DAC5662 www.ti.com SLAS425 – JULY 2004 DUAL, 12-BIT 200 MSPS DIGITAL-TO-ANALOG CONVERTER FEATURES APPLICATIONS • • • • • • • • • • • • • 12-Bit Dual Transmit DAC 200 MSPS Update Rate Single Supply: 3.0 V - 3.6 V High SFDR: 85 dBc at 5 MHz High IMD3: 78 dBc at 15.1 and 16.1 MHz WCDMA ACLR: 70 dB at 30.72 MHz Independent or Single Resistor Gain Control Dual or Interleaved Data On-Chip 1.2-V Reference Low Power: 330 mW Power-Down Mode: 15 mW Package: 48-Pin TQFP • • • • Cellular Base Transceiver Station Transmit Channel – CDMA: W-CDMA, CDMA2000, IS-95 – TDMA: GSM, IS-136, EDGE/UWC-136 Medical/Test Instrumentation Arbitrary Waveform Generators (ARB) Direct Digital Synthesis (DDS) Cable Modem Termination System (CMTS) WRTB WRTA CLKB CLKA DE MUX IOUTA1 Latch A 12−b DAC DA[11:0] IOUTA2 BIASJ_A IOUTB1 Latch B DB[11:0] 12−b DAC MODE IOUTB2 BIASJ_B GSET 1.2 V Reference EXTIO SLEEP DVDD DGND AVDD AGND Figure 1. DESCRIPTION The DAC5662 is a monolithic, dual-channel 12-bit high-speed digital-to-analog converter (DAC) with on-chip voltage reference. Operating with update rates of up to 200 MSPS, the DAC5662 offers exceptional dynamic performance and tight-gain and offset matching, characteristics that make it suitable in either I/Q baseband or direct IF communication applications. Each DAC has a high-impedance differential current output, suitable for single-ended or differential analog-output configurations. External resistors allow scaling the full-scale output current for each DAC separately or together, typically between 2 mA and 20 mA. An accurate on-chip voltage reference is temperature compensated and delivers a stable 1.2-V reference voltage. Optionally, an external reference may be used. The DAC5662 has two 12-bit parallel input ports with separate clocks and data latches. For flexibility, the DAC5662 also supports multiplexed data for each DAC on one port when operating in the interleaved mode. The DAC5662 has been specifically designed for a differential transformer coupled output with a 50-Ω doubly terminated load. For a 20-mA full-scale output current a 4:1 impedance ratio (resulting in an output power of 4 dBm) and 1:1 impedance ratio transformer (-2 dBm output power) are supported. Please be aware that an important notice concerning availability, standard warranty, and use in critical applications of Texas Instruments semiconductor products and disclaimers thereto appears at the end of this data sheet. PRODUCTION DATA information is current as of publication date. Products conform to specifications per the terms of the Texas Instruments standard warranty. Production processing does not necessarily include testing of all parameters. Copyright © 2004, Texas Instruments Incorporated DAC5662 www.ti.com SLAS425 – JULY 2004 The DAC5662 is available in a 48-pin thin quad FlatPack (TQFP). Pin compatibility between family members provides 12-bit (DAC5662) and 14-bit (DAC5672) resolution. Furthermore, the DAC5662 is pin compatible to the DAC2902 and AD9765 dual DACs. The device is characterized for operation over the industrial temperature range of -40 °C to 85 °C. AVAILABLE OPTIONS TA PACKAGED DEVICES 48-TQFP -40°C to 85°C DAC5662IPFB DAC5662IPFBR MODE AVDD IOUTA1 IOUTA2 BIASJ_A EXTIO GSET BIASJ_B IOUTB2 IOUTB1 AGND SLEEP DEVICE INFORMATION 48 47 46 45 44 43 42 41 40 39 38 37 1 36 2 35 3 34 33 4 5 Top View 48−Pin TQFP PFB Package 6 7 32 31 30 8 29 9 28 10 27 11 26 25 12 13 14 15 16 17 18 19 20 21 22 23 24 NC NC DB0 (LSB) DB1 DB2 DB3 DB4 DB5 DB6 DB7 DB8 DB9 NC NC DGND DVDD WRTA/WRTIQ CLKA/CLKIQ CLKB/RESETIQ WRTB/SELECTIQ DGND DVDD DB11 (MSB) DB10 DA11 (MSB) DA10 DA9 DA8 DA7 DA6 DA5 DA4 DA3 DA2 DA1 DA0 (LSB) TERMINAL FUNCTIONS TERMINAL I/O DESCRIPTION 38 I Analog ground 47 I Analog supply voltage BIASJ_A 44 O Full-scale output current bias for DACA BIASJ_B 41 O Full-scale output current bias for DACB CLKA/CLKIQ 18 I Clock input for DACA, CLKIQ in interleaved mode. CLKB/RESETI Q 19 I Clock input for DACB, RESETIQ in interleaved mode. DA[11:0] 1-12 I Data port A. DA11 is MSB and DA0 is LSB. DB[11:0] 23-34 I Data port B. DB11 is MSB and DB0 is LSB. DGND 15, 21 I Digital ground DVDD 16, 22 I Digital supply voltage EXTIO 43 I/O NAME NO. AGND AVDD 2 Internal reference output (bypass with 0.1 µF to AGND) or external reference input. DAC5662 www.ti.com SLAS425 – JULY 2004 DEVICE INFORMATION (continued) TERMINAL FUNCTIONS (continued) TERMINAL I/O DESCRIPTION NAME NO. GSET 42 I Gain-setting mode: H - 1 resistor, L - 2 resistors. Internal pullup. IOUTA1 46 O DACA current output. Full-scale with all bits of DA high. IOUTA2 45 O DACA complementary current output. Full-scale with all bits of DA low. IOUTB1 39 O DACB current output. Full-scale with all bits of DB high. IOUTB2 40 O DACB complementary current output. Full-scale with all bits of DB low. MODE 48 I Mode Select: H – Dual Bus, L – Interleaved. Internal pullup. 13, 14, 35, 36 - No connection SLEEP 37 I Sleep function control input: H – DAC in power-down mode, L – DAC in operating mode. Internal pulldown. WRTA/WRTIQ 17 I Input write signal for PORT A (WRTIQ in interleaving mode). WRTB/SELEC TIQ 20 I Input write signal for PORT B (SELECTIQ in interleaving mode). NC 3 DAC5662 www.ti.com SLAS425 – JULY 2004 ABSOLUTE MAXIMUM RATINGS over operating free-air temperature range (unless otherwise noted) (1) UNIT AVDD (2) Supply voltage range -0.5 V to 4 V DVDD (3) -0.5 V to 4 V Voltage between AGND and DGND -0.5 V to 0.5 V Voltage between AVDD and DVDD -0.5 V to 0.5 V Supply voltage range DB[11:0] (3) -0.5 V to DVDD + 0.5 V MODE, CLKA, CLKB, WRTA, WRTB (3) -0.5 V to DVDD + 0.5 V IOUTA1, IOUTA2, IOUTB1, IOUTB2 (2) -1.0 V to AVDD + 0.5 V SLEEP (2) -0.5 V to AVDD + 0.5 V DA[11:0] and EXTIO, BIASJ_A, BIASJ_B, Peak input current (any input) +20 mA Peak total input current (all inputs) -30 mA Operating free-air temperature range -40 °C to 85 °C Storage temperature range -65 °C to 150 °C 260 °C Lead temperature 1,6 mm (1/16 inch) from the case for 10 seconds (1) (2) (3) Stresses beyond those listed under “absolute maximum ratings” may cause permanent damage to the device. These are stress ratings only and functional operation of these or any other conditions beyond those indicated under “recommended operating conditions” is not implied. Exposure to absolute-maximum-rated conditions for extended periods may affect device reliability. Measured with respect to AGND. Measured with respect to DGND. ELECTRICAL CHARACTERISTICS over operating free-air temperature range, AVDD = DVDD = 3.3 V, IOUTFS = 20 mA, independent gain set mode (unless otherwise noted) PARAMETER TEST CONDITIONS MIN TYP MAX UNIT DC Specifications Resolution DC 12 Bits Accuracy (1) INL Integral nonlinearity DNL Differential nonlinearity 1 LSB = IOUTFS/212, TA = 25°C -2 ±0.3 2 LSB -2 ±0.2 2 LSB Analog Output Offset error Gain error 0.03 %FSR With external reference ±0.25 %FSR With internal reference ±0.5 %FSR current (2) 2 Maximum full-scale output current (2) 20 Minimum full-scale output Gain mismatch Output voltage compliance range (3) RO Output resistance CO Output capacitance With internal reference -2 0.07 -1 mA mA +2 1.25 %FSR V 300 kΩ 5 pF Reference Output Reference voltage Reference output current (4) (1) (2) (3) (4) 4 1.14 1.2 100 1.26 V nA Measured differentially through 50 Ω to AGND. Nominal full-scale current, IOUTFS, equals 32x the IBIAS current. The lower limit of the output compliance is determined by the CMOS process. Exceeding this limit may result in transistor breakdown, resulting in reduced reliability of the DAC5662 device. The upper limit of the output compliance is determined by the load resistors and full-scale output current. Exceeding the upper limit adversely affects distortion performance and intergral nonlinearity. Use an external buffer amplifier with high impedance input to drive any external load. DAC5662 www.ti.com SLAS425 – JULY 2004 ELECTRICAL CHARACTERISTICS (continued) over operating free-air temperature range, AVDD = DVDD = 3.3 V, IOUTFS = 20 mA, independent gain set mode (unless otherwise noted) PARAMETER TEST CONDITIONS MIN TYP MAX UNIT 1.25 V Reference Input VEXTIO Input voltage RI Input resistance CI 0.1 1 MΩ Small signal bandwidth 300 kHz Input capacitance 100 pF Temperature Coefficients Offset drift Gain drift 0 ppm of FSR/°C With external reference ±50 ppm of FSR/°C With internal reference ±50 ppm of FSR/°C ±20 ppm/°C Reference voltage drift ELECTRICAL CHARACTERISTICS over operating free-air temperature range, AVDD = DVDD = 3.3 V, IOUTFS = 20 mA, fDATA = 200 MSPS, fOUT = 1 MHz, independent gain set mode (unless otherwise noted) PARAMETER TEST CONDITIONS MIN TYP MAX 3 3.3 3.6 3 UNIT Power Supply AVDD Analog supply voltage DVDD Digital supply voltage IAVDD Supply current, analog IDVDD 3.3 3.6 V Including output current through load resistor 75 90 mA Sleep mode with clock 2.5 6 mA Sleep mode without clock 2.5 Supply current, digital 38 mA Sleep mode with clock 12.5 18 mA Sleep mode without clock <10 390 mW 330 Sleep mode without clock Power supply rejection ratio DPSRR TA Operating free-air temperature mA 25 Power dissipation APSSR V µA 15 mW -0.2 0.2 %FSR/V -0.2 0.2 %FSR/V -40 85 °C 5 DAC5662 www.ti.com SLAS425 – JULY 2004 ELECTRICAL CHARACTERISTICS AC specifications over operating free-air temperature range, AVDD = DVDD = 3.3 V, IOUTFS = 20 mA, independent gain set mode, differential 1:1 impedance ratio transformer coupled output, 50-Ω doubly terminated load (unless otherwise noted) PARAMETER TEST CONDITIONS MIN TYP MAX UNIT Analog Output fclk Maximum output update rate ts Output settling time to 0.1% (DAC) tr tf 200 MSPS 20 ns Output rise time 10% to 90% (OUT) 1.4 ns Output fall time 90% to 10% (OUT) 1.5 ns IOUTFS = 20 mA 55 pA/√Hz IOUTFS = 2 mA 30 pA/√Hz 1st Nyquist zone, TA = 25°C, fDATA = 50 MSPS, fOUT = 1 MHz, IOUTFS = 0 dB 81 dBc 1st Nyquist zone, TA = 25°C, fDATA = 50 MSPS, fOUT = 1 MHz, IOUTFS = -6 dB 83 dBc 1st Nyquist zone, TA = 25°C, fDATA = 50 MSPS, fOUT = 1 MHz, IOUTFS = -12 dB 81 dBc 1st Nyquist zone, TA = 25°C, fDATA = 100 MSPS, fOUT = 5 MHz 85 dBc 1st Nyquist zone, TA = 25°C, fDATA = 100 MSPS, fOUT = 20 MHz 78 dBc 71 dBc 1st Nyquist zone, TA = 25°C, fDATA = 200 MSPS, fOUT = 41 MHz 68 dBc 1st Nyquist zone, TA = 25°C, fDATA = 100 MSPS, fOUT = 5 MHz 73 dB 1st Nyquist zone, TA = 25°C, fDATA = 200 MSPS, fOUT = 20 MHz 67 dB W-CDMA signal with 3.84-MHz Bandwidth, fDATA = 61.44 MSPS, IF = 15.360 MHz 70 dB W-CDMA signal with 3.84-MHz Bandwidth, fDATA = 122.88 MSPS, IF = 30.72 MHz 70 dB Third-order two-tone intermodulation Each tone at -6 dBFS, TA = 25°C, fDATA = 200 MSPS, fOUT = 45.4 and 46.4 MHz 62 dBc Each tone at -6 dBFS, TA = 25°C, fDATA = 100 MSPS, fOUT = 15.1 and 16.1 MHz 78 dBc Each tone at -12 dBFS, TA = 25°C, fDATA = 100 MSPS, fOUT = 15.6, 15.8, 16.2, and 16.4 MHz 77 dBc Each tone at -12 dBFS, TA = 25°C, fDATA = 165 MSPS, fOUT = 68.8, 69.6, 71.2, and 72.0 MHz 56 dBc Each tone at -12 dBFS, TA = 25°C, fDATA = 165 MSPS, fOUT = 19.0, 19.1, 19.3, and 19.4 MHz 74 dBc TA = 25°C, fDATA = 165 MSPS, fOUT (CH1) = 20 MHz, fOUT (CH2) = 21 MHz 97 dBc Output noise Mid-scale transition AC Linearity SFDR Spurious free dynamic range 1st Nyquist zone, TMIN to TMAX, fDATA = 200 MSPS, fOUT = 20 MHz SNR ACLR IMD3 IMD Signal-to-noise ratio Adjacent channel leakage ratio Four-tone intermodulation Channel isolation 6 66 DAC5662 www.ti.com SLAS425 – JULY 2004 ELECTRICAL CHARACTERISTICS Digital specifications over operating free-air temperature range, AVDD = DVDD = 3.3 V, IOUTFS = 20 mA (unless otherwise noted) PARAMETER TEST CONDITIONS MIN TYP MAX UNIT Digital Input VIH High-level input voltage 2 3.3 VIL Low-level input voltage 0 0.8 V IIH High-level input current ±50 µA IIL Low-level input current ±10 µA IIH(GSET) High-level input current, GSET pin 7 µA IIL(GSET) Low-level input current, GSET pin -30 µA IIH(MODE) High-level input current, MODE pin -30 µA IIL(MODE) Low-level input current, MODE pin -80 µA CI Input capacitance 5 pF V SWITCHING CHARACTERISTICS Digital specifications over operating free-air temperature range, AVDD = DVDD = 3.3 V, IOUTFS = 20 mA (unless otherwise noted) PARAMETER TEST CONDITIONS MIN TYP MAX UNIT Timing - Dual Bus Mode tsu Input setup time 1 th Input hold time 1 tLPH Input clock pulse high time tLAT Clock latency (WRTA/B to outputs) tPD Propagation delay time ns ns 2 4 ns 4 clk 1.5 ns ns Timing - Single Bus Interleaved Mode tsu Input setup time 0.5 th Input hold time 0.5 tLAT Clock latency (WRTA/B to outputs) tPD Propagation delay time 4 ns 4 1.5 clk ns 7 DAC5662 www.ti.com SLAS425 – JULY 2004 TYPICAL CHARACTERISTICS INL - Integral Nonlinearity Error - LSB INTEGRAL NONLINEARITY vs INPUT CODE 0.4 0.3 0.2 0.1 -0.0 -0.1 -0.2 -0.3 -0.4 0 512 1024 1536 2048 2560 3072 3584 Input Code 4096 G001 Figure 2. DNL - Differential Nonlinearity Error - LSB DIFFERENTIAL NONLINEARITY vs INPUT CODE 0.20 0.15 0.10 0.05 -0.00 -0.05 -0.10 -0.15 -0.20 0 512 1024 1536 2048 Input Code Figure 3. 8 2560 3072 3584 4096 G002 DAC5662 www.ti.com SLAS425 – JULY 2004 TYPICAL CHARACTERISTICS (continued) SPURIOUS-FREE DYNAMIC RANGE vs OUTPUT FREQUENCY SPURIOUS-FREE DYNAMIC RANGE vs OUTPUT FREQUENCY 100 95 SFDR − Spurious-Free Dynamic Range − dBc SFDR − Spurious-Free Dynamic Range − dBc 100 0 dBfS 90 85 −6 dBfS 80 75 −12 dBfS 70 65 fdata = 52 MSPS Dual Bus Mode 60 −6 dBfS 90 0 dBfS 85 80 75 −12 dBfS 70 65 fdata = 78 MSPS Dual Bus Mode 60 0 4 8 12 16 20 fO − Output Frequency − MHz 24 0 5 10 15 20 25 30 fO − Output Frequency − MHz G003 Figure 4. Figure 5. SPURIOUS-FREE DYNAMIC RANGE vs OUTPUT FREQUENCY SPURIOUS-FREE DYNAMIC RANGE vs OUTPUT FREQUENCY 35 G004 100 SFDR − Spurious-Free Dynamic Range − dBc 100 SFDR − Spurious-Free Dynamic Range − dBc 95 0 dBfS 95 90 85 −6 dBfS 80 75 −12 dBfS 70 65 fdata = 100 MSPS Dual Bus Mode 60 95 90 0 dBfS 85 80 −6 dBfS 75 −12 dBfS 70 65 fdata = 165 MSPS Dual Bus Mode 60 0 5 10 15 20 25 30 fO − Output Frequency − MHz Figure 6. 35 40 G005 0 5 10 15 20 25 30 35 40 45 50 55 60 65 fO − Output Frequency − MHz G006 Figure 7. 9 DAC5662 www.ti.com SLAS425 – JULY 2004 TYPICAL CHARACTERISTICS (continued) SINGLE-TONE SPECTRUM SINGLE-TONE SPECTRUM 0 0 fdata = 78 MSPS fOUT = 15 MHz Dual Bus Mode fdata = 165 MSPS fOUT = 30.1 MHz Dual Bus Mode −20 Power − dBm Power - dBm -20 -40 -60 -80 −40 −60 −80 -100 0.0 7.8 15.6 23.4 31.2 −100 0.0 39.0 16.5 f - Frequency - MHz 33.0 49.5 66.0 82.5 f − Frequency − MHz G007 G008 Figure 8. Figure 9. TWO-TONE IMD3 vs OUTPUT FREQUENCY TWO-TONE IMD3 vs OUTPUT FREQUENCY 95 100 fdata = 78 MSPS Dual Bus Mode fdata = 165 MSPS Dual Bus Mode 95 90 85 Two-Tone IMD3 − dBc Two-Tone IMD3 − dBc 90 80 75 70 85 80 75 70 65 60 65 55 60 50 0 5 10 15 20 25 fO − Output Frequency − MHz Figure 10. 10 30 35 G009 0 10 20 30 40 fO − Output Frequency − MHz Figure 11. 50 G010 DAC5662 www.ti.com SLAS425 – JULY 2004 TYPICAL CHARACTERISTICS (continued) TWO-TONE SPECTRUM TWO-TONE SPECTRUM 0 0 fdata = 78 MSPS fOUT = 20.1 MHz and 21.1 MHz Dual Bus Mode −20 Power − dBm Power − dBm −20 −40 −60 −80 fdata = 165 MSPS fOUT = 30.1 MHz and 31.1 Mhz Dual Bus Mode −40 −60 −80 −100 19.0 19.5 20.0 20.5 21.0 21.5 −100 29.0 22.0 f − Frequency − MHz 29.5 30.0 30.5 31.0 G011 32.0 G012 Figure 12. Figure 13. POWER vs FREQUENCY POWER vs FREQUENCY −20 −20 fdata = 122.88 MSPS Baseband Signal ACPR = 72 dB Dual Bus Mode −40 Power − dBm −40 Power − dBm 31.5 f − Frequency − MHz −60 −80 −100 fdata = 122.88 MSPS IF = 30.72 MHz ACPR = 72 dB Dual Bus Mode −60 −80 −100 −120 0 1 2 3 4 5 6 7 8 9 10 f − Frequency − MHz −120 18 20 22 24 26 28 30 32 34 36 38 40 42 44 f − Frequency − MHz G013 Figure 14. G014 Figure 15. 11 DAC5662 www.ti.com SLAS425 – JULY 2004 DIGITAL INPUTS AND TIMING Digital Inputs The data input ports of the DAC5662 accept a standard positive coding with data bit D11 being the most significant bit (MSB). The converter outputs support a clock rate of up to 200 MSPS. The best performance will typically be achieved with a symmetric duty cycle for write and clock; however, the duty cycle may vary as long as the timing specifications are met. Similarly, the setup and hold times may be chosen within their specified limits. All digital inputs of the DAC5662 are CMOS compatible. Figure 16 and Figure 17 show schematics of the equivalent CMOS digital inputs of the DAC5662. The 12-bit digital data input follows the offset positive binary coding scheme. The DAC5662 is designed to operate with a digital supply (DVDD) of 3 V to 3.6 V. DVDD DA[11:0] DB[11:0] SLEEP CLKA/B WRTA/B Internal Digital In DGND Figure 16. CMOS/TTL Digital Equivalent Input With Internal Pulldown Resistor DVDD Internal Digital In GSET MODE DGND Figure 17. CMOS/TTL Digital Equivalent Input With Internal Pullup Resistor Input Interfaces The DAC5662 features two operating modes selected by the MODE pin, as shown in the following table • For dual-bus input mode, the device essentially consists of two separate DACs. Each DAC has its own separate data input bus, clock input, and data write signal (data latch-in). • In single-bus interleaved mode, the data should be presented interleaved at the I-channel input bus. The Q-channel input bus is not used in this mode. The clock and write input are now shared by both DACs. MODE PIN Mode pin connected to DGND Mode pin connected to DVDD Bus input Single-bus interleaved mode, clock and write input equal for both DACs Dual-bus mode, DACs operate independently 12 DAC5662 www.ti.com SLAS425 – JULY 2004 Dual-Bus Data Interface and Timing In dual-bus mode, the MODE pin is connected to DVDD. The two converter channels within the DAC5662 consist of two independent, 12-bit, parallel data ports. Each DAC channel is controlled by its own set of write (WRTA, WRTB) and clock (CLKA, CLKB) lines. The WRT lines control the channel input latches and the CLK lines control the DAC latches. The data is first loaded into the input latch by a rising edge of the WRT line The internal data transfer requires a correct sequence of write and clock inputs, since essentially two clock domains having equal periods (but possibly different phases) are input to the DAC5662. This is defined by a minimum requirement of the time between the rising edge of the clock and the rising edge of the write inputs. This essentially implies that the rising edge of CLK must occur at the same time or before the rising edge of the WRT signal. A minimum delay of 2 ns should be maintained if the rising edge of the clock occurs after the rising edge of the write. Note that these conditions are satisfied when the clock and write inputs are connected externally. Note that all specifications were measured with the WRT and CLK lines connected together. D[11:0] Valid Data tsu th t1ph WRT1/ WRT2 CLK1/ CLK2 tsettle tlat tpd IOUT or IOUT Figure 18. Dual Bus Mode Operation Single-Bus Interleaved Data Interface and Timing In single-bus interleaved mode, the MODE pin is connected to DGND. Figure 19 shows the timing diagram. In interleaved mode, the I- and Q-channels share the write input (WRTIQ) and update clock (CLKIQ and internal CLKDACIQ). Multiplexing logic directs the input word at the I-channel input bus to either the I-channel input latch (SELECTIQ is high) or to the Q-channel input latch (SELECTIQ is low). When SELECTIQ is high, the data value in the Q-channel latch is retained by presenting the latch output data to its input again. When SELECTIQ is low, the data value in the I-channel latch is retained by presenting the latch output data to its input. In interleaved mode, the I-channel input data rate is twice the update rate of the DAC core. As in dual-bus mode, it is important to maintain a correct sequence of write and clock inputs. The edge-triggered flip-flops latch the Iand Q-channel input words on the rising edge of the write input (WRTIQ). This data is presented to the I- and Q-DAC latches on the following falling edge of the write inputs. The DAC5662 clock input is divided by a factor of two before it is presented to the DAC latches. Correct pairing of the I- and Q-channel data is done by RESETIQ. In interleaved mode, the clock input CLKIQ is divided by two, which would translate to a non-deterministic relation between the rising edges of the CLKIQ and CLKDACIQ. RESETIQ ensures, however, that the correct position of the rising edge of CLKDACIQ with respect to the data at the input of the DAC latch is determined. CLKDACIQ is disabled (low) when RESETIQ is high. 13 DAC5662 www.ti.com SLAS425 – JULY 2004 D[11:0] Valid Data tsu th SELECTIQ WRTIQ CLKIQ RESETIQ tsettle tlat tpd IOUT or IOUT Figure 19. Single-Bus Interleaved Mode Operation 14 DAC5662 www.ti.com SLAS425 – JULY 2004 APPLICATION INFORMATION Theory of Operation The architecture of the DAC5662 uses a current steering technique to enable fast switching and high update rate. The core element within the monolithic DAC is an array of segmented current sources that are designed to deliver a full-scale output current of up to 20 mA. An internal decoder addresses the differential current switches each time the DAC is updated and a corresponding output current is formed by steering all currents to either output summing node, IOUT1 and IOUT2. The complementary outputs deliver a differential output signal, which improves the dynamic performance through reduction of even-order harmonics, common-mode signals (noise), and double the peak-to-peak output signal swing by a factor of two, compared to single-ended operation. The segmented architecture results in a significant reduction of the glitch energy, improves the dynamic performance (SFDR), and DNL. The current outputs maintain a very high output impedance of greater than 300 kΩ. When GSET is high (one resistor mode), the full-scale output current for both DACs is determined by the ratio of the internal reference voltage (1.2 V) and an external resistor RSET connected to BIASJ_A. When GSET is low (two resistor mode), the full-scale output current for each DACs is determined by the ratio of the internal reference voltage (1.2 V) and separate external resistors RSET connected to BIASJ_A and BIASJ_B. The resulting IREF is internally multiplied by a factor of 32 to produce an effective DAC output current that can range from 2 mA to 20 mA, depending on the value of RSET. The DAC5662 is split into a digital and an analog portion, each of which is powered through its own supply pin. The digital section includes edge-triggered input latches and the decoder logic, while the analog section comprises the current source array with its associated switches, and the reference circuitry. DAC Transfer Function Each of the DACs in the DAC5662 has a set of complementary current outputs, IOUT1 and IOUT2. The full-scale output current, IOUTFS, is the summation of the two complementary output currents: I I I OUTFS OUT1 OUT2 (1) The individual output currents depend on the DAC code and can be expressed as: I I Code OUT1 OUTFS 4096 I I 4095 Code OUT2 OUTFS 4096 (2) (3) where Code is the decimal representation of the DAC data input word. Additionally, IOUTFS is a function of the reference current IREF, which is determined by the reference voltage and the external setting resistor (RSET). V I 32 I 32 REF OUTFS REF R SET (4) In most cases, the complementary outputs drive resistive loads or a terminated transformer. A signal voltage develops at each output according to: V I R OUT1 OUT1 LOAD (5) V I R OUT2 OUT2 LOAD (6) The value of the load resistance is limited by the output compliance specification of the DAC5662. To maintain specified linearity performance, the voltage for IOUT1 and IOUT2 should not exceed the maximum allowable compliance range. 15 DAC5662 www.ti.com SLAS425 – JULY 2004 APPLICATION INFORMATION (continued) The total differential output voltage is: V V V OUTDIFF OUT1 OUT2 (2 Code 4095) V I R OUTDIFF OUTFS LOAD 4096 (7) (8) Analog Outputs AVDD S(1) IOUT1 RLOAD S(1)C IOUT2 S(2) S(2)C S(N) S(N)C Current Source Array RLOAD Figure 20. Analog Outputs The DAC5662 provides two complementary current outputs, IOUT1 and IOUT2. The simplified circuit of the analog output stage representing the differential topology is shown in Figure 20. The output impedance of IOUT1 and IOUT2 results from the parallel combination of the differential switches, along with the current sources and associated parasitic capacitances. The signal voltage swing that may develop at the two outputs, IOUT1 and IOUT2, is limited by a negative and positive compliance. The negative limit of –1 V is given by the breakdown voltage of the CMOS process and exceeding it compromises the reliability of the DAC5662 or even causes permanent damage. With the full-scale output set to 20 mA, the positive compliance equals 1.2 V. Note that the compliance range decreases to about 1 V for a selected output current of IOUTFS = 2 mA. Care should be taken that the configuration of DAC5662 does not exceed the compliance range to avoid degradation of the distortion performance and integral linearity. Best distortion performance is typically achieved with the maximum full-scale output signal limited to approximately 0.5 Vpp. This is the case for a 50-Ω doubly terminated load and a 20-mA full-scale output current. A variety of loads can be adapted to the output of the DAC5662 by selecting a suitable transformer while maintaining optimum voltage levels at IOUT1 and IOUT2. Furthermore, using the differential output configuration in combination with a transformer will be instrumental for achieving excellent distortion performance. Common-mode errors, such as even-order harmonics or noise, can be substantially reduced. This is particularly the case with high output frequencies. For those applications requiring the optimum distortion and noise performance, it is recommended to select a full-scale output of 20 mA. A lower full-scale range of 2 mA may be considered for applications that require low power consumption, but can tolerate a slight reduction in performance level. Output Configurations The current outputs of the DAC5662 allow for a variety of configurations. As mentioned previously, utilizing the converter’s differential outputs yield the best dynamic performance. Such a differential output circuit may consist of an RF transformer or a differential amplifier configuration. The transformer configuration is ideal for most applications with ac coupling, while op amps will be suitable for a dc-coupled configuration. 16 DAC5662 www.ti.com SLAS425 – JULY 2004 APPLICATION INFORMATION (continued) The single-ended configuration may be considered for applications requiring a unipolar output voltage. Connecting a resistor from either one of the outputs to ground converts the output current into a ground-referenced voltage signal. To improve on the dc linearity by maintaining a virtual ground, an I-to-V or op-amp configuration may be considered. Differential With Transformer Using an RF transformer provides a convenient way of converting the differential output signal into a single-ended signal while achieving excellent dynamic performance. The appropriate transformer should be carefully selected based on the output frequency spectrum and impedance requirements. The differential transformer configuration has the benefit of significantly reducing common-mode signals, thus improving the dynamic performance over a wide range of frequencies. Furthermore, by selecting a suitable impedance ratio (winding ratio) the transformer can be used to provide optimum impedance matching while controlling the compliance voltage for the converter outputs. Figure 21 and Figure 22 show 50-Ω doubly terminated transformer configurations with 1:1 and 4:1 impedance ratios, respectively. Note that the center tap of the primary input of the transformer has to be grounded to enable a dc-current flow. Applying a 20-mA full-scale output current would lead to a 0.5-Vpp output for a 1:1 transformer and a 1-Vpp output for a 4:1 transformer. In general, the 1:1 transformer configuration will have slightly better output distortion, but the 4:1 transformer will have 6 dB higher output power. 50 Ω 1:1 IOUT1 100 Ω RLOAD 50 Ω AGND IOUT2 50 Ω Figure 21. Driving a Doubly Terminated 50-Ω Cable Using a 1:1 Impedance Ratio Transformer 100 Ω 4:1 IOUT1 AGND RLOAD 50 Ω IOUT2 100 Ω Figure 22. Driving a Doubly Terminated 50-Ω Cable Using a 4:1 Impedance Ratio Transformer 17 DAC5662 www.ti.com SLAS425 – JULY 2004 APPLICATION INFORMATION (continued) Single-Ended Configuration Figure 23 shows the single-ended output configuration, where the output current IOUT1 flows into an equivalent load resistance of 25 Ω. Node IOUT2 should be connected to AGND or terminated with a resistor of 25 Ω to AGND. The nominal resistor load of 25 Ω gives a differential output swing of 1 Vpp when applying a 20-mA full-scale output current. IOUT1 RLOAD 50 Ω IOUT2 50 Ω 25 Ω AGND Figure 23. Driving a Doubly Terminated 50-Ω Cable Using a Single-Ended Output Reference Operation Internal Reference The DAC5662 has an on-chip reference circuit which comprises a 1.2-V bandgap reference and two control amplifiers, one for each DAC. The full-scale output current, IOUTFS, of the DAC5662 is determined by the reference voltage, VREF, and the value of resistor RSET. IOUTFS can be calculated by: V I 32 I 32 REF OUTFS REF R SET (9) The reference control amplifier operates as a V-to-I converter producing a reference current, IREF, which is determined by the ratio of VREF and RSET (see Equation 9). The full-scale output current, IOUTFS, results from multiplying IREF by a fixed factor of 32. Using the internal reference, a 2-kΩ resistor value results in a full-scale output of approximately 20 mA. Resistors with a tolerance of 1% or better should be considered. Selecting higher values, the output current can be adjusted from 20 mA down to 2 mA. Operating the DAC5662 at lower than 20-mA output currents may be desirable for reasons of reducing the total power consumption, improving the distortion performance, or observing the output compliance voltage limitations for a given load condition. It is recommended to bypass the EXTIO pin with a ceramic chip capacitor of 0.1 µF or more. The control amplifier is internally compensated and its small signal bandwidth is approximately 300 kHz. External Reference The internal reference can be disabled by simply applying an external reference voltage into the EXTIO pin, which in this case functions as an input. The use of an external reference may be considered for applications that require higher accuracy and drift performance or to add the ability of dynamic gain control. While a 0.1-µF capacitor is recommended to be used with the internal reference, it is optional for the external reference operation. The reference input, EXTIO, has a high input impedance (1 MΩ) and can easily be driven by various sources. Note that the voltage range of the external reference should stay within the compliance range of the reference input. 18 DAC5662 www.ti.com SLAS425 – JULY 2004 APPLICATION INFORMATION (continued) Gain Setting Option The full-scale output current on the DAC5662 can be set two ways: either for each of the two DAC channels independently or for both channels simultaneously. For the independent gain set mode, the GSET pin (pin 42) must be low (i.e. connected to AGND). In this mode, two external resistors are required — one RSET connected to the BIASJ_A pin (pin 44) and the other to the BIASJ_B pin (pin 41). In this configuration, the user has the flexibility to set and adjust the full-scale output current for each DAC independently, allowing for the compensation of possible gain mismatches elsewhere within the transmit signal path. Alternatively, bringing the GSET pin high (i.e. connected to AVDD), the DAC5662 switches into the simultaneous gain set mode. Now the full-scale output current of both DAC channels is determined by only one external RSET resistor connected to the BIASJ_A pin. The resistor at the BIASJ_2 pin may be removed, however this is not required since this pin is not functional in this mode and the resistor has no effect on the gain equation. Sleep Mode The DAC5662 features a power-down function which can be used to reduce the total supply current to less than 3.5 mA over the specified supply range if no clock is present. Applying a logic high to the SLEEP pin initiates the power-down mode, while a logic low enables normal operation. When left unconnected, an internal active pulldown circuit enables the normal operation of the converter. 19 PACKAGE OPTION ADDENDUM www.ti.com 11-Mar-2005 PACKAGING INFORMATION Orderable Device Status (1) Package Type Package Drawing Pins Package Eco Plan (2) Qty DAC5662IPFB ACTIVE TQFP PFB 48 250 Green (RoHS & no Sb/Br) CU NIPDAU Level-2-260C-1 YEAR DAC5662IPFBR ACTIVE TQFP PFB 48 1000 Green (RoHS & no Sb/Br) CU NIPDAU Level-2-260C-1 YEAR DAC5662IPFBRG4 ACTIVE TQFP PFB 48 1000 None Lead/Ball Finish Call TI MSL Peak Temp (3) Call TI (1) The marketing status values are defined as follows: ACTIVE: Product device recommended for new designs. LIFEBUY: TI has announced that the device will be discontinued, and a lifetime-buy period is in effect. NRND: Not recommended for new designs. Device is in production to support existing customers, but TI does not recommend using this part in a new design. PREVIEW: Device has been announced but is not in production. Samples may or may not be available. OBSOLETE: TI has discontinued the production of the device. (2) Eco Plan - May not be currently available - please check http://www.ti.com/productcontent for the latest availability information and additional product content details. None: Not yet available Lead (Pb-Free). Pb-Free (RoHS): TI's terms "Lead-Free" or "Pb-Free" mean semiconductor products that are compatible with the current RoHS requirements for all 6 substances, including the requirement that lead not exceed 0.1% by weight in homogeneous materials. Where designed to be soldered at high temperatures, TI Pb-Free products are suitable for use in specified lead-free processes. Green (RoHS & no Sb/Br): TI defines "Green" to mean "Pb-Free" and in addition, uses package materials that do not contain halogens, including bromine (Br) or antimony (Sb) above 0.1% of total product weight. (3) MSL, Peak Temp. -- The Moisture Sensitivity Level rating according to the JEDECindustry standard classifications, and peak solder temperature. Important Information and Disclaimer:The information provided on this page represents TI's knowledge and belief as of the date that it is provided. TI bases its knowledge and belief on information provided by third parties, and makes no representation or warranty as to the accuracy of such information. Efforts are underway to better integrate information from third parties. TI has taken and continues to take reasonable steps to provide representative and accurate information but may not have conducted destructive testing or chemical analysis on incoming materials and chemicals. TI and TI suppliers consider certain information to be proprietary, and thus CAS numbers and other limited information may not be available for release. In no event shall TI's liability arising out of such information exceed the total purchase price of the TI part(s) at issue in this document sold by TI to Customer on an annual basis. Addendum-Page 1 MECHANICAL DATA MTQF019A – JANUARY 1995 – REVISED JANUARY 1998 PFB (S-PQFP-G48) PLASTIC QUAD FLATPACK 0,27 0,17 0,50 36 0,08 M 25 37 24 48 13 0,13 NOM 1 12 5,50 TYP 7,20 SQ 6,80 9,20 SQ 8,80 Gage Plane 0,25 0,05 MIN 0°– 7° 1,05 0,95 Seating Plane 0,75 0,45 0,08 1,20 MAX 4073176 / B 10/96 NOTES: A. All linear dimensions are in millimeters. B. This drawing is subject to change without notice. C. Falls within JEDEC MS-026 POST OFFICE BOX 655303 • DALLAS, TEXAS 75265 IMPORTANT NOTICE Texas Instruments Incorporated and its subsidiaries (TI) reserve the right to make corrections, modifications, enhancements, improvements, and other changes to its products and services at any time and to discontinue any product or service without notice. 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