AD9522-4 Analog Devices, Inc., AD9522-4 Datasheet - Page 48
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AD9522-4
Manufacturer Part Number
AD9522-4
Description
12 Lvds/24 Cmos Output Clock Generator With Integrated 1.6 Ghz Vco
Manufacturer
Analog Devices, Inc.
Datasheet
1.AD9522-4.pdf
(84 pages)
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AD9522-4
CMOS Output Drivers
The user can also individually configure each LVDS output as a
pair of CMOS outputs, which provides up to 24 CMOS outputs.
When an output is configured as CMOS, CMOS Output A
and CMOS Output B are automatically turned on. For a given
differential pair, either CMOS Output A or Output B can be
turned on or off independently. The user can also select the
relative polarity of the CMOS outputs for any combination of
inverting and noninverting (see Register 0x0F0 to Register 0x0FB).
The user can power down each CMOS output as needed to save
power. The CMOS output power-down is individually controlled
by the enable CMOS output register (0x0F0[6:5] to 0x0FB[6:5]).
The CMOS driver is in tristate when it is powered down.
RESET MODES
The AD9522 has a power-on reset (POR) and several other
ways to apply a reset condition to the chip.
Power-On Reset
During chip power-up, a power-on reset pulse is issued when
VS reaches ~2.6 V (<2.8 V) and restores the chip either to the
setting stored in EEPROM (with the EEPROM pin = 1) or to
the on-chip setting (with the EEPROM pin = 0). At power-on,
the AD9522 also executes a SYNC operation, which brings the
outputs into phase alignment according to the default settings.
The output drivers are held in sync for the duration of the
internally generated power-up sync timer (~70 ms). The
outputs begin to toggle after this period.
Hardware Reset via the RESET Pin
RESET , a hard reset (an asynchronous hard reset is executed by
briefly pulling RESET low), restores the chip either to the setting
stored in EEPROM (the EEPROM pin = 1) or to the on-chip
setting (the EEPROM pin = 0). A hard reset also executes a
SYNC operation, which brings the outputs into phase alignment
according to the default settings. When EEPROM is inactive
(the EEPROM pin = 0), it takes ~2 μs for the outputs to begin
toggling after RESET is issued. When EEPROM is active (the
EEPROM pin = 1), it takes ~20 ms for the outputs to toggle after
RESET is brought high.
Soft Reset via the Serial Port
The serial port control register allows for a soft reset by setting
Bit 2 and Bit 5 in Register 0x000. When Bit 5 and Bit 2 are set,
the chip enters a soft reset mode and restores the chip either to
the setting stored in EEPROM (the EEPROM pin = 1) or to the
on-chip setting (the EEPROM pin = 0), except for Register 0x000.
Figure 55. CMOS Equivalent Output Circuit
VS_DRV
OUT1/
OUT1
Rev. 0 | Page 48 of 84
Except for the self-clearing bits, Bit 2 and Bit 5, Register 0x000
retains its previous value prior to reset. During the internal reset,
the outputs hold static. These bits are self-clearing. However, the
self-clearing operation does not complete until an additional
serial port SCLK cycle, and the AD9520 is held in reset until
that happens.
Soft Reset to Settings in EEPROM when EEPROM Pin = 0 via
the Serial Port
The serial port control register allows the chip to be reset to
settings in EEPROM when the EEPROM pin = 1 via 0xB02[1].
This bit is self-clearing. This bit does not have any effect when
the EEPROM pin = 0. It takes ~20 ms for the outputs to begin
toggling after the Soft_EEPROM register is cleared.
POWER-DOWN MODES
Chip Power-Down via PD
The AD9522 can be put into a power-down condition by pulling
the PD pin low. Power-down turns off most of the functions and
currents inside the AD9522. The chip remains in this power-down
state until PD is brought back to logic high. When taken out of
power-down mode, the AD9522 returns to the settings programmed
into its registers prior to the power-down, unless the registers
are changed by new programming while the PD pin is held low.
Powering down the chip shuts down the currents on the chip.
Because this is not a complete power-down, it can be called
sleep mode. The AD9522 contains special circuitry to prevent
runt pulses on the outputs when the chip is entering or exiting
sleep mode.
When the AD9522 is in a PD power-down, the chip is in the
following state:
•
•
•
•
•
•
•
•
•
The PLL is off (asynchronous power-down).
The VCO is off.
The CLK input buffer is off, but the CLK input dc bias
circuit is on.
In differential mode, the reference input buffer is off, but
the dc bias circuit is still on.
In singled-ended mode, the reference input buffer is off,
and the dc bias circuit is off.
All dividers are off.
All CMOS outputs are tristated.
All LVDS outputs are in power-down (high impedance)
mode.
The serial control port is active, and the chip responds to
commands.