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AD9690

Data Sheet

Rev. B | Page 30 of 78

130

120

110

100

1000

10000

ANALOG INPUT FREQUENCY (MHz)

12.5

100

200

400

800

Figure 81. Ideal SNR vs. Analog Input Frequency and Jitter

Treat the clock input as an analog signal in cases where aperture

jitter may affect the dynamic range of the AD9690. Separate

power supplies for clock drivers from the ADC output driver

supplies to avoid modulating the clock signal with digital noise.

If the clock is generated from another type of source (by gating,

dividing, or other methods), retime the clock by the original clock

at the last step. Refer to the AN-501 Application Note and the

AN-756 Application Note for more in-depth information about

jitter performance as it relates to ADCs.

Power-Down/Standby Mode

The AD9690 has a PDWN/STBY pin which can be used to

configure the device in power-down or standby mode. The

default operation is PDWN. The PDWN/STBY pin is a logic

high pin. When in power-down mode, the JESD204B link is

disrupted. The power-down option can also be set via

In standby mode, the JESD204B link is not disrupted and

transmits zeroes for all converter samples. This can be changed

using Register 0x571, Bit 7 to select /K/ characters.

Temperature Diode

The AD9690 contains a diode-based temperature sensor for

measuring the temperature of the die. This diode can output a

voltage and serve as a coarse temperature sensor to monitor the

internal die temperature.

The temperature diode voltage can be output to the FD pin

using the SPI. Use Register 0x028, Bit 0 to enable or disable the

diode. Configure the FD pin to output the diode voltage by

programming Register 0x040[2:0]. See Table 36 for more

information.

The voltage response of the temperature diode (SPIVDD =

1.8 V) is shown in Figure 82.

TEMPERATURE (°C)

0.60

0.65

0.70

0.75

0.80

0.85

0.90

–55 –45 –35 –25 –15 –5

15 25 35 45 55 65 75 85 95 105 115 125

Figure 82. Temperature Diode Voltage vs. Temperature

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