MAX7456EUI+T IC

Technical Specifications of MAX7456EUI+T

Datasheet	MAX7456EUI+T datasheet
Category	Integrated Circuits (ICs)
Family	Linear – Video Processing
Manufacturer	Maxim Integrated
Series	–
Packaging	Tape & Reel (TR)
Part Status	Obsolete
Type	OSD (On-Screen Display) Video Generator
Applications	Security Systems, Video Routing
Mounting Type	Surface Mount
Package / Case	28-TSSOP (0.173″, 4.40mm Width) Exposed Pad
Supplier Device Package	28-TSSOP-EP

MAX7456EUI+T General Description

The MAX7456EUI+T is an on-screen display (OSD) generator intended to produce an OSD according to user specifications and embed it in the output signal; it is monochrome, single-channel, and has a 3.3V supply voltage. Non-volatile character memory, an on-screen display (OSD) generator, an SPI-compatible interface for reading and writing OSD data, display memory, and a video driver are all included in the MAX7456EUI+T, which is also compatible with PAL and NTSC composite video signals.

Vertical sync (VSYNC), horizontal sync (HSYNC), and loss of sync (LOSYNC) are all available from this device for synchronizing multiple displays (LOS). Furthermore, it features a clock output signal (CLKOUT) that connects the device in a chain. The MAX7456EUI+T comes with a preloaded character set that allows it to show up to 256 12×18 pixel characters. The OSD synthesizer calculates each pixel’s amplitude based on data read from the character memory and the row brightness registers (RB0-RB15). Security switching systems, security cameras, industrial applications, in-car entertainment, and consumer electronics are just some of the many uses for the MAX7456EUI+T.

MAX7456EUI+T Features

• 256 Pictographs or User-Defined Characters in Integrated EEPROM.
• Size of Characters: 12 × 18 pixels.
• Characteristics such as blinking, inversion, and background control.
• Brightness can be chosen by row.
• Shows 30 Characters in Up to 16 Rows.
• Input sag compensation for the video driver.
• Clock outputs, HSYNC, VSYNC, and LOS.
• Generator of internal sync.
• PAL and NTSC compatibility.
• Serial Interface SPI-Compatible.
• Preprogrammed Character Set Delivered

MAX7456EUI+T Applications

• Security Switching Systems
• Security Cameras
• Industrial Applications
• In-Cabin Entertainment
• Consumer Electronics

MAX7456EUI+T Detailed Description

The MAX7456 is a monochrome, single-channel, on-screen display (OSD) generator with all the characteristics required to generate an OSD according to the user’s specifications and insert it into the output signal. The MAX7456 accepts both NTSC and PAL composite video signals. The device contains nonvolatile character memory, an OSD generator, an SPI-compatible interface for reading and writing OSD data, display memory, and a video driver (see the Simplified Functional Diagram). The MAX7456 also provides sync outputs for system synchronization, including vertical sync (VSYNC), horizontal sync (HSYNC), and loss of sync (LOSYNC) (LOS). A CLKOUT signal is a clock output that enables the chaining of several devices.

The input video stream is combined with the 12×18-pixel character set to generate a CVBS signal with on-screen display (OSD) video output. The NVM can reprogram up to 256 12 x 18 pixel characters. In NTSC mode, the display will include 13 rows of 30 characters. PAL format displays sixteen rows by thirty characters. The MAX7456 contains an internal video timing generator that can display the OSD image without an incoming video signal.

● Video Input

The MAX7456 may receive either NTSC or PAL CVBS signals at its VIN input. Internally clamped and requiring an AC coupling capacitor of 0.1 F, the video signal input is required. The required line-time distortion (LTD) and video clamp settling time can only be ensured with an input coupling capacitance of 0.1F. LTD shifts in the opposite direction of the video clamp settling time as the input coupling capacitance shifts.

● Input Clamp

As the sync tip at VIN is around 550mV, thanks to the MAX7456’s DC-restore clamp using the input coupling capacitor to rectify any DC shift in the input signal. The DC level at VIN is set to a level that is optimal for the on-chip sync detection and video processing. These circuits also filter out noise at low frequencies, such as the ubiquitous 60 Hz hum or other forms of additive low-frequency noise.

● Sync Separator

The sync separator picks up the video’s composite sync pulses, and the timing data is then used to produce HSYNC and VSYNC. It is also employed for LOS detection and synchronization of internal OSD. If VIN does not receive a sync signal for 32 lines in a row, LOS will be high, and vice versa if 32 horizontal sync signals are received. When the LOS situation is present and VM0[5] = 0 (Video Mode 0 register, bit 5), the OSD is the only content output to the VOUT. VM1[6:4] currently determines the grayscale value for the output picture, which is applied to the input image at VOUT.

Single-Channel Monochrome On-Screen Display with Integrated EEPROM

Timer Maker for Videos All of the video’s sync signals (VSYNC and HSYNC) are produced by a digital circuit called the video timing generator. It is possible to run VSYNC and HSYNC in sync with VIN, or to switch to internal sync mode and have them operate independently of any input. The 27MHz crystal in the video timing generator can be used to create either NTSC or PAL time.

● Crystal Oscillator

The video timing generator uses the system clock generated by the internal crystal oscillator. If an external 27MHz TTL clock is connected to CLKIN, the oscillator can be powered by that instead of the 27MHz crystal. If you want to use an external clock, you’ll need to connect the 27MHz TTL input clock to CLKIN and disconnect XFB.

● Display Memory

The NVM character memory holds the actual characters; the display memory simply stores 480-character addresses to get to them. An SPI-compatible serial interface allows the display memory to be programmed by the end user. An absolute coordinate on the screen is associated with the display-memory address. If you write to the screen’s memory during the vertical blanking interval, you can avoid a brief interruption in the OSD image. The VSYNC interrupt on the host processor can be used to start writing to the display memory, allowing this to happen.

● On-Screen Display (OSD) Generator

The OSD synthesizer uses input from the character memory, and Row Brightness registers to determine the amplitude of each individual pixel (RB0–RB15).

● OSD Insertion Mux

Choose between inserting an OSD pixel and the input visual signal with the OSD insertion mux. The bits of the OSD Insertion Mux (OSDM) register labeled Rise Time, Fall Time, and Switching Time determine how crisp the on-screen display (OSD) image will seem. The OSD image sharpness versus cross color/crossluma artifacts tradeoff is controlled by this register. Sharper pixels are created at lower time settings, however cross color/crossluma artifacts may become more pronounced. The user controls the optimal setting because the program’s needs determine it.

● Video-Driver Output

The MAX7456 has a gain of 2 on its video-driver output. With a high signal bandwidth of 6MHz (attenuation of 0.2dB), the driver can handle a maximum output swing of 2.4VP-P. Two typical video loads of 150 can be driven from the driver output.

● Sag Correction

Using sag correction, the output coupling capacitor can be physically and electrically shrunk while providing a serviceable level of line-time distortion. When a back-terminated coaxial cables 150 load and the output coupling capacitor form a high pass filter, this is known as sag correction. This threshold must be set below the vertical sync interval (25Hz for PAL and 30Hz for NTSC) to prevent field tilt. A large coupling capacitor, normally > 330 F, is required, and the breakpoint is traditionally set at a frequency of 5 Hz. The MAX7456 lowers the value of this capacitor, replacing it with two smaller capacitors (CSAG  and COUT) to achieve acceptable line-time distortion while significantly decreasing the size and cost of the coupling capacitors. If you are not utilizing SAG, please connect it to VOUT.

Conclusion

Finally, the MAX7456EUI+T is a versatile on-screen display generator with many potential uses. It’s great for use in surveillance equipment, business machinery, and home electronics thanks to its non-volatile character memory, ability to process composite video signals from both PAL and NTSC, and other advantages. As a trusted supplier of high-quality electronic components in China, ICRFQ is your one-stop-shop for the MAX7456EUI+T and other components. Our commitment to customer satisfaction, competitive pricing, and fast delivery times make us the ideal partner for all your electronic component needs. Contact us today and let us help you find the right components for your project.

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