ADC12D1800 Datasheet, PDF (64/84 Pages) National Semiconductor (TI) – 12-Bit, Single 3.6 GSPS ADC

ADC12D1800
SNAS500P – MAY 2010 – REVISED JULY 2015
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The temperature sensor reports temperature in two different formats for +127.875°C/-128°C range and
0°/255°C range. It has a Sigma-Delta ADC core which provides the first level of noise immunity. For
improved performance in a noisy environment, the temperature sensor includes programmable digital
filters for Remote Diode temperature readings. When the digital filters are invoked, the resolution for the
Remote Diode readings increases to 0.03125°C. For maximum flexibility and best accuracy, the
temperature sensor includes offset registers that allow calibration for other types of diodes.
Diode fault detection circuitry in the temperature sensor can detect the absence or fault state of a remote
diode: whether D+ is shorted to the power supply, D- or ground, or floating.
In the following typical application, the LM95213 is used to monitor the temperature of an ADC12D1800 as
well as an FPGA, see Figure 6-6. If this feature is unused, the Tdiode+/- pins may be left floating.
ADC12D1XXX
I_E = I_F
100 pF
I_R
7
D1+
5
D-
FPGA
I_E = I_F
I_R
100 pF
6
D2+
LM95213
Figure 6-6. Typical Temperature Sensor Application
6.1.5.2 Clocking Device
The clock source can be a PLL/VCO device such as the LMX2531LQxxxx family of products. The specific
device should be selected according to the desired ADC sampling clock frequency. The ADC12D1800RB
uses the LMX2531LQ1778E, with the ADC clock source provided by the Aux PLL output. Other devices
which may be considered based on clock source, jitter cleaning, and distribution purposes are the
LMK01XXX, LMK02XXX, LMK03XXX and LMK04XXX product families.
6.1.5.3 Amplifiers for Analog Input
The following amplifiers can be used for ADC12D1800 applications which require DC coupled input or
signal gain, neither of which can be provided with a transformer coupled input circuit. In addition, several
of the amplifiers provide single ended to differential conversion options:
AMPLIFIER
LMH3401
LMH5401
LMH6401
LMH6554
LMH6555
Table 6-6. Amplifier Recommendation
BANDWIDTH
7 GHz
8 GHz
4.5 GHz
2.8 GHz
1.2 GHz
BRIEF FEATURES
Fixed gain, single ended to differential conversion
Configurable Gain, single ended to differential
conversion
Digital Variable Controlled Gain
Configurable gain
Fixed gain
64
Application and Implementation
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