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Texas Instruments LM1246AAC/NA/NOPB
- Part No.:
- LM1246AAC/NA/NOPB
- Manufacturer:
- Texas Instruments
- Category:
- Video Processing
- Package:
- 24-DIP (0.300", 7.62mm)
- Datasheet:
-
LM1246AAC/NA/NOPB.pdf
- Description:
- IC VIDEO PREAMPLIFIER 24DIP
- Quantity:
- Payment:
- Shipping:
Inventory:3,293
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Product details
Overview
LM1246AAC/NA/NOPB from Texas Instruments (formerly National Semiconductor) is a 150 MHz RGB preamplifier IC for CRT monitor signal conditioning, integrating I²C-compatible control, 512-character OSD ROM/RAM, and four 8-bit DACs for CRT bias and brightness. It delivers 4.3 V max video output, ±0.5 dB gain matching across RGB channels, and supports 1024×768 @ 85 Hz with vertical/horizontal blanking synchronization. Used in low-cost bus-controlled monitors with integrated clamp functionality.
For engineers reviewing the LM1246AAC/NA/NOPB datasheet, LM1246AAC/NA/NOPB pinout, LM1246AAC/NA/NOPB application, or LM1246AAC/NA/NOPB equivalent, key selection considerations include its 150 MHz bandwidth, register-programmable vertical blanking width (3–127 lines), spot killer threshold (3.4–4.3 V), I²C interface timing compliance, and compatibility with LM246x driver and LM2479/80 bias ICs.
Technical Context
The LM1246AAC/NA/NOPB implements a fully addressable on-screen display engine with dual-mode character addressing (2-byte or bank-select), supporting up to 640 two-color characters or mixed 2-/4-color configurations. Its video path features AC-coupled high-impedance inputs with internal black-level clamping-eliminating external clamp capacitors-and programmable horizontal blank start position (0–64 pixels ahead of flyback edge).
It integrates a PLL-based OSD timing generator supporting 704–1152 pixels per line (max 111 MHz pixel clock), with auto-calibrating PLL Auto mode that dynamically selects optimal frequency range based on horizontal scan rate. The four DACs operate in two voltage modes (Mode 00: 0.7–4.2 V; Mode 01: 0.7–2.35 V), each with ±0.5 LSB monotonicity and 5% linearity error over temperature.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Bandwidth | 150 MHz (−3 dB), enabling full support for 1024×768 @ 85 Hz analog video signals without high-frequency roll-off. |
| Video Output Voltage | 4.3 V max (typ), sufficient to drive LM246x cathode drivers to 40 V peak-to-peak cathode swing. |
| Gain Matching | ±0.5 dB between RGB channels, ensuring consistent color balance without manual trim calibration. |
| DAC Resolution | 8-bit (256 steps), providing fine-grained control of CRT cutoff and brightness with <3% output variation across channels. |
| OSD Memory | 512-character ROM + 512-character RAM, configurable as single or dual independent windows for layered UI elements. |
| Supply Current | 250 mA (typ) active; 95 mA (typ) in Power Save Mode - 65% reduction enabling thermal management in compact monitor designs. |
| Spot Killer Threshold | 3.4–4.3 V (spec), automatically blanks outputs when VCC drops below safe operating level to prevent CRT damage. |
Pinout & Package
LM1246AAC/NA/NOPB is housed in a 24-lead molded plastic DIP package (NS package N24D), with 0.3-inch body width and standard through-hole mounting footprint.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 (V Flyback) | Vertical blanking & OSD sync input | Accepts logic-level or deflection-derived flyback pulses; triggers vertical blanking and initiates OSD frame timing. |
| 5–7 (Blue/Red/Green In) | AC-coupled RGB video inputs | High-impedance (>20 MΩ) inputs with internal DC restoration - no external clamp caps required. |
| 11 (SDA), 12 (SCL) | I²C bidirectional interface | Compatible with standard 100 kHz/400 kHz I²C buses; supports full register access including Page RAM and OSD configuration. |
| 13–16 (DAC 4–DAC 1) | Programmable analog outputs | DAC 4 acts as master brightness control modulating DAC 1–3 (Blue/Green/Red bias); all four are software-configurable via I²C. |
| 19–21 (Green/Red/Blue Out) | RGB video outputs | Drive LM246x cathode drivers directly; output swing up to 4.3 V with 3.1 ns rise time and <2% overshoot. |
| 22 (ABL) | Automatic Beam Limiter input | Analog feedback node for beam current regulation; gain reduction from −2 dB to −12 dB as ABL voltage drops from 4.8 V to 2.0 V. |
| 23 (CLAMP) | Clamp pulse input | Accepts TTL/CMOS logic; synchronizes internal black-level restoration to horizontal retrace timing. |
| 24 (H Flyback) | Horizontal blanking & OSD sync input | Current-reversal input; enables precise horizontal blank positioning and programmable start offset (0–64 pixels). |
Key Features
| Feature | Design Value |
|---|---|
| OSD Window Fade In/Fade Out | Hardware-accelerated transition control reduces visual flicker during menu navigation without MCU intervention. |
| OSD Half-Tone Transparency | Enables semi-transparent overlay rendering by blending OSD pixels with underlying video using programmable alpha weighting. |
| Video Data Detection | Auto-centering and auto-sizing logic detects active video region boundaries to align OSD windows without manual geometry setup. |
| OSD Override Mode | Disables video path entirely while displaying burn-in test patterns or diagnostic messages - zero video leakage during testing. |
| Power Saving Mode | Reduces supply current from 250 mA to 95 mA (65% drop) during standby, lowering thermal load and power supply requirements. |
Applications
| Low-Cost CRT Monitor OSD | 1024×768 @ 85 Hz Display System |
|---|---|
|
Use Scenario: Entry-level 15" and 17" CRT monitors requiring on-screen menus, geometry controls, and factory calibration overlays. IC Role / Device Role / Timing Role: Central RGB preamplifier and OSD controller; handles video amplification, black-level clamping, and real-time text/graphic overlay generation synchronized to H/V flyback. Use Value: Eliminates need for discrete clamp circuitry and external character ROM, reducing BOM count by ≥7 components versus discrete solutions. |
Use Scenario: High-refresh-rate CRT displays targeting 85 Hz vertical scan for reduced flicker in professional and medical imaging applications. IC Role / Device Role / Timing Role: Bandwidth-optimized video conditioner with 150 MHz channel response and auto-synchronized OSD rendering aligned to exact pixel timing. Use Value: Maintains full 1024×768 resolution fidelity at 85 Hz without chroma smearing or OSD jitter due to PLL Auto mode's adaptive lock range. |
| LM246x-Compatible CRT Driver Interface | Integrated CRT Bias Control System |
|
Use Scenario: Monitor designs using LM2467/LM2468 cathode drivers where precise gain matching and fast video slew are critical. IC Role / Device Role / Timing Role: Pre-driver stage delivering matched 2.0 VP-P outputs with ±0.5 dB inter-channel tracking and 3.1 ns rise time to LM246x inputs. Use Value: Enables direct interface with LM246x family without external level-shifting or gain compensation networks. |
Use Scenario: Systems requiring software-tunable CRT cutoff, screen brightness, and automatic beam limiting without analog potentiometers. IC Role / Device Role / Timing Role: Four-channel DAC subsystem with dedicated Blue/Green/Red bias and global brightness control, plus ABL feedback loop. Use Value: Replaces 4 discrete DACs + 1 ABL comparator + associated op-amps, reducing layout area and calibration complexity. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar RGB preamplifier with OSD applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LM1247ACX/NOPB | Same 24-pin DIP package and pinout; identical OSD ROM/RAM architecture but lower 100 MHz bandwidth and no PLL Auto mode. | Limited to ≤1024×768 @ 75 Hz; requires manual PLL register tuning; lacks fade-in/fade-out and half-tone transparency features. | Select when cost sensitivity outweighs bandwidth and advanced OSD feature requirements. |
| LM1237N/NOPB | 28-pin DIP; no integrated DACs; only 256-character OSD ROM; no ABL input or spot killer; 80 MHz bandwidth. | Suitable for basic OSD-only applications without CRT bias control; requires external DACs and beam limiter circuitry. | Choose for legacy designs where pin compatibility with older LM1237-based layouts is mandatory. |
Compared with LM1247ACX/NOPB and LM1237N/NOPB, LM1246AAC/NA/NOPB provides higher bandwidth (150 MHz vs. 100/80 MHz), integrated DAC-based bias control (reducing external component count), and autonomous PLL Auto mode - making it optimal for new 85 Hz CRT monitor designs requiring minimal firmware overhead and robust thermal protection.
Availability
LM1246AAC/NA/NOPB is available at Aetrix Electronics and suitable for low-cost CRT monitor manufacturing, 1024×768 display systems, and industrial embedded CRT interfaces requiring stable component supply and long-term obsolescence mitigation.
Supply support for LM1246AAC/NA/NOPB includes scheduled delivery planning, volume procurement assistance, BOM continuity management, traceable sourcing, and lifecycle availability coordination for OEM customers, industrial embedded developers, connected-device designers, and electronics production programs.
Manufacturer
Texas Instruments acquired National Semiconductor in 2011 and maintains full technical documentation, legacy support, and authorized distribution for the LM1246 series.
The LM1246AAC/NA/NOPB belongs to TI's legacy CRT interface product line, engineered specifically for cost-sensitive analog monitor systems requiring integrated video amplification, OSD, and programmable CRT bias control in a single IC.
FAQ
What is the maximum horizontal scan frequency supported by LM1246AAC/NA/NOPB?
The LM1246AAC/NA/NOPB supports horizontal frequencies from 25 kHz to 110 kHz depending on PLL configuration (PPL register setting). At PPL = 4, the upper limit is 110 kHz; at PPL = 7, it drops to 96 kHz. The PLL Auto mode automatically selects the optimal range to ensure stable OSD locking across variable input rates.
Does LM1246AAC/NA/NOPB require external clamp capacitors?
No. LM1246AAC/NA/NOPB performs black-level clamping directly on the AC-coupled video inputs using internal circuitry. This eliminates the need for external clamp capacitors at pins 5–7, simplifying PCB layout and improving reliability in high-vibration CRT environments.
How does the spot killer function protect the CRT in LM1246AAC/NA/NOPB?
The spot killer in LM1246AAC/NA/NOPB monitors VCC and blanks all RGB outputs when supply voltage falls below 3.4 V (typ). Once triggered, the IC remains in off-state until VCC is cycled below 0.5 V and restored - preventing phosphor burn-in during brownout conditions.
Can LM1246AAC/NA/NOPB drive LM246x cathode drivers directly?
Yes. LM1246AAC/NA/NOPB outputs deliver up to 4.3 V peak-to-peak into 8 pF loads with 3.1 ns rise time, matching the input requirements of LM2467/LM2468 drivers. Its gain-matched RGB channels (±0.5 dB) ensure uniform cathode drive without external trimming.
What is the purpose of DAC 4 in LM1246AAC/NA/NOPB?
In LM1246AAC/NA/NOPB, DAC 4 serves as a master brightness control that scales the output levels of DACs 1–3 (assigned to Blue, Green, Red bias). When DAC 4 is enabled in Mode 00, its value modulates the amplitude of the other three DACs - enabling unified brightness adjustment without recalculating individual bias values.
LM1246AAC/NA/NOPB Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- -
- Package/Case:
- 24-DIP (0.300", 7.62mm)
- Packaging:
- Tube
- Product Status:
- Obsolete
- Function:
- Preamplifier
- Applications:
- Video Display
- Standards:
- -
- Control Interface:
- I2C
- Voltage - Supply:
- 4.75V ~ 5.25V
- Mounting Type:
- Through Hole
- Grade:
- -
- Qualification:
- -
- Supplier Device Package:
- 24-DIP
LM1246AAC/NA/NOPB FAQ
1.How can I place an order for LM1246AAC/NA/NOPB through Aetrix?
Please submit a Request for Quotation (RFQ) for LM1246AAC/NA/NOPB on Aetrix. Our sales agent will provide a competitive quotation and guide you through the order confirmation once you accept the terms.
2.Are the price and stock information for LM1246AAC/NA/NOPB reliable?
The price and inventory of LM1246AAC/NA/NOPB are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LM1246AAC/NA/NOPB is usually 5 days.
3.What payment methods are accepted for LM1246AAC/NA/NOPB?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LM1246AAC/NA/NOPB transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LM1246AAC/NA/NOPB?
LM1246AAC/NA/NOPB orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LM1246AAC/NA/NOPB order is processed, you will receive an email with the shipment details and tracking number.
Note: Tracking information may take up to 24 hours to appear. Express delivery typically takes 3–5 business days.
5.How can I obtain technical support or documentation for LM1246AAC/NA/NOPB?
For technical support, including LM1246AAC/NA/NOPB datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LM1246AAC/NA/NOPB requirements.
6.How does Aetrix verify that LM1246AAC/NA/NOPB is sourced from the original manufacturer or authorized distributors?
All LM1246AAC/NA/NOPB products on Aetrix are procured from qualified distributors and authorized channels. Our dedicated quality assurance team conducts strict verification, including traceability checks and, if necessary, third-party testing. This ensures that LM1246AAC/NA/NOPB meets industry standards.
7.What is the process for return or replacement of LM1246AAC/NA/NOPB?
All LM1246AAC/NA/NOPB units undergo pre-shipment inspection (PSI). If there is an issue with LM1246AAC/NA/NOPB, returns or replacements are accepted under the following conditions:
1.Quantity discrepancies, incorrect items, or visible external defects (such as breakage or corrosion), acknowledged by Aetrix.
2.The issue is reported within 90 days of delivery.
3.The LM1246AAC/NA/NOPB part is unused and in its original packaging.
Return procedure for LM1246AAC/NA/NOPB:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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