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reference:instrumentation:zmoddac:reference-manual [2019/10/25 11:21] – [2.3. AWG I/V] Mircea Dabacan | reference:instrumentation:zmoddac:reference-manual [2019/11/04 07:36] – [2.4. AWG Out] Mircea Dabacan | ||
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* Channel type: single ended | * Channel type: single ended | ||
* Resolution: | * Resolution: | ||
- | * Absolute Resolution (amplitude ≤1.25V): 152μV | + | * Absolute Resolution (amplitude ≤1.25V): 167μV |
- | * Absolute Resolution (amplitude > | + | * Absolute Resolution (amplitude > |
* Accuracy - typical (|Vout| ≤ 1.25V): ±10mV ± 0.5% FIXME | * Accuracy - typical (|Vout| ≤ 1.25V): ±10mV ± 0.5% FIXME | ||
* Accuracy - typical (|Vout| > 1.25V): ±25mV ± 0.5% FIXME | * Accuracy - typical (|Vout| > 1.25V): ±25mV ± 0.5% FIXME | ||
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For high-gain: | For high-gain: | ||
- | $$I_{outAWGFS\_HG}=32 \cdot \frac{1V}{8k \Omega}=4mA\label{3}\tag{3}$$ | + | $$I_{outAWGFS\_HG}=32 \cdot \frac{1V}{8.06k \Omega}=3.97mA\label{3}\tag{3}$$ |
For low-gain: | For low-gain: | ||
Line 142: | Line 142: | ||
- | The Voltage | + | The IC5B output voltage |
$$ - V_{OUT\; | $$ - V_{OUT\; | ||
Line 148: | Line 148: | ||
Where (for high gain, respectively, | Where (for high gain, respectively, | ||
- | $$V_{OUT\; | + | $$V_{OUT\; |
$$V_{OUT\; | $$V_{OUT\; | ||
Line 154: | Line 154: | ||
{{: | {{: | ||
{{: | {{: | ||
- | {{: | + | |
+ | {{: | ||
{{: | {{: | ||
{{: | {{: | ||
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$$V_{AWG\; | $$V_{AWG\; | ||
- | The output voltage range depends on High- versus | + | The output voltage range depends on High-gain versus |
- | $$ - 5.49V < - 5V < V_{AWG\; | + | $$ - 5.49V < - 5V < V_{AWG\; |
$$ - 1.37V < 1.25V < V_{AWG\; | $$ - 1.37V < 1.25V < V_{AWG\; | ||
- | Low-gain is used to generate low amplitude signals with improved accuracy. Any amplitude of the output signal | + | Low-gain is used to generate low amplitude signals with improved accuracy. Any amplitude of the output signal |
With the 14-bit DAC, the absolute resolution of the AWG AC component is: | With the 14-bit DAC, the absolute resolution of the AWG AC component is: | ||
$$at\; | $$at\; | ||
- | $$at\; | + | $$at\; |
- | AD8021 is supplied with $\pm 8V$; to avoid saturation | + | AD8021 is supplied with +8.5V/-8V (the VCC8V0 voltage is in fact 8.5V). Conform |
- | $$ - 6.5V < 5V < V_{AWG\; | + | The nominal resistance of the PTC in the feedback loop is 33 ohm. The maximum current delivered by te AWG is 30mA. |
+ | |||
+ | To avoid saturation, the voltage in \ref{9} should stay in: | ||
+ | |||
+ | $$ -8V + 1.8V + 33\Omega *30mA = -5.21V | ||
Only inner (tighter) ranges are used in equations \ref{10} and \ref{12}, for providing tolerance margins. | Only inner (tighter) ranges are used in equations \ref{10} and \ref{12}, for providing tolerance margins. | ||
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* 4 * 1.33 = 5.32 (for HG: +/-5V) | * 4 * 1.33 = 5.32 (for HG: +/-5V) | ||
- | The R146 PTC thermistor provides thermal protection in case of an output | + | The R146 PTC thermistor provides thermal protection in case of an output |
The IC7 relay (non-latching) is OPEN at the power-on, decoupling the power-on glitch of the OpAmp from the load. It is CLOSED by the FPGA, via Q1. | The IC7 relay (non-latching) is OPEN at the power-on, decoupling the power-on glitch of the OpAmp from the load. It is CLOSED by the FPGA, via Q1. | ||
R37 is a pull down when IC7 is OPEN and a dummy load when IC7 is CLOSED. | R37 is a pull down when IC7 is OPEN and a dummy load when IC7 is CLOSED. | ||
- | D2 is an ESD suppressor. | + | D2 is an ESD suppressor. |
+ | |||
+ | R36 is the 50Ω AWG output impedance. | ||
---- | ---- | ||
==== 2.3. AWG output stage protection ==== | ==== 2.3. AWG output stage protection ==== | ||
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The protection circuit in [[reference: | The protection circuit in [[reference: | ||
- | $$\frac {AVCC8V0 \cdot R_{77}}{R_{72}+R_{77}} = \frac{(AVCC8V0 | + | $$\frac {AVCC8V0 \cdot R_{77}}{R_{72}+R_{77}} = \frac{(AVCC8V0 |
AVCC8V0AWG1 \cdot R_{73}}{R_{73}+R_{74}}$$ | AVCC8V0AWG1 \cdot R_{73}}{R_{73}+R_{74}}$$ | ||
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To trace the analog bandwidth of the DAC and output stage beyond the theoretical limit of f< | To trace the analog bandwidth of the DAC and output stage beyond the theoretical limit of f< | ||
- | * The AWG was set to generate a 20MGz rectangular signal, 100mV amplitude; | + | * The AWG was set to generate a 2MHz rectangular signal, 100mV amplitude; |
* the theoretical amplitudes of the fundamental and first 69 harmonics was computed; | * the theoretical amplitudes of the fundamental and first 69 harmonics was computed; | ||
- | * the actual amplitudes of the fundamental and first 69 harmonics | + | * the actual amplitudes of the fundamental and first 69 harmonics |
* the dB difference between the theoretical and measured amplitudes was plotted. This represents an approximation of the frequency characteristic of the DAC and output stage. | * the dB difference between the theoretical and measured amplitudes was plotted. This represents an approximation of the frequency characteristic of the DAC and output stage. | ||
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The 3dB bandwidth is close to the theoretical Nyquist limit for a 100MHz sampling system. This has the advantage of very sharp edges (see the rectangular signal in [[reference: | The 3dB bandwidth is close to the theoretical Nyquist limit for a 100MHz sampling system. This has the advantage of very sharp edges (see the rectangular signal in [[reference: | ||
- | the right side of [[reference: | + | the right side of [[reference: |
The typical Slew Rate of the AWG can be read in [[reference: | The typical Slew Rate of the AWG can be read in [[reference: | ||
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==== 4.3. AVCC8V0 ==== | ==== 4.3. AVCC8V0 ==== | ||
- | The user power supplies [[reference: | + | The user power supplies [[reference: |
* 1.4A current limit | * 1.4A current limit | ||
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==== 4.4. AVCC-8V0 ==== | ==== 4.4. AVCC-8V0 ==== | ||
- | The user power supplies [[reference: | + | The user power supplies [[reference: |
IC13 introduces the required inversion for the negative supply. [[https:// | IC13 introduces the required inversion for the negative supply. [[https:// |