kad5512p-21q72ep-i Intersil Corporation, kad5512p-21q72ep-i Datasheet - Page 17

• Manufacturer Part Number: kad5512p-21q72ep-i
• Description: Low Power 12-bit, 250/210/170/125msps Adc
• Manufacturer: Intersil Corporation

CLKOUTP
User-Initiated Reset
Recalibration of the ADC can be initiated at any time by
driving the RESETN pin low for a minimum of one clock
cycle. An open-drain driver with a drive strength of less than
0.5mA is recommended, RESETN has an internal high
impedance pull-up to OVDD. As is the case during power-on
reset, the SDO, RESETN and DNC pins must be in the
proper state for the calibration to successfully execute.
The performance of the KAD5512P changes with variations
in temperature, supply voltage or sample rate. The extent of
these changes may necessitate recalibration, depending on
system performance requirements. Best performance will be
achieved by recalibrating the ADC under the environmental
conditions at which it will operate.
A supply voltage variation of less than 100mV will generally
result in an SNR change of less than 0.5dBFS and SFDR
change of less than 3dBc.
In situations where the sample rate is not constant, best
results will be obtained if the device is calibrated at the
highest sample rate. Reducing the sample rate by less than
75MSPS will typically result in an SNR change of less than
0.5dBFS and an SFDR change of less than 3dBc.
Figures 25 and 26 show the effect of temperature on SNR
and SFDR performance without recalibration. In each plot,
the ADC is calibrated at +25°C and temperature is varied
over the operating range without recalibrating. The average
change in SNR/SFDR is shown, relative to the +25°C value.
RESETN
CLKN
CLKP
ORP
FIGURE 24. CALIBRATION TIMING
CALIBRATION
BEGINS
17
CALIBRATION
CALIBRATION
COMPLETE
TIME
KAD5512P
Analog Input
The ADC core contains a fully differential input (VINP/VINN)
to the sample and hold amplifier (SHA). The ideal full-scale
input voltage is 1.45V, centered at the VCM voltage of
0.535V as shown in Figure 27.
Best performance is obtained when the analog inputs are
driven differentially. The common-mode output voltage,
VCM, should be used to properly bias the inputs as shown in
Figures 28 through 30. An RF transformer will give the best
noise and distortion performance for wideband and/or high
intermediate frequency (IF) inputs. Two different transformer
input schemes are shown in Figures 28 and 29.
FIGURE 25. SNR PERFORMANCE vs TEMPERATURE AFTER
FIGURE 26. SFDR PERFORMANCE vs TEMPERATURE AFTER
-10
-15
15
10
-1
-2
-3
-4
-5
5
0
4
3
2
1
0
-40
-40
+25°C CALIBRATION
+25°C CALIBRATION
-15
-15
TEMPERATURE (°C)
TEMPERATURE (°C)
10
10
35
35
60
60
January 16, 2009
FN6807.1
85
85