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DAC7821

FEATURES DESCRIPTION

APPLICATIONS

DACRegister

Power-On

Reset

Control

Logic

DAC7821

REF

I 1

OUT

I 2

OUT

GND

DB0

DB11

12-Bit

R-2RDAC

InputLatch

ParallelBus

R/W

DAC7821

SBAS365B – OCTOBER 2005 – REVISED JULY 2007

12-Bit, Parallel Input, Multiplying

Digital-to-Analog Converter

• 2.5V to 5.5V Supply Operation

The DAC7821 is a CMOS 12-bit current output

digital-to-analog converter (DAC). This device

• Fast Parallel Interface:

operates from a single 2.5V to 5.5V power supply,

17ns Write Cycle

making it suitable for battery-powered and many

• Update Rate of 20.4MSPS

other applications.

• 10MHz Multiplying Bandwidth

This DAC operates with a fast parallel interface. Data

• ±10V Reference Input

readback allows the user to read the contents of the

• Low Glitch Energy: 5nV-s

DAC register via the DB pins. On power-up, the

internal register and latches are filled with zeroes

• Extended Temperature Range:

and the DAC outputs are at zero scale.

–40 ° C to +125 ° C

The DAC7821 offers excellent 4-quadrant

• 20-Lead TSSOP Packages

multiplication characteristics, with a large signal

• 12-Bit Monotonic

multiplying bandwidth of 10MHz. The applied

• ± 1LSB INL

external reference input voltage (V

REF

) determines

• 4-Quadrant Multiplication

the full-scale output current. An integrated feedback

resistor (R

) provides temperature tracking and

• Power-On Reset with Brownout Detection

full-scale voltage output when combined with an

• Readback Function

external current-to-voltage precision amplifier.

• Industry-Standard Pin Configuration

The DAC7821 is available in a 20-lead TSSOP

package.

• Portable Battery-Powered Instruments

• Waveform Generators

• Analog Processing

• Programmable Amplifiers and Attenuators

• Digitally-Controlled Calibration

• Programmable Filters and Oscillators

• Composite Video

• Ultrasound

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.

All trademarks are the property of their respective owners.

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.

Summary of content (21 pages)

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DAC7821 DA C7 821 SBAS365B – OCTOBER 2005 – REVISED JULY 2007 12-Bit, Parallel Input, Multiplying Digital-to-Analog Converter FEATURES • • • • • • • • • • • • • • 2.5V to 5.5V Supply Operation Fast Parallel Interface: 17ns Write Cycle Update Rate of 20.
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DAC7821 www.ti.com SBAS365B – OCTOBER 2005 – REVISED JULY 2007 This integrated circuit can be damaged by ESD. Texas Instruments recommends that all integrated circuits be handled with appropriate precautions. Failure to observe proper handling and installation procedures can cause damage. ESD damage can range from subtle performance degradation to complete device failure.
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DAC7821 www.ti.com SBAS365B – OCTOBER 2005 – REVISED JULY 2007 ELECTRICAL CHARACTERISTICS VDD = +2.5V to +5.5V; IOUT1 = Virtual GND; IOUT2 = 0V; VREF = +10V; TA = full operating temperature. All specifications –40°C to +125°C, unless otherwise noted.
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DAC7821 www.ti.com SBAS365B – OCTOBER 2005 – REVISED JULY 2007 TIMING INFORMATION R/W t1 t6 t2 t2 t7 t3 CS t4 t5 DATA VALID DATA t8 t9 DATA VALID TIMING REQUIREMENTS: 2.5 V to 4.5 V At tr = tf = 1ns (10% to 90% of VDD) and timed from a voltage level of (VIL + VIH)/2; VDD = +2.5V to +4.5V, VREF = +10V, IOUT2 = 0V. All specifications –40°C to +125°C, unless otherwise noted.
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DAC7821 www.ti.com SBAS365B – OCTOBER 2005 – REVISED JULY 2007 DEVICE INFORMATION IOUT1 1 20 RFB IOUT2 2 19 VREF GND 3 18 VDD DB11 (MSB) 4 17 R/W DB10 5 16 CS DAC7821 DB9 6 15 DB0 (LSB) DB8 7 14 DB1 DB7 8 13 DB2 DB6 9 12 DB3 DB5 10 11 DB4 TSSOP-20 TERMINAL FUNCTIONS TERMINAL TSSOP NO. NAME 1 IOUT1 DAC current output. 2 IOUT2 DAC analog ground. This pin is normally tied to the analog ground of the system. 3 GND Ground pin.
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DAC7821 www.ti.com SBAS365B – OCTOBER 2005 – REVISED JULY 2007 TYPICAL CHARACTERISTICS: VDD = +5V At TA = +25°C, unless otherwise noted. LINEARITY ERROR vs DIGITAL INPUT CODE DIFFERENTIAL LINEARITY ERROR vs DIGITAL INPUT CODE 1.0 1.0 TA = +25°C VREF = +10 V 0.8 0.6 0.6 0.4 DNL (LSB) INL (LSB) 0.4 0.2 0 -0.2 -0.4 -0.6 -0.8 -0.8 -1.0 512 1024 1536 2048 2560 3072 3584 4095 0 512 1024 1536 2048 2560 3072 3584 Digital Input Code Digital Input Code Figure 1. Figure 2.
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DAC7821 www.ti.com SBAS365B – OCTOBER 2005 – REVISED JULY 2007 TYPICAL CHARACTERISTICS: VDD = +5V (continued) At TA = +25°C, unless otherwise noted. SUPPLY CURRENT vs LOGIC INPUT VOLTAGE REFERENCE MULTIPLYING BANDWIDTH 3.0 6 0 -6 -12 -18 -24 -30 -36 -42 -48 -56 -60 -66 -72 -78 -84 -90 -96 -102 VDD = 5.0 V Attenuation (dB) Supply Current (mA) 2.5 0xFFF 0x800 0x400 0x200 0x100 0x080 0x040 0x020 0x010 0x008 0x004 0x002 0x001 2.0 1.5 1.0 VDD = 3.0 V VDD = 2.5 V 0.5 0 0 0.5 1.0 1.5 2.0 2.5 3.
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DAC7821 www.ti.com SBAS365B – OCTOBER 2005 – REVISED JULY 2007 TYPICAL CHARACTERISTICS: VDD = +5V (continued) At TA = +25°C, unless otherwise noted. SUPPLY CURRENT vs TEMPERATURE 2.0 0.2 VREF = +10 V 0.18 1.6 Leakage Current (nA) Quiescent Current (mA) 1.8 LEAKAGE CURRENT vs TEMPERATURE 1.4 1.2 1.0 VDD = +5.0 V 0.8 0.6 0.4 0.16 0.14 0.12 0.10 0.08 0.06 0.04 VDD = +2.5 V 0.2 0.02 0 0 -40 -20 0 20 40 60 80 100 120 -40 Temperature (°C) 0 20 40 60 Temperature (°C) Figure 13.
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DAC7821 www.ti.com SBAS365B – OCTOBER 2005 – REVISED JULY 2007 TYPICAL CHARACTERISTICS: VDD = +2.5V At TA = +25°C, unless otherwise noted. LINEARITY ERROR vs DIGITAL INPUT CODE DIFFERENTIAL LINEARITY ERROR vs DIGITAL INPUT CODE 1.0 1.0 TA = +25°C VREF = +10 V 0.8 0.6 0.6 0.4 DNL (LSB) INL (LSB) 0.4 0.2 0 -0.2 0 -0.2 -0.4 -0.6 -0.6 -0.8 -0.8 -1.0 0 512 1024 1536 2048 2560 3072 3584 4095 0 512 1024 1536 2048 2560 3072 3584 Digital Input Code Digital Input Code Figure 15.
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DAC7821 www.ti.com SBAS365B – OCTOBER 2005 – REVISED JULY 2007 TYPICAL CHARACTERISTICS: VDD = +2.5V (continued) At TA = +25°C, unless otherwise noted. MIDSCALE DAC GLITCH Output Voltage (50mV/div) Output Voltage (50mV/div) MIDSCALE DAC GLITCH Code 2047 to 2048 Code 2048 to 2047 DAC Update 2.0 1.8 DAC Update Time (50ns/div) Time (50ns/div) Figure 21. Figure 22. GAIN ERROR vs TEMPERATURE LEAKAGE CURRENT vs TEMPERATURE 0.2 VREF = +10 V 0.18 Leakage Current (nA) Gain Error (mV) 1.6 1.4 1.
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DAC7821 www.ti.com SBAS365B – OCTOBER 2005 – REVISED JULY 2007 THEORY OF OPERATION The DAC7821 is a single channel, current output, 12-bit digital-to-analog converter (DAC). The architecture, illustrated in Figure 25, is an R-2R ladder configuration with the three MSBs segmented. Each 2R leg of the ladder is either switched to IOUT1 or the IOUT2 terminal. The IOUT1 terminal of the DAC is held at a virtual GND potential by the use of an external I/V converter op amp.
PAGE 12
DAC7821 www.ti.com SBAS365B – OCTOBER 2005 – REVISED JULY 2007 APPLICATION INFORMATION Stability Circuit For a current-to-voltage design (see Figure 27), the DAC7821 current output (IOUT) and the connection with the inverting node of the op amp should be as short as possible and according to correct printed circuit board (PCB) layout design practices. For each code change, there is a step function.
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DAC7821 www.ti.com SBAS365B – OCTOBER 2005 – REVISED JULY 2007 Table 2. Suitable High Speed Operational Amplifiers from Texas Instruments (Multiple Channel Options) SUPPLY VOLTAGE (V) GBW PRODUCT (MHz) VOLTAGE NOISE nV/√Hz GBW (typ) (MHz) SLEW RATE (V/μs) VOS (typ) (μV) VOS (max) (μV) CMRR (min) (dB) THS4281 ±2.7 to ±15 38 12.5 35 500 3500 500 1000 SOT5-23, MSOP-8, SOIC-8 Very Low-Power High Speed Rail-To-Rail Input/Output Voltage Feedback Operational Amplifier THS4031 ±4.5 to ±16.
PAGE 14
DAC7821 www.ti.com SBAS365B – OCTOBER 2005 – REVISED JULY 2007 Positive Voltage Output Circuit As Figure 28 illustrates, in order to generate a positive voltage output, a negative reference is input to the DAC7821. This design is suggested instead of using an inverting amp to invert the output because of possible resistor tolerance errors. For a negative reference, VOUT and GND of the reference are level-shifted to a virtual ground and a –2.5V input to the DAC7821 with an op amp. +2.
PAGE 15
DAC7821 www.ti.com SBAS365B – OCTOBER 2005 – REVISED JULY 2007 Programmable Current Source Circuit A DAC7821 can be integrated into the circuit in Figure 30 to implement an improved Howland current pump for precise voltage-to-current conversions. Bidirectional current flow and high voltage compliance are two features of the circuit.
PAGE 16
DAC7821 www.ti.com SBAS365B – OCTOBER 2005 – REVISED JULY 2007 Parallel Interface Data are loaded to the DAC7821 as a 12-bit parallel word. The bidirectional bus is controlled with CS and R/W, allowing data to be written to or read from the DAC register. To write to the device, CS and R/W are brought low, and data available on the data lines fill the input register. The rising edge of CS latches the data and transfers the latched data-word to the DAC register.
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PACKAGE OPTION ADDENDUM www.ti.
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PACKAGE OPTION ADDENDUM www.ti.
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IMPORTANT NOTICE Texas Instruments Incorporated and its subsidiaries (TI) reserve the right to make corrections, enhancements, improvements and other changes to its semiconductor products and services per JESD46, latest issue, and to discontinue any product or service per JESD48, latest issue. Buyers should obtain the latest relevant information before placing orders and should verify that such information is current and complete.