Mumbai University > Electronics Engineering > Sem 8 > MEMS Technology

Marks: 5M

The DMD is a device with two storage structure-

1. The first storage is the array of SRAM on silicon substrate.
2. The size of memory determines the resolution of the display.
3. DMD is a TI (Texas Instruments) product.
4. For the first DMD, the memory is 768 bits X 576 bits CMOS SRAM with 96 Shift register with each of 16-bit peripheral for data i/p.
5. Following figure shows the schematic configuration of the SRAM input

1. Each Memory cell represents a pixel in a picture.
2. A state ‘1’ may represent a bright pixel and state ‘0’ will represent dark pixel of the picture.
3. The second storage of the DMD device is an array of micromechanical mirrors.
4. Each mirror is of size 17um X 17um and its located on top of a memory cell as shown in following figure.

1. The mirror can be turn to one of the two stable states.
2. A-10oC and +100C state, according to the state of the memory cell beneath the mirror.
3. For E.g- If the memory is in 1 state, then the mirror will flop to +10 state.
4. When the device is used for a display, data for a frame of a picture are loaded into the memory by a serial parallel input operation through shift register.
5. For the memory in the state 1 , the incident light on the mirror is reflected onto the screen to present the light spot.
6. if the state of the memory is 0, then the incident light on the mirror reflected out of screen which leaves a dark spot on the screen.
7. In this way, all the data in memory are translated to a frame of the picture on the screen.
8. As the mirror is very small, it can be flip flopped in high frequency and rate of bright display on a pixel represents the grey scale of the pixels.
9. For color displays, 3 DMD devices each for Green, Blue and Red Images have to be used.
10. A single DMD with a color wheel to split the time for the image of the 3 colors.