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AD61009ARSZRL

Low Power Mixer 3 V Receiver IF Subsystem

Analog Devices 

AD61009

Using the AD61009 with a Fast PRUP Control Signal

If the AD61009 is used in a system in which the PRUP signal

(Pin 3) is applied with a rise time less than 35 µs, anomalous

behavior occasionally occurs. The problem is intermittent, so it

will not occur every time the part is powered up under these

conditions. It does not occur for any other normal operating condi-

tions when the PRUP signal has a rise time slower than 35 µs.

Symptoms of operation with too fast a PRUP signal include low

gain, oscillations at the I or Q outputs of the device or no valid

data occurring at the output of the AD61009. The problem

causes no permanent damage to the AD61009, so it will often

operate normally when reset.

Fortunately, there is a very simple solution to the fast PRUP

problem. If the PRUP signal (Pin 3) is slowed down so that

the rise time of the signal edge is greater than 35 µs, the anoma-

lous behavior will not occur. This can be realized by a simple

RC circuit connected to the PRUP pin, where R = 4.7 kΩ and

C = 1.5 nF. This circuit is shown in Figure 12.

FROM PRUP

CONTROL SIGNAL

4.7k⍀

1.5nF

AD61009

PRUP

All designs incorporating the AD61009 should include

this circuitry.

Note that connecting the PRUP pin to the supply voltage will

not eliminate the problem since the supply voltage may have a

rise time faster than 35 µs. With this configuration, the 4.7 kΩ

series R and 1.5 nF shunt C should be placed between the

supply and the PRUP pin as shown in Figure 12.

AD61009 EVALUATION BOARD

The AD61009 evaluation board (Figures 13 and 14) consists of

an AD61009, ground plane, I/O connectors, and a 10.7 MHz

bandpass filter. The RF and LO ports are terminated in 50 Ω

to provide a broadband match to external signal generators to

allow a choice of RF and LO input frequencies. The IF filter is

at 10.7 MHz and has 330 Ω input and output terminations; the

board is laid out to allow the user to substitute other filters for

other IFs.

The board provides SMA connectors for the RF and LO port

inputs, the demodulated I and Q outputs, the manual gain con-

trol (MGC) input, the PLL input, and the power-up input. In

addition, the IF output is also available at an SMA connector;

this may be connected to the PLL input for carrier recovery to

realize synchronous AM and FM detection via the I and Q

demodulators, respectively. Table III lists the AD61009 Evalua-

tion Board’s I/O Connectors and their functions.

Figure 12. Proper Configuration of AD61009 PRUP Signal

REV. 0

–19–

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