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CS4172
CS4172
Single Air-Core Gauge Driver
Description
The CS4172 is a monolithic BiCMOS integrated circuit used to translate a digital 10-bit word from a microprocessor/microcontroller to complementary 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 control 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 Peripheral Interface (SPI) compatible serial connection using up to a 2MHz shift clock rate. The digital code, which is directly proportional 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 appropriate 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 supplying 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-protected against output short circuit conditions. The output drivers are disabled anytime the on-chip protection circuitry 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 automatically 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.
Features
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
16 Lead PDIP
SINSIN+ Gnd VBB SO
1
COS+ COSGnd Gnd NC ST CS SCLK
Block Diagram
VCC VBB
SI VCC OE
POR
LOGIC
SI SCLK CS
SIN+
Serial to Parallel Shift Register
VTOP D0 D6
16 Lead SO Wide
(internally fused leads)
SIN1
7 Bit DAC
VVAR VBAT
MUX
SIN
COS+ COSSO Gnd Gnd ST CS SCLK
COS+ COS OC
SIN+ VBB Gnd
SO D7 D9
R FAULT S Latch S
ST
Output Amplifiers
Gnd SI VCC OE
POR
OE
Gnd
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
Rev. 4/19/99
1
A
Company
CS4172
Absolute Maximum Ratings Supply Voltage VBB ....................................................................................................................................................................-1.0V to 15.0V VCC ......................................................................................................................................................................-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 (TJ) ..................................................................................................................................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
Electrical Characteristics: -40C TA 105C; 7.5V VBB 14V; 4.5V VCC 5.5V (unless otherwise specified)
PARAMETER TEST CONDITIONS MIN TYP MAX UNIT
s Supply Voltages and Currents VBB Quiescent Current Output disabled (OE = 0V) [RCOS, RSIN = RL(MIN)] @45 (code = XO080) VBB = 14V VCC Quiescent Current OE = high, VBB = 0V SCLK = 2.0MHz s Digital Inputs and Outputs Output High Voltage Output Low Voltage Output High Current Input High Voltage Input Low Voltage Input High Current Input Low Current s Analog Outputs Output Function Accuracy Output Shutdown Current, Source Output Shutdown Current, Sink Output Shutdown Current, Source Output Shutdown Current, Sink Coil Drive Output Voltage Minimum Load Resistance
1
5 175
mA mA
1
mA
SO, IOH = 0.8mA SO, IOL =0.8mA ST, IOL = 2.5mA ST, VCC = 5.0V CS, SCLK, SI, OE CS, SCLK, SI, OE CS, SCLK, SI, OE; VIN = 0.7 VCC CS, SCLK, SI, OE; VIN = 0.3 VCC
VCC - 0.8 0.4 0.8 25 0.7 VCC 0.3 VCC 1 1
V V V A V V A A
VBB = 14.0V VBB = 14.0V VBB = 7.5V VBB = 7.5V
-1.2 70 70 43 43 0.748 VBB 229 171 150
+1.2 250 250 250 250
deg mA mA mA mA V 1/2 1/2 1/2
TA = 105C TA = 25C TA = -40C
2
CS4172
Electrical Characteristics: -40C TA 105C; 7.5V VBB 14V; 4.5V VCC 5.5V (unless otherwise specified)
PARAMETER TEST CONDITIONS MIN TYP MAX UNIT
Shift Clock Frequency SCLK High Time SCLK Low Time SO Rise Time SO Fall Time SO Delay Time SI Setup Time SI Hold Time CS Setup Time CS Hold Time
2.0 175 175 0.75V to VCC - 1.2V; CL = 90pF 0.75V to VCC - 1.2V; CL = 90pF CL = 90pF 75 75 0 75 150 150 150
MHz ns ns ns ns ns ns ns ns ns
Package Pin Description
PACKAGE PIN# PIN SYMBOL FUNCTION
16 Lead SO Wide 1 2 3 4,5,12,13 6 7
16 Lead PDIP 1 2 4 3,13,14 6 7
SINSIN+ VBB Gnd SI VCC
Negative output for SINE coil. Positive output for SINE coil. Analog supply. Nominally 13.5V. Ground. Serial data input. Data present at the rising edge of the clock signal is shifted into the internal shift register. 5V logic supply. The internal registers and latches are reset by a POR generated by the rising edge of the voltage on this pin. Controls the state of the output buffers. A logic low on this pin turns them off. 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. 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. STATUS reflects the state of the outputs and is low anytime the outputs are disabled, either by OE or the internal protection circuitry. Requires external pull-up resistor. 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. Negative output for COSINE coil. Positive output for COSINE coil. No connection.
8 9
8 9
OE SCLK
10
10
CS
11
11
ST
14
5
SO
15 16
15 16 12
COSCOS+ NC
3
CS4172
Applications Information
Theory of Operation
Quadrant II q = 180 Tan-1
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 pointer indicator is attached to this shaft and in conjunction with a separate printed scale displays the vehicleOs speed or the engineOs speed. The disc (and pointer) respond to the vector sum of the voltages applied to the coils. Ideally, this relationship folsine lows a cosine equation. Since this is a transcendental and non-linear function, devices of this type use an approximation for this relationship. The SACD uses a tangential algorithm as shown in Figure 1. Only 1 output varies in any 45 degree range.
[
VSIN+ VSINVCOS+ VCOS-
]
For q = 90.176 to 134.824: VSIN = 0.748 VBB VCOS = -Tan(q 90) 0.748 VBB For q = 135.176 to 179.824: VSIN = Tan(180 q) 0.748 VBB VCOS = -0.748 VBB Quadrant III q = 180 + Tan-1
[
VSIN+ VSINVCOS+ VCOS-
]
For q = 180.176 to 224.824: VSIN = -Tan(q 180) 0.748 VBB VCOS = -0.748 VBB For q = 225.176 269.824: VSIN = -0.748 VBB VCOS = -Tan(270 q) 0.748 VBB Quadrant IV q = 360 Tan-1
Degrees of Rotation 0 Max (128) 45 90 135 180 225 270 315 360
SIN+ Output
Min (0) Max (128)
SIN Output
Min (0)
[
VSIN+ VSINVCOS+ VCOS-
]
Max (128)
COS+ Output
Min (0)
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 VBB VCOS = 0.748 VBB
VCOS+ 360/0 0.748VBB
Max (128)
COS Output
Min (0) 000 001 010 011 100 101 110 111 000
MUX bits (D9 D7)
Figure 1. Major gauge outputs.
Quadrant I q = Tan-1
[
VSIN+ VSINVCOS+ VCOS-
]
270 VSIN
q IV I 0.748VBB III 0.748VBB II 90 VSIN+
For q = 0.176 to 44.824: VSIN = Tanq 0.748 VBB VCOS = 0.748 VBB For q = 45.176 to 89.824: VSIN = 0.748 VBB VCOS = Tan(90 q) 0.748 VBB
0.748VBB 180 VCOS-
Graph 1. Major gauge response.
4
CS4172
Applications Information: continued To drive the gaugeOs 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. 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.
CS CSSetup CSHold
MSB Major Gauge (360)
D9 D8 D7 D6 D5 D4 D3 D2 D1
LSB
SCLK
D0
SI(Setup) SI(Hold)
D9 D7 select which octant
Divides a 45 octant into 128 equal parts to achieve a .35 resolution Code 0 12710
SI
Figure 2. Definition of serial word.
SO
SO(Rise, Fall) 10% - 90% SO(tpd)
Input Code Ideal (Decimal) Degrees 0 0 128 45 256 90 384 135 512 180 640 225 768 270 896 315 1023 359.65
Nominal Degrees 0.176 45.176 90.176 135.176 180.176 225.176 270.176 315.176 359.826
VSIN (V) 0.032 10.476 10.476 10.412 -0.032 -10.476 -10.476 -10.476 -0.032
VCOS (V) 10.476 10.412 -0.032 -10.476 -10.476 -10.412 0.032 10.476 10.476
Figure 3. Serial data timing diagram.
VCC
CS
SI
10 Bits
10 Bits
The 10 bits are shifted into the deviceOs 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 rising edge of the synchronous clock signal. Data in the shift
ST
OUTPUTS ENABLED
REGISTERS SET TO ZERO
Table 1. Nominal output for major gauge (VBB = 14V).
OE
REGISTERS SET TO ZERO
OUTPUTS ENABLED
Figure 4. Power-up sequence.
Application Diagram
VBAT VREG 5V 12V
CS-8156
ENABLE
360 Gauge
10k
SINSIN+ ST CS SI SCLK OE
Microcontroller
CS4172
COS+ COSVBB VCC
SO Next Driver
5
CS4172
Package Specification
PACKAGE DIMENSIONS IN mm (INCHES) PACKAGE THERMAL DATA
D Lead Count 16 Lead PDIP 16 Lead SO Wide* Metric Max Min 19.69 18.67 10.50 10.10 English Max Min .775 .735 .413 .398
Thermal Data RQJC typ RQJA typ
16 Lead PDIP 42 80
16 Lead SO Wide* 18 75
uC/W uC/W
Plastic DIP (N); 300 mil wide
7.11 (.280) 6.10 (.240)
8.26 (.325) 7.62 (.300) 3.68 (.145) 2.92 (.115)
1.77 (.070) 1.14 (.045)
2.54 (.100) BSC
.356 (.014) .203 (.008)
0.39 (.015) MIN. .558 (.022) .356 (.014) Some 8 and 16 lead packages may have 1/2 lead at the end of the package. All specs are the same.
REF: JEDEC MS-001
D
Surface Mount Wide Body (DW); 300 mil wide
7.60 (.299) 7.40 (.291)
10.65 (.419) 10.00 (.394)
0.51 (.020) 0.33 (.013)
1.27 (.050) BSC
2.49 (.098) 2.24 (.088)
2.65 (.104) 2.35 (.093)
1.27 (.050) 0.40 (.016)
REF: JEDEC MS-013
0.32 (.013) 0.23 (.009) D 0.30 (.012) 0.10 (.004)
Ordering Information
Part Number CS4172XN16 CS4172XDWF16 CS4172XDWFR16 *Internally Fused Leads
Rev. 4/19/99
Description 16 Lead PDIP 16 Lead SO Wide* 16 Lead SO Wide* (tape & reel)
Cherry Semiconductor Corporation reserves the right to make changes to the specifications without notice. Please contact Cherry Semiconductor Corporation for the latest available information. 6
(c) 1999 Cherry Semiconductor Corporation

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