AD6622SSLASHPCB datasheet(27/28 Pages) AD

27 / 28 page

AD6622

–27–

REV. 0

Driving Multiple TSP Serial Ports

When properly conﬁgured, the AD6622 will drive each SDFS

out of phase. Each new piece of data should be driven only into

the TSP that pulses its SDFS pin at that time.

In the UMTS example, L = 64 and NTSP = 4, so each serial port

need only accept every 4th input sample. Each serial port is

shifting at peak capacity, so sample 1, 2, and 3 begin shifting

into Serial Ports B, C, and D before Sample 0 is completed into

Serial Port A.

SDFSA

SDFSB

SDFSC

SDFSD

Figure 21. SDFS Timing for WBCDMA

RAM

COEF

FILTER

CIC

NCO

8.196MSPS 65.536MSPS

4.096

MCPS

1.024

MCPS

1.024

MCPS

1.024

MCPS

1.024

MCPS

65.536

MSPS

DAC

COMPLEX SIGNAL 32 BITS (16 I, 16 Q)

REAL OR IMAGINARY SIGNAL

AD6622

RAM

COEF

FILTER

CIC

NCO

8.196MSPS 65.536MSPS

RAM

COEF

FILTER

CIC

NCO

8.196MSPS 65.536MSPS

RAM

COEF

FILTER

CIC

NCO

8.196MSPS 65.536MSPS

Figure 22. Block Diagram for WBCDMA

0.5

1.0

COEF – J

Figure 23. Typical Impulse Response for WBCDMA

–70

–60

–50

–40

–30

–20

–10

–100

–90

–80

RAM COEFFICIENT FILTER

1000

2000

3000

4000

5000

6000

7000

8000

kHz

Figure 24. Typical FIR Frequency Response for WBCDMA

–70

–60

–50

–40

–30

–20

–10

–100

–90

–80

0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0

–110

–120

dB(AD6624(f))

()

HCIC(f)

LEVEL5

SPEC( f )

4.5 5.0 5.5 6.0 6.5 7.0 7.5 8.0

MHz

Figure 25. Typical Composite Frequency Response for

WBCDMA

THERMAL MANAGEMENT

The power dissipation of the AD6622 is primarily determined

by three factors: the clock rate, the number of channels active,

and the distribution of interpolation rates. The faster the clock

rate the more power dissipated by the CMOS structures of

the AD6622; the more channels active, the higher the overall

power of the chip. Low interpolation rates in the CIC stages

(CIC5, CIC2) results in higher power dissipation. All these factors

should be analyzed as each application has different thermal

requirements.

The AD6622 128-lead MQFP is specially designed to provide

excellent thermal performance. To achieve the best performance,

the power and ground leads should be connected directly to

planes on the PC board. This provides the best thermal transfer

from the AD6622 to the PC board.

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