Datasheet

AD9959
Rev. B | Page 10 of 44
Pin No. Mnemonic I/O
1
Description
24 CLK_MODE_SEL I
Control Pin for the Oscillator Section. Caution: Do not drive this pin beyond 1.8 V.
When high (1.8 V), the oscillator section is enabled to accept a crystal as the
REF_CLK source. When low, the oscillator section is bypassed.
27 LOOP_FILTER I
Connects to the external zero compensation network of the PLL loop filter.
Typically, the network consists of a 0 Ω resistor in series with a 680 pF capacitor
tied to AVDD.
29
CH0_IOUT
O Complementary DAC Output. Terminates into AVDD.
30 CH0_IOUT O True DAC Output. Terminates into AVDD.
35
CH1_IOUT
O Complementary DAC Output. Terminates into AVDD.
36 CH1_IOUT O True DAC Output. Terminates into AVDD.
40 to 43 P0 to P3 I
Data pins used for modulation (FSK, PSK, ASK), to start/stop the sweep accumulators
or used to ramp up/ramp down the output amplitude. The data is synchronous to
the SYNC_CLK (Pin 54). The data inputs must meet the setup and hold time
requirements of the SYNC_CLK. The functionality of these pins is controlled by the
profile pin configuration (PPC) bits (FR1[14:12]).
46 I/O_UPDATE I
A rising edge transfers data from the serial I/O port buffer to active registers.
I/O_UPDATE is synchronous to the SYNC_CLK (Pin 54). I/O_UPDATE must meet the
setup and hold time requirements of the SYNC_CLK to guarantee a fixed pipeline
delay of data to the DAC output; otherwise, a ±1 SYNC_CLK period of pipeline
uncertainty exists. The minimum pulse width is one SYNC_CLK period.
47
CS
I Active Low Chip Select. Allows multiple devices to share a common I/O bus (SPI).
48 SCLK I
Serial Data Clock for I/O Operations. Data bits are written on the rising edge of
SCLK and read on the falling edge of SCLK.
49 DVDD_I/O I 3.3 V Digital Power Supply for SPI Port and Digital I/O.
50 SDIO_0 I/O Data Pin SDIO_0 is dedicated to the serial port I/O only.
51, 52 SDIO_1, SDIO_2 I/O
Data Pin SDIO_1 and Data Pin SDIO_2 can be used for the serial I/O port or used to
initiate a ramp-up/ramp-down (RU/RD) of the DAC output amplitude.
53 SDIO_3 I/O
Data Pin SDIO_3 can be used for the serial I/O port or to initiate a ramp-up/ramp-down
(RU/RD) of the DAC output amplitude. In single-bit or 2-bit modes, SDIO_3 is used
for SYNC_I/O. If the SYNC_I/O function is not used, tie to ground or Logic 0. Do not
let SDIO_3 float in single-bit or 2-bit modes.
54 SYNC_CLK O
The SYNC_CLK runs at one-fourth the system clock rate; it can be disabled. I/O_UPDATE
or data (Pin 40 to Pin 43) is synchronous to the SYNC_CLK. To guarantee a fixed pipeline
delay of data to DAC output, I/O_UPDATE or data (Pin 40 to Pin 43) must meet the
setup and hold time requirements to the rising edge of SYNC_CLK; otherwise, a ±1
SYNC_CLK period of uncertainty occurs.
1
I = input, O = output.