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MAX9532 Datasheet(PDF) 7 Page - Maxim Integrated Products |
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MAX9532 Datasheet(HTML) 7 Page - Maxim Integrated Products |
7 / 13 page Detailed Description The MAX9532 DirectDrive video amplifier with short-to- battery protection features an internal 5-pole Butterworth lowpass filter with the amplifier configured with a gain of 4. The MAX9532 accepts DC-coupled or AC-coupled full-scale input signals of 0.5VP-P. Integrated short-to-battery protection prevents the MAX9532 from being damaged when the output is short circuited to the battery in automotive applications. DirectDrive Background Integrated video filter amplifier circuits operate from a single supply. The positive power supply usually cre- ates video output signals that are level-shifted above ground to keep the signal within the linear range of the output amplifier. For applications where the positive DC level is not acceptable, a series capacitor can be inserted in the output connection to eliminate the posi- tive DC level shift. The series capacitor cannot truly level shift a video signal because the average level of the video varies with picture content. The series capaci- tor biases the video output signal around ground, but the actual level of the video signal can vary significantly depending upon the RC time constant and the picture content. The series capacitor creates a highpass filter. Since the lowest frequency in video is the frame rate, which is between 24Hz and 30Hz, the pole of the highpass filter is ideally an order of magnitude lower in frequency than the frame rate. Therefore, the series capacitor must be very large, typically from 220µF to 3000µF. For space-constrained equipment, the series capacitor is unacceptable. Changing from a single series capacitor to a SAG network that requires two smaller capacitors can only reduce space and cost slightly. Video Amplifier When the full-scale video signal from a video DAC is 500mV, the black level of the video signal created by the video DAC is around 150mV. The MAX9532 shifts the black level to near ground at the output so that the active video is above ground and the sync is below ground. The amplifier needs a negative supply for the output stage to remain in the linear region when driving sync below ground. The MAX9532 includes an integrated charge pump and linear regulator to create a low-noise negative supply from the positive supply voltage. The charge pump inverts the positive supply to create a raw negative volt- age that is then fed into the linear regulator filtering out the charge-pump noise. Comparison Between DirectDrive Output and AC-Coupled Output The actual level of the video signal varies less with a DirectDrive output than with an AC-coupled output. The average video signal level changes depending upon the picture content. With an AC-coupled output, the average level changes according to the time constant formed by the series capacitor and series resistance (usually 150 Ω). For example, Figure 1 shows an AC- coupled video signal alternating between a completely black screen and a completely white screen. Notice the excursion of the video signal as the screen changes. DirectDrive Video Amplifier with Short-to-Battery Protection _______________________________________________________________________________________ 7 Pin Description PIN NAME FUNCTION 1VDD Positive Power Supply. Bypass VDD with a 1µF capacitor to GND. 2 C1P Charge-Pump Flying Capacitor Positive Terminal. Connect a 1µF ceramic capacitor from C1P to C1N. 3 CPGND Charge-Pump Ground. Connect to GND. 4 C1N Charge-Pump Flying Capacitor Negative Terminal. Connect a 1µF ceramic capacitor from C1P to C1N. 5 CPVSS Charge-Pump Negative Power Supply. Bypass CPVSS with a 1µF ceramic capacitor in parallel with a 10nF low ESL capacitor to GND. 6VSS Negative Power Supply. Connect VSS to CPVSS. 7 OUT Video Output 8 JACKSENSE Jack-Sense Input. Connect to the video output connector after the back-termination resistor. 9 GND Ground 10 IN Video Input |
Similar Part No. - MAX9532_11 |
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Similar Description - MAX9532_11 |
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