LUPA-1300 Datasheet, PDF (18/48 Pages) Cypress Semiconductor – 1.3 M Pixel High Speed CMOS Image Sensor

LUPA-1300
Datasheet
3.5 Temperature reference circuits
3.5.1 Temperature diode
The most commonly used temperature measurement is monitoring of the junction
voltage of a diode, therefore we also added a temperature diode to measure the
temperature of the silicon die. This diode junction voltage is generated by a "small",
forward biased, constant current flow (in between 10 and 100 µA).
This junction voltage has a nearly linear relationship with the temperature of the die
with a typical sensitivity of about 430°C per volt (2.3 mV per °C) for silicon
junctions.
3.5.2 Temperature module
On the same image sensor we have foreseen a module to verify the temperature on
chip and the variation of the output voltage (dark level of the pixel array) due to a
temperature variation. This module contains a copy of the complete signal path,
including a blind pixel, the column amplifiers and an output stage. It DC response
may serve a temperature calibration for the real signal. The temperature functionality
is given in figure 7. Between room temperature and 60 °C we see a voltage variation
of about 0.5 mV.
Due to different applied supply voltages, as there are: Vreset, Vmem, Vpix… an
offset between the output voltage of the temperature sensor and the output of a black
signal of the pixel array can occur. Depending on the working conditions of the
image sensor one can fine-tune the temperature module with its voltage supply. In
case one has a 6V signal for reset and a 4-6V signal for Vmem, a supply voltage of
5.5V for the temperature sensor will result in a closer match between this temperature
sensor and the black level of the image sensor. Changing the supply voltage of the
temperature sensor results only in a shift of the output voltage therefore the supply
voltage of the temperature module can be tuned to make the output of the module
equal to the dark signal of the pixel array at a certain working temperature.
Vsupply (V) 5
5.5
Vout @ 21°C 0.58 0.8
6
6.1 6.2 6.3 6.4 6.5
1.03 1.07 1.12 1.17 1.22 1.27
Cypress Semiconductor Corporation 3901 North First Street
San Jose, CA 95134 408-943-2600
Contact [e-mail] Document # : 38-05711 Rev.**( Revision 3.1) Page 18 of 48