Features

The range of power supply is wide: 7 v to 22 v

Gamma correction channel: 10

Integrated VCOM buffer

excellent output current driver:

Gama channel:

gt; 0.5 V, swing to the track at 30 mA (1)

vro When swinging to the track (1), the typical value is 100 mA

Large capacitor load driving capacity

Output in the rail

PowerPad #63722; software package

Low power/channel: lt; 500μA [500μA [500μA [ 123]

High ESD rated value: 8 KV HBM, 2 KV CDM, 300 V mm

25 ° C to+85 ° C

Instructions

BUF11705

is a multi -channel buffer for Gag in high -resolution LCD panels Horse correction. It is compatible with the existing BUF11702 and BUF11704 pins, working at a power supply voltage of up to 22V (maximum 24 V). The higher power supply voltage makes the response time of the large screen LCD panel faster and the image is brighter. This is especially important in LCD TV applications.

BUF11705 offers 10 gamma channels. In order to save more space and cost, BUF11705 integrates a VCOM channel with a capacity of greater than 100 mA.

BUF11705 is provided in the TSSOP-28 PowerPad package, which can significantly improve power consumption. This allows a large number of channels safely in a bag.

A circulating pin has been adopted to allow simple PCB wiring and maintaining costs. All inputs and outputs of the BUF11705 include internal ESD protection circuits, which can prevent functional failures under the voltage of 8 KV (HBM), 2 KV (CDM), and 300 V (MM).

(1), see the typical characteristic curve for details.

Input and output equivalent of the principle diagram

Typical features

exceeded the temperature range of the free air air, unless otherwise explained.

DC curve

AC curve

Small small Signal and large signal waveform curve

Application information

The requirements for the number of gamma corrected channels vary from panel. Therefore, the BUF11705 series gamma correction buffer uses 10 gamma channels and a VCOM channel to provide different channel combinations. The VCOM channel can be used to drive the VCOM node on the LCD panel.

Gamma corrected voltage is usually generated using a simple resistor rack, as shown in Figure 21. BUF11705 buffer various nodes on the Gamma corrected resistance. The low output impedance of the BUF11705 force the external gamma correction voltage on the corresponding reference node of the LCD source drive. FIG. 21 shows the BUF11705 driver LCD source driver in a typical box diagram and 10 -channel gama school with reference to the input example.

ESD rated value

BUF11705 has excellent ESD performance: 8 kV HBM; 2 KV CDM; and 300 V mm. These ESD rated values are allowed to increase manufacturing, reduce production failures and higher reliability.

The input voltage range gamma buffer

FIG. 22 shows a typical gamma correction curve with 10 gamma correction points (GMA1 to GMA10). It can be seen from this curve that the voltage requirements of each buffer are very different. The input level of various buffers matches the application carefully with the application. Cushioner 1 to 5 has an input level of VDD, but only swing in the range of 1V to GND. Cushion 1 to 5 has only one NMOS input level. The buffer 6 to 10 has only one PMOS input level. The input range of PMOS input level includes GND.

The output voltage swing gamma buffer

The output stage design matches the characteristics of the input level. This means that the output level of buffer 1 to 5 is very close to VDD (usually, VCC 100 MV at 10 mA). The ability of buffer 1 to 5 to swing to GND is limited. The swing of the buffer 6 to 10 is closer to GND than the VDD. The buffer 6 to 10 is designed to be very close to GND; usually, under 10 mA load current, GND+100 MV. For more details, seeType characteristics. This method greatly reduces the silicon area and total cost of the entire solution. However, due to this reason, the correct buffer must be connected to the correct gamma correction voltage. Connect the buffer 1 to the gamma voltage closest to VDD, and connect the buffer 2 to 5 to the sequential voltage. The buffer 10 should be connected to the gamma correction voltage closest to GND (or negative), and the buffer 9 to 6 should be connected to a higher -sequential voltage.

Public buffer (VCOM)

The public buffer output of the BUF11705 has a greater output drive capability than the Gamma buffer to meet the greater current needs of the public node of the drive LCD panel. Public buffer output is also designed to drive heavier capacitance loads. As shown in Figure 23, under high current ( gt; 100 mAh), excellent output swing can be achieved.

Capacity load driver

BUF11705 Design for absorption/provides large DC current. Its output level is designed to provide transients of output current without interference when the output voltage is almost interfered. However, sometimes very fast current pulse. Therefore, in the LCD source driver buffer application, it is normal to place the capacitor on the output end of the benchmark buffer. These capacitors improve the transient load adjustment, usually with 100PF or higher. BUF11705 Gamma buffer design is used to drive capacitors over 100 PF. When the output current is 10 mAh, the output can swing within the range of 150 millival from the orbit, as shown in Figure 24.

Application of more than 10 gamma channels

When more gamma correction channels are needed, two or more BUF11705 can be used in parallel The equipment, as shown in Figure 25. This ability provides an economical and efficient way to create more reference voltage by using four -channel computing amplifier or buffer. The configuration recommended in Figure 25 simplifies the layout. Various different channel versions provide high degree of flexibility, and also minimize total costs and space.

The complete LCD solution of TI

In addition Various power solutions and audio power solutions. Figure 26 shows TI's total IC solution.

The general precautions for the design of the power board

BUF11705 are provided in the heat -enhanced PowerPad package. This packaging is constructed with a lower -loaded lead frame, and the molds are installed on it, as shown in Figure 27 (a) and (b). This layout causes the lead frame to be exposed to the hot pad at the bottom of the packaging; see Figure 27 (C). Because of thisThe thermal pad has a direct heat contact with the mold, so it can obtain excellent thermal performance pads by providing a good heat path away from the heat.

PowerPad package allows assembly and thermal management at the same time in a manufacturing operation. During the surface of the surface (when welding), the thermal pads must be welded to the copper area below the packaging. By using the heat path in this copper area, the heat can be transmitted from the package to the ground layer or other heat dissipation devices. Always welding PowerPad to PCB, even low -power applications. This provides necessary thermal connections and mechanical connections between the lead framework and PCB.

The power supply of the power board must be connected to the negative electrode.

1. Prepare PCB with top etched patterns. Both wires and hot pads must be etched.

2. Place recommended holes in the thermalpad area. The ideal thermal pad size and thermal hole mode can be found in the technical briefing. The SLMA002 PowerPad thermal enhanced package can be downloaded from the following URL. The diameter of these holes should be 13 dense ear (0.33 mm). Keep them very small, so that the weld core is not a problem during the period of the pores.

3. You can place additional pores at any location on the hot plane outside the hot pad area. This helps dissipate the calories generated by the BUF11705 IC. These additional holes may be larger than the pores with 13 dense ears in the front diameter of the hot pad. They can be larger because they are not welded in the hot pad area; therefore, core suction is not a problem.

4. Connect all holes to the internal ground plane.

5. When connecting these holes to the ground plane, do not use a typical abdomen or wheel spoke connection method. The network connection has a high thermal resistance connection, which helps to slow the heat transfer during the welding process. The network connection makes the welding of the hole easier. However, in this application, in order to achieve the most effective heat transfer, low thermal resistance is required. Therefore, the holes under the BUF11705 PowerPad component should be connected to the internal ground layer and a complete connection around the entire electroplated hole.

6. The top welding of the top should be left to leave the packaging terminal and the thermal pads area, exposing 10 holes. The welding mask at the bottom should cover the hole in the hot pad area. This prevents welded from pulling away from the hot pad area during the return welding.

7. Apply the tiny paste to the exposed thermal pad area and all IC terminals.

8. With these preparation steps, the BUF11705 integrated circuit is simply placed in an appropriate position, and as a standard surface paste component to run the welded welding operation. This preparation work can make the parts correctly installed.

For the given θja, the maximum power consumption is shown in Figure 28, and the following formula is calculated:

]

Among them:

pd u003d Maximum power consumption (W)

tmax u003d Absolute maximum knot temperature (125 ° C)

ta u003d free environment air temperature (free environmental air temperature (° C)

θja u003d θjc+θca

θjc u003d the thermal coefficient from the connection to the shell (° C/w)

θca u003d the heat from the shell to the environmental airCoefficient (° C/W)