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| SPT1018 8-BIT, HIGH SPEED D/A CONVERTER FEATURES * 275 MWPS Conversion Rate - Version A * 165 MWPS Conversion Rate - Version B * Compatible with TDC1018 and HDAC10180 with Improved Performance * RS-343-A Compatible * Complete Video Controls: Sync, Blank, Bright and Reference White (Force High) * 10KH, 100K ECL Compatible * Single Power Supply * Registered Data and Video Controls * Differential Current Outputs * ESD Protected Data and Control Inputs APPLICATIONS * High Resolution Color or Monochrome Raster Graphics Displays * Medical Electronics: CAT, PET, MR Imaging Displays * CAD/CAE Workstations * Solids Modeling * General Purpose High-Speed D/A Conversion * Digital Synthesizers * Automated Test Equipment * Digital Transmitters/Modulators GENERAL DESCRIPTION The SPT1018 is a monolithic 8-bit digital-to-analog converter capable of accepting video data at a 165 or 275 MWPS rate. Complete with video controls (Sync, Blank, Reference White [Force High], Bright), the SPT1018 directly drives doublyterminated 50 or 75 ohm loads to standard composite video levels. The standard set-up level is 7.5 IRE. The SPT1018 is pin-compatible with the HDAC10180 and the TDC1018, with improved performance. The SPT1018 contains data and control input registers, video control logic, reference buffer, and current switches. The SPT1018 is available in a 24-lead PDIP package in the industrial temperature range. Contact the factory for military temperature and /883 versions. BLOCK DIAGRAM Sync, Blank, Bright, Ref - High Video Controls In D0 - D3 Video Data In 4 4 4 4 Out + Register Video Data In D4 - D7 (MSBs) 4 Output Current Switches Out - 4 To 15 Decode Feedthrough Convert 2 Ref+ Ref- Ref Buffer Comp Signal Processing Technologies, Inc. 4755 Forge Road, Colorado Springs, Colorado 80907, USA Phone: (719) 528-2300 FAX: (719) 528-2370 ABSOLUTE MAXIMUM RATING (Beyond which damage may occur)1 Supply Voltages VEE (measured to VCC) ............................... -7.0 to 0.5 V Input Voltages CONV, Data, and Controls .......................... V EE to 0.5 V (measured to VCC) Ref+ (measured to VCC) .............................. V EE to 0.5 V Ref- (measured to VCC) ............................... V EE to 0.5 V Temperature Operating, ambient ................................ -25 to +85 C junction ......................................... +175 C Lead, Soldering (10 seconds) ............................. +300 C Storage ..................................................... -60 to +150 C Note: 1. Operation at any Absolute Maximum Ratings is not implied. See Electrical Specifications for proper nominal applied conditions in typical applications. ELECTRICAL SPECIFICATIONS VCC =ground, VEE = -5.2 V 0.3 V, TA =TMIN to TMAX , CC = 0 pF, ISet = 1.105 mA, unless otherwise specified. PARAMETERS TEST CONDITIONS TEST LEVEL MIN TYP MAX UNITS DC ELECTRICAL CHARACTERISTICS Integral Linearity Error Differential Linearity Error Gain Error Gain Error Tempco Input Capacitance, REF+, REFCompliance Voltage, +Output Compliance Voltage, -Output Equivalent Output Resistance Output Capacitance Maximum Current, + Output Maximum Current, - Output Output Offset Current Input Voltage, Logic HIGH Input Voltage, Logic LOW Convert Voltage, Common Mode Range (VICM) Convert Voltage, Differential (VIDF) Input Current, Logic LOW, Data and Controls Input Current, Logic HIGH, Data and Controls Input Current, Convert 1.0 mASPT SPT1018 2 5/14/97 ELECTRICAL SPECIFICATIONS VCC =ground, VEE = -5.2 V 0.3 V, TA =TMIN to TMAX , CC = 0 pF, ISet = 1.105 mA, unless otherwise specified. PARAMETERS Input Capacitance, Data and Controls Power Supply Sensitivity Supply Current Maximum Conversion Rate Rise Time Rise Time Current Settling Time, Clocked Mode Current Settling Time, Clocked Mode Current Settling Time, Clocked Mode tSI Clock to Output Delay, Clocked Mode tDSC Data to Output Delay, Transparent Mode tDST Convert Pulse Width, ( Low or High) tPWL, tPWH Glitch Energy Reference Bandwidth, -3 dB Set-up Time, Data and Controls tS Hold Time, Data and Controls tH Slew Rate Clock Feedthrough TEST CONDITIONS LEVEL V VI VI MIN TYP 3.0 MAX UNITS pF DC ELECTRICAL CHARACTERISTICS -120 20 155 +120 220 A/V mA MWPS MWPS ns ns ns ns ns ns DYNAMIC CHARACTERISTICS (RL = 37.5 ohms, CL = 5 pF, TA = 25 C, ISet = 1.105 mA) B Grade A Grade 10% to 90% G.S. TA = TMIN to TMAX 10% to 90% G.S. RL = 25 ohms To 0.2% G.S. To 0.8% G.S. To 0.2% G.S. RL = 25 TA = TMIN to TMAX TA = TMIN to TMAX B Grade A Grade Area = 1/2 VT IV IV IV IV V V V V IV IV IV IV IV IV V V IV IV IV IV IV IV IV IV 165 275 1.6 2.0 1.0 7.0 5.5 4.5 2.2 3.2 3.0 1.8 4 1.0 1.0 1.0 0.5 0.5 390 325 -48 -48 4.0 4.5 6.0 6.0 TA = TMIN to TMAX TA = TMIN to TMAX 20% to 80% G.S. TA = TMIN to TMAX TA = TMIN to TMAX ns ns ns ns ns ns pV-s MHz ns ns ns ns V/S V/S dB dB TEST LEVEL CODES All electrical characteristics are subject to the following conditions: All parameters having min/ max specifications are guaranteed. The Test Level column indicates the specific device testing actually performed during production and Quality Assurance inspection. Any blank section in the data column indicates that the specification is not tested at the specified condition. TEST LEVEL I II III IV V VI TEST PROCEDURE 100% production tested at the specified temperature. 100% production tested at TA = +25 C, and sample tested at the specified temperatures. QA sample tested only at the specified temperatures. Parameter is guaranteed (but not tested) by design and characterization data. Parameter is a typical value for information purposes only. 100% production tested at TA = +25 C. Parameter is guaranteed over specified temperature range. SPT SPT1018 3 5/14/97 Figure 1 - Functional Diagram D0 - D7 8 Composite Video Controls CONV CONV Feedthrough 2 Decoding Logic Data Registers Current Sources And Switches Out + Out - 4 Current Source Biasing Amp + - VEE VCC Ref+ Ref- APPLICATION INFORMATION The SPT1018 is a high speed video digital-to-analog converter capable of conversion rates of up to 275 MWPS. This makes the device suitable for driving 1500 X 1800 pixel displays at 70 to 90 Hz update rates. The SPT1018 is separated into different conversion rate categories as shown in table I. The SPT1018 has 10 KH and 100K ECL logic level compatible video controls and data inputs. The complementary analog output currents produced by the devices are proportional to the product of the digital control and data inputs in conjunction with the analog reference current. The SPT1018 is segmented so that the four MSBs of the input data are separated into a parallel thermometer code. From here, fifteen identical current sinks are driven to fabricate sixteen coarse output levels. The remaining four LSBs drive four binary weighted current switches. The MSB currents are then summed with the LSBs, which provide a one-sixteenth of full scale contribution, to provide the 256 distinct analog output levels. The video control inputs drive weighted current sinks that are added to the output current to produce composite video output levels. These controls, Sync, Blank, Reference White (Force High), and Bright are needed in video applications. Another feature that similar video D/A converters do not have is the Feedthrough Control. This pin allows registered or unregistered operation of the video control and data inputs. In the registered mode, the composite functions are latched to the pixel data to prevent screen-edge distortions generally found on unregistered video DACs. Table I - The SPT1018 Family and Speed Designations PART NUMBER SPT1018A UPDATE 275 MWPS COMMENTS Suitable for 1200 X 1500 to 1500 X 1800 displays at 60 to 90 Hz update rate. Suitable for 1024 X 1280 to 1200 X 1500 displays at 60 to 90 Hz update rate. SPT1018B 165 MWPS SPT SPT1018 4 5/14/97 Figure 2 - Typical Interface Circuit Video Monitor FT FH Blank BRT Sync 4 OutR3 50/75 50/75 COAX R4 50/75 Video Control Inputs 4 D0 (LSB) D1 D2 D3 Output Current Switches Register Out+ Video Data Inputs NOTES: 1. V- = -1.2 V (typical) for LM113. D4 D5 D6 D7 (MSB) CONV 4 To 15 Decode Clock R1 500 R2 750 ISet LM113/313 V1 k CONV 2. V+ = -1.2 V V+ 3. ISet = T(R 1+R 2) 4. RL = R3 / / R4 5. VOut- = K 255-Digital Input Code 255 x I Set R L + [ KI x I Set x RL (Bright) ] V+ ( ISet * ) Ref+ 6. VSync = (K x ISet x RL) + (K2 x ISet x RL) Ref Buffer K = 15.8069 K1 = 1.7617 K2 = 10.0392 7. FB = Ferrite bead, Fair-rite P/N 217430011 or equivalent. VCC VEE COMP Ref.01 F 2 k - 5.2 V .01 F 8. All reference resistors 1/8 W 1% metal film power supply decoupling 50 V ceramic disc. 9. x = ECL Termination = VCC = AGND See figure 8 for detail on Ref Buffer. = DGND (digital input drivers). FB 10 F 10. -5.2 V 11. 10. TYPICAL INTERFACE CIRCUIT GENERAL A typical interface circuit using the SPT1018 in a color raster application is shown in figure 2. The SPT1018 requires few external components and is extremely easy to use. The very high operating speeds of the SPT1018 require good circuit layout, decoupling of supplies, and proper design of transmission lines. The following considerations should be noted to achieve best performance. INPUT CONSIDERATIONS Video input data and controls may be directly connected to the SPT1018. Note that all ECL inputs are terminated as closely to the device as possible to reduce ringing, crosstalk and reflections. A convenient and commonly used microstrip impedance is about 130 ohms, which is easily terminated using a 330 ohm resistor to VEE and a 220 ohm resistor to Ground. This arrangement gives a Thevenin equivalent termination of 130 ohms to -2 volts without the need for a -2 volt supply. Standard SIP (Single Inline Package) 220/330 resistor networks are available for this purpose. It is recommended that stripline or microstrip techniques be used for all ECL interface. Printed circuit wiring of known impedance over a solid ground plane is recommended. OUTPUT CONSIDERATIONS The analog outputs are designed to directly drive a dual 50 or 75 ohm load transmission system as shown. The source impedances of the SPT1018 outputs are high impedance current sinks. The load impedance (R L) must be 25 or 37.5 ohms to attain standard RS-343-A video levels. Any deviation from this impedance will affect the resulting video output levels proportionally. As with the data interface, it is important that the analog transmission lines have matched impedance throughout, including connectors and transitions between printed wiring and coaxial cable. The combination of matched source termination resistor RS and load terminator RL minimizes reflections of both forward and reverse traveling waves in the analog transmission system. The return path for analog output current is VCC which is connected to the source termination resistor RS. SPT SPT1018 5 5/14/97 POWER CONSIDERATIONS The SPT1018 operates from a single -5.2 V standard supply. Proper bypassing of the supplies will augment the SPT1018's inherent supply noise rejection characteristics. As shown in figure 2, each supply pin should be bypassed as close to the device as possible with 0.01 F and 10 F capacitors. The SPT1018 has two analog (VEE) power supply pins. Both supply pins should be properly bypassed as mentioned previously. This device also has two analog (VCC) ground pins. Both ground pins should be tied to the analog ground plane. Power and ground pins must be connected in all applications. If a +5 V power source is required, the ground pins (VCC) become the positive supply pins while the supply pins (VEE) become the ground pins. The relative polarities of the other input and output voltages must be maintained. REFERENCE CONSIDERATIONS The SPT1018 has two reference inputs: Ref+ and Ref-. These pins are connected to the inverting and noninverting inputs of an internal amplifier that serves as a reference buffer amplifier. The output of the buffer amplifier is the reference for the current sinks. The amplifier feedback loop is connected around one of the current sinks to achieve better accuracy. (See figure 8.) Since the analog output currents are proportional to the digital input data and the reference current (ISet), the full-scale output may be adjusted by varying the reference current. ISet is controlled through the Ref+ input on the SPT1018. A method and equations to set ISet is shown in figure 2. The Figure 3 - Timing Diagram SPT1018 uses an external negative voltage reference. The external reference must be stable to achieve a satisfactory output and the Ref- pin should be driven through a resistor to minimize offsets caused by bias current. The value for ISet can be varied with the 500 ohm trimmer to change the full scale output. A double 50 ohm load (25 ohm) can be driven if ISet is increased 50% more than ISet for doubly terminated 75 ohm video applications. COMPENSATION The SPT1018 provides an external compensation input (COMP) for the reference buffer amplifier. In order to use this pin correctly, a capacitor should be connected between COMP and VEE as shown in figure 2. Keep the lead lengths as short as possible. If the reference is to be kept as a constant, use a large capacitor (.01 F). The value of the capacitor determines the bandwidth of the amplifier. If modulation of the reference is required, smaller values of capacitance can be used to achieve up to a 1 MHz bandwidth. DATA INPUTS AND VIDEO CONTROLS The SPT1018 has standard single-ended data inputs. The inputs are registered to produce the lowest differential data propagation delay (skew) to minimize glitching. There are also four video control inputs to generate composite video outputs. These are Sync, Blank, Bright and Reference White or Force High. Also provided is the Feedthrough control as mentioned earlier. The controls and data inputs are all 10 KH and 100K ECL compatible. In addition, all have internal pulldown resistors to leave them at a logic low so the pins are inactive when not used. This is useful if the devices are applied as standard DACs without the need for video controls or if less than eight bits are used. tPWH CONV -1.3 V CONV tPWL tS tH -1.3 V Data Control Inputs tDST tDSC 1/2 LSB OUT OUT + tSI 1/2 LSB SPT SPT1018 6 5/14/97 Table II - Video Control Operation (Output values for set-up = 10 IRE and 75 ohm standard load) Sync 1 0 Blank X 1 Ref White X X Bright X X Data Input X X Out - (mA) 28.57 20.83 Out - (V) -1.071 -0.781 Out - (IRE) -40 0 Description Sync Level Blank Level 0 0 0 0 1 1 1 0 X X 0.00 1.95 0.000 -0.073 110 100 Enhanced High Level Normal High Level 0 0 0 0 0 0 0 0 000... 111... 19.40 1.95 -0.728 -0.073 7.5 100 Normal Low Level Normal High Level 0 0 0 0 0 0 1 1 000... 111... 17.44 0.00 -0.654 0.000 17.5 110 Enhanced Low Level Enhanced High Level The SPT1018 is usually configured in the synchronous mode. In this mode, the controls and data are synchronized to prevent pixel dropout. This reduces screen-edge distortions and provides the lowest output noise while maintaining the highest conversion rate. By leaving the Feedthrough (FT) control open (low), each rising edge of the convert (CONV) clock latches decoded data and control values into a D-type internal register. The registered data is then converted into the appropriate analog output by the switched current sinks. When FT is tied high, the control inputs and data are not registered. The analog output asynchronously tracks the input data and video controls. Feedthrough itself is asynchronous and usually used as a DC control. The controls and data have to be present at the input pins for a set-up time of ts before, and a hold time of th after, the rising edge of the clock (CONV) in order to be synchronously registered. The set-up and hold times are not important in the asynchronous mode. The minimum pulse widths high (tPWH) and low (tPWL) as well as settling time become the limiting factors. (See figure 3.) The video controls produce the output levels needed for horizontal blanking, frame synchronization, etc., to be compatible with video system standards as described in RS-343-A. Table II shows the video control effects on the analog output. Internal logic governs Blank, Sync, and Force High so that they override the data inputs as needed in video applications. Sync overrides both the data and other controls to produce full negative video output (figure 9). Reference White video level output is provided by Force High, which drives the internal digital data to full scale output or 100 IRE units. Bright gives an additional 10% of full scale value to the output level. This function can be used in graphic displays for highlighting menus, cursors or warning messages. Again, if the devices are used in non-video applications, the video controls can be left open. CONVERT CLOCK For best performance, the clock should be ECL driven, differentially, by utilizing CONV and CONV (figure 4). By driving the clock this way, clock noise and power supply/ output intermodulation will be minimized. The rising edge of the clock synchronizes the data and control inputs to the SPT1018. Since the actual switching threshold of CONV is determined by CONV, the clock can be driven single-ended by connecting a bias voltage to CONV . The switching threshold of CONV is set by this bias voltage. ANALOG OUTPUTS The SPT1018 has two analog outputs that are high impedance, complementary current sinks. The outputs vary in proportion to the input data, controls and reference current values so that the full scale output can be changed by setting ISet as mentioned earlier. In video applications, the outputs can drive a doubly terminated 50 or 75 ohm load to standard video levels. In the standard configuration of figure 5, the output voltage is the product of the output current and load impedance and is between 0 and -1.07 V. The Out- output (figure 9) will provide a video output waveform with the Sync pulse bottom at the -1.07 V level. The Out+ is inverted with Sync up. SPT SPT1018 7 5/14/97 Figure 4 - CONVert, CONVert Switching Levels V IDF 0.0 V V ICM MIN external load, such as two other DAC reference inputs. (See the SPT1019 data sheet). The circuits shown in figure 6 illustrate how a single SPT1019 may be used as a master reference in a system with multiple DACs (such as RGB). The other DACs are simply slaved from the SPT1019's reference output. The SPT1018s shown are especially well-suited to be slaved to a SPT1019 for a better TC tracking from DAC-to-DAC, since they are essentially SPT1019s without the reference. The SPT1018 is pin-compatible with the TDC1018, that does not have an internal reference. Although either the TDC1018 or the SPT1018 may be slaved from an SPT1019, the higher performance SPT1018 and the above mentioned DAC-to-DAC TC tracking is the best choice for new designs. No external reference is required for operation of the SPT1019, as this function is provided internally. The internal reference is a bandgap type and is suitable for operation over extended temperature ranges. The SPT1018 must use an external reference. -1.3 V CONV V ICM MAX CONV Figure 5A - Standard Load Video Monitor OUT- 75 COAX RS 75 RL 75 SPT1018 OUT + 75 COAX RS 75 RL 75 Inverse Video Figure 6 - Typical RGB Graphics System SPT1019 (Master) R SPT1018 (Slave) Ref+ Ref- G SPT1018 (Slave) Ref+ Ref- B Figure 5B - Test Load OUT + OUT CL <5 pF RL 37.5 Video Out 0 to -1 Volt ISet R1 R2 500 750 Ref Out IRef 500 750 500 750 ISet ISet 1 k ISet 1 k Figure 7 - Burn-In Circuit TYPICAL RGB GRAPHICS SYSTEM In an RGB graphics system, the color displayed is determined by the combined intensities of the red, green and blue (RGB) D/A converter outputs. A change in gain or offset in any of the RGB outputs will affect the apparent hue displayed on the CRT screen. Thus, it is very important that the outputs of the D/A converters track each other over a wide range of operating conditions. Since the D/A output is proportional to the product of the reference and digital input code, a common reference should be used to drive all three D/As in an RGB system to minimize RGB DAC-to-DAC mismatch and improve TC tracking. The SPT1019 contains an internal precision bandgap reference which completely eliminates the need for an external reference. The reference can supply up to 50 A to an -5.9 V (Max 200 mA) 6.5 6.5 24 Pin DIP All Resistors Are 5% 1/4 W cc Clock = -0.9 to -1.7 V, 100 kHz VEE Out1 k -1.2 V (Max 1.5 mA) Ref- (Max 50 mA) (Max 50 mA) Out+ 100 100 1 k Ref+ 1 k -1.3 V (Max 60 A) CONV CONV 1 k Clock (Max 60 A) VCC (Max 1.5 mA) SPT SPT1018 8 5/14/97 Figure 8 - DAC Output Circuit Current Sink #1 Current Sink #N Out+ Out- Reference Amplifier Ref+ Reference Current Ref- + - ISeg ISeg VEE Comp Figure 9 - Video Output Waveform for Standard Load IRE 110 100 0 mV -73 mV Bright Normal High (White) 256 Gray Levels Video Normal Low (Black) 7.5 0 -728 mV -781 mV Blank -40 -1071 mV Sync Figure 10 - Equivalent Input Circuits - Data, Clock, Controls and Reference VCC Ref- Conv Ref+ Reference Segment Switch Conv I Bias VEE Data and Controls V IBias IBias IBias VEE 80 k IBias VEE SPT SPT1018 9 5/14/97 PACKAGE OUTLINE 24-Lead PDIP SYMBOL INCHES MIN MAX 0.125 0.015 0.100 typ 0.055 0.008 0.150 typ 0.600 0.530 1.245 0.070 0.190 0.135 0.022 0.065 0.012 0.625 0.550 1.255 0.080 MILLIMETERS MIN MAX 4.83 3.18 0.38 2.54 typ 1.40 0.20 3.81 typ 15.24 13.46 31.62 1.78 3.43 0.56 1.65 0.30 15.88 13.97 31.88 2.03 K A B C D E F 24 I 1 G H I J K J H A G B F D C E SPT SPT1018 10 5/14/97 PIN ASSIGNMENTS PIN FUNCTIONS Name D3 D2 D1 D0 VEE CONV CONV FT VCC FH Blank BRT Sync RefRef+ COMP OutOut+ D7 D6 D5 D4 Function Data Bit 3 Data Bit 2 Data Bit 1 Data Bit 0 (LSB) Negative Supply Convert Clock Input Convert Clock Input Complement Register Feedthrough Control Positive Supply Data Force High Control Video Blank Input Video Bright Input Video Sync Input Reference Current - Input Reference Current + Input Compensation Input Output Current Negative Output Current Positive Data Bit 7 (MSB) Data Bit 6 Data Bit 5 Data Bit 4 D3 D2 D1 D0 VEE CONV CONV FT VCC FH Blank BRT 1 2 3 4 5 6 7 8 9 10 11 12 24 23 22 21 20 D4 D5 D6 D7 VEE Out + Out VCC Comp Ref+ RefSync PDIP 19 18 17 16 15 14 13 ORDERING INFORMATION PART NUMBER SPT1018AIN SPT1018BIN DESCRIPTION 8-BIT, 275 MWPS DAC 8-BIT, 165 MWPS DAC TEMPERATURE RANGE -25 to +85 C -25 to +85 C PACKAGE 24L PDIP 24L PDIP Signal Processing Technologies, Inc. reserves the right to change products and specifications without notice. Permission is hereby expressly granted to copy this literature for informational purposes only. Copying this material for any other use is strictly prohibited. WARNING - LIFE SUPPORT APPLICATIONS POLICY - SPT products should not be used within Life Support Systems without the specific written consent of SPT. A Life Support System is a product or system intended to support or sustain life which, if it fails, can be reasonably expected to result in significant personal injury or death. Signal Processing Technologies believes that ultrasonic cleaning of its products may damage the wire bonding, leading to device failure. It is therefore not recommended, and exposure of a device to such a process will void the product warranty. SPT SPT1018 11 5/14/97 |
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