TDC-GPX acam messelectronic gmbh, TDC-GPX Datasheet - Page 16

• Manufacturer Part Number: TDC-GPX
• Description: Precision Time Interval Measurement
• Manufacturer: acam messelectronic gmbh

1.6.2 Supply voltages
Although the TDC-GPX is a fully digital circuit, some
analog measures affect the circuit. The reason is that
the TDC is based on the internal analog measure
'propagation delay time' which is influenced by tem-
perature and supply voltage. A good layout of the sup-
ply voltage is essential for good measurement results.
It should be high capacitive and of low inductance.
There are several connections for power supply pro-
vided at the TDC-GPX:
For a good stabilization we recommend the use of
5 * 47 µF, one for each Vddc pin.
1 * 47 µF for Vddc-h.
1 * 47 µF for Vddc-o.
5 * 47 µF, total for Vddo and Vdde.
Recommended capacitors:
Taiyo-Yuden LMK325BJ476MM, 47µF, 1210
The supply voltage for the core should not be higher
than the supply voltage of the I/O plus 0.6 V. Other-
wise the signal flow could be disturbed.
All ground pins should be connected to a ground plane
on the printed circuit board.
Vddc, Vddc-h and Vddc-o are floating and are supplied
from the resolution adjust voltage regulator.
Vddo should be provided by a fixed voltage regulator to
avoid disturbances caused by the inputs supply.
Vddo
Vddc
Vddc-h
Vddc-o
Vdde
Vsso
Vssc
Vssc-h
Vssc-o
acam-messelectronic gmbh - Am Hasenbiel 27 - D-76297 Stutensee-Blankenloch - Germany - www.acam.de
- I/O supply voltage
- Core supply voltage
- Supply for the Hamac
- Supply for the ring oscillator
- Supply of LVPECL inputs
- I/O GND
- Core GND
- Hamac GND
- Ring oscillator GND
16
Power consumption
The current consumption is about 45 mA in R- and G-
mode and 39mA in I-mode idle plus 5 mA per million
events. At 1 million continuous events per second the
junction temperature will increase to 17 °C above
ambient.
The thermal resistance Rth j-a is 96K/W (still air) for
the TQFP package and 105K/W for the TFBGA pack-
age. With available heatsinks it can be reduced to
35k/W (still air), due to a very small Rthj-c of the
package.
The maximum junction temperature is
Tj max = 125 °C.
1.6.3 Design Rules
As shown in Figure 15 the supply voltage of the meas-
uring unit, Vddc-o/h, is provided by an adjustable lin-
ear regulator. It is strongly recommended to use only
LM317 or LM1117 regulators, because only for these
regulators the circuit is tested and approved. Do not
use low drop regulators because these regulators’
reference refers to the output voltage and the regula-
tion might be in conflict with the PLL regulation. The
input voltage of the regulator should be
the maximum output voltage of the PLL regulation
circuit is not limited by the voltage regulator’s voltage
drop of 1.2 V to 1.3 V.
Also for the other supply voltages, Vddc, Vddo & Vdde,
linear regulators are recommended. Switched mode
regulators will introduce a lot of noise to the meas-
urement.
The width of the strip line between the regulator’s
output and the TDC-GPX power supply pins should be
at least 50 mil.
For more detailed information concerning the PLL
regulation circuit please refer to application note no.
13 at the end of this document.
TDC-GPX
5 V so that