ADRF5473BCZ datasheet(13/17 Pages) AD

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Data Sheet

ADRF5473

THEORY OF OPERATION

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Rev. 0 | 13 of 17

The ADRF5473 incorporates a 6-bit fixed attenuator array that

offers an attenuation range of 31.5 dB in 0.5 dB steps. An integrat-

ed driver provides both serial and parallel mode control of the

attenuator array (see Figure 24).

Note that when referring to a single function of a multifunction pad

in this data sheet, only the portion of the pad name that is relevant

is mentioned. For full pad names of the multifunction pads, refer to

the Pin Configuration and Function Descriptions section.

POWER SUPPLY

The ADRF5473 requires a positive supply voltage applied to the

VDD pad and a negative supply voltage applied to the VSS pad.

Bypassing capacitors are recommended on the supply lines to filter

high frequency noise.

The power-up sequence is as follows:

1. Connect GND.

2. Power up the VDD and VSS voltages. Power up VSS after VDD to

avoid current transients on VDD during ramp up.

3. Power up the digital control inputs. The order of the digital

control inputs is not important. However, powering the digital

control inputs before the VDD voltage supply can inadvertently

forward bias and damage the internal ESD structures. To avoid

this damage, use a series 1 kΩ resistor to limit the current

flowing into the control pad. Use pull-up or pull-down resistors if

the controller output is in a high impedance state after the VDD

voltage is powered up and the control pads are not driven to a

valid logic state.

4. Apply an RF input signal to ATTIN or ATTOUT.

The power-down sequence is the reverse order of the power-up

sequence.

Power-Up State

The ADRF5473 has internal power-on-reset circuity. This circuitry

sets the attenuator to the maximum attenuation state (31.5 dB)

when VDD and VSS voltages are applied, and LE is set to low.

RF INPUT AND OUTPUT

Both RF ports (ATTIN and ATTOUT) are dc-coupled to 0 V. No dc

blocking is required at the RF ports when the RF line potential is

equal to 0 V.

The ADRF5473 supports bidirectional operation at a lower power

level. The power handling of the ATTIN and ATTOUT ports are

different. Therefore, the bidirectional power handling is defined by

the ATTOUT port. Refer to the RF input power specifications in

Table 1.

Table 7. Truth Table

Digital Control Input1

Attenuation State (dB)

Low

0 (reference)

Low

High

0.5

Low

High

Low

1.0

Low

High

Low

2.0

Low

High

Low

4.0

Low

High

Low

8.0

High

Low

16.0

High

31.5

1 Any combination of the control voltage input states shown in this table provides an attenuation equal to the sum of the bits selected.

Figure 24. Simplified Circuit Diagram

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