TDC-GP2 acam messelectronic gmbh, TDC-GP2 Datasheet - Page 30

• Manufacturer Part Number: TDC-GP2
• Description: Precision Time Interval Measurement
• Manufacturer: acam messelectronic gmbh

For heatmeter application please do note use X7R or
similar capacitors.
Current consumption
By means of the TDC technology the temperature
measurement needs an extremely low current, much
less than an A/D converter does.
A full temperature measurement with 2 sensors, 2
references am PT1000 sensor type, including all
calculations takes less than 2.5µAs. With one
temperature measurement in 30 seconds (typical for
heatmeters) the average current consumption is 0.08
µA only. This is about 50 times less than other
solutions. A PT500 sensor doubles the current.
Note:
During temperature measurement the start input has
to be enabled.
Error detection
Additionally the temperature unit checks the
plausibility of the results. It is able to detect a short
circuit of the sensor or an open sensor. The TDC-GP2
provides in the relevant output register an error code
instead of a measurement value.
1. Short circuit: equivalent to a very short time interval
(< 8 x Tref = 2 µs @ 4 MHz). The TDC-GP2 writes a 0x0
to the output register of the shorted sensor.
2. Broken sensor: equivalent to no stop signal or
timeout. The TDC-GP2 writes a 0xFFFFFFFF into the
output register of the open sensor.
Table 3: Analog specifikation
Parameter
Resolution RMS
SNR
Absolut Gain-Error
Gain-Drift vs. Vio
Gain-Drift vs. Temp
Uncalibrated Offset
Offset Drift vs. Temp
PSRR
Condition: Vio = Vcc = 3.3 V, PT1000, 150nF charging
capacitor
5.4 SPI-interface
acam-messelectronic gmbh - Am Hasenbiel 27 - D-76297 Stutensee-Blankenloch - Germany - www.acam.de
Value
typ.
16.0
96
0,1
0,08
0,0008
<0.01
<0,2
>100
Unit
Bit
dB
%
%/V
%/C
%
ppm/C
dB
30
The serial interface is compatible with the 4-wire SPI
standard. It needs the SerialSelectNot (SSN) and can
not operated as 3-wire interface.
SSN
SCK
SI
SO
The TDC-GP2 does only support the following SPI mode:
The timings are shown in
Figure 1: Write and
Figure 2: Read. It is mandatory to set the SSN – line to
High-state for at least 50ns between each Read-/Write
sequence.
SSN as Reset
The SerialSelectNot (SSN) line is the HIGH-active reset
for the serial interface. After SSN is set to LOW
different operations can be addressed, not depending
on the status of the interface before the reset.
OPCodes
8 Bit OP Code
MSB
LSB
1 0 0 0 0 ADR2
1 0 1 1 0 ADR2
0 1 1 1 0
0 1 0 1 0
0 0 0 0 0
0 0 0 0 0
0 0 0 0 0
0 0 0 0 0
The transfer starts with the MSB and is finished
sending the LSB. After sending the last Bit TDC-GP2
transfers the data into the target register or executes
the command. It is not possible to do incremental
writing. Each register must be addressed separately.
When reading from the chip it is necessary to send the
opcode first, too. With the first positive edge of the
clock following the opcode the TDC-GP2 sends the MSB
Clock Phase Bit =1
Clock Polarity Bit =0
0
0
0
0
0
1
- Slave Select
- SPI Clock
- SPI Data In
- SPI Data Out
ADR1
ADR1
0
0
0
1
1
0
ADR0 Write into address
ADR0 Read from address
0
0
1
0
1
0
TDC-GP2
Description
ADR
ADR
Init
Power On Reset
Start_Cycle
Start_Temp
Start_Cal_Resonator
Start_Cal_TDC