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+ | ====== Circuit design details====== | ||
+ | // [[ctsd_adc_90nm|go to project home]] // | ||
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+ | ===== ADC noise budgetting ===== | ||
+ | * For a dynamic range of 86dB, measured at -15dBFS input signal (at 85C) | ||
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+ | ^ Noise source ^ noise spec ^ Noise referred to ADC i/p ^ %contribution| | ||
+ | ^ Integrator1 Amp| 10 uV|20 uV|20%| | ||
+ | ^ ADC i/p resistors| 23.3 uV|23.3 uV|30%| | ||
+ | ^ DAC isource| 23.3 uV (referred to i/p resistors)|23.3 uV|30%| | ||
+ | ^ Quantization| 96 dB |19 uV|20%| | ||
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+ | * ADC i/p resistor is chosen to be 400 ohms single ended. | ||
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+ | ===== Integrator1 OTA ===== | ||
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+ | * Two different architectures are used to evaluate modulator performance with different mismatch-levels in the replica-o/p-current sources. The summary of the results are given here --> {{:updates_amp1_architecture.pdf?800}} | ||
+ | * **OTA1 architecture:** 2-stage amplifier with cap-coupled feedforward compensation | ||
+ | {{:amp1.png?1000}} | ||
+ | * ** Small-signal/Noise performance ** | ||
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+ | ^ Parameter:^worst value^worst corner (mos,temp,cap,res)| | ||
+ | ^ DC gain:|49.8 dB |SF_mos, 85C, min_cap | | ||
+ | ^ UGB:|2.61 GHz |FS_mos, 85C, max_cap | | ||
+ | ^ Phase Margin:|48.3 degree |SS_mos, 85C, min_cap | | ||
+ | ^ Amp i/p noise:|10.3 uV |SS_mos, 85C, min_cap | | ||
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+ | * **Random Mismatch :** | ||
+ | * The o/p NMOS drain current is the most sensitive to random mismatch. The random current variation in the o/p NMOS transistor is under 10%. | ||
+ | * The random current variation in the o/p PMOS transistor is under 3%. | ||
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+ | * **Total supply current (OTA + bias)= 5.54mA** | ||
+ | * ** SNDR performance : ** | ||
+ | * SNDR vs Replica matching (FF_mos, 85C, min_cap) | ||
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+ | ^ replica matching :^90%^95%^98%^100%^103%^105%^108%^110%| | ||
+ | ^ SNDR for 100mV i/p signal:|96.8 dB|97.7 dB|97.1 dB|96.2 dB|96.2 dB|97.5 dB| 97.6 dB|96.6 dB| | ||
+ | ^ SNDR for 300mV i/p signal:|94.6 dB |94.7 dB |96.2 dB|94.7 dB|94.7 dB|94.5 dB|95.4 dB|95.4 dB| | ||
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+ | * SNDR across corners (10% replica matching) | ||
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+ | ^ Parameter:^worst value^worst corner (mos,temp,cap,res)| | ||
+ | ^ SNDR for 100mV i/p signal:|95.7 dB |SF_mos, 85C, min_cap | | ||
+ | ^ SNDR for 300mV i/p signal:|94.1 dB |FS_mos, 0C, min_cap | | ||