參數(shù)資料
型號: AN642
廠商: Maxim Integrated Products, Inc.
英文描述: Analog-to-Digital Converter Captures 1Gsps
中文描述: 模擬到數(shù)字轉(zhuǎn)換器捕捉1Gsps的
文件頁數(shù): 2/7頁
文件大?。?/td> 269K
代理商: AN642
www.maxim-ic.com/an642
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resistors), additional credit goes to the MAX104's design team for creating an efficient and effective ADC
architecture.
Most high-speed ADCs that sample more than several hundred megahertz have input bandwidths that are
limited to no more than their maximum sampling frequency to improve noise performance. One example is
the signal-to-noise ratio (SNR). This limited input bandwidth may rule out use in applications where
bandwidths of interest in the input spectrum are higher, and an undersampling approach is needed. Also, if
the input signal is changing rapidly during conversion, the effective number of bits (ENOB) and SNR will
be reduced. The MAX104's on-chip 2.2GHz full-power-bandwidth T/H amplifier
(Figure 2)
increases
dynamic performance significantly and supports more precise capture of fast analog data at extremely high
conversion rates.
Figure 2. The MAX104's full-power bandwidth is shown as a function of input amplitude.
Bandgap reference
The MAX104 features an on-board +2.5V precision bandgap reference, which can be activated by
connecting the bandgap reference's output contact (REFOUT) to the in-phase input (REFIN) of the internal
reference amplifier. The negative input of this amplifier is internally tied to the reference ground (GNDR).
The REFOUT port can provide a current of up to 2.5mA for external devices. This is enough drive for two
MAX104s configured for interleaved operation (to achieve a sampling rate of 2 gigasamples per second, or
2Gsps). Since the bandgap reference source is internally compensated, external bypass components are not
needed with REFOUT connections.
To overdrive the internal reference, an external precision reference can be connected to the REFIN pin with
REFOUT left floating. The external reference may then be used to adjust the full-scale range of the
MAX104.
The MAX104's T/H amplifier input circuit design reduces the input signal requirement and supports a full-
scale signal input range of 500mV peak-to-peak. Obtaining a full-scale digital output with a differential
input requires 250mV applied between the positive (VIN+) and the negative input (VIN-) pins. Midscale
digital output codes occur at an input of 0V.
For a zero-scale digital output code, the negative input (VIN-) must be 250mV above the positive input
(VIN+). The high-performance differential T/H amplifier enables the MAX104 to be used in single-ended
input configurations without any degradation in dynamic performance. For a typical single-ended
configuration, the analog input signal is coupled to the T/H amplifier stage at the in-phase input pad
(VIN+), while the inverted phase input (VIN-) pad is referenced to ground. Single-ended operation
supports an input amplitude of 500mV peak-to-peak, centered at approximately 0V. For minimizing
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