ADV7122KSTZ50

The ADV7122KSTZ50 is a triple 8-bit high-speed video digital-to-analog converter from Analog Devices, optimized for high-resolution video graphics and digital display applications. This device integrates three independent 8-bit current-steering DAC channels — one each for Red, Green, and Blue video signals — capable of operating at update rates up to 50 mega-samples per second, supporting display resolutions up to 1280×1024 at standard VESA refresh rates. Each DAC channel provides complementary current outputs (IOUT and IOUT-bar), giving the system designer flexibility in configuring the load termination and output voltage swing. The full-scale output current is programmable from 2 mA to 26 mA via a single external resistor (RSET), allowing optimization for different display types and load impedances. The ADV7122 incorporates a 1.0 V on-chip bandgap voltage reference that eliminates the need for an external reference in most applications. Key video-specific features include a common blanking input (BLANK) that simultaneously forces all three DAC outputs to blanking level (zero output current) for video retrace intervals, and integrated TTL-level sync-on-green functionality that adds composite sync information to the green channel output, reducing external component count in systems that use sync-on-green video standards. The current-steering architecture delivers excellent dynamic performance with low glitch energy (0.5 nV·s typical), ensuring clean video transitions without visible artifacts. The device operates from a single 5V supply with modest power consumption, and features a power-down mode that reduces supply current to less than 10 microamps for power-sensitive applications. Housed in a compact 48-lead LQFP package with industrial temperature range (-40°C to +85°C), the ADV7122KSTZ50 is a versatile video DAC solution for graphics controllers, set-top boxes, medical imaging displays, and professional video equipment.

The ADV7122 is a current-steering (also called current-mode or current-source) video DAC. Each of its three 8-bit DAC channels contains an array of 255 equally weighted current sources plus a constant bias current. Each current source is switched to either the IOUT output or the IOUT (complementary) output based on the corresponding bit value in the input digital word — bits set to ‘1’ direct their current to IOUT, while bits set to ‘0’ direct their current to IOUT. The sum of IOUT and IOUT always equals the full-scale current, making the outputs complementary. This architecture is preferred for high-speed video applications because it achieves very fast switching speeds — the current sources can be switched on and off in sub-nanosecond times — and produces low glitch energy because both outputs always carry current (no sudden current steps to zero). The full-scale output current is set by an external resistor RSET connected to the FS ADJUST pin, which programs a reference current that is mirrored to all 255 individual current sources. The on-chip 1.0 V bandgap reference provides a stable voltage reference for the reference current generator. The three DACs share a common clock input (CLK), and all three channels update simultaneously on each clock edge, ensuring perfect channel-to-channel alignment — critical for maintaining proper color balance and timing in RGB video systems. The BLANK input, when asserted, overrides the digital inputs and forces all three DAC outputs to blanking level (zero output current), which corresponds to the black level in video signals. The sync function for the green channel (sync-on-green) is implemented by adding a controlled current step to the green DAC output during the sync interval, embedding the horizontal and vertical sync pulses into the green channel’s analog output. Overall, this architecture delivers the speed, precision, and video-specific features required for high-performance analog video display systems.

The ADV7122KSTZ50 is packaged in a 48-lead LQFP. Key pin groups:

Note: Exact pin numbers may vary depending on package variant. Refer to the official ADV7122 datasheet for complete pin assignments, package dimensions, and recommended PCB layout guidelines.

• Video Graphics Controllers: Serves as the RAMDAC (RAM + DAC) output stage in VGA/SVGA graphics controllers and display adapters, converting digital framebuffer RGB data to analog video signals for CRT and analog LCD monitors
• Digital Set-Top Boxes & TVs: Used in digital TV receivers, cable/satellite set-top boxes, and DVD/Blu-ray players as the analog video output stage for component video (YPbPr) and RGB outputs
• Medical Imaging Displays: Found in ultrasound machines, patient monitors, and diagnostic imaging equipment where accurate DNL/INL and consistent channel matching ensure reliable color and grayscale reproduction
• Professional Video Equipment: Used in video production switchers, character generators, broadcast monitors, and video test equipment where high-speed, low-glitch DAC performance is critical for signal integrity
• Video Wall Processors: Deployed in multi-display video wall controllers and matrix switchers requiring high-channel-count, high-speed DACs per output
• Industrial & Avionics Displays: Used in cockpit displays, HMI panels, and ruggedized industrial monitors requiring reliable operation over wide temperature ranges (industrial -40°C to +85°C range)
• Video Test Pattern Generators: Forms the core of programmable video test generators that produce precise analog video test signals with controlled timing and amplitude for display and video equipment testing
• Machine Vision & Inspection Systems: Used in industrial camera systems and automated optical inspection equipment as the analog video output or reference signal source