Datasheet

AD9222 Data Sheet

Rev. F | Page 34 of 60

HARDWARE INTERFACE

The pins described in Table 14 compose the physical interface

between the user’s programming device and the serial port of

the AD9222. The SCLK and CSB pins function as inputs when

using the SPI. The SDIO pin is bidirectional, functioning as an

input during write phases and as an output during readback.

If multiple SDIO pins share a common connection, care should

be taken to ensure that proper V

levels are met. Assuming the

same load for each AD9222, Figure 83 shows the number of SDIO

pins that can be connected together and the resulting V

level.

05967-037

NUMBER OF SDIO PINS CONNECTED TOGETHER

(V)

1.715

1.720

1.725

1.730

1.735

1.740

1.745

1.750

1.755

1.760

1.765

1.770

1.775

1.780

1.785

1.790

1.795

1.800

0 302010 40 50 60 70 80 90 100

Figure 83. SDIO Pin Loading

This interface is flexible enough to be controlled by either serial

PROMS or PIC mirocontrollers, providing the user with an

alternative method, other than a full SPI controller, to program

the ADC (see the AN-812 Application Note).

If the user chooses not to use the SPI, these dual-function pins

serve their secondary functions when the CSB is strapped to

AVDD during device power-up. See the Theory of Operation

section for details on which pin-strappable functions are

supported on the SPI pins.