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SA5778 Serial triple gauge driver (STGD)
Product specification Supersedes data of 1997 May 27 IC18 Data Handbook 1998 Apr 03
Philips Semiconductors
Philips Semiconductors
Product specification
Serial triple gauge driver (STGD)
SA5778
DESCRIPTION
The Serial Triple Gauge Driver (STGD), is a single chip air core driver providing drive to one major gauge, and two minor gauges, for automotive applications such as Speedometer, Fuel, Temperature, Tachometer, Volts, and Oil pressure information display. The STGD operates in conjunction with a microcontroller receiving serial data inputs, and can provide status back to the microcontroller either serially or via a status line. The protocol is compatible with the Philips Single Gauge Driver (SGD) and Dual Gauge Driver (DGD). The STGD also includes a protected battery supply for external single Serial Gauge Drivers or Dual Gauge Drivers.
FEATURES
* Major Gauge 10-bit resolution Drive provides 0.35 resolution
- Sine/Cosine outputs for 360 operation - 0.2 accuracy typical throughout entire range
* Minor gauge drivers provide 0.35 resolution
- 112 operation - 0.5 accuracy typical throughout entire range
* Serial Data Input
- Supports interface from microcontrollers - Compatible with Philips SGD SA5775A and DGD SA5777A
PIN CONFIGURATION
SIN+ RUN GOE SwCONTROL SwBATT1 GND GND GND GND VBATT SwBATT2 DATAOUT COM C2- 1 2 3 4 5 6 7 8 9 10 11 12 13 14 28 27 26 25 24 23 22 21 20 19 18 17 16 15 SIN- COS+ COS- ST SCLK GND GND GND GND CS DATAIN C1- C1+ C2+
* Serial Data Output
- Permits the STGD to be wired in series using a common chip select to additional STGDs, SGDs, and DGDs - Permits fault status information to be returned to the microcontroller
* Over Voltage Protection, Over Temperature Protection and Low
Standby Current Operation - Gauge drivers disabled when supply voltage exceeds specified operating voltage, protection to 40V. - Gauge drivers disabled when die temperature exceeds operating range - External switch may supply overvoltage protected battery supply to other devices operating off battery
* Thermally Enhanced SO-28 surface mount package
SR01116
Figure 1. Pin Configuration
BLOCK DIAGRAM
SCLK DATAIN CS GOE RUN VBATT BIAS, TSD SwBATT, COMMON REFERENCE 9-BIT DATA LATCH ENABLE 7-BIT Tan DAC 7-BIT Tan DAC 7-BIT, SINE /COSINE DAC 9-BIT DATA LATCH 10-BIT DATA LATCH 4-BIT STATUS LATCH ST MINOR GAUGE 2 10-BIT SR MINOR GAUGE 1 10-BIT SR MAJOR GAUGE 10-BIT SR DATAOUT
MUX
MUX
MUX
SwBATT1
SwBATT2
COS+
SwControl
COS-
COM
GND
SIN+
SIN-
C2-
C2+
C1-
C1+
SR01117
Figure 2. STGD Internal Block Diagram
1998 Apr 03
2
853-2055 19199
Philips Semiconductors
Product specification
Serial triple gauge driver (STGD)
SA5778
ORDERING INFORMATION
DESCRIPTION 28-Pin Small Outline (SO) thermally enhanced Package TEMPERATURE RANGE -40 to +105C ORDER CODE SA5778D DWG # SOT136-1
PIN DESCRIPTION
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Mnemonic GND Pin No. Type I I I I Name and Function 6,7,8,9,20, 21,22,&23 10 3 2 4 Circuit Ground Potential. The pins are used for heat dissipation to board. All pins should be soldered to foil on the board per the thermal management description. Battery supply voltage Gauge Output Enable: A high on this input enables normal operation of the gauge coil drivers. See Table 1. RUN (Ignition): Input to sense the state of the Ignition switch. See Table 1. VBATT GOE RUN SwCONTROL SwBATT1 SwBATT2 O I I Switched Battery Control: Control output to switch on a protected VBATT supply via an external PNP transistor. This output is controlled by the RUN input, GOE input and the on chip protection circuits. 5, 11 Switched Battery Supplies: Used as the reference level for the DACs, bias voltage for the second coils of the minor gauges, and the supply for the output buffers for the major and minor gauges. One supplies the major gauge drivers and related circuits, while the other supplies the minor gauge circuits. Both SwBATT inputs must be connected to the control transistor as the two inputs are not connected internally. Serial Clock: Used to clock data into and out of the STGD. Data is shifted MSB first. Data In: Data is loaded on the rising edge of SCLK and is shifted in MSB first. SCLK 24 18 12 25 I I DATAIN DATAOUT ST O O Data Out: Is provided to permit the STGD to pass status information back to the controlling microcontroller, and to allow multiple devices to be connected in series. Status Output: This is an open drain output. Status outputs from several devices may be wire OR'ed together. This output is low when the outputs are disabled due to a fault condition. The outputs may be disabled due to shorted outputs, over temperature, power up reset, or the GOE control pin and this condition is reflected on the ST pin. The outputs will also be disabled due to an over voltage condition, however this is not reported on the ST pin as over voltage should be a transient condition. CS 19 I Chip Select: Active high chip select input. When CS is high, the part is enabled to receive data on the DATAin pin and output data on the DATAout pin. A low to high transition of CS captures device status in the shift register for output. A high to low transition of CS loads gauge data from the shift register into the data latches. Sine Positive: Driver output to sine coil of major gauge, positive side. Sine Negative: Driver output to sine coil of major gauge, negative side. SIN+ SIN- 1 O O O O O O O O O 28 27 26 16 17 15 14 13 COS+ COS- C1+ C1- C2- C2+ Cosine Positive: Driver output to cosine coil of major gauge, positive side. Cosine Negative: Driver output to cosine coil of major gauge, negative side. Coil 1 Positive: Driver output to driven coil of minor gauge 1, positive side. Coil 2 Positive: Driver output to driven coil of minor gauge 2, positive side. Coil 1 Negative: Driver output to driven coil of minor gauge 1, negative side. Coil 2 Negative: Driver output to driven coil of minor gauge 2, negative side. COM Common: Driver output for junction of bias coils for minor gauges. This output is regulated to half of SwBATT.
ABSOLUTE MAXIMUM RATINGS
SYMBOL VBATT VIN1 VIN2 VIN3 PD TJ
PARAMETER
RATING 40 -1 to +7
UNIT V V V V
Battery supply voltage, with recommended 1KW series resistor Input voltage; Data In, CS, SCLK, GOE Input voltage; SwBATT
-1 to +24 -1 to +40 1400
Input voltage; RUN, with recommended RC Circuit Power Dissipation (Tamb = 105C) SO-28 Package Ambient operating temperature Junction temperature1 Thermal Impedance
mw C C
Tamb JA
-40 to +105 +150/+160
See Thermal Management Section
C/W
NOTE: 1. 160C junction temperature is permitted during high battery (>16V) fault operation 1998 Apr 03 3
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1998 Apr 03 VSWBATT VDRIVE2,3 SYMBOL SYMBOL VDRIVE1 ISWBATT ACC2,3 IBATTSB tSCLKH VOVSD tSCLKL FSCLK VBATT RLMIN ACC1 VCOM VOH2 VOH1 IBATT VOL2 VOL1 tCSH tCYC tCSL IOH VIH tDR tHD tSU tDF VIL IIH IIL VBATT = 7.5 to 16V; Tamb = -40 to +105C
AC ELECTRICAL CHARACTERISTICS
VBATT = 8.0 to 16V; Tamb = -40 to +105C
DC ELECTRICAL CHARACTERISTICS
Philips Semiconductors
Serial triple gauge driver (STGD)
DATAOUT fall time
DATAOUT rise time
SCLK high to DATAIN hold time
DATAIN setup to SCLK high time
SCLK low to CS low time
CS high to SCLK high time
SCLK HIGH time
SCLK LOW time
Clock frequency
Clock cycle time
Minor gauge bias voltage
Minimum coil load resistance
Coil drive voltage, minor gauges
Coil drive voltage, major gauge
Output function accuracy, minor gauges
Output function accuracy, major gauge
Input low current
Input high current
Battery overvoltage shutdown voltage
Input low voltage
Input high voltage
Output low voltage
Output low voltage
Off state output current
Output high voltage
Output high voltage
Battery supply current, standby
Switched battery supply current, operating
Battery supply current, operating
Switched battery supply voltage
Battery supply voltage
PARAMETER
PARAMETER
IOB (Source or Sink) RL = RLMIN
3.6 to 0.8V; CL = 90pF
0.8 to 3.6V; CL = 90pF
TCYC
Tamb = 105C Tamb = 25C Tamb = -40C
RL = RLMIN; minor gauges, G2 & G3
RL = RLMIN; major gauge, G1
CS, SCLK, DATAIN, RUN GOE; VIL=1.5
CS, SCLK, DATAIN, RUN GOE; VIH = 3.5
VBATT
CS, SCLK, DATAIN, GOE, RUN
CS, SCLK, DATAIN, GOE, RUN
SwCONTROL,
ST, DATAOUT, IOL = 1.5 mA
ST, VOH = 5 V
SwCONTROL, IOH = 10A
DATAOUT, IOH = 300A
VBATT = 12 V
Normal operating range
VBATT = VBATTMAX RL = RLMIN
Normal operating range
Normal operating range
TEST CONDITION
IOL = 20 mA @ VBATTMIN
IOL = 50 mA @ VBATTMAX
TEST CONDITION
4
0.475 x SwBATT
-1.0
-0.5
MIN
MIN
175
175
625
226 171 127
3.5
4.0
7.5
75 75 75 75 70 68 18 40 8
LIMITS
LIMITS
TYP
TYP
74
71
0.525 x SwBATT
Product specification
MAX
MAX
+1.0
+0.5
1.60
400
1.5
1.2
1.5
0.4
0.5
75 75 80 78 10 10 23 25 60 16 16
SA5778
% SwBATT
% SwBATT
UNITS
UNITS
MHz
Deg
Deg
ma
ma
A
A
A
A
ns ns ns ns ns ns ns ns ns V V V V V V V V V V V
Philips Semiconductors
Product specification
Serial triple gauge driver (STGD)
SA5778
J1850 PROTOCOL CONTROLLER
4 GOE 80C51 MICRO- CONTROLLER SERIAL SA5778 SERIAL TRIPLE GAUGE DRIVER 2
360 MAJOR GAUGE
AU5780 J1850 VPW TRANSCEIVER ADDITIONAL GAUGE DRIVERS; SA5775A OR SA5777A PROTECTED BY SA5778
2
112 MINOR GAUGE
RUN IGNITION
J1850 BUS
VBATT
SR01118
Figure 3. System Connections for the STGD
FUNCTIONAL DESCRIPTION
Figure 1 shows the pin-out of the STGD, which is packaged in an SO-28 pin package, enhanced for improved thermal management. Four pins on each side of the package serve as a heat spreader to remove heat from the die, and also function as the ground connection. The recommended mounting includes an area of copper on the PC board to aid in thermal management. Figure 2 is a block diagram of the STGD. A serial interface connects the STGD to the microcontroller. A data output pin is provided to permit the STGD to be wired in series with other Philips air core gauge drivers such as the Serial Gauge Driver, SA5775, and the Dual Gauge Driver, SA5777 or additional STGDs. Status information may be passed back to the microcontroller via a status output, or via the serial interface. Figure 3 shows the connection of the STGD in a typical application.
MICROCONTROLLER DATAOUT SCLK PORT N DATAIN INT DATAIN SCLK CS DATAOUT ST ADDITIONAL GAUGE DRIVER(S), SA5775A, SA5777A OR SA5778 SA5778 SERIAL TRIPLE GAUGE DRIVER
5V
DATAIN SCLK CS DATAOUT ST
APPLICATION INFORMATION
Figure 4 demonstrates the connections between the STGD, the microcontroller, and optionally additional gauge drivers such as the SGD and DGD. With an active high on the chip select input (CS), data is shifted into the STGD through DATAIN on the rising edge of SCLK. Several gauge drivers may be wired in series using a common chip select and clock line, when more than three gauges are needed. The DATAOUT pins are cascaded to the DATAIN pins of the following gauge drivers. Status information can be returned to the microcontroller via the ST pins of each gauge driver. These are open-drain, active low outputs, which may be wire OR'ed together to signal that a fault, such as a thermal shut down, has occurred within one of the gauge drivers. This pin may be connected to a microcontroller port pin for polling in software, or may be connected to an external interrupt input to cause entry into an interrupt service routine. The STGD, may also pass status information back to the microcontroller serially. The rising edge of chip select loads status information into the shift register for the first four bits that will be shifted out of the STGD by the shift clock. Figure 11 shows the data bits within the shift register. A low on the ST pin signals that one or more status bits have been set in the status register. A high indicates all status bits are reset. The status output bits include minor gauge over current, major gauge over current, thermal shutdown and RUN. Gauge data is captured in latches by the falling edge of the chip select.
SR01119
Figure 4. Serial Communications Between STGD, Microcontroller and Other Gauge Drivers Figure 5 shows the gauge connections to the STGD. The major gauge, G1, supports full 360 operation with two coils driven. The seven least significant bits of the gauge information are converted to an analog level by digital-to-analog converter. The display range is divided into eight sections, two sections per quadrant. The coils are driven with a Sine/Cosine approximation. The three most significant bits of gauge display information control the multiplexer to select which coil is fed by the DAC and which coil receives a fixed bias. The multiplexer also determines the polarity of the voltages supplied to the coils. The minor gauges, G2 and G3, each have one coil driven by a DAC. The other coils of each gauge are wired in series with the switched battery supply to supply the bias. The switched battery supply is turned off during over voltage conditions. Only 9-bits of information are required for the minor gauges, however, 10-bits are shifted through the part to maintain compatibility with the SGD and DGD. Hence, all gauges, both major and minor, are supplied with 10-bit data for consistency.
1998 Apr 03
5
Philips Semiconductors
Product specification
Serial triple gauge driver (STGD)
SA5778
DATAIN SCLK ST CS GOE RUN VBATT THERMAL PROTECTION SwBATT, BIAS
DATA / STATUS SHIFT REGISTERS DATA OUT STATUS LATCH DATA LATCHES
placed in a standby mode with a low on both the GOE and RUN input pin. In this mode, battery current drain is minimized. The SwBATT1 and SwBATT2 inputs are the supply for the DACs, and the output buffers driving the coils including the COM output which stabilizes the voltages applied to the bias coils of the minor gauges. Both SwBATT1 and SwBATT2 should be connected to the collector of the control transistor as these inputs are not connected internally and supply different portions of the circuit. This switched battery supply is protected from voltages exceeding the specified operating range and is controlled by the SwCONTROL output. This supply may optionally be used to supply additional circuits which operate from unregulated battery supplies but which need protection from over voltage transients. Typical devices which may benefit from this protection include the Serial Gauge Driver, SA5775A and Dual Gauge Driver, SA5777A, which are often used in conjunction with the STGD in 4 and 5 gauge applications. This switched battery supply is turned off when the STGD enters the standby mode in response to the RUN and GOE inputs both being low, or a VBATT supply exceeding the specified operating range. The switched battery supply depends on the RUN signal to prevent undesired needle movement on the minor gauges when going from standby to active mode. This movement would otherwise occur if the voltage to the fixed bias coils of the minor gauges was switched on before the coil voltages provided by the DACs within the STGD were defined. The start up jump is prevented as follows. In the sleep mode the switched battery supply is off, and the gauge drive outputs of the STGD are in a high impedance state. The gauges are in their zero position from the previous power-down sequence. When the RUN input goes high, but the GOE is kept low, the STGD enters the start up mode in which the minor gauges are driven to zero, the internal 5V regulator for the logic is turned on, and the switched battery supply is turned on to supply the bias coil and STGD output buffers. However, the output buffers for the major gauge remain in the high impedance output state. The microcontroller may load values into the STGD via the serial interface while GOE is low. When the microcontroller applies a high to GOE, the major gauge output buffers are enabled. When the RUN signal is removed the STGD continues to operate in the normal mode, however, the controlling microcontroller should also monitor RUN and, when it goes low, send a series of values to the STGD to move the needles to their zero positions before taking GOE low to put the part in the standby mode. Table 1 describes the operation and control of the SwBATT supply, the output buffers, and the operations normally performed by the microcontroller. Normal operation of a vehicle will follow the sequence of the truth table from top to bottom. The RUN input is typically connected to the switched ignition voltage, while GOE is controlled by the microcontroller.
SwControl
ENABLE
DIGITAL-to-ANALOG CONVERTERS and OUTPUT MULTIPLEXERS
COS+
SwBATT1
SwBATT2
SwBATT TRANSISTOR
112 MINOR GAUGES
GND
COS-
COM
360 MAJOR GAUGE SR01120
Figure 5. Gauge Connections to the STGD
18-24V REFERENCE VBATT GOE RUN 10K
+ -
5V REGULATOR
SIN-
SIN+ 5V LOGIC
C2-
C2+
C1-
C1+
OUTPUT BUFFER SUPPLY 1K DAC REFERENCES SwControl RB VBATT SwBATT1/2 BIAS COILS EXTERNAL GAUGE DRIVERS
SR01121
Figure 6. Gauge Enable/Standby Circuit and Over Voltage Protection Circuit Figure 6 shows the protection and gauge enable logic for the STGD. The battery supply voltage VBATT is monitored, and if the supply exceeds the specified operating range, the STGD is put in a shutdown mode in which the output buffers are disabled. The STGD will also enter the shutdown mode by excessive die temperature, and will return to normal operation when the die temperature decreases to within specified limits. Thermal shutdown may occur at VBATT supply voltages over 16V at high ambient temperatures near 105C. Internal logic will continue to function and status may be read out to determine the source of the shutdown. The STGD may be
1998 Apr 03
6
Philips Semiconductors
Product specification
Serial triple gauge driver (STGD)
SA5778
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RUN Input 1=High 0 GOE Input 1=High 0 SwControl 1=ON 0 Swbatt1,2 Voltage Off Minor Gauge Driver Outputs High Impedance Major Gauge Driver Outputs High Impedance High Impedance System Status Standby mode 1 0 1 VBATT Enabled (output forced to zero) Start up mode, sets minor gauge driver to zero position, and disables major gauge driver. Load values into STGD via the serial port. Normal Operating mode. Periodically update gauge data as required by the application. 1 1 1 VBATT Enabled Enabled 0 1 1 VBATT Off Enabled Enabled Power down sequence. Load a series of values into the STGD to return needles to zero before power is removed. Returned to standby mode (same as first row of table) 0 0 0 High Impedance High Impedance
Table 1. Truth Table
THERMAL MANAGEMENT AND POWER DISSIPATION
The actual value used is dependent on the current needed to keep the PNP in saturation.
The power dissipated by the STGD has three components. The first term in the equation below represents the power dissipated in the STGD from current through the coil resistance. This component of the power dissipation is a function of both the battery voltage and the coil resistance. Most of the external loads such as the coils are resistive, so the current drawn by the output buffers is proportional to the supply voltage, resulting in power dissipation that is proportional to the square of the supply voltage for these circuits. The highest power dissipation for a given coil driver will occur when the coil voltage is being driven to 50% of VBATT. Thus the power dissipated by each coil driver is (VBATT/2)* (VBATT/2Rc) or VBATT(VBATT/4Rc). If the coil resistance of the two minor gauge coils and the two coils of the major gauge all have the same resistance, then the maximum total power dissipation of the drivers becomes 4*VBATT(VBATT/4Rc) or simply VBATT(VBATT/Rc). Much of the internal analog circuits appears to the supply pins as a current sink and is represented by the second term. The current drawn by these circuits is relatively constant despite changes in supply voltage, resulting in power dissipation that is proportional to the supply voltage. Finally some power is dissipated in driving the external PNP transistor used to control the switched battery supply. The total power dissipation is a combination of these components and may be calculated from the formula: PD=VBATT(VBATT/RC)+VBATT(0.012) + VOL2(VBATT-VOL2-VBE(PNP))/RB Where: PD = Power dissipation in watts VBATT = Battery supply voltage in volts RC = Coil resistance in ohms at ambient temperature including any self heating effects VOL2 = Output low voltage of the SwCONTROL pin as specified in the DC Characteristics VBE(PNP)= The VBE drop of the external PNP transistor RB = Resistor is series with base of external PNP transistor. The minimum value of RB = VBATTMAXIOL=16/0.050=320
All gauges at 45 to a quadrant axis, as this is the highest internal power dissipation position. If only the nominal coil resistance is known at a given nominal ambient temperature such as 25C, the coil operating resistance at a high temperature ambient may be calculated using the following formula: RCA = RCN (1+(0.4%/C)*((TSH+Tamb)-25C)) Where:
RCA = Resistance of Coil at Ambient temperature, including self heating RCN = Nominal Resistance of Coil at 25C, without self heating Tamb = Ambient temperature, C TSH = Self heating of coil, C 0.4%/C = Resistance increase coefficient for copper Figure 7 shows power dissipation plotted as a function of coil resistance and voltage. Since coil resistance is a function of temperature, the maximum power dissipation plotted will only occur at the lowest specified operating temperature. The power dissipation is lowest at the highest ambient temperature because of the increase in coil resistance with temperature. This maximum power dissipation will only occur during a fault condition in which the system voltage rises to 18V, generally because of a failed voltage regulator controlling the vehicles battery voltage. Power dissipation will be lower when air core meter movements with higher nominal coil resistance are used.
1998 Apr 03
7
Philips Semiconductors
Product specification
Serial triple gauge driver (STGD)
SA5778
3.0 POWER (W) 2.5
125
POWER DISSIPATION FOR COIL RESISTANCE IN OHMS AND OPERATING BATTERY VOLTAGE
150
175 2.0 235
1.5
325 LOAD RESISTANCE ()
1.0
0.5
0.0 10.5 12.5 13.5 14.5 15.5 16.5 17.5 11.5 7.5 8.5 9.5 10 12 13 14 15 16 17 18 11 8 9
VSWBATT (V)
SR01430
Figure 7. Power Dissipation of the STGD as a Function of Coil Resistance and Operating Voltage The STGD is specified to operate up to VBATTmax. The over voltage shutdown circuit will turn off the output buffers and the switched battery supply when the battery voltage reaches VOVSD. Over temperature conditions will also cause the output buffers to be disabled. The STGD employs a thermally enhanced SO-28 package. The center four pins on each side are fused to the die pad to create a path for removal of heat from the package to the copper foil on the PC board. An area of copper foil is required on the PC board for heat dissipation at higher power dissipation levels. In order to determine the size of the copper foil required, both thermal testing and thermal modeling were used. The effective JA (thermal resistance, junction to ambient) was determined using both single and double sided PCBs with heat-sinking copper foil areas. Figures 8 and 9 show the effect of PCB copper foil area on the effective thermal resistance of the STGD part/PCB system. Figure 8 shows the thermal resistance of the STGD mounted on a PC board with heat-sinking copper on the component side only. Figure 9 is a similar plot for a two sided PC board (same size copper areas on each side). Both plots assume a 60 x 60 x 1.57 mm FR4 board with varying square-shaped sizes of 2 oz. copper. The two sided board also assumes 8 thermal bias with 0.36 mm2 cross section. It is important to note that at such a high ambient temperature (worst case of 105C assumed), radiation is just as significant as convection in the dissipation of heat. Good radiation is highly dependent on the emissivity of the heated surface, so the thermal radiation properties of the copper foil should be considered. Bare, clean copper is a good thermal conductor, but it has a low emissivity, and is therefore a bad radiator. It is recommended that the copper areas intended for heat dissipation be left covered with solder mask or otherwise blackened to increase the emissivity, thereby improving the heat radiating ability of the board.
1998 Apr 03
8
Philips Semiconductors
Product specification
Serial triple gauge driver (STGD)
SA5778
50
JA (C/W)
45
40
1.4W LIMIT
35
30
25 0 500 1000 1500 2000 2500 3000 3500
PCB COPPER HEAT SINK AREA (SQ mm)
SR01497
Figure 8. JA for SO28 with 8 Fused Pins One-sided PCB (2 oz. Copper), e = 0.9, Tamb = 105C, P = 1.4-1.8W
45
JA (C/W)
40 1.4W LIMIT
35
30
25 0 500 1000 1500 2000 2500 3000
PCB COPPER HEAT SINK AREA (SQ mm)
SR01498
Figure 9. JA for SO28 with 8 Fused Pins Two-sided PCB (2 oz. Copper), e = 0.9, Tamb = 105C, P = 1.4-1.8W
1998 Apr 03
9
Philips Semiconductors
Product specification
Serial triple gauge driver (STGD)
SA5778
Sample Calculations for Power Dissipation and Thermal Management
Worst Case Example The worst case example will occur when the STGD is operating at VBATTMAX (16V, in the highest specified ambient temperature (105C), and with the lowest specified coil resistance (171 ohms at 25C). Typical coil self heating of 15C is assumed. Calculation of Coil resistance operating at 105C ambient.
R CA=
From Figure 8, the copper area required, using a single sided board, to keep the junction temperature within limits is approximately 2200 mm2. Figure 9 shows 1200 mm2 is required on each side of a double-sided board. The above example illustrates the worst case situation of the STGD operating in at a maximum battery voltage, with the lowest nominal coil resistance (171 at room temperature), and at the highest ambient temperature. This will produce the highest junction temperature. At lower ambient temperatures the power dissipation may be higher because the coil resistance is decreased, however the junction temperature will be lower.
RCN (1+(0.4%W/C)*((TSH+Tamb)-25C))
= 171 x(1+(0.4%((15+105)-25))) = 236 Ohms at Tamb=105C, with 15C of self heating. Calculation of STGD power dissipation at 16 volt operation. PD = VBATT (VBATT/RC) + VBATT (0.012) +VOL2 (VBATT - VOL2 - VBE(PNP)) / RL = 16(16/236)+16(0.012)+1.5(16-1.5-0.5)/320 = 1.085+0.192+0.066 Watts = 1.34 Watts Required board area and Junction Temperature calculation The maximum junction temperature desired is 150C. The permissible temperature rise and required JA may be calculated as: T = Tj-Tamb JA = T/PD Where; T = Temperature rise in C PD = Power dissipation Tj = Junction Temperature Tamb = Ambient Temperature T = TJ-Tamb = 150 - 105 = 45C JA = T/PD=55C/1.34 watts = 33C/W.
Serial Interface
Figure 10 demonstrates the serial interface timing referenced in the AC specifications. Figure 11 shows the order of information transfer through the serial interface. On a low to high transition of the CS pin, status information replaces the four most significant bits of data in the shift register and are the first bits shifted out. Output data is changed on the falling edge of SCLK, while input data is captured on the rising edge of SCLK. Major gauge data is loaded first, starting with the most significant bit, followed by minor gauge 1 data then minor gauge 2 data.
tCYC tCF tCSH SCLK 1 29 tSCLKL 30 tSCLKH tCR tCSL
CS
30 CLOCK CYCLES
DATAIN
D29
D1
D0*
tSU
tHD
tDR DATAOUT S4 D1*
tDF D0*
SR01499
Figure 10. Serial Interface Timing
1998 Apr 03
10
Philips Semiconductors
Product specification
Serial triple gauge driver (STGD)
SA5778
MINOR GAUGE 2 DATA IN
MINOR GAUGE 1
MAJOR GAUGE/STATUS DATA OUT
D0 D1 D2 D3 D4 D5 D6 D7 D8 D9 D10 D11 D12 D13 D14 D15 D16 D17 D18 D19 D20 D21 D22 D23 D24 D25 D26 D27 D28 D29 LSB MSB LSB MSB LSB MSB
During Read out: D26: RUN Input State; D27: Thermal Shutdown; 1 = RUN input high 0 = RUN input low 1 = Shutdown 0 = Normal operation 1 = Over Current Shutdown 0 = Normal operation 1 = Over Current Shutdown 0 = Normal operation
SR01123
D28: Minor Gauge Over Current; D29: Major Gauge Over Current;
Figure 11. Internal Shift Register
15
10 DIFFERENTIAL OUTPUT VOLTAGE
COS
SIN
5
0 0 127 255 383 511 639 767 895 1023
-5
-10
-15
INPUT CODE
SR01500
Figure 12. Major Gauge Output Voltages (VSWBATT = 14V)
1998 Apr 03
11
Philips Semiconductors
Product specification
Serial triple gauge driver (STGD)
SA5778
14.00 12.00 10.00 8.00 6.00 C+ - C- (VOLTS) 4.00 2.00 0.00 -2.00 -4.00 -6.00 -8.00 -10.00 -12.00 -14.00 31 63 95 127 159 INPUT CODE 191 223 255 287 319
SL00462
Figure 13. Typical Minor Gauge Output Voltage vs. Input Code (VSWBATT = 14V)
0.5 x VSWBATT
ASSUMING CODE 0 IS 0: CODE 0 31 63 POSITION -56.097 -45.194 -33.940 -22.685 -11.430 -0.176 11.079 22.333 33.588 44.843 56.097
-56
+56
95 127 159 191
-0.744 x VSWBATT TOTAL SPAN = 112.15 STEP SIZE = 0.35
0.744 x VSWBATT
223 255 287 319
IDEAL ANGLE(DEGREE)=CODE/319*2* ArcTan (0.744/0.5)-ArcTan(0.744/0.5) SR01501
Figure 14. Minor Gauge Total Span
1998 Apr 03
12
Philips Semiconductors
Product specification
Serial triple gauge driver (STGD)
SA5778
120
100
80 ANGLE (DEGREES)
60
40
20
0 0 15 31 41 63 79 95 111 127 159 175 143 INPUT CODE 191 207 223 239 255 271 287 303 319
SL00464
Figure 15. Meter Position (degrees) vs. Input Code for Minor Gauges
1998 Apr 03
13
Philips Semiconductors
Product specification
Serial triple gauge driver (STGD)
SA5778
SO28: plastic small outline package; 28 leads; body width 7.5mm
SOT136-1
1998 Apr 03
14
Philips Semiconductors
Product specification
Serial triple gauge driver (STGD)
SA5778
NOTES
1998 Apr 03
15
Philips Semiconductors
Product specification
Serial triple gauge driver (STGD)
SA5778
Data sheet status
Data sheet status Objective specification Preliminary specification Product specification Product status Development Qualification Definition [1] This data sheet contains the design target or goal specifications for product development. Specification may change in any manner without notice. This data sheet contains preliminary data, and supplementary data will be published at a later date. Philips Semiconductors reserves the right to make chages at any time without notice in order to improve design and supply the best possible product. This data sheet contains final specifications. Philips Semiconductors reserves the right to make changes at any time without notice in order to improve design and supply the best possible product.
Production
[1] Please consult the most recently issued datasheet before initiating or completing a design.
Definitions
Short-form specification -- The data in a short-form specification is extracted from a full data sheet with the same type number and title. For detailed information see the relevant data sheet or data handbook. Limiting values definition -- Limiting values given are in accordance with the Absolute Maximum Rating System (IEC 134). Stress above one or more of the limiting values may cause permanent damage to the device. These are stress ratings only and operation of the device at these or at any other conditions above those given in the Characteristics sections of the specification is not implied. Exposure to limiting values for extended periods may affect device reliability. Application information -- Applications that are described herein for any of these products are for illustrative purposes only. Philips Semiconductors make no representation or warranty that such applications will be suitable for the specified use without further testing or modification.
Disclaimers
Life support -- These products are not designed for use in life support appliances, devices or systems where malfunction of these products can reasonably be expected to result in personal injury. Philips Semiconductors customers using or selling these products for use in such applications do so at their own risk and agree to fully indemnify Philips Semiconductors for any damages resulting from such application. Right to make changes -- Philips Semiconductors reserves the right to make changes, without notice, in the products, including circuits, standard cells, and/or software, described or contained herein in order to improve design and/or performance. Philips Semiconductors assumes no responsibility or liability for the use of any of these products, conveys no license or title under any patent, copyright, or mask work right to these products, and makes no representations or warranties that these products are free from patent, copyright, or mask work right infringement, unless otherwise specified. Philips Semiconductors 811 East Arques Avenue P.O. Box 3409 Sunnyvale, California 94088-3409 Telephone 800-234-7381 (c) Copyright Philips Electronics North America Corporation 1998 All rights reserved. Printed in U.S.A. Date of release: 04-98 Document order number: 9397 750 03715
Philips Semiconductors
1998 Apr 03 16

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