Datasheet

CCD

OUTPUT

OB ImagePixel

ImagePixel OBPixel

Pixel

CLPOB

CLPDM

Not Recommended for New Designs

VSP2582

SBES002B –JUNE 2008–REVISED JUNE 2011

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The CCD has several dummy and Optical Black pixels per line. The placement of these pixels depends on the

CCD manufacturer, but are usually at the beginning and end of the line with the imaging pixels in between.

During the time the dummy pixels are being read from the CCD, it is recommended to activate CLPDM. During

the time the Optical Black pixels are being read, it is recommended to activate CLPOB. If there are only a few

dummy pixels, then the leakage from capacitor C

may become excessive. In this case, extend the active period

of CLPDM into the Optical Black pixels. Do not activate CLPDM and CLPOB at the same time; each of these

pixel types must be used only as either a dummy pixel (CLPDM active) or an Optical Black pixel (CLPOB active).

Typically for CLPOB about 20 pixels per line are sufficient and for CLPDM about CLPDM about 10-20 pixels are

sufficient. Figure 8 shows typical timing for CLPDM and CLPOB for a line of CCD readout.

Under default conditions, SHP and SHD are active on the rising edge; CLPOB and CLPDM are active low. The

active state of each signal can be selected by register settings.

SHP, SHD, CLPOB, and CLPDM are active at low periods or upon a rising edge at the default setting of the

serial interface; each active polarity can be selected by a register setting.

Figure 8. Timing for CLPOB and CLPDM

Voltage Reference

All reference voltages and bias currents used on the device are created from an internal bandgap circuitry. The

VSP2582 has symmetrical independent voltage reference for each channel.

Both channels of CDS and the ADC use three primary reference voltages. REFP (1.5 V) and REFN (1.0 V) are

individual references. REFP and REFN are buffered on-chip. The ADC full-scale range is determined by twice

the difference voltage between REFP and REFN.

REFP and REFN should be heavily decoupled with appropriate capacitors.

Hot Pixel Rejection

Sometimes an OB pixel output signal from the CCD includes unusual signal levels that are caused by pixel

defection. If this level reaches full-scale level, it may affect OB level stability. The VSP2582 is able to reject an

unusually large pixel level (hot pixel) at the OB pixel. This function may contribute to CCD yield improvement

which is caused by OB pixel failure.

The rejection level for hot pixels is able to programmed through the serial interface. When the OB pixel level

exceeds that level, the VSP2582 omits it and uses the previous pixel level for OB level calculation.

Product Folder Links: VSP2582