Inside

• 16-bit Analog Interface for DSP Solutions
• Integrated power supply and audio for wireless systems
• TI offers industry's first complete range of 1394 design kits
• Mixed-Signal & Analog CD-based designer's guide
• 400 PDPI linear image sensor with electronic shutter capability
• Optocoupler with feedback for analog signals
• Booming 1 W output with improved fidelity
• TL16PIR552 Dual UART with IrDA and IEEE 1284
• High-Speed Peripheral GeoPort™/AppleTalk™ Transceivers
• Single-Ended to Differential SCSI Converter Chipset
• Wireless and Telecommunications Data Book
• Opto-isolated feedback amplifier in "gull wing" package

400 DPI linear image sensor with electronic shutter capability

Product Features

• 400 Dots per inch pixel pitch
• High Linearity and Uniformity for 256 grey scale applications
• Low image lag ... 0.5%
• 2 MHz output data rate
• Single 5-V supply
• Characterized for operation from 0^o to 70^oC

The TSL1401 is the newest member of the linear sensor array family offered by TI. This CMOS device has a pixel pitch of 400 dots per inch, maximum clock speed of 2 MHz and linearity and uniformity specs making it ideal for applications such as contact image scanning, rotary and linear encoding, edge detection and level sensing. The TSL1401 also incorporates a new hold function which provides added control over pixel integration. The hold function causes all pixels to start and stop integration at the same time, rather than sequentially as each pixel is clocked out. This helps eliminate image skewing which can be a problem with conventional linear arrays. Additionally, the clock can be gated to provide an electronic shutter function, further increasing the flexibility of the device.

The sensor consists of 128 photodiodes arranged in a linear array. Light energy falling on each photodiode generates a photocurrent which is integrated by the active integration circuitry associated with each pixel. During the exposure time, a sampling capacitor is connected to the output of the integrator through an analog switch . The amount of charge accumulated at each pixel is directly proportional to the light intensity and the exposure (integration) time.

In many applications, particularly when the target is moving at a high speed, it is necessary to have fine control over the exposure period. In some cases this can be accomplished by strobing the light source, but becomes very difficult when using incandescent or fluorescent bulbs. This control can be accomplished through the electronic shutter feature on the TSL1401. The shutter feature can be activated by clocking in the SI pulse and then stopping or gating the clock. Integration is then stopped, and the pixels can be clocked out at a later time. Integration begins again after the 18^th clock pulse.