ATA5278 ATMEL Corporation, ATA5278 Datasheet - Page 7

• Manufacturer Part Number: ATA5278
• Description: Stand-alone Antenna Driver
• Manufacturer: ATMEL Corporation

3.5
4832D–RKE–12/07
I/O Voltage Interface
The main element of this circuit is the parallel inverting stage which generates the clock signal in
conjunction with the external reference device. During power-down mode, these inverters are
shut down and the pull-down structure on the OSCI pin is active. As soon as the SPI enables the
oscillator, the pull-down is disabled and the inverters are powered up. Now, the clock signal
assessment stage monitors the signal on the OSCI pin. As soon as the amplitude and the period
reach acceptable values, one of the two inverters (i.e., the drivers) is shut down in order to
reduce power dissipation in the external reference device.
assessment.
Figure 3-5.
All digital I/O pins, including the reset input pin NRES, are passed through the internal voltage
interface before they reach their concerning blocks. This interface prevents possible compensa-
tion currents, as the control logic of the ATA5278 is supplied by the internal 5V regulator. It is
capable of handling I/O voltages between 3.15V and 5.5V, determined by the voltage applied to
the VIF pin.
The pins NRES and S_CS are additionally equipped with a pull-up and a pull-down structure
respectively in order to ensure a defined behavior of the ATA5278 in case of a broken connec-
tion. If the NRES line is broken, the pull-up structure keeps the input in passive state and normal
operation is possible. A broken S_CS line will cause a permanently disabled SPI and S_DO pin,
so communication between the microcontroller and other SPI bus members is still possible. For
further details on the voltage interface, please refer to the table
page
Second inverter
Clock signal for
Clock signal for
27.
enable signal
OSCO signal
enable signal
internal logic
internal logic
Oscillator
Oscillator Signal Assessment
t > t
LOW,max
Figure 3-5
“Electrical Characteristics” on
t < t
illustrates the period
LOW,max
ATA5278
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