, Fall)
10% - 90%
SI
(Hold)
SI
(Setup)
SCLK
SI
SO
CS
Hold
CS
CS
Setup
Input Code
Ideal
Nominal
V
SIN
V
COS
(Decimal)
Degrees
Degrees
(V)
(V)
0
0
0.176
0.032
10.476
128
45
45.176
10.476
10.412
256
90
90.176
10.476
-0.032
384
135
135.176
10.412
-10.476
512
180
180.176
-0.032
-10.476
640
225
225.176
-10.476
-10.412
768
270
270.176
-10.476
0.032
896
315
315.176
-10.476
10.476
1023
359.65
359.826
-0.032
10.476
Major
Gauge
(360
)
D9
D8
D7
D6
D5
D4
D3
D2
D1
D0
D9 D7 select
which octant
Divides a 45
octant into 128 equal parts
to achieve a .35
resolution
Code 0 127
10
MSB
LSB
Application Diagram
ENABLE
CS4172
10k
SCLK
SI
COS-
COS+
SIN-
SIN+
SO
OE
CS
ST
V
BB
V
CC
Microcontroller
Next Driver
360
Gauge
V
BAT
V
REG
CS-8156
5V
12V
Thermal
16 Lead
16 Lead
Data
PDIP
SO Wide*
R
QJC
typ
42 18
C/W
R
QJA
typ
80 75
C/W
CS4172
6
Part Number
Description
CS4172XN16
16 Lead PDIP
CS4172XDWF16
16 Lead SO Wide*
CS4172XDWFR16
16 Lead SO Wide* (tape & reel)
D
Lead Count
Metric
English
Max
Min
Max
Min
16 Lead PDIP
19.69
18.67
.775
.735
16 Lead SO Wide*
10.50
10.10
.413
.398
1999 Cherry Semiconductor Corporation
Rev. 4/19/99
Ordering Information
Package Specification
PACKAGE DIMENSIONS IN mm (INCHES)
PACKAGE THERMAL DATA
Cherry Semiconductor Corporation reserves the right to
make changes to the specifications without notice. Please
contact Cherry Semiconductor Corporation for the latest
available information.
*Internally Fused Leads
Surface Mount Wide Body (DW); 300 mil wide
Plastic DIP (N); 300 mil wide
0.39 (.015)
MIN.
2.54 (.100) BSC
1.77 (.070)
1.14 (.045)
D
Some 8 and 16 lead
packages may have
1/2 lead at the end
of the package.
All specs are the same.
.203 (.008)
.356 (.014)
REF: JEDEC MS-001
3.68 (.145)
2.92 (.115)
8.26 (.325)
7.62 (.300)
7.11 (.280)
6.10 (.240)
.356 (.014)
.558 (.022)
1.27 (.050) BSC
7.60 (.299)
7.40 (.291)
10.65 (.419)
10.00 (.394)
D
0.32 (.013)
0.23 (.009)
1.27 (.050)
0.40 (.016)
REF: JEDEC MS-013
2.49 (.098)
2.24 (.088)
0.51 (.020)
0.33 (.013)
2.65 (.104)
2.35 (.093)
0.30 (.012)
0.10 (.004)
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