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ISL76161
Data Sheet September 9, 2008 FN6720.1
12-Bit, +3.3V, 130MSPS, High Speed D/A Converter
The ISL76161 is a 12-bit, 130MSPS (Mega-Samples Per Second), CMOS, high speed, low power, D/A (digital to analog) converter, designed specifically for use in radar systems or high performance communication systems, such as base transceiver stations utilizing 2.5G or 3G cellular protocols.
Features
* High Speed. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 130MSPS * Low Power . . . . . 103mW with 20mA Output at 130MSPS * Adjustable Full Scale Output Current . . . . . 2mA to 20mA * Excellent Spurious Free Dynamic Range (73dBc to Nyquist, f S = 130MSPS, fOUT = 10MHz) * Automotive Qualified Component * Extended Temperature Operation: -40C to +105C
Pinout
ISL76161 (28 LD TSSOP) TOP VIEW
D11 (MSB) 1 D10 2 D9 3 D8 4 D7 5 D6 6 D5 7 D4 8 D3 9 D2 10 D1 11 D0 (LSB) 12 DCOM 13 DCOM 14 28 CLK 27 DVDD 26 DCOM 25 NC 24 AVDD 23 COMP 22 IOUTA 21 IOUTB 20 ACOM 19 NC 18 FSADJ 17 REFIO 16 REFLO 15 SLEEP
* +3.3V Power Supply * 3V LVCMOS Compatible Inputs * UMTS Adjacent Channel Power = 70dB at 19.2MHz * EDGE/GSM SFDR = 90dBc at 11MHz in 20MHz Window * Pb-Free (RoHS Compliant)
Applications
* Automotive Radar Systems - 24GHz and 77GHz Radar for Adaptive Cruise Control * Cellular Infrastructure - Single or Multi-Carrier: IS-136, IS-95, GSM, EDGE, CDMA2000, WCDMA, TDS-CDMA * Wireless Communication Systems * High Resolution Imaging Systems * Arbitrary Waveform Generators
Ordering Information
PART NUMBER (Note 1) ISL76161AVZ ISL76161AVZ-T* ISL76161AVZ-TK* PART MARKING ISL76161 AVZ ISL76161 AVZ ISL76161 AVZ CLOCK SPEED 130MHz 130MHz 130MHz TEMP. RANGE (C) -40 to +105 -40 to +105 -40 to +105 PACKAGE (Pb-Free, Note 2) 28 Ld TSSOP 28 Ld TSSOP Tape and Reel 28 Ld TSSOP Tape and Reel PKG. DWG. # M28.173 M28.173 M28.173
*Please refer to TB347 for details on reel specifications. NOTES: 1. These parts have been qualified in accordance with AECQ100 rev F recommendations, some exceptions may apply. Request qualification plan for further details. 2. These Intersil Pb-free plastic packaged products employ special Pb-free material sets, molding compounds/die attach materials, and 100% matte tin plate plus anneal (e3 termination finish, which is RoHS compliant and compatible with both SnPb and Pb-free soldering operations). Intersil Pb-free products are MSL classified at Pb-free peak reflow temperatures that meet or exceed the Pb-free requirements of IPC/JEDEC J STD-020.
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CAUTION: These devices are sensitive to electrostatic discharge; follow proper IC Handling Procedures. 1-888-INTERSIL or 1-888-468-3774 | Intersil (and design) is a registered trademark of Intersil Americas Inc. Copyright Intersil Americas Inc. 2008. All Rights Reserved All other trademarks mentioned are the property of their respective owners.
ISL76161 Typical Applications Circuit
ISL76161 (25, 19) NC D11 D10 D9 D8 D7 D6 D5 D4 D3 D2 D1 D0 D11 (MSB) (1) D10 (2) D9 (3) D8 (4) D7 (5) D6 (6) D5 (7) D4 (8) D3 (9) D2 (10) D1 (11) D0 (LSB) (12) CLK (28) DCOM (26, 13, 14) (20) ACOM BEAD + 10F 10H 0.1F DVDD (27) (24) AVDD (23) COMP 0.1F FERRITE BEAD 10H 0.1F 10F + +3.3V (VDD) 1:1, Z1:Z2 (22) IOUTA (21) IOUTB 50 (18) FSADJ RSET (50) REPRESENTS ANY 50 LOAD 1.94k (15) SLEEP (16) REFLO (17) REFIO 0.1F ONE CONNECTION DCOM ACOM
50
Functional Block Diagram
IOUTA IOUTB
CASCODE (LSB) D0 D1 D2 D3 D4 D5 D6 D7 D8 D9 UPPER 5-BIT DECODER COMP CLK INT/EXT VOLTAGE REFERENCE 38 SWITCH MATRIX 38 INPUT LATCH CURRENT SOURCE
7 LSBs + 31 MSB SEGMENTS
D10
D11
BIAS GENERATION
REFLO REFIO
FSADJ
SLEEP
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FN6720.1 September 9, 2008
ISL76161 Pin Descriptions
PIN NO. 1 through 12 PIN NAME D11 (MSB) through D0 (LSB) SLEEP DESCRIPTION Digital Data Bit 11, (Most Significant Bit) through Digital Data Bit 0, (Least Significant Bit).
15
Control Pin for Power-Down mode. Sleep Mode is active high; Connect to ground for Normal Mode. Sleep pin has internal 20A active pull-down current. Connect to analog ground to enable internal 1.2V reference or connect to AVDD to disable internal reference. Reference voltage input if internal reference is disabled. Reference voltage output if internal reference is enabled. Use 0.1F cap to ground when internal reference is enabled. Full Scale Current Adjust. Use a resistor to ground to adjust full scale output current. Full Scale Output Current = 32 x VFSADJ/RSET. No Connect. These should be grounded, but can be left disconnected. The complementary current output of the device. Full scale output current is achieved when all input bits are set to binary 0. Current output of the device. Full scale output current is achieved when all input bits are set to binary 1. Connect 0.1F capacitor to ACOM. Analog Supply (+3.0V to +3.6V). Connect to Analog Ground. Connect to Digital Ground. Digital Supply (+3.0V to +3.6V). Clock Input.
16
REFLO
17
REFIO
18
FSADJ
19, 25 21
NC IOUTB
22 23 24 20 13, 14, 26 27 28
IOUTA COMP AVDD ACOM DCOM DVDD CLK
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ISL76161
Absolute Maximum Ratings
Digital Supply Voltage DVDD to DCOM . . . . . . . . . . . . . . . . . +4.0V Analog Supply Voltage AVDD to ACOM. . . . . . . . . . . . . . . . . . +4.0V Grounds, ACOM TO DCOM . . . . . . . . . . . . . . . . . . . -0.3V to +0.3V Digital Input Voltages (D9-D0, CLK, SLEEP). . . . . . . . DVDD + 0.3V Reference Input Voltage Range. . . . . . . . . . . . . . . . . . AVDD + 0.3V Analog Output Current (IOUT) . . . . . . . . . . . . . . . . . . . . . . . . . 24mA
Thermal Information
Thermal Resistance (Typical, Note 3) JA(C/W) TSSOP Package . . . . . . . . . . . . . . . . . . . . . . . . . . . 84 Maximum Junction Temperature . . . . . . . . . . . . . . . . . . . . . . +150C Maximum Storage Temperature Range . . . . . . . . . .-65C to +150C Pb-Free Reflow Profile. . . . . . . . . . . . . . . . . . . . . . . . .see link below http://www.intersil.com/pbfree/Pb-FreeReflow.asp
Operating Conditions
Temperature Range . . . . . . . . . . . . . . . . . . . . . . . . .-40C to +105C
CAUTION: Do not operate at or near the maximum ratings listed for extended periods of time. Exposure to such conditions may adversely impact product reliability and result in failures not covered by warranty.
NOTE: 3. JA is measured with the component mounted on a high effective thermal conductivity test board in free air. See Tech Brief TB379 for details.
Electrical Specifications
AVDD = DVDD = +3.3V, VREF = Internal 1.2V, IOUTFS = 20mA, TA = +25C for All Typical Values; Parameters with MIN and/or MAX limits are 100% tested at +25C, unless otherwise specified. Temperature limits established by characterization and are not production tested. TA = -40C TO +105C
PARAMETER SYSTEM PERFORMANCE Resolution Integral Linearity Error, INL Differential Linearity Error, DNL Offset Error, IOS Offset Drift Coefficient Full Scale Gain Error, FSE
TEST CONDITIONS
MIN
TYP
MAX
UNITS
12 "Best Fit" Straight Line (Note 9) (Note 9) IOUTA (Note 9) (Note 9) With External Reference (Notes 4, 9) With Internal Reference (Notes 4, 9) -1.25 -1 -0.006 -3 -
0.5 0.5 0.1 0.5 0.5 50 100 20 2 1.25 -1.0
+1.25 +1 +0.006 +3 -
Bits LSB LSB % FSR ppm FSR/C % FSR % FSR ppm FSR/C ppm FSR/C mA mA V V
Full Scale Gain Drift
With External Reference (Note 9) With Internal Reference (Note 9)
Full Scale Output Current, IFS
RSET = 1.94k (Maximum FS output) RSET = 20k (Minimum FS output)
Output Voltage Compliance - High Voltage Limit Output Voltage Compliance - Low Voltage Limit DYNAMIC CHARACTERISTICS Maximum Clock Rate, fCLK Output Rise Time Output Fall Time Output Capacitance Output Noise IOUTFS = 20mA IOUTFS = 2mA Full Scale Step Full Scale Step
130 -
150 1.5 1.5 10 50 30
-
MHz ns ns pF pA/Hz pA/Hz
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ISL76161
Electrical Specifications
AVDD = DVDD = +3.3V, VREF = Internal 1.2V, IOUTFS = 20mA, TA = +25C for All Typical Values; Parameters with MIN and/or MAX limits are 100% tested at +25C, unless otherwise specified. Temperature limits established by characterization and are not production tested. (Continued) TA = -40C TO +105C PARAMETER TEST CONDITIONS MIN TYP MAX UNITS
AC CHARACTERISTICS (Using Figure 12 with RDIFF = 100, RLOAD = RA = RB = 50, Full Scale Output = -2.0dBm) Spurious Free Dynamic Range, SFDR Within a Window Spurious Free Dynamic Range, SFDR to Nyquist (fCLK/2) fCLK = 130MSPS, fOUT = 20.2MHz, 20MHz Span (Notes 6, 8) fCLK = 130MSPS, fOUT = 50.5MHz (Notes 6, 8) fCLK = 130MSPS, fOUT = 40.4MHz (Notes 6, 8) fCLK = 130MSPS, fOUT = 20.2MHz (Notes 6, 9) fCLK = 130MSPS, fOUT = 10.1MHz (Notes 6, 8) fCLK = 130MSPS, fOUT = 5.05MHz, T = +25C (Notes 6, 8) fCLK = 130MSPS, fOUT = 5.05MHz, T = -40C to +105C (Notes 6, 8) fCLK = 100MSPS, fOUT = 40.4MHz (Notes 6, 8) fCLK = 80MSPS, fOUT = 30.3MHz (Notes 6, 8) fCLK = 80MSPS, fOUT = 20.2MHz (Notes 6, 8) fCLK = 80MSPS, fOUT = 10.1MHz (Notes 6, 8, 10) fCLK = 80MSPS, fOUT = 5.05MHz (Notes 6, 8) fCLK = 50MSPS, fOUT = 20.2MHz (Notes 6, 8) fCLK = 50MSPS, fOUT = 10.1MHz (Notes 6, 8) fCLK = 50MSPS, fOUT = 5.05MHz (Notes 6, 8) Spurious Free Dynamic Range, SFDR in a Window with Eight Tones fCLK = 130MSPS, fOUT = 17.5MHz to 27.9MHz, 1.3MHz Spacing, 35MHz Span (Notes 6, 8) fCLK = 80MSPS, fOUT = 10.8MHz to 17.2MHz, 811kHz Spacing, 15MHz Span (Notes 6, 8) fCLK = 50MSPS, fOUT = 6.7MHz to 10.8MHz, 490kHz Spacing, 10MHz Span (Notes 6, 8) Spurious Free Dynamic Range, fCLK = 78MSPS, fOUT = 11MHz, in a 20MHz Window, RBW = 30kHz SFDR in a Window with EDGE or GSM (Notes 6, 8, 10) Adjacent Channel Power Ratio, ACPR with UMTS VOLTAGE REFERENCE Internal Reference Voltage, VFSADJ Internal Reference Voltage Drift Internal Reference Output Current Sink/Source Capability Reference Input Impedance Reference Input Multiplying Bandwidth (Note 8) DIGITAL INPUTS D11-D0, CLK (Note 5) (Note 5) 0.7 * DVDD -25 -20 -10 0.3 * DVDD +25 +20 +10 V V A A A Reference is not intended to be externally loaded Pin 18 Voltage with Internal Reference 1.2 1.23 40 0 1 1.0 1.3 V ppm/C A M MHz fCLK = 76.8MSPS, fOUT = 19.2MHz, RBW = 30kHz (Notes 6, 8, 10) 70 67 85 57 62 69 73 77 60 63 69 70 76 68 73 77 68 75 77 90 70 dBc dBc dBc dBc dBc dBc dBc dBc dBc dBc dBc dBc dBc dBc dBc dBc dBc dBc dBc dB
Input Logic High Voltage with 3.3V Supply, VIH Input Logic Low Voltage with 3.3V Supply, VIL Sleep Input Current, IIH Input Logic Current, IIH, IL Clock Input Current, IIH, IL
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ISL76161
Electrical Specifications
AVDD = DVDD = +3.3V, VREF = Internal 1.2V, IOUTFS = 20mA, TA = +25C for All Typical Values; Parameters with MIN and/or MAX limits are 100% tested at +25C, unless otherwise specified. Temperature limits established by characterization and are not production tested. (Continued) TA = -40C TO +105C PARAMETER Digital Input Capacitance, CIN TIMING CHARACTERISTICS Data Setup Time, tSU Data Hold Time, tHLD Propagation Delay Time, tPD Minimum CLK Pulse Width, tPW1 , tPW2 See Figure 13 See Figure 13 See Figure 13 See Figure 13, (Note 11) 1.5 1.5 1 2 ns ns Clock Period ns TEST CONDITIONS MIN TYP 5 MAX UNITS pF
POWER SUPPLY CHARACTERISTICS (Note 5) AVDD Power Supply DVDD Power Supply Analog Supply Current (IAVDD) (Note 9) (Note 9) 3.3V, IOUTFS = 20mA 3.3V, IOUTFS = 2mA Digital Supply Current (IDVDD) Supply Current (IAVDD) Sleep Mode Power Dissipation 3.3V (Note 7) 3.3V, IOUTFS = Don't Care 3.3V, IOUTFS = 20mA (Note 7) 3.3V, IOUTFS = 20mA 3.3V, IOUTFS = 2mA (Note 7) Power Supply Rejection NOTES: 4. Gain Error measured as the error in the ratio between the full scale output current and the current through RSET (typically 625A). Ideally, the ratio should be 32. 5. Power supply current measurements are performed with all digital inputs at either DVDD or DCOM 6. Spectral measurements made with differential transformer coupled output and no external filtering. For multitone testing, the same pattern was used at different clock rates, producing different output frequencies but at the same ratio to the clock rate. 7. Measured with the clock at 130MSPS and the output frequency at 5MHz. 8. See "Definition of Specifications" on page 9. 9. Recommended operation is from 3.0V to 3.6V. Operation below 3.0V is possible with some degradation in spectral performance. Reduction in analog output current may be necessary to maintain spectral performance. 10. See "Typical Performance" plots on page 7. 11. Tested in production with a clock pulse width of 50% duty cycle. Single Supply (Note 8) 2.7 2.7 -0.125 3.3 3.3 27.5 10 3.7 1.5 103 110 45 3.6 3.6 28.5 5 111 120 +0.125 V V mA mA mA mA mW mW mW %FSR/V
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FN6720.1 September 9, 2008
ISL76161 Typical Performance (+3.3V Supply, Using Figure 11 with RDIFF = 100 and RLOAD = 50)
SPECTRAL MASK FOR GSM900/DCS1800/PCS1900 P > 43dBm NORMAL BTS WITH 30kHz RBW
FIGURE 1. EDGE AT 11MHz, 78MSPS CLOCK (91+dBc @ f = +6MHz)
FIGURE 2. EDGE AT 11MHz, 78MSPS CLOCK (75dBc - NYQUIST, 6dB PAD)
SPECTRAL MASK FOR GSM900/DCS1800/PCS1900 P > 43dBm NORMAL BTS WITH 30kHz RBW
FIGURE 3. GSM AT 11MHz, 78MSPS CLOCK (90+dBc @ f = +6MHz, 3dB PAD)
FIGURE 4. GSM AT 11MHz, 78MSPS CLOCK (75dBc - NYQUIST, 9dB PAD)
FIGURE 5. FOUR EDGE CARRIERS AT 12.4MHz TO 15.6MHz, 800kHz SPACING, 78MSPS (71dBc - 20MHz WINDOW)
FIGURE 6. FOUR GSM CARRIERS AT 12.4MHz TO 15.6MHz, 78MSPS (73dBc - 20MHz WINDOW, 6dB PAD)
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ISL76161 Typical Performance (+3.3V Supply, Using Figure 11 with RDIFF = 100 and RLOAD = 50)
(Continued)
SPECTRAL MASK UMTS TDD P > 43dBm BTS
FIGURE 7. UMTS AT 19.2MHz, 76.8MSPS (70dB 1stACPR, 70dB 2ndACPR)
FIGURE 8. ONE TONE AT 10.1MHz, 80MSPS CLOCK (71dBc - NYQUIST, 6dB PAD)
FIGURE 9. TWO TONES (CkHzF = 6) AT 8.5MHz, 50MSPS CLOCK, 500kHz SPACING (82dBc - 10MHz WINDOW, 6dB PAD)
FIGURE 10. FOUR TONES (CF = 8.1) AT 14MHz, 80MSPS CLOCK, 800kHz SPACING (70dBc - NYQUIST, 6dB PAD)
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ISL76161 Definition of Specifications
Adjacent Channel Power Ratio, ACPR, is the ratio of the average power in the adjacent frequency channel (or offset) to the average power in the transmitted frequency channel. Differential Linearity Error, DNL, is the measure of the step size output deviation from code to code. Ideally, the step size should be 1 LSB. A DNL specification of 1 LSB or less guarantees monotonicity. EDGE, Enhanced Data for Global Evolution, a TDMA standard for cellular applications which uses 200kHz BW, 8-PSK modulated carriers. Full Scale Gain Drift, is measured by setting the data inputs to be all logic high (all 1s) and measuring the output voltage through a known resistance as the temperature is varied from TMIN to TMAX . It is defined as the maximum deviation from the value measured at room temperature to the value measured at either TMIN or TMAX . The units are ppm of FSR (full scale range) per C. Full Scale Gain Error, is the error from an ideal ratio of 32 between the output current and the full scale adjust current (through RSET). GSM, Global System for Mobile Communication, a TDMA standard for cellular applications which uses 200kHz BW, GMSK modulated carriers. Integral Linearity Error, INL, is the measure of the worst case point that deviates from a best fit straight line of data values along the transfer curve. Internal Reference Voltage Drift, is defined as the maximum deviation from the value measured at room temperature to the value measured at either TMIN or TMAX . The units are ppm per C. Offset Drift, is measured by setting the data inputs to all logic low (all 0s) and measuring the output voltage at IOUTA through a known resistance as the temperature is varied from TMIN to TMAX . It is defined as the maximum deviation from the value measured at room temperature to the value measured at either TMIN or TMAX . The units are ppm of FSR (full scale range) per C. Offset Error, is measured by setting the data inputs to all logic low (all 0s) and measuring the output voltage of IOUTA through a known resistance. Offset error is defined as the maximum deviation of the IOUTA output current from a value of 0mA. Output Voltage Compliance Range, is the voltage limit imposed on the output. The output impedance should be chosen such that the voltage developed does not violate the compliance range. Power Supply Rejection, is measured using a single power supply. The nominal supply voltage is varied 10% and the change in the DAC full scale output is noted. 9 Reference Input Multiplying Bandwidth, is defined as the 3dB bandwidth of the voltage reference input. It is measured by using a sinusoidal waveform as the external reference with the digital inputs set to all 1s. The frequency is increased until the amplitude of the output waveform is 0.707 (-3dB) of its original value. Spurious Free Dynamic Range, SFDR, is the amplitude difference from the fundamental signal to the largest harmonically or non-harmonically related spur within the specified frequency window. Total Harmonic Distortion, THD, is the ratio of the RMS value of the fundamental output signal to the RMS sum of the first five harmonic components. UMTS, Universal Mobile Telecommunications System, a W-CDMA standard for cellular applications which uses 3.84MHz modulated carriers.
Detailed Description
The ISL76161 is a 12-bit, current out, CMOS, digital to analog converter. The maximum update rate is at least 130MSPS and can be powered by a single power supply in the recommended range of +3.0V to +3.6V. Operation with clock rates higher than 130MSPS is possible; please contact the factory for more information. It consumes less than 120mW of power when using a +3.3V supply, the maximum 20mA of output current, and the data switching at 130MSPS. The architecture is based on a segmented current source arrangement that reduces glitch by reducing the amount of current switching at any one time. In previous architectures that contained all binary weighted current sources or a binary weighted resistor ladder, the converter may have had a substantially larger amount of current turning on and off at certain, worst-case transition points, such as midscale and quarter scale transitions. By greatly reducing the amount of current switching at these major transitions, the overall glitch of the converter is dramatically reduced, improving settling time, transient problems, and accuracy.
Digital Inputs and Termination
The ISL76161 digital inputs are guaranteed to 3V LVCMOS levels. The internal register is updated on the rising edge of the clock. To minimize reflections, proper transmission line termination should be implemented. If the lines driving the clock and the digital inputs are long 50 lines, then proper transmission line termination techniques should be used. Termination is not likely needed as long as the digital waveform source is within a few inches of the DAC. For digital drivers with very high speed edge rates, it is recommended that the user consider series resistors (50 to 200) immediately prior to the DAC's inputs in order to reduce the amount of noise.
Power Supply
Separate digital and analog power supplies are recommended. The allowable supply range is +2.7V to +3.6V. The
FN6720.1 September 9, 2008
ISL76161
recommended supply range is +3.0 to 3.6V (nominally +3.3V) to maintain optimum SFDR. However, operation down to +2.7V is possible with some degradation in SFDR. Reducing the analog output current can help the SFDR at +2.7V. The SFDR values stated in the "Electrical Specifications" table on page 4 were obtained with a +3.3V supply.
Analog Output
IOUTA and IOUTB are complementary current outputs. The sum of the two currents is always equal to the full scale output current minus one LSB. If single ended use is desired, a load resistor can be used to convert the output current to a voltage. It is recommended that the unused output be either grounded or equally terminated. The voltage developed at the output must not violate the nominal output voltage compliance range of -1.0V to 1.25V. ROUT (the impedance loading each current output) should be chosen so that the desired output voltage is produced in conjunction with the output full scale current. If a known line impedance is to be driven, then the output load resistor should be chosen to match this impedance. The output voltage equation is:
V OUT = I OUT x R OUT (EQ. 2)
Ground Planes
Separate digital and analog ground planes should be used. All of the digital functions of the device and their corresponding components should be located over the digital ground plane and terminated to the digital ground plane. The same is true for the analog components and the analog ground plane.
Noise Reduction
To minimize power supply noise, 0.1F capacitors should be placed as close as possible to the converter's power supply pins, AVDD and DVDD . Also, the layout should be designed using separate digital and analog ground planes and these capacitors should be terminated to the digital ground for DVDD and to the analog ground for AVDD . Additional filtering of the power supplies on the board is recommended.
The most effective method for reducing the power consumption is to reduce the analog output current, which dominates the supply current. The maximum recommended output current is 20mA.
Voltage Reference
The internal voltage reference of the device has a nominal value of +1.23V with a 40ppm/C drift coefficient over the full temperature range of the converter. It is recommended that a 0.1F capacitor be placed as close as possible to the REFIO pin, connected to the analog ground. The REFLO pin (16) selects the reference. The internal reference can be selected if pin 16 is tied low (ground). If an external reference is desired, then pin 16 should be tied high (the analog supply voltage) and the external reference driven into REFIO, pin 17. The full scale output current of the converter is a function of the voltage reference used and the value of RSET. IOUT should be within the 2mA to 20mA range, though operation below 2mA is possible, with performance degradation. If the internal reference is used, VFSADJ will equal approximately 1.2V (pin 18). If an external reference is used, VFSADJ will equal the external reference. The calculation for IOUT (Full Scale) is:
I OUT ( Full Scale ) = ( V FSADJ R ) x 32 SET (EQ. 1)
Differential Output
IOUTA and IOUTB can be used in a differential-tosingle-ended arrangement to achieve better harmonic rejection. With RDIFF = 50 and RLOAD = 50, the circuit in Figure 11 will provide a 500mVP-P (-2dBm) signal at the output of the transformer if the full scale output current of the DAC is set to 20mA (used for the "Electrical Specifications" table on page 4). Values of RDIFF = 100 and RLOAD = 50 were used for the "Typical Performance" curves on page 7. The center tap in Figure 11 must be grounded. In the circuit in Figure 12, the user is left with the option to ground or float the center tap. The DC voltage that will exist at either IOUTA or IOUTB if the center tap is floating is IOUTDC x 2 x (RA//RB) V because RDIFF is DC shorted by the transformer, and the DC currents from each output add constructively. If the center tap is grounded, the DC voltage is 0V. Recommended values for the circuit in Figure 12 are RA = RB = 50, RDIFF = 100, assuming RLOAD = 50. The performance of Figure 11 and Figure 12 is basically the same, however leaving the center tap of Figure 12 floating allows the circuit to find a more balanced virtual ground, theoretically improving the even order harmonic rejection, but likely reducing the signal swing available due to the output voltage compliance range limitations.
If the full scale output current is set to approximately 20mA by using the internal voltage reference (1.2V) and a 1.94k RSET resistor, then the input coding to output current will resemble those shown in Table 1.
TABLE 1. INPUT CODING vs. OUTPUT CURRENT WITH INTERNAL REFERENCE AND RSET = 1.91k INPUT CODE (D11-D0) 11 11111 11111 10 00000 00000 00 00000 00000 IOUTA (mA) 20 10 0 IOUTB (mA) 0 10 20
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ISL76161
REQ = 0.5 x (RLOAD // RDIFF) AT EACH OUTPUT VOUT = (2 x IOUTA x REQ)V 1:1 RDIFF IOUTA RLOAD
Propagation Delay
The converter requires two clock rising edges for data to be represented at the output. Each rising edge of the clock captures the present data word and outputs the previous data. The propagation delay is therefore 1/CLK, plus <2ns of settling. See Figure 13.
PIN 21 PIN 22 ISL76161
IOUTB
RLOAD REPRESENTS THE LOAD SEEN BY THE TRANSFORMER
FIGURE 11. OUTPUT LOADING FOR DATASHEET MEASUREMENTS
REQ = RA // [ 0.5 x (RLOAD // RDIFF) ], WHERE RA=RB AT EACH OUTPUT RA PIN 21 PIN 22 ISL76161 IOUTB RDIFF IOUTA RB VOUT = (2 x IOUTA x REQ)V RLOAD
RLOAD REPRESENTS THE LOAD SEEN BY THE TRANSFORMER
FIGURE 12. ALTERNATIVE OUTPUT LOADING
Timing Diagram
tPW1
tPW2
CLK
50%
tSU tHLD D11-D0 W0
tSU tHLD W1
tSU tHLD W2 W3
tPD
tPD OUTPUT = W0
IOUT
OUTPUT = W-1
OUTPUT = W1
FIGURE 13. PROPAGATION DELAY, SETUP TIME, HOLD TIME AND MINIMUM PULSE WIDTH DIAGRAM
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FN6720.1 September 9, 2008
ISL76161 Thin Shrink Small Outline Plastic Packages (TSSOP)
N INDEX AREA E E1 -B1 2 3 L 0.05(0.002) -AD -CSEATING PLANE A 0.25 0.010 GAUGE PLANE 0.25(0.010) M BM
M28.173
28 LEAD THIN SHRINK SMALL OUTLINE PLASTIC PACKAGE INCHES SYMBOL A A1 A2 b c MIN 0.002 0.031 0.0075 0.0035 0.378 0.169 MAX 0.047 0.006 0.051 0.0118 0.0079 0.386 0.177 MILLIMETERS MIN 0.05 0.80 0.19 0.09 9.60 4.30 MAX 1.20 0.15 1.05 0.30 0.20 9.80 4.50 NOTES 9 3 4 6 7 8o Rev. 0 6/98
A1 0.10(0.004) A2 c
D E1 e E L
e
b 0.10(0.004) M C AM BS
0.026 BSC 0.246 0.0177 28 0o 8o 0.256 0.0295
0.65 BSC 6.25 0.45 28 0o 6.50 0.75
NOTES: 1. These package dimensions are within allowable dimensions of JEDEC MO-153-AE, Issue E. 2. Dimensioning and tolerancing per ANSI Y14.5M-1982. 3. Dimension "D" does not include mold flash, protrusions or gate burrs. Mold flash, protrusion and gate burrs shall not exceed 0.15mm (0.006 inch) per side. 4. Dimension "E1" does not include interlead flash or protrusions. Interlead flash and protrusions shall not exceed 0.15mm (0.006 inch) per side. 5. The chamfer on the body is optional. If it is not present, a visual index feature must be located within the crosshatched area. 6. "L" is the length of terminal for soldering to a substrate. 7. "N" is the number of terminal positions. 8. Terminal numbers are shown for reference only. 9. Dimension "b" does not include dambar protrusion. Allowable dambar protrusion shall be 0.08mm (0.003 inch) total in excess of "b" dimension at maximum material condition. Minimum space between protrusion and adjacent lead is 0.07mm (0.0027 inch). 10. Controlling dimension: MILLIMETER. Converted inch dimensions are not necessarily exact. (Angles in degrees)
N
All Intersil U.S. products are manufactured, assembled and tested utilizing ISO9000 quality systems. Intersil Corporation's quality certifications can be viewed at www.intersil.com/design/quality
Intersil products are sold by description only. Intersil Corporation reserves the right to make changes in circuit design, software and/or specifications at any time without notice. Accordingly, the reader is cautioned to verify that data sheets are current before placing orders. Information furnished by Intersil is believed to be accurate and reliable. However, no responsibility is assumed by Intersil or its subsidiaries for its use; nor for any infringements of patents or other rights of third parties which may result from its use. No license is granted by implication or otherwise under any patent or patent rights of Intersil or its subsidiaries.
For information regarding Intersil Corporation and its products, see www.intersil.com 12
FN6720.1 September 9, 2008

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