数据搜索系统,热门电子元器件搜索 |
|
ISL59110 数据表(PDF) 8 Page - Intersil Corporation |
|
ISL59110 数据表(HTML) 8 Page - Intersil Corporation |
8 / 10 page 8 FN6104.4 March 15, 2007 presenting a 0V input to most single supply driven amplifiers will saturate the output stage of the amplifier resulting in a clipped sync tip and degrading the video image. A larger positive reference may offset the input above its positive range. The ISL59110 features an internal sync clamp and offset function to level shift the entire video signal to the best level before it reaches the input of the amplifier stage. These features are also helpful to avoid saturation of the output stage of the amplifier by setting the signal closer to the best voltage range. The simplified block diagram of the ISL59110 in Figure 24 is divided into four sections. The first, Section A is the Sync Clamp. The AC coupled video sync signal is pulled negative by a current source at the input of the comparator amplifier. When the sync tip goes below the comparator threshold the output comparator is driven negative, The PMOS device turns on clamping sync tip to near ground level. The network triggers on the sync tip of video signal. The Sallen Key Low Pass Filter The Sallen Key is a classic low pass configuration illustrated in Figure 24. This provides a very stable low pass function, and in the case of the ISL59110, a three-pole roll-off at around 8MHz. The three-pole function is accomplished with an RC low pass network placed in series with and before the Sallen Key. One pole provided by the RC network and poles two and three provided by the Sallen Key for a nice three- pole roll-off at around 8MHz. If more aggressive, multiple- pole roll-offs are needed, multiple ISL59110 can be placed in series. There will, of course, be a loss of bandwidth as additional devices are added. AC Output Coupling and the SAG Network Composite video signals carry viable information at frequencies as low as 30Hz up to 5MHz. When a video system output is AC coupled it is critical that the filter represented by the output coupling capacitor and the surrounding resistance network provide a band pass function with a low pass band low enough to exclude very low frequencies down to DC, and with a high pass band pass sufficiently high to include frequencies at the higher end of the video spectrum. FIGURE 25. SAG NETWORK AND AC COUPLING CAPACITORS Typically this is accomplished with 220µF coupling capacitor, a large and somewhat costly solution providing a low frequency pole around 5Hz. If the size of this capacitor is even slightly reduced we have found that the accompanying phase shift in the 50Hz to 100Hz frequency range results in field tilt resulting in a degraded video image. The internal SAG network of the ISL59110 replaces the 220µF AC coupling capacitor with a network of two smaller capacitors as shown in Figure 25. Additionally, the network is designed to place a zero in the ~30Hz range, providing a small amount of peaking to compensate the phase response associated with field tilt. DC Output Coupling The ISL59110 internal sync clamp makes it possible to DC couple the output to a video load, eliminating the need for any AC coupling capacitors, thereby saving board space and additional expense for capacitors. This makes the ISL59110 extremely attractive for portable video applications. Additionally, this solution completely eliminates the issue of field tilt in the lower frequency. The trade off is greater demand of supply current. Typical load current for AC coupled is around 3mA, compared to typical 6mA used when DC coupling. FIGURE 26. DC COUPLE R6 R5 R4 R7 C5 C4 ROUT RL SAG NETWORK AC COUPLING CAPACITOR - + TELEVISION OR VCR ROUT ENABLE ISL59110 |
类似零件编号 - ISL59110 |
|
类似说明 - ISL59110 |
|
|
链接网址 |
隐私政策 |
ALLDATASHEETCN.COM |
ALLDATASHEET是否为您带来帮助? [ DONATE ] |
关于 Alldatasheet | 广告服务 | 联系我们 | 隐私政策 | 链接交换 | 制造商名单 All Rights Reserved©Alldatasheet.com |
Russian : Alldatasheetru.com | Korean : Alldatasheet.co.kr | Spanish : Alldatasheet.es | French : Alldatasheet.fr | Italian : Alldatasheetit.com Portuguese : Alldatasheetpt.com | Polish : Alldatasheet.pl | Vietnamese : Alldatasheet.vn Indian : Alldatasheet.in | Mexican : Alldatasheet.com.mx | British : Alldatasheet.co.uk | New Zealand : Alldatasheet.co.nz |
Family Site : ic2ic.com |
icmetro.com |