© Teledyne UK Limited 2020
Document subject to disclaimer on page 1
A1A-795787 Version 1, page 6
POWER UP/POWER DOWN
When powering the device up or down it is critical that any specified maximum rating is not exceeded. This includes
ensuring that reverse bias voltages cannot be momentarily applied.
The CCD has 2 substrate connections. The front substrate FSS for the output circuit is set to 0 V initially and then,
after drain and gate biases have been applied, raised to the typical value for IMO devices to achieve low dark
current. The back substrate BSS is applied to the back surface of the CCD. To get full depletion a low or negative
potential is applied. A guard drain is designed to isolate front and back substrates.
If there is a current flowing between FSS and BSS when switching on the guard drain, the insulation below the
guard ring might not form properly. It is therefore advised to first set both FSS and BSS to 0V, then switch on the
guard drain and all other biases and clocks in the order stated below, before applying any negative bias to BSS.
The recommended power up order of all biases and clocks is listed in the table below.
BIAS/CLOCK
LABEL
POWER UP
ORDER
Comment
Front Substrate
FSS
1
Set to 0V at this stage
Back Substrate
BSS
1
Set to 0V at this stage
Guard Drain
GD
2
Reset Drain
RD
2
Output Drain
OD
2
Output Gate
OG
3
Image Clock High
IØH
4
Image Clock Low
IØL
4
Register Clock High
RØH
4
Register Clock Low
RØL
4
Reset Gate High
ØRH
4
Reset Gate Low
ØRL
4
Front Substrate
FSS
5
Set to desired voltage
Back Substrate
BSS
6
Set to desired voltage
All levels must be settled before powering up the next group of biases. There can be a delay between the
bias/clocks in any stated group.
It is also important to ensure that excess currents do not flow in the OS pins. Such currents could arise from rapid
charging of a signal coupling capacitor or from an incorrectly biased DC-coupled preamplifier.
