ad5933 Analog Devices, Inc., ad5933 Datasheet - Page 9

• Manufacturer Part Number: ad5933
• Description: 1 Msps 12-bit Impedance Converter, Network Analyzer
• Manufacturer: Analog Devices, Inc.

Preliminary Technical Data
The DFT algorithm is represented by
Both the real and Imaginary data register have 15 bits of data
and one sign bit. The 15 bits of data are in 2’s compliment
format. The magnitude of the signal can be represented by
This magnitude that’s returned is a scaled valued of the actual
complex impedance measured. The multiplication factor
between the magnitude returned and the actual impedance is
called the GAIN FACTOR. The user needs to then calculate this
GAIN FACTOR value and use it for calibration in the system.
TEMPERATURE SENSOR
The temperature sensor is a 13-bit digital temperature sensor
with a 14th bit that acts as a sign bit. The block houses an on-
chip temperature sensor, a 13-bit A/D converter and a reference
circuit. The A/D converter section consists of a conventional
successive-approximation converter based around a capacitor
DAC.
The on-chip temperature sensor allows an accurate measure-
ment of the ambient device temperature to be made. The
specified measurement range of the sensor is −40°C to +150°C.
At +150°C. The structural integrity of the device starts to
deteriorate when operated at voltage and temperature
maximum specifications.
Temperature Conversion Details
The conversion clock for the part is internally generated; no
external clock is required except when reading from and writing
to the serial port. In normal mode, an internal clock oscillator
runs an automatic conversion sequence. During this automatic
conversion sequence, a conversion is initiated every 1 second. At
this time, the part powers up its analog circuitry and performs a
temperature conversion. This temperature conversion typically
takes 800 µs, after which time the analog circuitry of the part
automatically shuts down. The analog circuitry powers up again
X(f) = SUM x(n)[Cos(n)-jSine(n)]
Magnitude =
Figure 8.
R + I
2
2
Rev. PrA | Page 9 of 20
when the 1 second timer times out and the next conversion
begins. The result of the most recent temperature conversion is
always available in the serial output register because the serial
interface circuitry never shuts down.
The temperature sensor block will default to a power-down
state. To perform a temperature measurement a command is
written to the control register. After the temperature operation
is complete, the block automatically powers down until the next
temperature command is issued.
In normal conversion mode, the internal clock oscillator is reset
after every read or write operation. This causes the device to
start a temperature conversion, the result of which is typically
available 800 µs later. Similarly, when the part is taken out of
shutdown mode, the internal clock oscillator is started and a
conversion is initiated. The conversion result is available 800 µs
later, typically. Reading from the device before a conversion is
complete causes the block to stop converting; the part starts
again when serial communication is finished.
Temperature Value Register
The temperature value register is a 16-bit read-only register that
stores the temperature reading from the ADC in 13-bit twos
complement format plus a sign bit. The two MSB bits are don’t
cares. DB13 is the sign bit. The ADC can theoretically measure a
255°C temperature span. The internal temperature sensor is
guaranteed to a low value limit of –40°C and a high limit of
+150°C.
Table 4. Temperature Data Format
Temperature
−40°C
−30°C
−25°C
−10°C
−0.03125°C
0°C
+0.03125°C
+10°C
+25°C
+50°C
+75°C
+100°C
+125°C
+150°C
Temperature Conversion Formula
1.
2.
Positive Temperature = ADC Code(d)/32
Negative Temperature = (ADC Code*(d) – 16384)/32
*Using all 14 bits of the data byte, includes the sign bit.
Negative Temperature = (ADC Code(d)* – 8192)/32
*DB13 (sign bit) is removed from the ADC code
Digital Output DB13…DB0
11, 1011 0000 0000
11, 1100 0100 0000
11, 1100 1110 0000
11, 1110 1100 0000
11, 1111 1111 1111
00, 0000 0000 0000
00, 0000 0000 0001
00, 0001 0100 0000
00, 0011 0010 0000
00, 0110 0100 0000
00, 1001 0110 0000
00, 1100 1000 0000
00, 1111 1010 0000
01, 0010 1100 0000
AD5933